Hydrogen Line Survey

[Kevin Wilson]

I spent the better part of Memorial Day doing a survey of Quadrant 3 of the Milky Way. The attached image shows the area of the six scans I made. These were 30-second integrations. I have also attached an image showing the combined spectra of the scans. All have the same general profile with a bump around 1420.3 MHz (presumably the hydrogen line) and another around 1419.5 MHz (source unknown), plus some noise at the left end of the scans. A scan of an area away from the galactic plane removes both bumps but leaves the noise at the left side.

I have two questions:

First, does anyone have any idea what the bump at 1419.5 could be? I thought it was just interference, but because it disappeared when pointed away from the galactic plane that explanation doesn't seem to fit.

Second, should the scans of hydrogen across that area show bumps with identical red shifts? I would have expected the speed of the hydrogen to be different at various points, so I'm surprised  they all spanned 1420.23–1420.37 MHz. The only difference is in the signal strength. Is that normal? I want to make sure that what I am detecting is actually the hydrogen line and not something else.

I made scans that included integrations of up to 10 minutes, but those didn't seem to change the basic profile of the spectrum. All the scans combine in the attached spectrum were 30-second integrations.

Any help on this would be appreciated. I'm new to radio astronomy, but I've been doing visual astronomy as a hobby for 40 years. This horn antenna for hydrogen is my second radio astronomy build.

System:

• horn antenna
• Nooelec LDA with hydrogen line filter
• Nooelec SDR dongle
• Raspberry Pi 4 using GNU Radio with a spectrometer created by the Digital Signal Processing in Radio Astronomy (DSPIRA) group at the University of West Virginia
• SMU9250 to read altitude and azimuth

Kevin A. Wilson

[Hamish Barker]

those spectra don't look like milky way spectra taken with a horn antenna (how big? I assume something like 0.5m2 area?).

Are the units up the vertical axis decibels or just linear?

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/f9838596-08e5-46e4-8784-f6730134f36en%40googlegroups.com.

[Kevin Wilson]

The antenna has a 0.43 m^2 area. The scale is linear, showing the relative strength of the signal. This is an uncalibrated spectrum. I can do both a cold and hot calibration, but the results are similar. 

You received this message because you are subscribed to a topic in the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe.
To unsubscribe from this group and all its topics, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_JoHEKCD06uVmaK-XaXCH2c7OA_z8oCW%3Dsk7rX0uw62SA%40mail.gmail.com.

[Jon Wallace]

Kevin,

I have written up my first attempts at detecting the H line with a SDR and it might be helpful for you to read through that (https://www.radio-astronomy.org/pdf/JonWallace-Article-SARAJournal-Feb-2019.pdf). There was also a good article in the journal last month.

I am not an engineer so will not be able to troubleshoot, but your peaks don't look like hydrogen line peaks and they should vary somewhat (the galaxy appears to move towards and away from us so the Doppler shift should show). Perhaps you could do a 24 hour scan at 1 Declination and see how the signal varies as I did for a test. 

For such a small horn, you will need longer integration - I used 5 minutes. When I did 30 seconds on SDR# I got nothing. I have some trouble shooting ideas in my article that might be worth checking - like pointing at a cement floor to get a baseline...

Best of luck and hang in there! Someone here will help you find the problem.

Jon

--

[Hamish Barker]

Have you checked the swr of the feed to ensure that it's well matched to the 50ohm LNA impedance? If you don't have one yet, I very highly recommend purchase of these reduced function vna units. Well worth the price since it enables easy optimisation of antenna performance. Don't forget to also purchase a calibration set of short, open and 50 ohm terminations.

https://youtu.be/ZpKoLvqOWyc

Alternatively the nano vna can do the same and much more but is more complicated to use. 

Cheers,

Hamish

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/2065709629.614671.1622550410540%40connect.xfinity.com.

[Kevin Wilson]

My thanks to everyone for their help. I'm looking into several of the issues you mentioned.

One thing I find confusing is why that bump is showing up where red-shifted hydrogen would be. It seems like it is something in the plane of the galaxy, because when I take a reading looking away from the plane the bump disappears (as you can see in the attached).

Kevin A. Wilson

Maryland City, MD

he/him/his

You received this message because you are subscribed to a topic in the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe.
To unsubscribe from this group and all its topics, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_JNnkjd0%2BW5xncv%3DwR6_OFgDhsC1tTuw7Hgq0MUW4bVCw%40mail.gmail.com.

[Hamish Barker]

ok, that plot appears to be the raw response of the system. I don't know which software you are using, but the spectral response of the RTLSDR (and nooelec smartee) units is usually a much bigger variation than the actual H1 signal for small dishes. (circa 10x). What you need to do is save the response curve for pointing away from the plane (hopefully not accidentally getting some other H1 cloud, or the actual galaxy in your antenna sidelobe. Then subtract that off-target response from your on-target spectra. Perhaps you did this already, but it doesn't look like it. 

The big bump at left end of your spectrum looks as though it is either a "birdy" of the receiver (filter spike). Subtracting away the off-target response will help a lot, BUT the gain of the receiver and LNA are still somewhat temperature sensitive, so what was a good subtraction at one temperature, may leave you with a residual of the response curve at a different temperature. Some people use passive temperature control (PTC) warming pads to control the LNA temperature. Theoretically one could use thermoelectric peltier coolers, but consistent temperature control is harder and condensation can be an issue also. In practice, the slight noise penalty of operating the LNA at a slightly elevated temperature is more than offset by the stable gain response over the spectral range. But such temperature control is an advanced/optional thing for later. 

Your original curves did seem a bit odd. I wonder if you are getting any signal at all. 

Have you posted a view of your feed horn, waveguide and 1/4 wave probe in the waveguide? What is the probe length, and how far from the shorted (closed off with a metal cap) end of the waveguide and what are the waveguide dimensions?

As I said, the antenna analyser is a very useful bit of equipment as it enables you to confirm that you actually have an antenna with a reasonably flat response at your target frequency, and that the impedance is close to 50 ohms resistive, and not highly reactive (imaginary part of the impedance which is a complex number function of frequency), as that could otherwise give you strange responses. If you can find some local amateur radio people, particularly if they are doing earth-moon-earth work, they are very likely to have a VNA to be able to test your horn antenna impedance.

Another possible snag: is your LNA connected very close to the horn antenna? you want as little cable (or no cable if possible with regard to weatherproofing) between the 1/4 wave probe and the LNA as possible, as the signal is very weak.

Are you running the receiver at 50 dB gain? you need everything you can get!

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNawn58dxbAyK8NDP-9kCbgNGr8PTX0Hez3DHDfyLs7BXA%40mail.gmail.com.

[Kevin Wilson]

The only picture I have is below. I'll try to get some close ups of the telescope in a day or two. I have it set up at a friend's house right now because he has an open area for viewing that my apartment lacks.

The telescope is made of aluminum. Here are the measurements:

• Waveguide: 17.71 cm × 8.29 cm × 19.7 cm
• Calculated waveguide wavelength: 26.3 cm
• Probe distance from reflector: 6.57 cm
• Horn aperture: 73.2 cm × 59.8 cm
• Calculated gain: 19.65 dB
• Calculated phase errors: E = 0.374, H = 0.520
• Probe length: 5.26 cm
• Calculated directivity: 16.1 dB

My LNA is close to the horn. It is connected to the probe by a 6" 50 ohm cable. The LDA is then connected to the SDR dongle via another  6" 50 ohm cable.

Another question I have is whether the horn antenna needs to be conductive. As I understand it, the antenna gradually changes the impedance so it matches the impedance of the waveguide. The only place a current needs to be generated is in the probe. But I have seen some people talking about making sure their entire antenna is conductive. Mine should be, since it is all aluminum, but I haven't tested it.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BiazQUYfhZ3VRFzy%3Dy8zCAABpGvOAnSen%3DmYEhYeZyeQ%40mail.gmail.com.

[Jon Wallace]

Hi,

I have made a horn from aluminum sided insulation and it definitely needs to be conductive. You can check using a simple ohm meter and see if you get close to zero when touching two different sides. I had to use a special aluminum tape (they are not all the same and some don't work!) to make sure the sides were electrically connected. I also connected my LNA directly to the probe - no wire necessary.

Hopefully someone else will reply to help with other stuff.

Best of luck!

Jon

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNbrKoczZOL74FWwGt0RPhZwN4S7EmaKeRQk6J84nKE6GQ%40mail.gmail.com.

[Anthony]

@kevin Wilson,

What software are you using for the spectra analysis?

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNawn58dxbAyK8NDP-9kCbgNGr8PTX0Hez3DHDfyLs7BXA%40mail.gmail.com.

[Kevin Wilson]

I'm using a GNU Radio spectronomer developed by the DSPIRA Project at the University of West Virginia. It handles integration and allows for hot and cold calibration. 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65Tw3XGXp2CXNUObx-d1x2%3Dod6Zv5SgqG4qq4zEbFnTRYPQ%40mail.gmail.com.

[Hamish Barker]

your dimensions look fine. Is the probe mounted on the centreline of the 17.7cm wide side of the waveguide, and the specified 6.57cm from the short (metal end cap/plate)?

It might be worth trying also with the sdr# windows software (I have used it but prefer to use a raspberry pi running the rtl-power-fftw software, plotting on gnuplot).

Also, have you tried watching the response to pointing the horn at the sun and at various offset angles? Or simply record the transit (which will take quite a while with your horn as the beam angle will be about 30 degrees or so.)

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNbrKoczZOL74FWwGt0RPhZwN4S7EmaKeRQk6J84nKE6GQ%40mail.gmail.com.

[Jon Wallace]

Hi,

I thought the horn was too small to detect the Sun. You might try standing in front of the horn and comparing it to pointing it to cold concrete - should yield very different values...

Take care!

Jon

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BYavmfqGRkxijw-EA0GiXeqdAytsRnxsTpmHiHyL_p2Q%40mail.gmail.com.

[Kevin Wilson]

To answer Hamish's questions: Yes, the probe is mounted at the center of the long side (give or take a few millimeters), and it is mounted the appropriate distance from the reflector. I've also used a multimeter to test the continuity, and current is able to flow between all the surfaces with low resistance.

I have have tried several different programs to get readings:

• A spectrometer made by DSPIRA (built on GNU Radio); this is the program that I used in the pictures I shared in the initial post.
• SDR#; I have run this from my desktop computer, but given the portability limitations on a desktop, I usually prefer to run SDR# SpyServer on my Raspberry Pi and connect to that from my desktop; I get an out of memory error when I try to use the IF Average plugin, so I haven't been able to do long integrations with this.
• I have also used the Virgo spectrometer created by Apostolos Spanakis-Misirlis.

I was unaware of the rtl-power-fftw program. I'll have to give that a try this weekend.

At this point, I'm at a loss as to why it isn't working (or rather, why it is working but showing odd results). I was hoping connectivity was the problem, as I had not considered it in building the scope. But since it is built entirely of aluminum, the connectivity was already there. I'm currently trying to locate a VNA to analyze the horn antenna. I would really prefer not to have to buy one, so I've sent out a request to the Astronomical Society of Greenbelt (of which I am a member) to see if any of them have one. Greenbelt is the home of NASA's Goddard Space Flight Center, so we have some members who really know their stuff.

If anyone on here has any more ideas, I'm open to trying anything.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/1548828213.466835.1622765767844%40connect.xfinity.com.

[fasleitung3]

Hi Kevin,

a couple of thoughts on your experiment:

It has been demonstrated by several people that a horn like yours is perfectly suited for observing hydrogen. So unless there is some flaw which has not been identified yet there should be no problem. From your description everything looks fine. It may be helpful to have some photos of the details just to double check.

Also, your receiving chain with filtered LNA and a RTL-SDR look ok to me as well.

I am not familiar with the software you are using. But as it has been successfully used by others my assumption is that is should be ok for that purpose.

I have to agree with others that your spectrum does not look like it is from hydrogen, even though there is a bump at about the right frequency. What one would expect is a spectral peak coming out of clearly visible noise. You have hardly any visible noise so that indicates that it is "too good to be true".

You have some very strong other signals in your spectrum. This shows that you have unwanted signals of fairly high intensity. This may actually overload your RTL-SDR or at least overshadow your actual signal. So my suggestion is to look into that and see if it can be eliminated.

A fist check would be to disconnect the LNA from the horn and take a spectrum with the input left open or even better terminate this with 50 Ohm. Your spectrum should then show the typical "double hump" structure which is intrinsic to the RTL-SDR. There should be not too many spurious lines and no very strong signal. If that is the case, then your receiving chain should roughly be ok.

If you then reconnect your horn and again get the very strong signal your antenna is picking something up which interfers with your wanted signal. What is the environment like you are in? If it is a area where lot of RF can be expected (downtown area?) then you may need to have a filter in front of the LNA. While one always wants to avoid this as it spoils the noise figure there may be the need to do that. If you have the possibility to move the setup somewhere else where there is less RF in the air this could be helpful to spot the problem.

I hope this helps for your further steps,

Wolfgang

[Jon Wallace]

OK,

Four things I found when I tried and wrote about in my article. Not sure if you've checked these - they are basic but...

1) my first problem was my power supply - it was linear, fully regulated but not good enough - had to install caps across inputs on LNAs.

2) cold solder joint - I found one of my solder joints on an LNA was intermittent - re-soldering fixed that

3) With a small horn, you need to integrate for at least 5 minutes.

4) with any SDR, you need to subtract a baseline - the bandpass is terrible and you'll never see a signal. You can either gather a section of blanks sky (make sure it IS blank!!!) or do what was suggested for me - put the horn aimed at a cool cement floor

You can read about these in my article on the SARA page. (search first experience).

 

BTW: if it makes you feel any better, I started RA in the 80's and back then nothing was available so I had to start from scratch with little knowledge and so it took me 10 years to get my unit working - quite an education though. Given that, I'd much prefer the SDR which I got working and gathered enough data to do things with within a month! Once again, hang in there and best of luck!

Jon

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNaA-HjwzsmqBjf5Mi02oC1aOMDpzraCSbP3V6ErH_HDRA%40mail.gmail.com.

[Larry Mayfield]

Hmmm, give or take a few millimeters?  A millimeter   is 0.0394 inches or thereabouts. A “few” might make a difference?  I was always reminded of trying to get the very best precision when fabricating and locating the important parts.  

 

Larry

Pahrump, nv

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNaA-HjwzsmqBjf5Mi02oC1aOMDpzraCSbP3V6ErH_HDRA%40mail.gmail.com.

[Kevin Wilson]

I agree. But this is a telescope I made with the tools I have available, most of which are hand tools. It would be possible to be more precise if I had a professional metal brake, but I did the best I could under the circumstances. If it turns out that that 1-2 millimeters makes a big difference, I can go back and make a new waveguide.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/000601d75959%24a03eca70%24e0bc5f50%24%40mayfco.com.

[Larry Mayfield]

Dr. Wilson, I wasn’t trying to be disparaging.  

 

I have been and am still in this situation myself, lol.  I was just trying to sort out things that might be causing you issues in your signal acquisition and processing.  2 mm is a pretty large discrepancy (I think and that may be in error) at nearly 0.08 inches.  If you had the aluminum sheet metal in small gauge thickness, I bet you  could lay it out in the sheet and then have an air conditioning shop or even a high school shop class cut the pieces out for you. Then use aluminum angle at the corners and with a hand drill , drill and then install pop rivets to make the corners.  Hack saw and a small vise would be almost all you need.  I make a lot of stuff similarly.   

 

Keep plugging away at it and I am sure you will resolve it all to your satisfaction!

 

Larry

Pahrump, NV 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNby5gsi%3D%3DnH8Uz69maiKTG%3DN6fEiq1DdMAHuAYgOyhSvA%40mail.gmail.com.

[Kevin Wilson]

I didn't take it as disparaging at all. I appreciate any help I can get. As I said, if it turns out that it makes a big difference, I'll redo it. 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/002401d75964%24d616f770%248244e650%24%40mayfco.com.

[Hamish Barker]

I don't think dimensions are the issue. I've seen posts where people got a milky way H1 spectrum from a very rough aluminium foil scoop shape.

As wolfgang suggests, step by step is a good way to go. First with 50 ohm termination or pointing the horn straight down onto dirt or concrete. See what that spectrum looks like. the lack of noise between the time-varying parts of your spectra does seem to indicate either a signal processing issue, or perhaps something with the filter.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNYK0wRvQ%3D2_DJJguV71R6bxF4gmA16uBJN2Nj5LC%2BsPOw%40mail.gmail.com.

[Hamish Barker]

perhaps try the dirt-view with and without the filter/lna. there should be a big difference.

[Kevin Wilson]

I just ran several different configurations:

• Hydrogen line LNA with bandpass filter, powered by Bias-T
• Hydrogen line LNA with bandpass filter, powered by USB connection  
  
• Hydrogen line LNA with bandpass filter, powered by USB connection, plus full-spectrum LNA, powered by Bias-T
  
• SDR connected directly to antenna with no LNA
• SDR not connected to anything (I don't have a resistor cap, so this is as close as I can come)

The last one produced a slight double hump spectrum. The rest all produced the spectrum with the spike on the far left, a three-prong bump around 1419.5 MHz, and a bump at 1420.23–1420.37 MHz. The only difference was the magnitude of these bumps. I also tried both hot calibrated readings (from pointing at my apartment wall) and uncalibrated reading. All produced the same profile, just at different levels.

A friend in the local astronomy club has put me in touch with some of the astronomers at the University of Maryland, and they are willing to have me bring in the scope for testing with a VNA along with a noise producer. I'm hoping that will locate the source of the problem.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com.

[Hamish Barker]

hmm,  sounds like the LNA is not the problem, but if the last option was with no cable or anything, perhaps the cable is the problem.

what cable are you using? is it (and the connections in use) rated for use above 1GHz?

for sure testing with a VNA and noise source should permit diagnosis of the fault.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com.

[Kevin Wilson]

The cable is RG316 coax with SMA couplings, which is rated for up to 3 GHz.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com.

[Hamish Barker]

Well I am as stumped as you. I Look forward to hearing what the vna analysis raises.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNY%2BVNCQDT8pmt5SWLjwrcC6jdr8Ufyx6O3a3T01MLfOQA%40mail.gmail.com.

[Checker]

Hi Kevin,

If you like the SDR# with IF Average Plugin, please checkout my a paper i just finished about my troubles and solution to the SDR# and Plugin problem. In summary i had to get a newer laptop with 8 GB RAM and faster CPU. there might be some other info in there that will help you out as well as some photos of what equipment im running. Please find paper attached. I just posted a timelapse of the H1 this afternoon, maybe check that out.

73,

Dan

[Checker]

Hi again Kevin, the coax you are using caught my eye..... im wondering if you might have got that cable from Amazon ? as i have.... the problem is that some of those cables are made with reverse polarity for network connections and Amazon doesnt always say that in the descriptions. You can test the cable with an ohm meter, just touch the center pin at one end of the cable and the outer part of the connecter at the opposite end of the cable, if you get continuity it is a reverse polarity cable and i dont think that works well for our purpose. Just a thought.

73,

Dan

[Kevin Wilson]

Dan,

Thanks for the suggestion. I did get the cables from Amazon, but I just tested them and the polarity appears to be correct (i.e., inner to inner and outer to outer). I just downloaded your article and I look forward to reading it.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com.

[Jim Hannon]

Reverse polarity for SMA does not mean the the center pin and shell are
swapped.
https://www.spo-comm.de/en/blog/know-how/what-is-the-difference-between-sma-and-rp-sma

Jim Hannon

> * Hydrogen line LNA with bandpass filter, powered by Bias-T
> * Hydrogen line LNA with bandpass filter, powered by USB
> connection
> * Hydrogen line LNA with bandpass filter, powered by USB

> connection, plus full-spectrum LNA, powered by Bias-T

> * SDR connected directly to antenna with no LNA
> * SDR not connected to anything (I don't have a resistor

> disparaging. ____
>
> __ __

>
> I have been and am still in this situation
> myself, lol.  I was just trying to sort out
> things that might be causing you issues in
> your signal acquisition and processing.  2
> mm is a pretty large discrepancy (I think
> and that may be in error) at nearly 0.08
> inches.  If you had the aluminum sheet metal
> in small gauge thickness, I bet you  could
> lay it out in the sheet and then have an air
> conditioning shop or even a high school shop
> class cut the pieces out for you. Then use
> aluminum angle at the corners and with a
> hand drill , drill and then install pop
> rivets to make the corners.  Hack saw and a
> small vise would be almost all you need.  I

> make a lot of stuff similarly. ____
>
> __ __

>
> Keep plugging away at it and I am sure you

> will resolve it all to your satisfaction!____
>
> __ __
>
> Larry____
>
> Pahrump, NV ____
>
> __ __
>
> *From:* sara...@googlegroups.com
> <sara...@googlegroups.com> *On Behalf Of
> *Kevin Wilson
> *Sent:* Friday, June 4, 2021 9:12 AM
> *To:* sara...@googlegroups.com
> *Subject:* Re: [SARA] Hydrogen Line Survey____
>
> __ __

>
> I agree. But this is a telescope I made with
> the tools I have available, most of which
> are hand tools. It would be possible to be
> more precise if I had a professional metal
> brake, but I did the best I could under the
> circumstances. If it turns out that that 1-2
> millimeters makes a big difference, I can go

> back and make a new waveguide.____
>
>
> ____
>
> Kevin A. Wilson____
>
> Maryland City, MD____
>
> he/him/his____
>
> __ __
>
> __ __

>
> On Fri, Jun 4, 2021 at 11:52 AM Larry

> Mayfield <drm...@mayfco.com> wrote:____

>
> Hmmm, give or take a few millimeters?  A
> millimeter   is 0.0394 inches or
> thereabouts. A “few” might make a
> difference?  I was always reminded of
> trying to get the very best precision
> when fabricating and locating the

> important parts. ____
>
> ____
>
> Larry____
>
> Pahrump, nv____
>
> ____
>
> *From:* sara...@googlegroups.com
> <sara...@googlegroups.com> *On Behalf Of
> *Kevin Wilson
> *Sent:* Thursday, June 3, 2021 8:24 PM
> *To:* sara...@googlegroups.com
> *Cc:* Hamish Barker <hamish...@gmail.com>
> *Subject:* Re: [SARA] Hydrogen Line
> Survey____
>
> ____

>
> To answer Hamish's questions: Yes, the
> probe is mounted at the center of the
> long side (give or take a few
> millimeters), and it is mounted the
> appropriate distance from the reflector.
> I've also used a multimeter to test the
> continuity, and current is able to flow
> between all the surfaces with low

> resistance.____
>
> ____

>
> I have have tried several different

> programs to get readings:____
>
> * A spectrometer made by DSPIRA
> <https://wvurail.org/dspira-lessons/HornOperation_runningSpectrometer>

> (built on GNU Radio); this is the
> program that I used in the pictures

> I shared in the initial post.____
> * SDR#; I have run this from my

> desktop computer, but given the
> portability limitations on a
> desktop, I usually prefer to run
> SDR# SpyServer on my Raspberry Pi
> and connect to that from my desktop;
> I get an out of memory error when I
> try to use the IF Average plugin, so
> I haven't been able to do long

> integrations with this.____
> * I have also used the Virgo
> spectrometer
> <https://github.com/0xCoto/Virgo>
> created by Apostolos
> Spanakis-Misirlis.____

>
> I was unaware of the rtl-power-fftw
> program. I'll have to give that a try

> this weekend.____
>
> ____

>
> At this point, I'm at a loss as to why
> it isn't working (or rather, why it is
> working but showing odd results). I was
> hoping connectivity was the problem, as
> I had not considered it in building the
> scope. But since it is built entirely of
> aluminum, the connectivity was already
> there. I'm currently trying to locate a
> VNA to analyze the horn antenna. I would
> really prefer not to have to buy one, so
> I've sent out a request to the
> Astronomical Society of Greenbelt (of
> which I am a member) to see if any of
> them have one. Greenbelt is the home of
> NASA's Goddard Space Flight Center, so
> we have some members who really know

> their stuff.____
>
> ____

>
> If anyone on here has any more ideas,

> I'm open to trying anything.____
>
>
> ____
>
> Kevin A. Wilson____
>
> Maryland City, MD____
>
> he/him/his____
>
> ____
>
> ____

>
> On Thu, Jun 3, 2021 at 8:16 PM Jon

> Wallace <wall...@comcast.net> wrote:____
>
> Hi, ____

>
> I thought the horn was too small to
> detect the Sun. You might try
> standing in front of the horn and
> comparing it to pointing it to cold
> concrete - should yield very

> different values... ____
>
> Take care! ____
>
> Jon ____

>
> On 06/03/2021 7:44 PM Hamish
> Barker <hamish...@gmail.com>

> wrote: ____
>
> ____
>
> ____

>
> your dimensions look fine. Is
> the probe mounted on the
> centreline of the 17.7cm wide
> side of the waveguide, and the
> specified 6.57cm from the short

> (metal end cap/plate)? ____
>
> ____

>
> It might be worth trying also
> with the sdr# windows software
> (I have used it but prefer to
> use a raspberry pi running the
> rtl-power-fftw software,

> plotting on gnuplot). ____
>
> ____

>
> Also, have you tried watching
> the response to pointing the
> horn at the sun and at various
> offset angles? Or simply record
> the transit (which will take
> quite a while with your horn as
> the beam angle will be about 30

> degrees or so.) ____
>
> ____

>
> On Thu, Jun 3, 2021 at 5:47 AM
> Kevin Wilson <

> kevinaw...@gmail.com> wrote: ____

>
> The only picture I have is
> below. I'll try to get some
> close ups of the telescope
> in a day or two. I have it
> set up at a friend's house
> right now because he has an
> open area for viewing that

> my apartment lacks. ____
>
> ____

>
> The telescope is made of
> aluminum. Here are the

> measurements: ____
>
> * Waveguide: 17.71 cm ×
> 8.29 cm × 19.7 cm____
> * Calculated waveguide
> wavelength: 26.3 cm____
> * Probe distance from
> reflector: 6.57 cm____
> * Horn aperture: 73.2 cm ×
> 59.8 cm____
> * Calculated gain: 19.65
> dB____
> * Calculated phase errors:
> E = 0.374, H = 0.520____
> * Probe length: 5.26 cm____
> * Calculated directivity:
> 16.1 dB____

>
> My LNA is close to the horn.
> It is connected to the probe
> by a 6" 50 ohm cable. The
> LDA is then connected to the
> SDR dongle via another  6"

> 50 ohm cable. ____
>
> ____

>
> Another question I have is
> whether the horn antenna
> needs to be conductive. As I
> understand it, the antenna
> gradually changes the
> impedance so it matches the
> impedance of the waveguide.
> The only place a current
> needs to be generated is in
> the probe. But I have seen
> some people talking about
> making sure their entire
> antenna is conductive. Mine
> should be, since it is all
> aluminum, but I haven't

> tested it. ____
>
>
> ____
>
> Kevin A. Wilson ____
>
> Maryland City, MD ____
>
> he/him/his ____
>
> ____

>
> On Wed, Jun 2, 2021 at 12:58
> AM Hamish Barker <

> hamish...@gmail.com> wrote: ____

> look like it. ____

> thing for later. ____
>
> ____

>
> Your original curves did
> seem a bit odd. I wonder
> if you are getting any

> signal at all. ____
>
> ____

>
> Have you posted a view
> of your feed horn,
> waveguide and 1/4 wave
> probe in the waveguide?
> What is the probe
> length, and how far from
> the shorted (closed off
> with a metal cap) end of
> the waveguide and what
> are the waveguide

> dimensions? ____
>
> ____

> horn antenna impedance. ____
>
> ____

>
> Another possible snag:
> is your LNA connected
> very close to the horn
> antenna? you want as
> little cable (or no
> cable if possible with
> regard to
> weatherproofing) between
> the 1/4 wave probe and
> the LNA as possible, as
> the signal is very weak.

> ____
>
> ____

>
> Are you running the
> receiver at 50 dB gain?
> you need everything you

> can get! ____
>
> ____

>
> On Wed, Jun 2, 2021 at
> 2:18 PM Kevin Wilson <
> kevinaw...@gmail.com>

> wrote: ____

>
> My thanks to
> everyone for their
> help. I'm looking
> into several of the
> issues you

> mentioned. ____
>
> ____

>
> One thing I find
> confusing is why
> that bump is showing
> up where red-shifted
> hydrogen would be.
> It seems like it is
> something in the
> plane of the galaxy,
> because when I take
> a reading looking
> away from the plane
> the bump disappears
> (as you can see in

> the attached). ____
>
>
> ____
>
> Kevin A. Wilson ____
>
> Maryland City, MD ____
>
> he/him/his ____
>
> ____

>
> On Tue, Jun 1, 2021
> at 4:25 PM Hamish
> Barker <
> hamish...@gmail.com>

> wrote: ____

> terminations. ____
>
> ____
>
> https://youtu.be/ZpKoLvqOWyc
> <https://youtu.be/ZpKoLvqOWyc>
> ____
>
> ____

>
> Alternatively
> the nano vna can
> do the same and
> much more but is
> more complicated

> to use. ____
>
> ____
>
> Cheers, ____
>
> Hamish ____
>
> ____

>
> On Wed, Jun 2,
> 2021, 00:26 Jon
> Wallace <
> wall...@comcast.net>

> wrote: ____
>
> Kevin, ____

>
> I have
> written up
> my first
> attempts at
> detecting
> the H line
> with a SDR
> and it might
> be helpful
> for you to
> read through
> that
> (https://www.radio-astronomy.org/pdf/JonWallace-Article-SARAJournal-Feb-2019.pdf

> <https://www.radio-astronomy.org/pdf/JonWallace-Article-SARAJournal-Feb-2019.pdf>).

> There was
> also a good
> article in
> the journal

> last month. ____

> test. ____

>
> For such a
> small horn,
> you will
> need longer
> integration
> - I used 5
> minutes.
> When I did
> 30 seconds
> on SDR# I
> got nothing.
> I have some
> trouble
> shooting
> ideas in my
> article that
> might be
> worth
> checking -
> like
> pointing at
> a cement
> floor to get
> a

> baseline... ____

>
> Best of luck
> and hang in
> there!
> Someone here
> will help
> you find the

> problem. ____
>
> Jon ____

>
> On
> 06/01/2021
> 1:53 AM
> Kevin
> Wilson <
> kevinaw...@gmail.com>

> wrote: ____
>
> ____
>
> ____

> side. ____
>
> ____
>
> I have
> two
> questions:
> ____
>
> ____

> fit. ____
>
> ____

> ____
>
> ____

> ____
>
> ____

>
> Any help
> on this
> would be
> appreciated.
> I'm new
> to radio
> astronomy,
> but I've
> been
> doing
> visual
> astronomy as
> a hobby
> for 40
> years.
> This
> horn
> antenna
> for
> hydrogen
> is my
> second
> radio
> astronomy build.

> ____
>
> ____
>
> System: ____
>
> * horn
> antenna____
> * Nooelec
> LDA
> with
> hydrogen
> line
> filter____
> * Nooelec
> SDR
> dongle____
> * Raspberry

> Pi 4
> using GNU
> Radio with
> a
> spectrometer
> created
> by
> the
> Digital
> Signal
> Processing
> in
> Radio Astronomy
> (DSPIRA)
> group at
> the
> University
> of
> West

> Virginia____
> * SMU9250
> to
> read
> altitude
> and
> azimuth____
>
> Kevin A.
> Wilson ____
>
> ____

> <https://groups.google.com/d/msgid/sara-list/f9838596-08e5-46e4-8784-f6730134f36en%40googlegroups.com?utm_medium=email&utm_source=footer>.
> ____
>
> ____

> https://groups.google.com/d/msgid/sara-list/2065709629.614671.1622550410540%40connect.xfinity.com
> <https://groups.google.com/d/msgid/sara-list/2065709629.614671.1622550410540%40connect.xfinity.com?utm_medium=email&utm_source=footer>.
> ____
>
> ____

>
> --
> --
> You received
> this message
> because you are
> subscribed to
> the Google
> Groups "Society
> of Amateur Radio
> Astronomers" group.
> To post to this
> group, send
> email to
> sara...@googlegroups.com
>
> To unsubscribe
> from this group,
> send email to
> sara-list-...@googlegroups.com
>
> For more
> options, visit
> this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
>
> ---
> You received
> this message
> because you are
> subscribed to a
> topic in the
> Google Groups
> "Society of
> Amateur Radio
> Astronomers" group.
> To unsubscribe
> from this topic,
> visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

>
> To unsubscribe
> from this group
> and all its
> topics, send an
> email to
> sara-list+...@googlegroups.com.
>
> To view this
> discussion on
> the web visit
> https://groups.google.com/d/msgid/sara-list/CAAdNG_JNnkjd0%2BW5xncv%3DwR6_OFgDhsC1tTuw7Hgq0MUW4bVCw%40mail.gmail.com

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JNnkjd0%2BW5xncv%3DwR6_OFgDhsC1tTuw7Hgq0MUW4bVCw%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> ____
>
> ____

> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNawn58dxbAyK8NDP-9kCbgNGr8PTX0Hez3DHDfyLs7BXA%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNawn58dxbAyK8NDP-9kCbgNGr8PTX0Hez3DHDfyLs7BXA%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> ____
>
> ____

>
> --
> --
> You received this
> message because you are
> subscribed to the Google
> Groups "Society of
> Amateur Radio
> Astronomers" group.
> To post to this group,
> send email to
> sara...@googlegroups.com
> To unsubscribe from this
> group, send email to
> sara-list-...@googlegroups.com
>
> For more options, visit
> this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
>
> ---
> You received this
> message because you are
> subscribed to a topic in
> the Google Groups
> "Society of Amateur
> Radio Astronomers" group.
> To unsubscribe from this
> topic, visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

>
> To unsubscribe from this
> group and all its
> topics, send an email to
> sara-list+...@googlegroups.com.
>
> To view this discussion
> on the web visit

> https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BiazQUYfhZ3VRFzy%3Dy8zCAABpGvOAnSen%3DmYEhYeZyeQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BiazQUYfhZ3VRFzy%3Dy8zCAABpGvOAnSen%3DmYEhYeZyeQ%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> ____
>
> ____

> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNbrKoczZOL74FWwGt0RPhZwN4S7EmaKeRQk6J84nKE6GQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNbrKoczZOL74FWwGt0RPhZwN4S7EmaKeRQk6J84nKE6GQ%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> ____
>
> ____

> https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BYavmfqGRkxijw-EA0GiXeqdAytsRnxsTpmHiHyL_p2Q%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BYavmfqGRkxijw-EA0GiXeqdAytsRnxsTpmHiHyL_p2Q%40mail.gmail.com?utm_medium=email&utm_source=footer>.
> ____

>
> --
> --
> You received this message because
> you are subscribed to the Google
> Groups "Society of Amateur Radio
> Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send
> email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because
> you are subscribed to a topic in the
> Google Groups "Society of Amateur
> Radio Astronomers" group.
> To unsubscribe from this topic,
> visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

> To unsubscribe from this group and
> all its topics, send an email to
> sara-list+...@googlegroups.com.
> To view this discussion on the web
> visit

> https://groups.google.com/d/msgid/sara-list/1548828213.466835.1622765767844%40connect.xfinity.com
> <https://groups.google.com/d/msgid/sara-list/1548828213.466835.1622765767844%40connect.xfinity.com?utm_medium=email&utm_source=footer>.____

>
> --
> --
> You received this message because you
> are subscribed to the Google
> Groups "Society of Amateur Radio
> Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send
> email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you
> are subscribed to the Google Groups
> "Society of Amateur Radio Astronomers"
> group.
> To unsubscribe from this group and stop
> receiving emails from it, send an email
> to sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNaA-HjwzsmqBjf5Mi02oC1aOMDpzraCSbP3V6ErH_HDRA%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNaA-HjwzsmqBjf5Mi02oC1aOMDpzraCSbP3V6ErH_HDRA%40mail.gmail.com?utm_medium=email&utm_source=footer>.____

>
> --
> --
> You received this message because you
> are subscribed to the Google
> Groups "Society of Amateur Radio
> Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send
> email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you
> are subscribed to a topic in the Google
> Groups "Society of Amateur Radio
> Astronomers" group.
> To unsubscribe from this topic, visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

> To unsubscribe from this group and all
> its topics, send an email to
> sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/000601d75959%24a03eca70%24e0bc5f50%24%40mayfco.com
> <https://groups.google.com/d/msgid/sara-list/000601d75959%24a03eca70%24e0bc5f50%24%40mayfco.com?utm_medium=email&utm_source=footer>.____

>
> --
> --
> You received this message because you are
> subscribed to the Google
> Groups "Society of Amateur Radio
> Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are
> subscribed to the Google Groups "Society of
> Amateur Radio Astronomers" group.
> To unsubscribe from this group and stop
> receiving emails from it, send an email to
> sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNby5gsi%3D%3DnH8Uz69maiKTG%3DN6fEiq1DdMAHuAYgOyhSvA%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNby5gsi%3D%3DnH8Uz69maiKTG%3DN6fEiq1DdMAHuAYgOyhSvA%40mail.gmail.com?utm_medium=email&utm_source=footer>.____

>
> --
> --
> You received this message because you are
> subscribed to the Google
> Groups "Society of Amateur Radio
> Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are
> subscribed to a topic in the Google Groups
> "Society of Amateur Radio Astronomers" group.
> To unsubscribe from this topic, visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

> To unsubscribe from this group and all its
> topics, send an email to
> sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/002401d75964%24d616f770%248244e650%24%40mayfco.com
> <https://groups.google.com/d/msgid/sara-list/002401d75964%24d616f770%248244e650%24%40mayfco.com?utm_medium=email&utm_source=footer>.

>
> --
> --
> You received this message because you are
> subscribed to the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are
> subscribed to the Google Groups "Society of
> Amateur Radio Astronomers" group.
> To unsubscribe from this group and stop
> receiving emails from it, send an email to
> sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNYK0wRvQ%3D2_DJJguV71R6bxF4gmA16uBJN2Nj5LC%2BsPOw%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNYK0wRvQ%3D2_DJJguV71R6bxF4gmA16uBJN2Nj5LC%2BsPOw%40mail.gmail.com?utm_medium=email&utm_source=footer>.

>
> --
> --
> You received this message because you are subscribed to
> the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To post to this group, send email to
> sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are subscribed to
> a topic in the Google Groups "Society of Amateur Radio
> Astronomers" group.
> To unsubscribe from this topic, visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

> To unsubscribe from this group and all its topics, send
> an email to sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com?utm_medium=email&utm_source=footer>.

>
> --
> --
> You received this message because you are subscribed to the
> Google
> Groups "Society of Amateur Radio Astronomers" group.
> To post to this group, send email to sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are subscribed to the
> Google Groups "Society of Amateur Radio Astronomers" group.
> To unsubscribe from this group and stop receiving emails
> from it, send an email to sara-list+...@googlegroups.com.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com?utm_medium=email&utm_source=footer>.

>
> --
> --
> You received this message because you are subscribed to the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To post to this group, send email to sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en

> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are subscribed to a topic
> in the Google Groups "Society of Amateur Radio Astronomers" group.
> To unsubscribe from this topic, visit
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>.

> To unsubscribe from this group and all its topics, send an email
> to sara-list+...@googlegroups.com.
>
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com?utm_medium=email&utm_source=footer>.

>
> --
> --
> You received this message because you are subscribed to the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To post to this group, send email to sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are subscribed to the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to sara-list+...@googlegroups.com

> <mailto:sara-list+...@googlegroups.com>.

> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com
> <https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com?utm_medium=email&utm_source=footer>.

--
WB0TXL
WEB Page http://www.ocrslc.net/
Blog http://jimhannon.wordpress.com
CoCoRaHS station IA-LN-7
42,11.90N,91,39.26W

[Checker]

Hi Kevin,

I stand corrected on the RP SMA ( see the post below from jmha ), that means the cable i rcv'd was shorted and no good.

73,

Dan

[Checker]

Hi Jim,

Thats interesting..... to me that is changing Gender of the connector, changing polarity to me is reversing + and -  ( positive & negative ).  :))

73,

Dan

AL7RS

[Jim Hannon]

I don't know why they called it reverse polarity probably sounds better
than reverse sex. The FCC asked that antenna connectors for WIFI be RP
in an effort to prevent an un-certified antenna being used. A lot of
good that did :)
BTW the gender of a connector is determined by the outermost mating part
of the connector.
Jim Hannon

> <https://wvurail.org/dspira-lessons/HornOperation_runningSpectrometer <https://wvurail.org/dspira-lessons/HornOperation_runningSpectrometer>>

>
> > (built on GNU Radio); this is the
> > program that I used in the pictures
> > I shared in the initial post.____
> > * SDR#; I have run this from my
> > desktop computer, but given the
> > portability limitations on a
> > desktop, I usually prefer to run
> > SDR# SpyServer on my Raspberry Pi
> > and connect to that from my desktop;
> > I get an out of memory error when I
> > try to use the IF Average plugin, so
> > I haven't been able to do long
> > integrations with this.____
> > * I have also used the Virgo
> > spectrometer

> > <https://github.com/0xCoto/Virgo <https://github.com/0xCoto/Virgo>>

> <https://groups.google.com/d/msgid/sara-list/f9838596-08e5-46e4-8784-f6730134f36en%40googlegroups.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/2065709629.614671.1622550410540%40connect.xfinity.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JNnkjd0%2BW5xncv%3DwR6_OFgDhsC1tTuw7Hgq0MUW4bVCw%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNawn58dxbAyK8NDP-9kCbgNGr8PTX0Hez3DHDfyLs7BXA%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNawn58dxbAyK8NDP-9kCbgNGr8PTX0Hez3DHDfyLs7BXA%40mail.gmail.com?utm_medium=email&utm_source=footer>>.
>
> > ____
> >
> > ____
> >
> > --
> > --
> > You received this
> > message because you are
> > subscribed to the Google
> > Groups "Society of
> > Amateur Radio
> > Astronomers" group.
> > To post to this group,
> > send email to
> > sara...@googlegroups.com
> > To unsubscribe from this
> > group, send email to
> > sara-list-...@googlegroups.com
> >
> > For more options, visit
> > this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>

> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> >
> > ---
> > You received this
> > message because you are
> > subscribed to a topic in
> > the Google Groups
> > "Society of Amateur
> > Radio Astronomers" group.
> > To unsubscribe from this
> > topic, visit
> >
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>
> >

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>>.
> >
> > To unsubscribe from this
> > group and all its
> > topics, send an email to
> > sara-list+...@googlegroups.com.
> >
> > To view this discussion
> > on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BiazQUYfhZ3VRFzy%3Dy8zCAABpGvOAnSen%3DmYEhYeZyeQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BiazQUYfhZ3VRFzy%3Dy8zCAABpGvOAnSen%3DmYEhYeZyeQ%40mail.gmail.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BiazQUYfhZ3VRFzy%3Dy8zCAABpGvOAnSen%3DmYEhYeZyeQ%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNbrKoczZOL74FWwGt0RPhZwN4S7EmaKeRQk6J84nKE6GQ%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BYavmfqGRkxijw-EA0GiXeqdAytsRnxsTpmHiHyL_p2Q%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_%2BYavmfqGRkxijw-EA0GiXeqdAytsRnxsTpmHiHyL_p2Q%40mail.gmail.com?utm_medium=email&utm_source=footer>>.
>
> > ____
> >
> > --
> > --
> > You received this message because
> > you are subscribed to the Google
> > Groups "Society of Amateur Radio
> > Astronomers" group.
> > To post to this group, send email to
> > sara...@googlegroups.com
> > To unsubscribe from this group, send
> > email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>

> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because
> > you are subscribed to a topic in the
> > Google Groups "Society of Amateur
> > Radio Astronomers" group.
> > To unsubscribe from this topic,
> > visit
> >
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>
> >

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>>.
> > To unsubscribe from this group and
> > all its topics, send an email to
> > sara-list+...@googlegroups.com.
> > To view this discussion on the web
> > visit
> >
> https://groups.google.com/d/msgid/sara-list/1548828213.466835.1622765767844%40connect.xfinity.com
> <https://groups.google.com/d/msgid/sara-list/1548828213.466835.1622765767844%40connect.xfinity.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/1548828213.466835.1622765767844%40connect.xfinity.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNaA-HjwzsmqBjf5Mi02oC1aOMDpzraCSbP3V6ErH_HDRA%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNaA-HjwzsmqBjf5Mi02oC1aOMDpzraCSbP3V6ErH_HDRA%40mail.gmail.com?utm_medium=email&utm_source=footer>>.____
>
> >
> > --
> > --
> > You received this message because you
> > are subscribed to the Google
> > Groups "Society of Amateur Radio
> > Astronomers" group.
> > To post to this group, send email to
> > sara...@googlegroups.com
> > To unsubscribe from this group, send
> > email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>

> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because you
> > are subscribed to a topic in the Google
> > Groups "Society of Amateur Radio
> > Astronomers" group.
> > To unsubscribe from this topic, visit
> >
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>
> >

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>>.
> > To unsubscribe from this group and all
> > its topics, send an email to
> > sara-list+...@googlegroups.com.
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/000601d75959%24a03eca70%24e0bc5f50%24%40mayfco.com
> <https://groups.google.com/d/msgid/sara-list/000601d75959%24a03eca70%24e0bc5f50%24%40mayfco.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/000601d75959%24a03eca70%24e0bc5f50%24%40mayfco.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNby5gsi%3D%3DnH8Uz69maiKTG%3DN6fEiq1DdMAHuAYgOyhSvA%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNby5gsi%3D%3DnH8Uz69maiKTG%3DN6fEiq1DdMAHuAYgOyhSvA%40mail.gmail.com?utm_medium=email&utm_source=footer>>.____
>
> >
> > --
> > --
> > You received this message because you are
> > subscribed to the Google
> > Groups "Society of Amateur Radio
> > Astronomers" group.
> > To post to this group, send email to
> > sara...@googlegroups.com
> > To unsubscribe from this group, send email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>

> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because you are
> > subscribed to a topic in the Google Groups
> > "Society of Amateur Radio Astronomers" group.
> > To unsubscribe from this topic, visit
> >
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>
> >

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>>.
> > To unsubscribe from this group and all its
> > topics, send an email to
> > sara-list+...@googlegroups.com.
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/002401d75964%24d616f770%248244e650%24%40mayfco.com
> <https://groups.google.com/d/msgid/sara-list/002401d75964%24d616f770%248244e650%24%40mayfco.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/002401d75964%24d616f770%248244e650%24%40mayfco.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNYK0wRvQ%3D2_DJJguV71R6bxF4gmA16uBJN2Nj5LC%2BsPOw%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNYK0wRvQ%3D2_DJJguV71R6bxF4gmA16uBJN2Nj5LC%2BsPOw%40mail.gmail.com?utm_medium=email&utm_source=footer>>.
>
> >
> > --
> > --
> > You received this message because you are subscribed to
> > the Google
> > Groups "Society of Amateur Radio Astronomers" group.
> > To post to this group, send email to
> > sara...@googlegroups.com
> > To unsubscribe from this group, send email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>

> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because you are subscribed to
> > a topic in the Google Groups "Society of Amateur Radio
> > Astronomers" group.
> > To unsubscribe from this topic, visit
> >
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>
> >

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>>.
> > To unsubscribe from this group and all its topics, send
> > an email to sara-list+...@googlegroups.com.
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JbKOj3yiJpTn%2BxgFEn-kocf2fWaaxMDfuXcVMYNAs%3D%3Dg%40mail.gmail.com?utm_medium=email&utm_source=footer>>.
>
> >
> > --
> > --
> > You received this message because you are subscribed to the
> > Google
> > Groups "Society of Amateur Radio Astronomers" group.
> > To post to this group, send email to sara...@googlegroups.com
> > To unsubscribe from this group, send email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because you are subscribed to the
> > Google Groups "Society of Amateur Radio Astronomers" group.
> > To unsubscribe from this group and stop receiving emails
> > from it, send an email to sara-list+...@googlegroups.com.
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAP%3DsJNZVTfdAggDG6qJOxRAUA%2BN%2B7d3Hg0RyFqOet_02zsi-gQ%40mail.gmail.com?utm_medium=email&utm_source=footer>>.
>
> >
> > --
> > --
> > You received this message because you are subscribed to the Google
> > Groups "Society of Amateur Radio Astronomers" group.
> > To post to this group, send email to sara...@googlegroups.com
> > To unsubscribe from this group, send email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>

> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because you are subscribed to a topic
> > in the Google Groups "Society of Amateur Radio Astronomers" group.
> > To unsubscribe from this topic, visit
> >
> https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>
> >

> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe
> <https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe>>.
> > To unsubscribe from this group and all its topics, send an email
> > to sara-list+...@googlegroups.com.
> >
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com
> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/CAAdNG_JBjBj9STXREM5cX3EreaR2BM0Wc4aZBvDoTC8ecO5p7Q%40mail.gmail.com?utm_medium=email&utm_source=footer>>.
>
> >
> > --
> > --
> > You received this message because you are subscribed to the Google
> > Groups "Society of Amateur Radio Astronomers" group.
> > To post to this group, send email to sara...@googlegroups.com
> > To unsubscribe from this group, send email to
> > sara-list-...@googlegroups.com
> > For more options, visit this group at
> > http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> > <http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>>
> > ---
> > You received this message because you are subscribed to the Google
> > Groups "Society of Amateur Radio Astronomers" group.
> > To unsubscribe from this group and stop receiving emails from it,
> send
> > an email to sara-list+...@googlegroups.com
> > <mailto:sara-list+...@googlegroups.com>.
> > To view this discussion on the web visit
> >
> https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com
> <https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com>
>
> >

> <https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com?utm_medium=email&utm_source=footer

> <https://groups.google.com/d/msgid/sara-list/7bfede14-a0a9-4858-bacc-662f8c8489a4n%40googlegroups.com?utm_medium=email&utm_source=footer>>.
>
>
> --
> WB0TXL

> WEB Page http://www.ocrslc.net/ <http://www.ocrslc.net/>
> Blog http://jimhannon.wordpress.com <http://jimhannon.wordpress.com>
> CoCoRaHS station IA-LN-7
> 42,11.90N,91,39.26W
>
>

> --
> --
> You received this message because you are subscribed to the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To post to this group, send email to sara...@googlegroups.com
> To unsubscribe from this group, send email to
> sara-list-...@googlegroups.com
> For more options, visit this group at
> http://groups.google.com/group/sara-list?hl=en
> <http://groups.google.com/group/sara-list?hl=en>
> ---
> You received this message because you are subscribed to the Google
> Groups "Society of Amateur Radio Astronomers" group.
> To unsubscribe from this group and stop receiving emails from it, send
> an email to sara-list+...@googlegroups.com
> <mailto:sara-list+...@googlegroups.com>.
> To view this discussion on the web visit

> https://groups.google.com/d/msgid/sara-list/15c66cf9-920c-4c39-b6f5-e5eaf842a511n%40googlegroups.com
> <https://groups.google.com/d/msgid/sara-list/15c66cf9-920c-4c39-b6f5-e5eaf842a511n%40googlegroups.com?utm_medium=email&utm_source=footer>.

[Kevin Wilson]

I decided to tape all the edges, even though I had connectivity between all the surfaces. I used 2" copper tape with conductive adhesive.

Plots 1 and 2 are readings of the Milky Way in the same general area (just north of Orion). I did separate cold calibrations for each reading, and both the calibrations and the readings were 5-minutes of integration. These use the Virgo program (https://github.com/0xCoto/Virgo).

Plot 3 is an uncalibrated, 30-second integration using the DSPIRA program that I used before. As you can see, I'm still getting roughly the same spectrum.

I've been communicating with the astronomy department at the University of Maryland. They are willing to do some testing with a frequency generator and a VNA, so I am hoping that will let me know whether the problem is with the antenna, the receiver, or how I am using the software.

Kevin A. Wilson

Maryland City, MD

he/him/his

To unsubscribe from this topic, visit https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe.

To unsubscribe from this group and all its topics, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/9757b55c-5ee8-1041-057e-61355a715c21%40fmtcs.com.

[Hamish Barker]

Looks like either rfi or a software glitch. Try changing location and/or software.

[Kevin Wilson]

After several weeks of trying to figure out the problem, I think I may have fixed it.

Below are two observations I made this afternoon. Both are 5-minute integrations that are then calibrated against a cold area of the sky. Observation 1 (Quadrant 3) shows a red shift as expected, while Observation 2 (Quadrant 3) shows a slight blue shift. The third image shows the targets of the observations and the boundary between quadrants 2 and 3. Both are taken near the galactic anticenter, so the shifts aren't large. When I took a reading away from the galactic plane, I got a fairly flat, noisy line.

These seem to match the expected hydrogen line in that region, but I would appreciate additional input.

I decided that I was making observations too close to my apartment, resulting in a lot of RFI. I wanted to get into a secluded area, but my setup had two problems. First, it needs a power supply to run the Raspberry Pi and power the LNA. Second, it needs a WiFi connection so I can ssh to it from my desktop computer. I solved the first problem by buying a power converter for my car so I could power the rig from the cigarette lighter. The second problem I solved by adding a touchscreen to the Raspberry Pi so I can operate it without my desktop computer. I was also able to move the Raspberry Pi away from the telescope so any RFI from the Raspberry Pi itself would not be as strong.

These observations were taken using the Virgo RA Project (https://github.com/0xCoto/Virgo). Unfortunately, the scales for the two readings are different, as both were automatically adjusted to show the entire height of the RFI spike at 1420.8 MHz. 

Thoughts?

Kevin A. Wilson

Maryland City, MD

he/him/his

To unsubscribe from this topic, visit https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe.

To unsubscribe from this group and all its topics, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_KMvcVNfPvMnc0OYZGC40SoD2CH0aT-g1jn%3D_37DScpGg%40mail.gmail.com.

[Checker]

GM Kevin,

I would say you have HI there..... i scanned the region of Elnath before, one Data file i had is close to what you got.

73,

Dan

[Kevin Wilson]

Dan,

Thanks for the response. I did several additional scans yesterday of quadrant 1, and I was able to isolate two arms of the galaxy in some of them.

What scripts do you use to plot your data?

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/bc373eb3-2557-438b-9fef-4f9529cd1937n%40googlegroups.com.

[Checker]

GM Kevin,

I use SDR# with the IF Average Plugin to collect the Data, then, Thanks to Jon Wallace for getting me going with Spreadsheets, i use OpenOffice Calc to make the Plots. I have also figured out how to use LabPlot to make Plots by following most of the same steps.

73,

Dan

[Kevin Wilson]

I finally got around to purchasing a NanoVNA. The SWR on the horn antenna is 2.6:1. As I understand it, that's not great for a receiver but it isn't horrible either. Other than the SWR, are there any other useful readings to take with the NanoVNA? What can I do to improve the SWR?

Kevin A. Wilson

Maryland City, MD

he/him/his

On Tue, Jun 1, 2021 at 4:25 PM Hamish Barker <hamish...@gmail.com> wrote:

Have you checked the swr of the feed to ensure that it's well matched to the 50ohm LNA impedance? If you don't have one yet, I very highly recommend purchase of these reduced function vna units. Well worth the price since it enables easy optimisation of antenna performance. Don't forget to also purchase a calibration set of short, open and 50 ohm terminations.

https://youtu.be/ZpKoLvqOWyc

Alternatively the nano vna can do the same and much more but is more complicated to use. 

Cheers,

Hamish

On Wed, Jun 2, 2021, 00:26 Jon Wallace <wall...@comcast.net> wrote:

Kevin,

I have written up my first attempts at detecting the H line with a SDR and it might be helpful for you to read through that (https://www.radio-astronomy.org/pdf/JonWallace-Article-SARAJournal-Feb-2019.pdf). There was also a good article in the journal last month.

I am not an engineer so will not be able to troubleshoot, but your peaks don't look like hydrogen line peaks and they should vary somewhat (the galaxy appears to move towards and away from us so the Doppler shift should show). Perhaps you could do a 24 hour scan at 1 Declination and see how the signal varies as I did for a test. 

For such a small horn, you will need longer integration - I used 5 minutes. When I did 30 seconds on SDR# I got nothing. I have some trouble shooting ideas in my article that might be worth checking - like pointing at a cement floor to get a baseline...

Best of luck and hang in there! Someone here will help you find the problem.

Jon

On 06/01/2021 1:53 AM Kevin Wilson <kevinaw...@gmail.com> wrote:

 

 

I spent the better part of Memorial Day doing a survey of Quadrant 3 of the Milky Way. The attached image shows the area of the six scans I made. These were 30-second integrations. I have also attached an image showing the combined spectra of the scans. All have the same general profile with a bump around 1420.3 MHz (presumably the hydrogen line) and another around 1419.5 MHz (source unknown), plus some noise at the left end of the scans. A scan of an area away from the galactic plane removes both bumps but leaves the noise at the left side.

 

I have two questions:

 

First, does anyone have any idea what the bump at 1419.5 could be? I thought it was just interference, but because it disappeared when pointed away from the galactic plane that explanation doesn't seem to fit.

 

Second, should the scans of hydrogen across that area show bumps with identical red shifts? I would have expected the speed of the hydrogen to be different at various points, so I'm surprised  they all spanned 1420.23–1420.37 MHz. The only difference is in the signal strength. Is that normal? I want to make sure that what I am detecting is actually the hydrogen line and not something else.

 

I made scans that included integrations of up to 10 minutes, but those didn't seem to change the basic profile of the spectrum. All the scans combine in the attached spectrum were 30-second integrations.

 

Any help on this would be appreciated. I'm new to radio astronomy, but I've been doing visual astronomy as a hobby for 40 years. This horn antenna for hydrogen is my second radio astronomy build.

 

System:

• horn antenna

• Nooelec LDA with hydrogen line filter

• Nooelec SDR dongle

• Raspberry Pi 4 using GNU Radio with a spectrometer created by the Digital Signal Processing in Radio Astronomy (DSPIRA) group at the University of West Virginia

• SMU9250 to read altitude and azimuth

Kevin A. Wilson

 

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---

You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.

To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/f9838596-08e5-46e4-8784-f6730134f36en%40googlegroups.com.

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---

You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.

To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/2065709629.614671.1622550410540%40connect.xfinity.com.

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to a topic in the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this topic, visit https://groups.google.com/d/topic/sara-list/inga8E-KY7w/unsubscribe.
To unsubscribe from this group and all its topics, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAAdNG_JNnkjd0%2BW5xncv%3DwR6_OFgDhsC1tTuw7Hgq0MUW4bVCw%40mail.gmail.com.

[Marcus D Leech]

Length and position of the feed probe. 

Sent from my iPhone

On Aug 23, 2021, at 10:59 AM, Kevin Wilson <kevinaw...@gmail.com> wrote:



To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNY%3DmZpx0ww2ChGkqcOGypXC2ONtNkxfPThG9wizthj92g%40mail.gmail.com.

[Kevin Wilson]

I've already optimized both of those.

Kevin A. Wilson

Maryland City, MD

he/him/his

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/56D4FD06-B7BF-410B-8A66-B312D7C2821E%40gmail.com.

[bsn...@gmail.com]

I've been following this thread since the beginning.

Glad to see you purchased a NanoVNA, marvelous little tool.

Before you check the SWR perhaps you should check the coax itself?

I was recently using high quality, direct-burial 50 ohm coax that I was given. Did not appear to have been used or abused but it could barely get a signal to the SDR!

SWR measurement show a decent match to the antenna. Replaced connectors at each end --- no improvement.

I finally decided to follow W2AEW's procedure for testing the coax itself. The NanoVNA showed numerous "faults" along the 70 feet.

Replaced the cable and signals are now reaching the SDR.  Old coax went to the metal recycler. 

Just a thought...good luck....bill...

[Kevin Wilson]

Thanks for the suggestion. I don't use any coax. The LNA comes straight off the waveguide and goes directly into the SDR. The SDR is connected to the Raspberry Pi by a 10' USB cable. 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/083fcce7-d24b-44e4-b963-79f8fff48fd2n%40googlegroups.com.

[Anthony]

Hi Kevin,

Question, running the LNA off of the waveguide to the SDR, directly to your Raspberry PI, are the LNA & SDR protected from the weather or do you disconnect? In my setup, I'm looking to do something similar but need to determine if the LNA & SDR can be protected from rain or can they handle the outside elements?

Thanks. 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAP%3DsJNYEoqx9C%3DSFrs8LWariiN8hmXHF61qOb4B6WbLdp%3D71pw%40mail.gmail.com.

[Marcus D. Leech]

On 2021-08-25 4:58 p.m., Anthony wrote:

Hi Kevin,

Question, running the LNA off of the waveguide to the SDR, directly to your Raspberry PI, are the LNA & SDR protected from the weather or do you disconnect? In my setup, I'm looking to do something similar but need to determine if the LNA & SDR can be protected from rain or can they handle the outside elements?

Thanks.

I use PIeces of 1-1/2" ABS with end-caps to protect things like LNAs. When I need to enclose chunkier bits of electronics I often use 3" or 4" PVC drainpipe, with
  end-caps.  I generally *DONT* glue the end caps on, but use PVC electrical tape to seal them up.  I usually arrange for the thing to be notionally vertical and have
  a few very-small (3mm) drain holes in the end that is notionally ground-facing.  This allows it to "breathe" and thus not end up cryo-pumping moisture into the
  enclosure, which then condenses and over time your enclosure will fill up with water.  Having some strategic vent holes precludes this from happening quite
  nicely.

I have run LNAs literally for *years* with an arrangement like that without issue.  I tend to use appropriate bulkhead RF connectors to get signals in/out of the
  enclosure--on the input to the LNA I try to arrange for there to be the bare-minimum connector "stack up" between the waveguide probe and the LNA.  After
  the LNA, I use a short (15cm) piece of small-diameter SMA-terminated cable.  This allows me to have enclosures that don't need to be perfectly sized to the
  LNA.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65TyVJ5xgHHTyu2dLZUnFSMmJZ3Ei2OVmk%2BM4RMUoYyxLZQ%40mail.gmail.com.

[Marcus D. Leech]

On 2021-08-25 4:58 p.m., Anthony wrote:

Hi Kevin,

Question, running the LNA off of the waveguide to the SDR, directly to your Raspberry PI, are the LNA & SDR protected from the weather or do you disconnect? In my setup, I'm looking to do something similar but need to determine if the LNA & SDR can be protected from rain or can they handle the outside elements?

Thanks.

I use PIeces of 1-1/2" ABS with end-caps to protect things like LNAs. When I need to enclose chunkier bits of electronics I often use 3" or 4" PVC drainpipe, with
  end-caps.  I generally *DONT* glue the end caps on, but use PVC electrical tape to seal them up.  I usually arrange for the thing to be notionally vertical and have
  a few very-small (3mm) drain holes in the end that is notionally ground-facing.  This allows it to "breathe" and thus not end up cryo-pumping moisture into the
  enclosure, which then condenses and over time your enclosure will fill up with water.  Having some strategic vent holes precludes this from happening quite
  nicely.

I have run LNAs literally for *years* with an arrangement like that without issue.  I tend to use appropriate bulkhead RF connectors to get signals in/out of the
  enclosure--on the input to the LNA I try to arrange for there to be the bare-minimum connector "stack up" between the waveguide probe and the LNA.  After
  the LNA, I use a short (15cm) piece of small-diameter SMA-terminated cable.  This allows me to have enclosures that don't need to be perfectly sized to the
  LNA.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65TyVJ5xgHHTyu2dLZUnFSMmJZ3Ei2OVmk%2BM4RMUoYyxLZQ%40mail.gmail.com.

[djl]

Hi Anthony:  If I put holes as you suggest, my pipes will fill up with mud-dauber wasps nests. Very fine screen works. For larger enclosures, I throw in bug-killer vapor strips.  Have to vacuum the bugs out in the spring, but at least no nests...

Don

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/1032322e-e659-a5cc-fea4-475449b0694d%40gmail.com.

------------
The whole world is a straight man.
----------------------
Dr. Don Latham  AJ7LL
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304

[Kevin Wilson]

Mine isn't protected from the weather, but I never leave it set up outside. I live in an apartment, so I have to take it with me and set it up whenever I observe.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/CAKU65TyVJ5xgHHTyu2dLZUnFSMmJZ3Ei2OVmk%2BM4RMUoYyxLZQ%40mail.gmail.com.

[Anthony]

Hi Don,

So true, I'm constantly spraying bug spray on the feedhorn to keep insects out after a few days. I'm working on a cap to keep the birds from nesting as well.  

One night I went out to calibrate the SDR/LNA, with one of those head flashlights, talking about bugs flying right in your face! I even tried the red light, but couldn't see much, moving forward all RAS telescope work is in the day time for me!  :-D

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/1f5df0bb4f1c52fc601e4b783056d567%40montana.com.

[Dave Typinski]

Marcus, what is "cryo-pumping"? If the PVC enclosure were sealed, how is water
vapor going to fill the thing up over time?
--
Dave

[Marcus D. Leech]

On 2021-08-25 7:28 p.m., Dave Typinski wrote:
> Marcus, what is "cryo-pumping"?  If the PVC enclosure were sealed, how
> is water vapor going to fill the thing up over time?
> --
> Dave

Day/night thermal cycles in the summer months tend to cause water vapor
to enter due to internal weak pressure changes.

Certainly if an enclosure is *truly* hermetically sealed this won't
happen.  But in much amateur-produced gear, you get
  water-vapor incursion through connectors, etc.  It's easier to just
have some small vent holes than to attempt a full-blown
  hermetic seal--particularly if equipment is likely to require service.

This article is similar to ones I've read in the past on the subject:

https://blog.se.com/power-management-metering-monitoring-power-quality/2013/10/29/electrical-enclosures-warm-dry-keeps-condensation-away/

[Dave Typinski]

Hi Marcus,

Aha. That makes sense. Thank you.

Proper sealing is important. I have some underground feeds that run through
around 100 feet of 2½" PVC conduit. Each end has PVC caps taped with Scotch
2228 mastic tape (Lowe's carries it). All conduit joints are glued with PVC
cement. The coaxial fittings installed in the PVC caps are bulkhead-style with
O-rings.

Had given thought to installing a Schrader valve in each of the PVC caps and
flushing & charging the conduit with a few PSI of dry nitrogen. Decided that
was overkill.

Replaced some of the conduit-ized RG-58 with LMR-240 a while ago. The old coax
had been entombed in that conduit for about five years. Was dry as a bone when
I pulled it out.
--
Dave

[Paul Oxley]

Marcus

The water condenses from the change from hot moist air to cold dry air. So an additional way to avoid this would be to keep the experiment in hot dry air. Desert anyone?

Paul

--
--
You received this message because you are subscribed to the Google
Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com
To unsubscribe from this group, send email to
sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.

To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+unsub...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/485b0151-e016-f09c-c73f-999e79b454d0%40gmail.com.

[Larry Mayfield]

I am dead certain that there are many of the list members who can explain this far, far, better than I can. So when they reply to correct what I have just written, pay attention, lol (me too!).

'Think of cyro pumping as a simple system, say your auto coolant recovery system, when it gets hot, it build pressure in the system and may put a bit of coolant into a catch bottle. When it cools off it reduces in volume and pressure and sucks the water in the coolant catch bottle back into the system. With high vacuum system there is a cryogenic trap used in the system to slow down the molecules at very low pressure and they get trapped and essentially frozen in the place to further reduce the chamber pressure. Not the same but more understandable, lol. For a wave guide or feed then if there is a cap on the opening it needs to have a small hole. When it gets hot from the heat of the day, the pressure builds up inside the feed and pumps air out. When it gets cooler the flow is reversed. The small volume heats and cools quicker than ambient so there is always an in and out pumping action . '

At least that is how my engineering mind sees it working ( also worked on a lot of high vac system). The purpose of the method is to prevent condensation from building up inside the feed system and developing corrosion I suspect. Or mold or?

I am dead certain that there are many of the list members who can explain this far, far, better than I can. So when they reply to correct what I have just written, pay attention, lol (me too!).



Larry
Pahrump, NV

-----Original Message-----
From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Marcus D. Leech
Sent: Wednesday, August 25, 2021 4:50 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Hydrogen Line Survey

--
--
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To post to this group, send email to sara...@googlegroups.com To unsubscribe from this group, send email to sara-list-...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/sara-list?hl=en
---
You received this message because you are subscribed to the Google Groups "Society of Amateur Radio Astronomers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/485b0151-e016-f09c-c73f-999e79b454d0%40gmail.com.

[Marcus D. Leech]

On 2021-08-25 8:11 p.m., Paul Oxley wrote:

Marcus

The water condenses from the change from hot moist air to cold dry air. So an additional way to avoid this would be to keep the experiment in hot dry air. Desert anyone?

Paul

Indeed, some of us here don't have to worry much about the cryo-pumping problem, and more, perhaps about enclosures full of
  juvenile scorpions :)

But for those of us who live in places where the summer months are hot and humid during the day, and very often much cooler at night,
  we have to worry about the cryo-pumping problem.  Effecting a truly-hermetic seal is possible, but a huge pain and can fail quite easily.
  Sooooo, we tend to drill very small vent holes (or larger holes covered with insect screen), and arrange for there to be *liquid* water
  tightness, but make no attempt to gas-seal the enclosure.

I learned this lesson several years ago--had an experiment that was working fine for many weeks in the summer, until it wasnt.  Opened up the
  enclosure and it was half-full of condensate.  Replaced the electronics, drilled a few small vent holes, never had the problem again...

I *can* be awkward to arrange for this when your LNA enclosure is right on the side of the feed, and your dish tracks through "awkward" angles.

To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/1811086724.1654497.1629936701082%40mail.yahoo.com.

[Paul Oxley]

Marcus

The seepage is one of the reasons I chose to use perforated aluminum stock for my conical design. The holes are small enough that they will not disrupt the RF integrity. They also reduce the weight of the antenna for one person handling. Additionally, they will allow easier bending the cone into its shape.

The design includes a 3 foot ring on the open end to stabilize the shape. It also has a ring midway down the cone for the same purpose and for mounting near the center of gravity considering the waveguide piece and cone weight.

Paul

https://groups.google.com/d/msgid/sara-list/7e4daeaa-fc3b-e7b9-4250-19b216cafaab%40gmail.com

.

[Marcus D. Leech]

On 2021-08-25 9:13 p.m., Paul Oxley wrote:

Marcus

The seepage is one of the reasons I chose to use perforated aluminum stock for my conical design. The holes are small enough that they will not disrupt the RF integrity. They also reduce the weight of the antenna for one person handling. Additionally, they will allow easier bending the cone into its shape.

The design includes a 3 foot ring on the open end to stabilize the shape. It also has a ring midway down the cone for the same purpose and for mounting near the center of gravity considering the waveguide piece and cone weight.

Paul

That sounds like a "serious piece of iron".  Good luck with it.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/490521722.1679715.1629940399264%40mail.yahoo.com.

[Lester Veenstra]

Or better still, keep the active area a bit warmer than surroundings, either by normal electronics , or with an additional warming resistor. 

 

The enclosure becomes the condensing surface, not the active circuit.

 

The final, necessary touch, is a weep hole at the lowest point to let the condensed water out.

 

Trying to seal boxes is doomed to failure, unless you go to hermetic extremes that will pass a hydrogen leak test. Be better way is breathing holes that let the water vapor out, naturally, before it condenses, and finally, the hot/cool division of surfaces for what remains to condense on.

 

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y

les...@veenstras.com

 

452 Stable Ln (HC84 RFD USPS Mail)

Keyser WV 26726

 

GPS: 39.336826 N  78.982287 W (Google)

GPS: 39.33682 N  78.9823741 W (GPSDO)

 

 

Telephones:

Home:                     +1-304-289-6057

US cell                    +1-304-790-9192

Jamaica cell:           +1-876-456-8898

 

 

From: sara...@googlegroups.com [mailto:sara...@googlegroups.com] On Behalf Of Paul Oxley
Sent: Wednesday, August 25, 2021 8:12 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Hydrogen Line Survey

 

Marcus

To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/1811086724.1654497.1629936701082%40mail.yahoo.com.

[Lester Veenstra]

Or in extremes, keep the chamber pressurized with dry nitrogen.

 

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y

les...@veenstras.com

 

452 Stable Ln (HC84 RFD USPS Mail)

Keyser WV 26726

 

GPS: 39.336826 N  78.982287 W (Google)

GPS: 39.33682 N  78.9823741 W (GPSDO)

 

 

Telephones:

Home:                     +1-304-289-6057

US cell                    +1-304-790-9192

Jamaica cell:           +1-876-456-8898

 

 

From: sara...@googlegroups.com [mailto:sara...@googlegroups.com] On Behalf Of Paul Oxley
Sent: Wednesday, August 25, 2021 8:12 PM
To: sara...@googlegroups.com
Subject: Re: [SARA] Hydrogen Line Survey

 

Marcus

To unsubscribe from this group and stop receiving emails from it, send an email to sara-list+...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/1811086724.1654497.1629936701082%40mail.yahoo.com.

[Captain Anne Flint]

Hi Lester, 

What kind of screen wire material - aluminum or plastic ‘fabric’? Assuming it matters. 

Thanks, 

Wende 

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/0d6f01d79aa7%24b3b1aa20%241b14fe60%24%40com.

[Lester Veenstra]

metal   copper screen or galvanized mesh (Chicken wire  square ½ inch grid foe example)

for example

https://www.amazon.com/MAPORCH-Upgraded-Hardware-Galvanized-Cabinets/dp/B08NJ9WX67/ref=sr_1_9?dchild=1&keywords=wire+mesh&qid=1630011716&sr=8-9

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/9B372089-AB3A-4021-B05B-3AD5553F1835%40gmail.com.

[Captain Anne Flint]

thanks Lester. it even comes with tin snips included! wende

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/0ddd01d79abd%24ad18a950%240749fbf0%24%40com.

[Lester Veenstra]

All you need is small plastic tie wraps to hold new grid to old grid

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/2D1A0668-7C7E-4D1B-AD4C-2D5E13DA7B87%40gmail.com.