6.7 GHz methanol maser line, the receiver project for small dishes

[Dimitry UA3AVR]

Eduard et all,

here i share a short text about my 6.7 GHz receiver. Hope this is just begining of greater project, i'm looking forward to improve the receiver, and the shared info could be helpful.

My greetings & regards, Dimitry UA3AVR.

[Eduard Mol]

Hi Dimitry,

Thank you for sharing this info. I hope it will also inspire other amateurs to try this out, especially since you demonstrated such a good first result on W3(OH) despite poor weather conditions.

Keep up the good work!

Regards,

Eduard

Op ma 6 mrt. 2023 om 20:12 schreef Dimitry UA3AVR <ua3avr...@gmail.com>

Eduard et all,

here i share a short text about my 6.7 GHz receiver. Hope this is just begining of greater project, i'm looking forward to improve the receiver, and the shared info could be helpful.

My greetings & regards, Dimitry UA3AVR.

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[James Morris]

Thanks for the write-up. What size dish is this, and how are you
controlling azimuth?


James W7TXT

[Dimitry UA3AVR]

Hi, James ... sorry for missing a size info in the text. Dish size - 1.8 m, azimuth and elevation are controlled by own software written in LabVIEW with a source tracking. 40 min of intergration time is almost a real time of source measurements. The dish positioning was calibrated by known Moon position on the sky; the Sun would be more convinient, but it is too low on the sky  this season here, unfortunately.

Many regards, Dimitry UA3AVR.

вторник, 7 марта 2023 г. в 06:38:08 UTC+3, James Morris:

[Dimitry UA3AVR]

Hi all. Here the W3(OH) line 6.7 GHz yesterday. The weather was more quiet; some clouds, but it seems not too dense. The line doesn't reach the expected peak level >3000 Jy. There is a probability I strongly underestimated my Tsys (or overestimate the antenna performance) in the level calculations. But the lunar noise measurements does not indicate that (the Moon temperature 225 K with uniform distribution across the disk was taken as a reference). Is it a maser variability seen?

Hope also to try the Cepheus A from the Eduard's catalog. The 12 GHz line out there was not seen last autumn at all; it is interesting about 6.7 GHz.

With greetings & regards, Dimitry UA3AVR.

понедельник, 6 марта 2023 г. в 22:26:09 UTC+3, Eduard Mol:

[Eduard Mol]

Hi Dimitry,

I just checked this source in the Ibaraki methanol maser database- the Japanese maser monitoring program has made their data available online (

http://vlbi.sci.ibaraki.ac.jp/iMet/data/133.9+10/)

It seems like the W3(OH) 6.6GHz maser has been fairly stable over the last few years at around 3000 Jy, with some minor variation.

Regards,

Eduard

Op wo 8 mrt. 2023 om 09:49 schreef Dimitry UA3AVR <ua3avr...@gmail.com>

Hi all. Here the W3(OH) line 6.7 GHz yesterday. The weather was more quiet; some clouds, but it seems not too dense. The line doesn't reach the expected peak level >3000 Jy. There is a probability i strongly underestimated my Tsys (or overestimate the antenna performance) in the level calculations. But the lunar noise measurements do not indicate that (the Moon temperature 225 K with uniform distribution across the disk was taken as a reference). Is it a maser variability seen?

With greetings&regards, Dimitry UA3AVR.

понедельник, 6 марта 2023 г. в 22:26:09 UTC+3, Eduard Mol:

Hi Dimitry,

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/5beba310-676f-45f2-9ff4-c74ba775f2f7n%40googlegroups.com.

[Dimitry UA3AVR]

OK, Eduard, thanks ... would leave that as a puzzle.

среда, 8 марта 2023 г. в 12:03:21 UTC+3, Eduard Mol:

[fasleitung3]

Hi Dimity,

Thank you for sharing the information about your setup. Using the Terrasat components for downconversion is a nice approach. Following your recommendation I have ordered the item via ebay (the one not requiring modification). I could not find any further information about the device. In particular, I could not find what the voltage needs to be to power the device. Can you give any advice there?

I am planning to do some lab tests with it as a preparation for a later methanol maser experiment. It will not be anytime soon as I still need to figure out what LNA to use or build, and then I still need a feedhorn. We will see how that goes.

Best regards,

Wolfgang

--

[Dimitry UA3AVR]

Hi Wolfgang, thanks,

these data are important, but missing in the text, sorry. The nominal supply voltage for Terrasat downconverter is +5.5 V, single rail. My module works well with +5 V and without degrading in performance. 

About LNA. I have ordered chips CMD283C3 for LNA, they works at 6.7 GHz with NF<0.8 dB; i think it is satisfactory. They need a simple PCB, a milled enclosure is available also. LNA with single FETs in the input stage could give NF less 0.5-0.6 dB, but stability and input VSWR of such stage is under questions. I would inform about progress in LNA building. 

Feed design is a separate issue; i'm looking for low noise dual-mode feedhorn, possibly with septum (circular polarization). I think the feedhorn design is defined by reflector characteristics (the dish F/D). The best way is to manufacture the feed under a special project. Using feedhorns initially intended for 5.7 GHz EME may be problematic.

With greetings & regards, Dimitry UA3AVR.

среда, 8 марта 2023 г. в 13:57:51 UTC+3, fasleitung3:

[Marcus D. Leech]

On 08/03/2023 05:57, 'fasleitung3' via Society of Amateur Radio Astronomers wrote:

Hi Dimity,

Thank you for sharing the information about your setup. Using the Terrasat components for downconversion is a nice approach. Following your recommendation I have ordered the item via ebay (the one not requiring modification). I could not find any further information about the device. In particular, I could not find what the voltage needs to be to power the device. Can you give any advice there?

I am planning to do some lab tests with it as a preparation for a later methanol maser experiment. It will not be anytime soon as I still need to figure out what LNA to use or build, and then I still need a feedhorn. We will see how that goes.

Best regards,

Wolfgang

To be clear, we're just talking about a mixer here, correct?  You still need to supply L.O. signal?

Am Montag, den 06.03.2023, 11:12 -0800 schrieb Dimitry UA3AVR:

Eduard et all,

here i share a short text about my 6.7 GHz receiver. Hope this is just begining of greater project, i'm looking forward to improve the receiver, and the shared info could be helpful.

My greetings & regards, Dimitry UA3AVR.

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[Dimitry UA3AVR]

>>You still need to supply L.O. signal?

Yes, this module needs LO with levels 3-4 dBm. 

среда, 8 марта 2023 г. в 20:09:56 UTC+3, Marcus D. Leech:

[Marcus D. Leech]

On 08/03/2023 12:49, Dimitry UA3AVR wrote:

>>You still need to supply L.O. signal?

Yes, this module needs LO with levels 3-4 dBm.

Ah.  IN that case, MiniCircuits makes some suitable mixers--in case the supply of these TerraSat things dries up :)

https://www.minicircuits.com/WebStore/dashboard.html?model=ZX05-83-S%2B

It's a "Level 7" -- which means +7dBm on the LO input.

If you have something like a USRP B2xx, you can use the TX side as your LO--possibly with a bit of a gain bump--I think it
  runs out of steam at about +5dBm on the TX outputs.

To view this discussion on the web visit https://groups.google.com/d/msgid/sara-list/71ce03d5-2d74-4f91-8edc-caf6ef879cf7n%40googlegroups.com.

[Marcus D. Leech]

On 08/03/2023 09:50, Dimitry UA3AVR wrote:

Hi Wolfgang, thanks,

these data are important, but missing in the text, sorry. The nominal supply voltage for Terrasat downconverter is +5.5 V, single rail. My module works well with +5 V and without degrading in performance. 

About LNA. I have ordered chips CMD283C3 for LNA, they works at 6.7 GHz with NF<0.8 dB; i think it is satisfactory. They need a simple PCB, a milled enclosure is available also. LNA with single FETs in the input stage could give NF less 0.5-0.6 dB, but stability and input VSWR of such stage is under questions. I would inform about progress in LNA building. 

Feed design is a separate issue; i'm looking for low noise dual-mode feedhorn, possibly with septum (circular polarization). I think the feedhorn design is defined by reflector characteristics (the dish F/D). The best way is to manufacture the feed under a special project. Using feedhorns initially intended for 5.7 GHz EME may be problematic.

Here in North America, CTS-sized copper tubing (used for plumbing) with a notional size of 1-1/4" has an ID that's just about
  perfect for a 6.7GHz circular waveguide feed.

You can get thin-walled brass tubing in that size range as well.   Certainly fine for a first cut.

I made one up for my 6.7GHz experiments (that never went anywhere) from a scrap of 1-1/4" CTS tubing several years back.

With greetings & regards, Dimitry UA3AVR.

среда, 8 марта 2023 г. в 13:57:51 UTC+3, fasleitung3:

Hi Dimity,

Thank you for sharing the information about your setup. Using the Terrasat components for downconversion is a nice approach. Following your recommendation I have ordered the item via ebay (the one not requiring modification). I could not find any further information about the device. In particular, I could not find what the voltage needs to be to power the device. Can you give any advice there?

I am planning to do some lab tests with it as a preparation for a later methanol maser experiment. It will not be anytime soon as I still need to figure out what LNA to use or build, and then I still need a feedhorn. We will see how that goes.

Best regards,

Wolfgang

Am Montag, den 06.03.2023, 11:12 -0800 schrieb Dimitry UA3AVR:

Eduard et all,

here i share a short text about my 6.7 GHz receiver. Hope this is just begining of greater project, i'm looking forward to improve the receiver, and the shared info could be helpful.

My greetings & regards, Dimitry UA3AVR.

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[Dimitry UA3AVR]

Hi Marcus

>If you have something like a USRP B2xx, 

>you can use the TX side as your LO

USRP in TX mode as LO source is a good idea. Unfortunately, my USRP with PC works indoor, but downconverter with LO is placed outdoor, near the dish feed. Plus, the TX sampling requires additional PC resources and needs additional time. It's better when the PC is loaded just by RX sampling and on-fly averaging (integration) during the measurements.

With greetings & regards, Dimitry UA3AVR.

среда, 8 марта 2023 г. в 21:03:02 UTC+3, Marcus D. Leech:

[fasleitung3]

Thanks, Dimitry, for the additional information.

I am not sure when (or if at all) we will be able to do a 6 GHz methanol maser experiement. I still need to think whether it is doable to use one of our existing dishes. Our 10m dish would be ideal but it is a Cassegrain setup and therefore hard to modify of 6 GHz. We will see. The choice of the dish will obviously determine what feed we need ot build.

Anyway, we will try out the downconversion first and then take from there...

Wolfgang

[Marcus D. Leech]

On 11/03/2023 16:30, 'fasleitung3' via Society of Amateur Radio Astronomers wrote:

Thanks, Dimitry, for the additional information.

I am not sure when (or if at all) we will be able to do a 6 GHz methanol maser experiement. I still need to think whether it is doable to use one of our existing dishes. Our 10m dish would be ideal but it is a Cassegrain setup and therefore hard to modify of 6 GHz. We will see. The choice of the dish will obviously determine what feed we need ot build.

Anyway, we will try out the downconversion first and then take from there...

Wolfgang

That's one of the reasons we converted our Cassegrain antenna to prime-focus.   Easier to feed, but more of a PITA to
  service.    A 21cm feed for it would be very large (like 0.7m horn aperture), and would require that we modify the feed
  pedestal by removing the top 25cm or so, AND it would make adding other frequencies more painful.

Although at 6.7GHz, getting a horn-type feed setup with adequate gain shouldn't be that horrific.  My recollection with ours
  was that the 21cm feed horn for the sub-reflector would need about 25dB gain.

Am Mittwoch, den 08.03.2023, 06:50 -0800 schrieb Dimitry UA3AVR:

Hi Wolfgang, thanks,

these data are important, but missing in the text, sorry. The nominal supply voltage for Terrasat downconverter is +5.5 V, single rail. My module works well with +5 V and without degrading in performance. 

About LNA. I have ordered chips CMD283C3 for LNA, they works at 6.7 GHz with NF<0.8 dB; i think it is satisfactory. They need a simple PCB, a milled enclosure is available also. LNA with single FETs in the input stage could give NF less 0.5-0.6 dB, but stability and input VSWR of such stage is under questions. I would inform about progress in LNA building. 

Feed design is a separate issue; i'm looking for low noise dual-mode feedhorn, possibly with septum (circular polarization). I think the feedhorn design is defined by reflector characteristics (the dish F/D). The best way is to manufacture the feed under a special project. Using feedhorns initially intended for 5.7 GHz EME may be problematic.

With greetings & regards, Dimitry UA3AVR.

среда, 8 марта 2023 г. в 13:57:51 UTC+3, fasleitung3:

Hi Dimity,

Thank you for sharing the information about your setup. Using the Terrasat components for downconversion is a nice approach. Following your recommendation I have ordered the item via ebay (the one not requiring modification). I could not find any further information about the device. In particular, I could not find what the voltage needs to be to power the device. Can you give any advice there?

I am planning to do some lab tests with it as a preparation for a later methanol maser experiment. It will not be anytime soon as I still need to figure out what LNA to use or build, and then I still need a feedhorn. We will see how that goes.

Best regards,

Wolfgang

Am Montag, den 06.03.2023, 11:12 -0800 schrieb Dimitry UA3AVR:

Eduard et all,

here i share a short text about my 6.7 GHz receiver. Hope this is just begining of greater project, i'm looking forward to improve the receiver, and the shared info could be helpful.

My greetings & regards, Dimitry UA3AVR.

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[Dimitry UA3AVR]

Hi Eduard and all,
here the yesterday results for W3(OH) with worst possible assumptions about my Tsys. The peak flux is about 2000 Jy; in other previous observations the peak is in the range 1000-2000 Jy.
1. A small antenna positioning error (appeared after the winter) is corrected;
2. The system performance was cheched again by the Moon observation (taking the Moon temperature ~210 K with flat distribution over the disk);
3. Weather conditions almost not affect;
4. Attempts to detect W51 and Cepheus A were not successful, although, at least, one of them should be seen even with the worst Tsys.

With greetings & regards, Dimitry UA3AVR.

среда, 8 марта 2023 г. в 12:03:21 UTC+3, Eduard Mol:

[Dimitry UA3AVR]

Hi all,

it seems the Cepheus A line 6.7 GHz is seen after all. The maser is variable significantly. The two peak spectrum is possible, see pictures at http://vlbi.sci.ibaraki.ac.jp/iMet/data/109.8+21/; this possibility makes an identification of the maser easier. Peak velocities are reproduced well. Levels are calculated with Tsys=150 K, integration time ~1 hour, observations 2023-04-15. The peak near 10 km/s is not identified. 

Waiting for a new LNA and hope the two peak spectrum will be seen more clear. PCBs for LNA are ready (see the picture), chips are expected in 1-2 days, enclosures (from devices https://aliexpress.ru/item/32910023861.html) arrived already.

Greetings & regards, 

Dimitry Fedorov UA3AVR.

пятница, 7 апреля 2023 г. в 11:08:24 UTC+3, Dimitry UA3AVR:

[Dimitry UA3AVR]

Hi all. There is some progress with LNA building. Details are at the appended file with 6.7 GHz receiver project, including Noise Figure and S-parameters measurements. 

Greetings & regards, Dimitry UA3AVR.

P.S. I have some amount of PCBs as a remainder after building the test sample; i could share the PCBs too. I could also fully assemble and test the LNA, but, unfortunately, a remainder of chips CMD283C3 is limited (only 2 pcs are in my disposal now).

понедельник, 17 апреля 2023 г. в 14:48:57 UTC+3, Dimitry UA3AVR:

[fasleitung3]

A quick update on this:

I did a quick and dirty test of the Terrasat downconverter. RF input was 6.7 GHz @ -40 dBm, LO was 5.280 GHz @ 0 dBm, so the IF was at 1420 MHz. I found a conversion gain of 20 dB, increasing the LO power did not seem to improve the conversion gain much. The IF was chosen so that H-Line filters can be used as IF filters should the need arise later on. The unit was powered with the nominal 5.5V drawing about 280 mA. A more careful characterization is planned for a later stage.

All in all I can say I am happy with what I am seeing.

Cheers,

Wolfgang

[Adrian]

Hi

 Just received my shipment of the four MDC6471-035 downconverters from ebay and had a look at the circuit. Mention has been made of removing the input ceramic chip to increase the spectrum range. I am curious if this chip has any active elements for input gain. I think that I can make out what appear to be stripline-like filters and perhaps even some possible active elements in the middle between what look like the 2 individual segments?  I don't have the equipment to do so but is anyone likely to check and see if beyond the obvious filter elements it also provides any input gain. I will certainly be interested for any further update developments of the project and of the circuit spectrum analysis.

Adrian

[Jeff Kruth]

That "chip" is a -3dB Lange coupler used to implement a balanced Amplifier, probably GaAs FETs. That is , if you are referring to the ceramic substrate on the top. There are two transistor chips between the two Lange couplers. Lange couplers generally have octave bandwidths, so the coupler should cover the Methanol maser range.

I would NOT remove this unless you want to remove the front end amplifier.

J. Kruth 

 

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[A. C.]

Jeff,

  Many thanks for the information. Although I'm not familiar with the Lange coupler, just getting my feet wet on microwave circuitry, you certainly confirmed my suspicion of it serving as a front end LNA of some sorts..

Next step, as others have documented, are an additional front end LNA amp to establish a lower noise figure and an appropriate feed for my prime focus 180cm dish.

Adrian

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"My God, it's full of stars!"
 Dave Bowman

[LTO Observatory]

Very impressive, and thank you, Dimitry!

It is good to have amateur radio astronomy projects that go beyond hydrogen, for there is so much else to explore and learn.

Again, thank you for sharing.

[Dimitry UA3AVR]

Hi to all,

the project file with latest progress in receiver building is updated and enclosed. Info about new LNA with Qorvo chips with Terrasat module 6.4-7.1 GHz as a downconverter is included.

With greetings & regards, Dimitry UA3AVR.

суббота, 27 мая 2023 г. в 14:53:36 UTC+3, LTO Observatory:

[Captain Anne Flint]

Thanks Dmitri - Wende

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<6,7 GHz receiver project_2022-06-19.pdf>

[Anthony]

Very nice work, Dimitry!

That's some VNA you've got there! 

--