Advice needed for mounting Discovery Dish hydrogen line feed on a 2.4m parabolic dish

[Ayushman Tripathi]

Hi everyone,

I'm upgrading from my 1-meter dish to a 2.4-meter mesh parabolic dish (C/Ku Band, f/d Ratio - 0.40, Focal Length - 28 inches, Punch Sheet - Aluminum Sheet, Wind load operational - 95 kmph).

I will be installing this dish at a remote rural location, where it will operate mostly unattended, with only occasional visits to rotate or re-aim it.

My feed is the Discovery Dish hydrogen-line feed from KrakenRF.
(docs:
https://github.com/krakenrf/discoverydish_docs/wiki/02.-Dish,-Feed-and-Enclosure-Assembly
https://github.com/krakenrf/discoverydish_docs/wiki).

The signal chain inside this feed is
Antenna → LNA1 → Filter1 → LNA2 → Filter2 → Output
using QPL9547 LNA chips and SAW filters.

The new dish includes the usual circular scalar-ring mount for a TV LNB, and I’m trying to determine the best way to adapt or replace that bracket to hold the Discovery feed at the exact focal point while maintaining proper illumination for this deeper reflector to utilize it to its maximum.

If anyone has any ideas, I would really appreciate your input.

I'll point it toward a part of the sky with strong, reliable hydrogen-line emission so it continues collecting data even when I’m not physically present, which it'll upload daily to OneDrive. Later, I also plan to use the same system for SETI narrowband observations.

Thanks in advance!

[Ayushman Tripathi]

Here's an image of the feed, it looks like its URL is broken in the above post.

[Alex P]

I would Strongly Suggest you NOT use that feed .. that dipole has a poor beam pattern,

and a good Dish deserves a good Feed !

For a 2.4m Dish, go with a tuned cylindrical waveguide  aka "Cantenna"

https://www.changpuak.ch/electronics/cantenna.php

Regards,

Alex P

[b alex pettit jr]

[Ayushman Tripathi]

Hi, Alex.

Thanks a lot! for the advice,

I'll get the materials needed to make a new feed that is shown in your document, thanks.

Also, do you think there is a way to reuse this feed's LNAs, filters, etc.? As it has dual LNAs and filters.

Its documentation says this:

Designed for prime focus satellite dishes, the Discovery Dish Feed comes in various versions for different applications and satellite bands:

• Hydrogen Line: 1380 MHz – 1460 MHz. Explore the Galactic Hydrogen Line peak at 1420.42 MHz. Observe the Doppler shift caused by galactic spin.

• All-in-One Unit: Integrates the feed antenna, LNA, filters, and cable, eliminating separate purchases and the need to weatherproof individual components.

• Signal Chain: Antenna → LNA1 → Filter1 → LNA2 → Filter2 → Output. Uses the QPL9547 LNA chip and SAW filters.

• Power: Bias tee 3.3V–5V, 120mA. Compatible with RTL-SDR Blog and Airspy dongles.

• Skew Adjustability: Feed head rotates for skew alignment.

• Weatherproof Enclosure: IP65-rated for standard weather conditions.

Dish Compatibility: Best with the Discovery Dish, but works with most prime focus dishes using an adapter, including typical 600x900 mm WiFi Grid Dishes.

Thanks.

[b alex pettit jr]

Hello Ayushman,

I suggest purchasing a $45 nooelec SAWbird H1+ 1420MHz LNA for the Cantenna

Hopefully they will have them in stock soon....

Here is info on a Cantenna easier to fabricate from galvanized sheet and tube.

( you might find home heating duct tube , or a large can from coffee, etc that will work for the feed )

With the 2.4m dish, you might consider building the choke ring to optimize the beam-width 

https://www.setileague.org/hardware/feedchok.htm

The use of a single scalar-mode choke on a cylindrical feedhorn has been explored extensively by Barry Malowanchuk, VE4MA. He has presented a nicely optimized dish feed for the amateur 5 cm (5760 MHz) band. [3] By fortuitous coincidence, the frequency for which Barry designed his horn is almost precisely four times that of the neutral hydrogen line. Since dimensions for waveguide scale linearly with wavelength, if we desire to build a hydrogen line feed using Barry's design, all we need do is multiply all of his dimensions precisely by four. This scaling process gives us the working dimensions shown in Table 1 below.

Feedhorn dimensions are typically selected to illuminate the surface of a dish as fully and uniformly as possible, to achieve the highest possible antenna gain. Industry practice is to utilize a 10 dB edge illumination taper. That is, with respect to the center of the dish, signals reaching the feed from the very edge of the dish are 10 dB lower in amplitude. With simple cylindrical waveguide feedhorns, the result is typically a 55% efficient antenna system. For most communications applications, where range and margin are a function of recovered signal strength, this is indeed an appropriate design technique.

SETI, on the other hand, is a unique application in that the strength of the anticipated receive signal is entirely unknown. Our range and sensitivity are largely noise- limited. That is, in order to maximize our sensitivity, we need to reduce antenna noise temperature to the absolute minimum. This can be accomplished by deliberately under-illuminating the dish. Let's calculate an example based upon a 5 meter parabolic reflector operating at the 1420 MHz Hydrogen line. If we use a 15 dB illumination taper, the antenna gain goes down almost one dB (from +34.8 to +34.0 dBi), as efficiency drops to say 45%. But for a SETI system with a low noise front end, reducing antenna gain and efficiency actually improves sensitivity. Here's how:

Let's imagine our receiver uses a GaAs PHEMT front end, running at 50 K receive noise temperature. With a dish designed for optimum gain, the antenna noise temperature, dominated by Earth-seeing sidelobes, is about 50 K. The overall system noise temperature is thus 100 K, and sensitivity (given 10 Hz bin width and 10 second integration) is on the order of 1.3 E-22 W/m^2. Now under-illuminate for 10 K of antenna noise. Antenna gain decreases 0.8 dB as discussed above, but overall noise temperature reduces to 60 K, a 2.2 dB decrease in noise. System sensitivity is now 9.4 E-23 W/m^2, a net system improvement of 1.4 dB!

Is the cited sensitivity adequate to the task of meaningful SETI? In 1977, NASA SP-419, The Search for Extraterrestrial Intelligence articulated this goal on page 21: "Existing antennas could be used to search ... the entire microwave window to as low as ~10 E-23 W/m^2 in a few years of observing time." By increasing to 120 seconds the integration time constant of the system just described, overall sensitivity improves to on the order of 2.7 E-23 W/m^2. Thus, two decades later, amateur SETI is just now closing in on NASA's sensitivity goal for SETI sky surveys.

The chief determinant of illumination taper for scalar-ring feedhorns is the placement of the choke ring along the waveguide feedhorn. The choke ring must be designed so as to slide back and forth on the waveguide horn, in order to optimize the illumination pattern of the feed for noise vs. gain, as well as the particular focal length to diameter ratio (F/D) of the dish being used. Here are the critical dimensions for the distance between the front of the horn and the back of the choke ring. They are shown in Table 2 for dishes of various F/D ratios, for both lowest antenna noise temperature (the preferred condition for SETI) and greatest antenna gain (which you would choose for a transmit antenna). All dimensions are in cm (inches).

Prototypes of this feed have been fabricated from sheet copper and galvanized sheet steel. Materials do not appear particularly critical. The flange by which the scalar ring attaches to the waveguide horn assembly can be drilled and tapped for set-screws, or notched to simulate finger-stock, and held in place with a large hose clamp. Radio 

Regards,

Alex

==============================================================

[andrew....@googlemail.com]

That is amazing, Ayushman – I asked ChatGPT (sorry guys!) what advantages of 2.4m over 1m were for H-Line, and this is what it said today….

NB If you join us in the H-Line group meetings, please show us loads of photos, and tell us all about finding the dish, buying it, installing it (or your hopes on installing it including info on site), info on how you will feed it, how long the coax will be and where and what PC and software you hope to use, etc. etc. – if you don’t have that info don’t worry, you can talk about your thoughts, and other members may have suggestions that might help.

The mount shown in the photo is non-tracking – does that mean you intend to do H-Line drift scans with this dish? (where you point in one direction and allow Earth to rotate bringing 360 degrees of sky across the dish over 24 hrs.)

One question to whole group, can you do pulsar observations with 2.4m dish from radio quiet site? I know several people here do them with 3m dishes.

Andy

 

Upgrading from a 1-metre dish to a 2.4-metre dish for 1420 MHz hydrogen-line work brings several big improvements. The gains are mainly in sensitivity, signal-to-noise ratio, and angular resolution.

Below is a clear breakdown:

---

1. Sensitivity increase (~5.7× more collecting area)

Dish sensitivity scales with collecting area, which goes as πr².

• 1 m dish area ≈ 0.79 m²
• 2.4 m dish area ≈ 4.52 m²

Area ratio ≈ 5.7×

This means:

• You collect ~5.7 times more power from the hydrogen-line emission.
• Your signal-to-noise ratio improves by about √5.7 ≈ 2.4× (if system noise stays similar).

This is the biggest real-world benefit:
► Weaker sources become detectable, and integration times shorten dramatically.

---

2. Better angular resolution (~2.4× improvement)

Beamwidth is roughly:

θ ≈ λ / D

At 1420 MHz, λ ≈ 0.21 m.

• 1 m dish → beam ~12°
• 2.4 m dish → beam ~5°

So you get:

• Sharper beam, less spillover
• Ability to distinguish finer structure in the hydrogen profile
• Less sensitivity to unwanted off-axis noise sources

---

3. Lower noise from spillover and ground pickup

A larger dish has a:

• narrower illumination pattern from the feed
• reduced ground spillover
• lower effective noise temperature

This helps the system temperature (Tsys) drop, improving SNR further.

---

4. Faster, cleaner integrations

Because you start with higher SNR:

• You need less integration time for the same quality spectrum
• Or you can integrate longer but achieve much cleaner line profiles
• Baselines become smoother
• Drift-scan results are significantly improved

---

5. Ability to detect more subtle astrophysical structure

With a 2.4 m dish you can:

• Resolve Galactic rotation curves more clearly
• See multiple velocity components in the Milky Way more distinctly
• Detect structure in the hydrogen layer that a 1 m dish has trouble separating

Many Radio JOVE-type feeds and simple LNAs perform noticeably better when paired with larger apertures for this reason.

---

Summary

Upgrading from 1 m → 2.4 m gives:

Improvement	Factor
Collecting area	5.7×
Signal-to-noise	~2.4×
Angular resolution	~2.4× better
Integration time needed	~1/6 for same quality
Ability to see Galactic features	Much better

If you’re doing serious hydrogen-line spectroscopy—especially velocity mapping—the upgrade is a very large step up.

---

Thanks in advance!

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[andrew....@googlemail.com]

I didn’t realise that was the official name, Alex, for a cantenna – a “tuned cylindrical waveguide”…..

 

In future, when I am doing talks at astronomy clubs in UK on radio astronomy, I will no longer have a cantenna on my 150cm dish, but now I have upgraded to a very serious sounding tuned cylindrical waveguide!!!!

 

Andy

 

From: 'Alex P' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Sent: 19 November 2025 01:15
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

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[andrew....@googlemail.com]

Of a large coffee can………..

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[fasleitung3]

There is one important effect which ChatGPT misses:

Hydrogen emission is an extended source. Therefore, you also need to consider that a smaller dish is looking at more hydrogen due to its wider beam width. Because of that, the power does not scale with the collecting area of the dish. In fact, if Hydrogen would be evenly distributed over the sky, the received power would be independent of the dish size. So 1. from ChatGPT is not true for hydrogen emission. It would be valid for sources < beam width, though.

Other than that, the main benefit of having a higher resolution remains vaild.

Best regards,

Wolfgang

[b alex pettit jr]

With the operative word being TUNED *

* Tuned : mechanically and electrically adjusted, aligned, positioned, tested :  Optimized for Maximum Performance.

Alex P

=====================================================

I didn’t realise that was the official name, Alex, for a cantenna – a “Tuned Cylindrical Waveguide”…..

 

[Ayushman Tripathi]

Hi Alex,

Thank you so much for the detailed explanation, the choke-ring information, and for pointing me toward Barry’s document. This will make things much easier when I start working on the cantenna. I really appreciate you taking the time, it’s extremely helpful.

I actually wanted to buy the Nooelec SAWbird H1+ right from the beginning, but it has been out of stock everywhere for months. That’s the only reason I ended up getting the Discovery Dish H1 feed. If I bought a separate LNA, finding a proper 1420 MHz SAW filter was also proving difficult, and I wasn’t sure if the ones on eBay were genuinely good or just generic & untested.

I did see some options on the GPIO Labs store, but the SAWbird would still be my first choice because of the fully integrated design.

If anyone knows a source where the SAWbird H1+ is currently in stock, I’d definitely be interested in purchasing one. Otherwise, I’ll try to pick up a wideband Nooelec LNA that is available, source a suitable filter, and build a proper cantenna + LNA + choke-ring setup for the 2.4 m dish. I can continue using the Discovery Dish feed on my smaller grid dish.

Thanks again for your help and the references—they really make things clearer.

Regards,
Ayushman

[Ayushman Tripathi]

Hi Andrew,

Thanks so much! Yes, I’d be happy to join the meetings and share photos, updates, and everything as the installation progresses. I’ll really enjoy doing that.

I bought this dish: https://www.solid.sale/Solid-Dish-Antenna/8ft-Dish
(I actually received a slightly upgraded version of it as bought from an antenna solution provider) The price was quite reasonable—about $110 (USD) plus $20 shipping—and it even comes with a free mounting pole that has built-in elevation adjustment. It’s a surprisingly reliable brand from what I’ve seen. I could have gone for a larger dish, but since I’ll only be visiting the site once every 4–5 months, I wanted something big but still manageable to mount and keep secure. With this one, I can simply cement the supplied pole onto the roof.

I’ll be running the setup on a Raspberry Pi 500 with an SDR server, and it will upload the daily data to OneDrive automatically. I’ll also set up Tailscale or DDNS for remote access, since it will be using a cellular LTE/5G router for internet.

And yes — using ChatGPT etc. has been helpful.

Claude Code is also great for calculations and programming, also it can create whole Python GUIs for Virgo etc. It runs directly in the terminal and handles math/programming really well. Of course, it’s always best to double-check anything AI produces, but it can save a lot of time: https://claude.com/product/claude-code

Looking forward to joining the meetings and sharing progress soon!

Regards,
Ayushman

[b alex pettit jr]

I'm, going to check on the status of the SAWbird .. will post the reply.

Alex

[Marcus D. Leech]

On 2025-11-19 10:41, Ayushman Tripathi wrote:

Hi Andrew,

Thanks so much! Yes, I’d be happy to join the meetings and share photos, updates, and everything as the installation progresses. I’ll really enjoy doing that.

I bought this dish: https://www.solid.sale/Solid-Dish-Antenna/8ft-Dish
(I actually received a slightly upgraded version of it as bought from an antenna solution provider) The price was quite reasonable—about $110 (USD) plus $20 shipping—and it even comes with a free mounting pole that has built-in elevation adjustment. It’s a surprisingly reliable brand from what I’ve seen. I could have gone for a larger dish, but since I’ll only be visiting the site once every 4–5 months, I wanted something big but still manageable to mount and keep secure. With this one, I can simply cement the supplied pole onto the roof.

I’ll be running the setup on a Raspberry Pi 500 with an SDR server, and it will upload the daily data to OneDrive automatically. I’ll also set up Tailscale or DDNS for remote access, since it will be using a cellular LTE/5G router for internet.

And yes — using ChatGPT etc. has been helpful.

Claude Code is also great for calculations and programming, also it can create whole Python GUIs for Virgo etc. It runs directly in the terminal and handles math/programming really well. Of course, it’s always best to double-check anything AI produces, but it can save a lot of time: https://claude.com/product/claude-code

Looking forward to joining the meetings and sharing progress soon!

Regards,
Ayushman

The prices listed on that site are really good.   But, I'm pretty sure that international shipping would be horrific.

Prices here (if you can get them at all!) are horrendous.   For example, from Tek2000.com, a 12ft works out to about C$4500.00 apiece!

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[Andrew Thornett]

SAWBird H1 LNA Barebones version (without plastic case) are still available directly from Nooelec, but they arent on their website - you need to contact them via their contact page amd they will set up an order for you.

Andy

Sent from Outlook for Android

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Marcus D. Leech <patchv...@gmail.com>
Sent: Wednesday, November 19, 2025 3:52:36 PM
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Advice needed for mounting Discovery Dish hydrogen line feed on a 2.4m parabolic dish

 

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[Andrew Thornett]

Hi Alex,

With regards to tuning the cantenna, which aspects are those, in your opinion, that must be just right?

Andy

Sent from Outlook for Android

---

From: Andrew Thornett <andrew....@googlemail.com>
Sent: Wednesday, November 19, 2025 4:46:06 PM

[b alex pettit jr]

Everything . Each incremental  improvement helps with the final result ... It takes time ...

and using a calibrated spectrum display such as via  SDR#  is required for the task. 

( and IF-avg for confirmation of the improvement )

Alex

[b alex pettit jr]

Well,,, there is probably one or two more important than others : the factors currently most 'maligned'.

BUT, without changing and testing things, you'll not be able to identify them .... 

and so we go back to the original reply  "Everything"

[Bob the Science Guy]

Marcus that is pretty much the same thing I have sitting on the ground next to the observatory waiting for the time to build it.  I'll be following your progress with interest and will hit you up for advice next summer.

Bob

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[Marcus D. Leech]

On 2025-11-19 12:01, Bob the Science Guy wrote:

Marcus that is pretty much the same thing I have sitting on the ground next to the observatory waiting for the time to build it.  I'll be following your progress with interest and will hit you up for advice next summer.

Bob

Hey, if your country's political situation improves, I might even be convinced to travel to MI to help out.

We're actually pouring concrete for two new dish projects at the observatory on Friday.    There'll be a 2.5m near the entrance--mostly as a "prop" but also permanently pointed at
  V669 Cas. to pick up the bright OH+ maser emissions, and the H1 in that region--dual polarization feed with a broad-enough response to give us both 1.6GHz and 1.4GHz.
  I have a 4-channel receiver that I'll dedicate to this project.

The other one will be for some satellite and other radio astronomy work--a 3m, located on the "front lawn" of the observatory, with a Az/El mount supplied to us by
  Sub-lunar systems.  We'll situate it so that we can add another 3m in the future, to support interferometry.

The concrete work has taken much longer than anticipated, as we moved from "let's mix it ourselves" to "sweet Cthulu, that's a lot of concrete, let's get it delivered".
  Minimum delivery is 1m**3, which meant we decided to enlarge the excavations a bit to "soak up" the considerable excess implied by a 1m**3 minimum
  load delivery.  There is a local company that does "mix on site", but they were singularly uninterested in such a small project. 

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[Marcus D. Leech]

On 2025-11-19 11:47, 'Andrew Thornett' via Society of Amateur Radio Astronomers wrote:

Hi Alex,

With regards to tuning the cantenna, which aspects are those, in your opinion, that must be just right?

Andy

Probe placement w.r.t. the distance from the back-short, and probe length.   That is, assuming that you stick to a 150mm diameter.

The guide wavelength (lambda-g) grows *quickly* as you shrink the diameter of the guide.    The guide *length* isn't critical as long as it's
  longer than about 1 lambda-g.   I generally make my circular wave-guides about 250mm long, or sometimes longer.  There's very little
  penalty in making them longer (within reason).  An important loss mechanism in wave-guides is the skin resistance of the inside wave-guide
  surface.  So, longer guides from "improvised" materials are probably not a good idea.  But anything between 1 and 2 lambda-g in
  guide length should be fine.

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[b alex pettit jr]

And, the positioning of the waveguide at the proper dish<>feed spacing.

=========================================

On Wednesday, November 19, 2025 at 12:44:37 PM EST, Marcus D. Leech <patchv...@gmail.com> wrote:

On 2025-11-19 11:47, 'Andrew Thornett' via Society of Amateur Radio Astronomers wrote:

Hi Alex,

With regards to tuning the cantenna, which aspects are those, in your opinion, that must be just right?

Andy

Probe placement w.r.t. the distance from the back-short, and probe length.   That is, assuming that you stick to a 150mm diameter.

The guide wavelength (lambda-g) grows *quickly* as you shrink the diameter of the guide.    The guide *length* isn't critical as long as it's
  longer than about 1 lambda-g.   I generally make my circular wave-guides about 250mm long, or sometimes longer.  There's very little
  penalty in making them longer (within reason).  An important loss mechanism in wave-guides is the skin resistance of the inside wave-guide
  surface.  So, longer guides from "improvised" materials are probably not a good idea.  But anything between 1 and 2 lambda-g in
  guide length should be fine.

[Marcus D. Leech]

On 2025-11-19 12:57, 'b alex pettit jr' via Society of Amateur Radio Astronomers wrote:

And, the positioning of the waveguide at the proper dish<>feed spacing.

THIS!

It is typically the case that the phase-center of a circular-waveguide feed is just inside the entrance to the guide.

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[b alex pettit jr]

With the extended wifi dish @ focal length 35cm, I could detect spacing changes in 1cm steps .. 

That's hard to guess without making operational measurements.

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[James Abshier]

Also the SNR scales directly with area ratio not the square root of the area ratio.

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[andrew....@googlemail.com]

This all fits with my understanding so far:

 

(i)                  Distance of probe from bottom of can really matters.

(ii)                Length of probe matters, although this can be compensated for by cutting probe slightly long and nibbling bits off whilst checking SWR with NanoVNA, until get close to 1:1.

(iii)               Recently, discovered what probe is made of also matters – 1/8-inch copper tubing seems to be very effective and better than simple wire.

 

Alex/Marcus/anyone else – please correct above!

 

Andy

 

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: 19 November 2025 17:57
To: sara...@googlegroups.com
Subject: Re: [SARA] Advice needed for mounting Discovery Dish hydrogen line feed on a 2.4m parabolic dish

 

And, the positioning of the waveguide at the proper dish<>feed spacing.

 

=========================================

 

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[Marcus D. Leech]

On 2025-11-19 13:26, andrew.thornett via Society of Amateur Radio Astronomers wrote:

This all fits with my understanding so far:

 

(i)                  Distance of probe from bottom of can really matters.

(ii)                Length of probe matters, although this can be compensated for by cutting probe slightly long and nibbling bits off whilst checking SWR with NanoVNA, until get close to 1:1.

(iii)               Recently, discovered what probe is made of also matters – 1/8-inch copper tubing seems to be very effective and better than simple wire.

 

Alex/Marcus/anyone else – please correct above!

A thin piece of wire will provide a good match over a much smaller bandwidth than a piece of tubing.   In other words, if you make your
  probe from tubing, it will be more "forgiving".  I've used 6mm tubing in he past, and it always works out well...

Getting a perfect 1:1 VSWR match with a waveguide-to-coax transition is very difficult, and don't stress too much if you can't get it perfect.

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[andrew....@googlemail.com]

What do you think is a practical VSWR match that can be achieved by amateurs?

Andy

 

From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Marcus D. Leech
Sent: 19 November 2025 18:36
To: sara...@googlegroups.com
Subject: Re: [SARA] Advice needed for mounting Discovery Dish hydrogen line feed on a 2.4m parabolic dish

 

On 2025-11-19 13:26, andrew.thornett via Society of Amateur Radio Astronomers wrote:

This all fits with my understanding so far:

 

1.                  Distance of probe from bottom of can really matters.

2.                  Length of probe matters, although this can be compensated for by cutting probe slightly long and nibbling bits off whilst checking SWR with NanoVNA, until get close to 1:1.

3.                  Recently, discovered what probe is made of also matters – 1/8-inch copper tubing seems to be very effective and better than simple wire.

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[Marcus D. Leech]

On 2025-11-19 13:44, andrew.thornett via Society of Amateur Radio Astronomers wrote:

What do you think is a practical VSWR match that can be achieved by amateurs?

Andy

 

Once you get below 2:1, further improvement may be quite frustrating.  Waveguide-to-coax transitions are tricky, and the "pros" often do some really weird things
  to get it below 2:1.   Probes of odd shapes, sometimes combined with a tuning screw on the opposite face of the guide, or adjacent to the probe.  In addition, the
  match will be affected by whether the feed is on the dish or not.   Which makes tweaking it ever-more-delightful as your dish gets larger and the feed gets more
  awkward to service....

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[andrew....@googlemail.com]

Thanks.

 

Also – recently I tried using two probes same length, same distance from bottom cantenna – it seems to me that this has adversely affected the signal power level detected on both probes – is that a sensible suggestion?

 

Andy

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[b alex pettit jr]

[Marcus D. Leech]

On 2025-11-19 13:57, 'b alex pettit jr' via Society of Amateur Radio Astronomers wrote:

Nice.  I have never personally been able to achieve better than 1.4:1 on the bench with a circular wave-guide and probe.   Speaking with other radio astronomers
  at the time, they said that was their experience as well.   But yours is a lovely counter-example.   Was this measurement on-dish, or on the bench?

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[Marcus D. Leech]

On 2025-11-19 13:56, andrew.thornett via Society of Amateur Radio Astronomers wrote:

Thanks.

 

Also – recently I tried using two probes same length, same distance from bottom cantenna – it seems to me that this has adversely affected the signal power level detected on both probes – is that a sensible suggestion?

 

Andy

What do you mean by two probes?  Two probes at 90deg angles to each other?

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[b alex pettit jr]

Pretty sure that was on bench .. 

This is one of the Yagis  ... just takes tedious adjustments 

[b alex pettit jr]

................ just takes tedious adjustments 

AND, a having a system Small enough to make quick tweaks and observe the VNA traces in real time.

[Marcus D. Leech]

On 2025-11-19 14:50, 'b alex pettit jr' via Society of Amateur Radio Astronomers wrote:

Pretty sure that was on bench .. 

This is one of the Yagis  ... just takes tedious adjustments 

This demonstrates nicely that YAGI antennas are inherently narrow-band resonant systems, with a steep VSWR "notch" very-apparent in
  this VNA plot.

On Wednesday, November 19, 2025 at 02:29:56 PM EST, Marcus D. Leech <patchv...@gmail.com> wrote:

On 2025-11-19 13:57, 'b alex pettit jr' via Society of Amateur Radio Astronomers wrote:

Nice.  I have never personally been able to achieve better than 1.4:1 on the bench with a circular wave-guide and probe.   Speaking with other radio astronomers
  at the time, they said that was their experience as well.   But yours is a lovely counter-example.   Was this measurement on-dish, or on the bench?

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[Lester Veenstra]

From: Lester Veenstra [mailto:m0...@veenstras.com]
Sent: Wednesday, November 19, 2025 12:34 PM
To: 'sara...@googlegroups.com'
Cc: 'sara-...@veenstras.com'
Subject: RE: [SARA] Advice needed for mounting Discovery Dish hydrogen line feed on a 2.4m parabolic dish

 

I have them tested, documented, with case, direct from me (SARA Store)

 

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y W8YCM/6Y 6Y8LV (Reformed USNSG CTM1)

 

To get past GMAIL SPAM FILTER reconstruct a return address from

lester  "aptsign"  veenstras  "dot"  com

 

452 Stable Ln

Keyser WV 26726 USA

 

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

[fasleitung3]

Hot news: The SAWbird H1+ is now back in stock at Noolec!

Wolfgang

[Ayushman Tripathi]

Hi Markus,

Yes, I was surprised by that price as well. Once I get the dish set up and have tested it a bit, I can check what the shipping cost to the USA might be. You could also ask the manufacturer directly if they can ship from their factory, if it’s being produced there, sea freight should make it much more affordable.

Hi Alex, Andrew, thank you both. I contacted Nooelec, and they replied saying they’ve added the SAWbird+ H1 back now to their webstore. So I’ll go ahead and purchase it now.

Thank you all for the help—I’ll try to build a proper Cantenna during the next few weekends and will share updates and photos as I make progress.

Thanks,
Ayushman

[Don Latham]

My $.02: Have used brass standoff  on type N connectors for strength. Solder spacer on. Then put a screw in the end of the spacer. Small hole in the opposite side of the can allows for tuning the screw. hint, slightly flat threads on brass screw (SLIGHYLY!). Adjustment with sdr.

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From: "sara" <sara...@googlegroups.com>
To: "sara" <sara...@googlegroups.com>
Sent: Wednesday, November 19, 2025 12:55:35 PM

Subject: Re: [SARA] Advice needed for mounting Discovery Dish hydrogen line feed on a 2.4m parabolic dish

................ just takes tedious adjustments 

AND, a having a system Small enough to make quick tweaks and observe the VNA traces in real time.

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[Jonathan Pettingale]

I have had success with these. I cut to length and sleeve for 1420MHz.  N Female Bulkhead w/ 2.4GHz Radiator (Cantenna Type) – JEFA Tech