Death of the LRO-H2 Solar Cooker Radio Telescope

[Andrew Thornett]

.....or more accurately moth-balling = the six solar cooker petals might see the light of day again.....possibly....if one day I am in a forgiving mood.

There is a story in the Biblical New Testament where Jesus curses a fig tree for not producing figs = the same has happened here - this dish is cursed for not producing good quality hydrogen line data and is condemned to the hellish regions of my garage to suffer for all eternity, or at least until it has paid its penance. 

Andy

_._,_._,

[Sławomir Klimek]

I tested this dish and also a 180 cm on L-band satellites. The signal quality was poor, comparable to optimized 80–90 cm offset antenna
terribly wide focal point.

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[Andrew Thornett]

Im not surprised! Ive been blaming myself but now I suspect the dish is just bad.

Likely in my view (but as yet untested/not proven) that similar rolled steel dishes from China also perform poorly in H-line.

I also dont know if this performance issue is manufacturer dependent.

Andy

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Sławomir Klimek <slawomir...@gmail.com>
Sent: Monday, 15 June 2026 18:54:07
To: sara...@googlegroups.com <sara...@googlegroups.com>
Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

 

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[dave bracey]

How do these petal dishes perform at their intended function of cooking?

Presumably if they are that bad at focusing 21cm they won't do too well at focusing infra red either?

D

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[Andrew Thornett]

I dont know but when I first got it my leg got rather hot at one point close to it.

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Sent: Monday, 15 June 2026 21:22:38

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[Stephen Arbogast]

Well.....  I did the usual   Googling and ChatGPT   and found that  steel is not a good conductor and a solar cooker may not  be a good parabola.

[Stephen Arbogast]

My small  Discovery Dish is  aluminum, a  good  conductor,   very  small   but it  works, dipole feed.   With  help  from  Ted  Cline  using  ezRA   I am  getting  decent  results...
See..      attached...   the  scale  needs adjustment.

[Stephen Arbogast]

And by the  way  you did not  fail!    Your  experience would   be  good   paper for the   journal.

[Stephen Arbogast]

This is very good    example   of  refining  Physics....   https://www.youtube.com/watch?v=IhlSqwZBW1M

[Marcus D. Leech]

On 2026-06-15 18:29, 'Stephen Arbogast' via Society of Amateur Radio Astronomers wrote:

Well.....  I did the usual   Googling and ChatGPT   and found that  steel is not a good conductor and a solar cooker may not  be a good parabola.

Steel isn't the best conductor, but it's a conductor.   Consider, the Lovell 70m telescope in the UK is galvanized steel, as is the ARO 47m dish in
  Algonquin park.  That it's steel is a red-herring.  Pressed-steel dishes are used for Ku-band and C-band satellite service.  

I have a friend in Florida who is using one of these solar-cooker dishes for satellite work, and is about to use it for H1--he noted no particuarly
  problem for L-band satellite work.

There are a few people in the EME community using them successfully also, and I set-up a young student with one in the early winter locally.

To view this discussion visit https://groups.google.com/d/msgid/sara-list/39099869-49d2-401f-a4a9-baba826c5189n%40googlegroups.com.

[Stephen Arbogast]

If we    consider boundary  conditions  on   the surface  a  steel dish of  course    there  will be some reflection  but  how  much ?   

[Stephen Arbogast]

Is your  friend's  solar cooker a  good parabola?

[Marcus D. Leech]

On 2026-06-16 00:43, 'Stephen Arbogast' via Society of Amateur Radio Astronomers wrote:

Is your  friend's  solar cooker a  good parabola?

Seems likely, given his satellite success.

To view this discussion visit https://groups.google.com/d/msgid/sara-list/c332a0dc-c31a-4e89-94ae-cf2ce6e0dbc0n%40googlegroups.com.

[Stephen Arbogast]

Is it the  same one  that Andrew is  using?

[Marcus D. Leech]

On 2026-06-16 00:54, 'Stephen Arbogast' via Society of Amateur Radio Astronomers wrote:

Is it the  same one  that Andrew is  using?

I have no way of knowing that for sure.

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[Marko Cebokli]

The requirements for a radio reflector are similar to the requirements for an optical telescope mirror, say 1/8 wavelength. So for 21cm, the reflector needs to deviate less than 2.5cm from an ideal prarabola.

Steel is OK as a radio reflector, most satellite TV dishes are made of steel - you can see the old ones slowly rusting. A semi conductive paint (metal particles) could eat some signal, don't know how much, since I never encountered an antenna painted this way.

A good solar reflector with a 1m focal distance, should focus the Sun into a 2cm diameter spot. Less than that, if the focal length is shorter. I guess the cooker intentionally deviates from a parabola, to avoid burning a hole into your steak!

Marko Cebokli

16.06.2026 06:43, je 'Stephen Arbogast' via Society of Amateur Radio Astronomers napisal

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[Stephen Arbogast]

I disagree..    If you consider   boundary  requirements  at the surface  of  any metal  for  reflection of E&M  you will  find steel is  less  performant but if the   power is  high enough  from  satellites  then no  problem. We   are dealing   with  very  weak signals  from  hyper fine transitions  of neutral  Hydrogen  atoms...   We need  to consider  the entire link equation.

[Marcus D. Leech]

On 2026-06-16 01:16, 'Stephen Arbogast' via Society of Amateur Radio Astronomers wrote:

I disagree..    If you consider   boundary  requirements  at the surface  of  any metal  for  reflection of E&M  you will  find steel is  less  performant but if the   power is  high enough  from  satellites  then no  problem. We   are dealing   with  very  weak signals  from  hyper fine transitions  of neutral  Hydrogen  atoms...   We need  to consider  the entire link equation.

...and, as I said earlier, there are several radio telescopes in the world that use a steel surface.   It's a red herring.  My first, 1.5m, radio telescope was a steel dish.
   It worked just fine, and performed roughly as theory would predict for 1.5m reflector.  This was over 20 years ago.    Since then, I've used 1m offset steel dishes
  for H1 work.  Worked just fine.

Also, H1 isn't "very weak" (at least compared to other astrophysical 'signals').    It varies over the sky from about 10K to almost 100K in brightness temperature.
  That's "boatloads" compared to other types of emissions you might want to look at.

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[Stephen Arbogast]

Grab  a  copy  of   Jackson, Classical  Electrodynamics,    and do the    Physics  for   boundary value problems..  Steel  is  not  a good conductor/reflector..     and yes  you  are  more the Engineering   type ..  I  get caught up on Physics   Theory

[Sławomir Klimek]

 To be fair, the exact same dish is used for EME with success

https://www.facebook.com/groups/1671017662924655/posts/28254766674123059

To view this discussion visit https://groups.google.com/d/msgid/sara-list/175c6b5f-9fca-4904-a970-8f33fbffb6afn%40googlegroups.com.

[Stephen Arbogast]

But  show us   your  link   equation... how much  power  are you  transmitting  and  how much power are  you  receiving?   Please  report  the details  of  your system...

[Stephen Arbogast]

Your  set up  looks cool!

[Sławomir Klimek]

not my setup. I've only seen it many times on FB groups

To view this discussion visit https://groups.google.com/d/msgid/sara-list/ad339870-a2fc-435e-88e7-1a266110f861n%40googlegroups.com.

[Sławomir Klimek]

feed documentation:
https://onedrive.live.com/?redeem=aHR0cHM6Ly8xZHJ2Lm1zL2YvYy80NjVlMGY4NDEyNmQ5ZTJmL0lnQ012Q2RjeU5hSFNvMzkwcGVCT3NpeUFkODdiVURqMTR0dHRSRmVZQlpINm1RP2U9bEd6Y0t0JmZiY2xpZD1Jd1kyeGphd1NkeHNSbGVIUnVBMkZsYlFJeE1BQmljbWxrRVRFNE5IWlRhRlpFUkZaRFYwbEplRFp6YzNKMFl3WmhjSEJmYVdRUU1qSXlNRE01TVRjNE9ESXdNRGc1TWdBQkh0TDdmaVVpaXUwUUItamhVdUJ2YktBNUNvb2JMV2xPaGpjLW9pNC03WWZHTzRRRXZnZ1BZby1KQWFHbl9hZW1fTzZITGY2UXdRUTIwRkN0N2RRNzJGQQ&id=465E0F84126D9E2F%21s5c27bc8cd6c84a878dfdd297813ac8b2&cid=465E0F84126D9E2F

[Alex P]

a Galvanized Steel scalar-mode choke on a cylindrical feedhorn and a very small H Line System

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

Alex Pettit

[Stephen Arbogast]

Steel is  a  moderate conductor  of electricity......   Yes it works

See   https://www.google.com/search?client=ubuntu-sn&channel=fs&q=is+steell+a++god+conducter

Show  your   link  equation   for   your  design...

[b alex pettit jr]

"  link  equation  "  ???   please restate request

[Robert Meade]

Andrew,

Did you try with the discovery feed on this dish or just the loop and cantenna feeds?

- Robert 

[Stephen Arbogast]

Here  is  an explanation of  the link equation used  in telecom  ..... gives  you an idea of what  we  are  dealing  with........things to think about...   https://www.google.com/search?client=ubuntu-sn&channel=fs&q=link+equation

[Stephen Arbogast]

I can't make it to  Eastern Conference  but I just  signed  up for  online  .....

[Andrew Thornett]

I didn't try rhe Discovery feed. Id just had enough of it not working and gave up!

Andy

Sent from Outlook for Android

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From: 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Tuesday, 16 June 2026 08:03:49
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

To view this discussion visit https://groups.google.com/d/msgid/sara-list/e60c5013-70eb-4d8f-9693-73878d82171an%40googlegroups.com.

[Andrew Thornett]

https://www.astronomy.me.uk/what-is-the-link-equation-also-known-as-the-link-budget-equation-and-how-does-it-apply-to-amateur-radio-astronomy

Sent from Outlook for Android

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From: 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Tuesday, June 16, 2026 8:03:51 am
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

To view this discussion visit https://groups.google.com/d/msgid/sara-list/e60c5013-70eb-4d8f-9693-73878d82171an%40googlegroups.com.

[Andrew Thornett]

If at some point the SARA board agreed to hold a SARA conference outsode of the USA, where would you all like to go (or more importantly where would you like to go so much that youll pay to go there?

Andy

Sent from Outlook for Android

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

Sent: Tuesday, June 16, 2026 8:29:43 am

To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

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[Peet Denny]

Jodrell Bank! :) 

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[b alex pettit jr]

The problem with this Communication Link Budget equation

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

And this "Radio Astronomy" derivative :

is that they disregard  Ground Noise Spillover which is a significant performance factor in radio astronomy signal reception.

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

I have never calculated the Tsys for any of my antennas as the value assumes ideal electrical and mechanical fabrication is employed.

Measurement is difficult.   The classic "S7" Calibration Standard is too small a Reference Source for wide beam width antennas ... 

I have used Dec+40deg @ RA20:30Hrs for my comparisons and hardware optimization.

Their Hline Signal level over Cold_Sky Noise performance is usually quite high. 

They of course lack the angular resolution of larger aperture systems.

Regards,

Alex Pettit

[Andrew Thornett]

Hi Alex,

I am really pleased you have sent this message. Recently I have been exploring Tsys and trying to understand it.

So your thoughts come at the ideal time for me. I am going to spend some time thinking this through. 

Andy

Sent from Outlook for Android

---

From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Tuesday, 16 June 2026 10:44:23
To: 'Andrew Thornett' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

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[b alex pettit jr]

This is the most important takeaway :

Tsys values assume ideal electrical and mechanical fabrication techniques are employed.

Alex

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

[b alex pettit jr]

And understanding what that even Means is not trivial.

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

[Andrew Thornett]

Yes I noticed that, and that the issue it raises is more relevant to small telescopes with wide beamwidths.

I also noticed the missing effect of ground noise spill-over, although couldn't it be argued that is incorporated in the term reflecting losses in receiving equipment?

Andy

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Sent: Tuesday, June 16, 2026 11:13:05 am
To: 'Andrew Thornett' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

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[Marko Cebokli]

Satellite TV also runs at very small signal margins, because the dishes are made as small as practical. If there was a considerable difference, the sat TV dish makers would use a material, that would enable them to make smaller dishes, because small size is a big selling point.

Of course, you would not make a high-Q resonator from steel, but for an antenna reflector, where you have only a single reflection,  it would be very hard to measure the difference between a steel and a aluminium (or even silver) reflector, on an antenna test site.

A similar comparison can be made in visible light - do you find a polished steel ball bearing ball much less reflective than a silver mirror?

Marko Cebokli

16.06.2026 07:36, je 'Stephen Arbogast' via Society of Amateur Radio Astronomers napisal

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[Andrew Thornett]

Hi Stephen, 

I suspect those are two of the 3 really good reasons why my solar cooker RT (and by implication the large number of steel petal satellite dishes on sale of various sizes) doesn't work well. 

The 3^rd one is flexure.

I am going to perform a simple test- i have been given an 140cm communications dish (the real McKoy) which used to adorn the side of an university physics dept building.

I am going to install that and if that works well 1^st time then it will demonstrate that maybe we ought to stay away from solar cooker dishes!

Having said that, please could I ask owners of petal dishes on this group (and especially solar cooker dishes) to respond to this post with their opinions on how well the dishes work, ideally with some plots.

I do not wish to denigrate them all if others are finding they are working well.

I realise that I may just have had a bad specimen. And one does not make a good sample!

Andy

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---

From: 'Stephen Arbogast' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Monday, June 15, 2026 11:29:37 pm
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

Well.....  I did the usual   Googling and ChatGPT   and found that  steel is not a good conductor and a solar cooker may not  be a good parabola.

[b alex pettit jr]

This might be a 'simple' project on which to develop  experimental testing techniques.

Calibrate  Quantify  Compare  Correct

Tuning : 

===========

Learn to use a nano VNA & experiment with the size & spacing of the 3 elements

Operational Evaluation

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

I've verified the calibration of SDR# & IFavg.

Signal calibration means referencing the HLine amplitude to Cold_Sky

Compare the calibrated results to another condition, make a guess

Correct .. then repeat the cycle .. plot spectra

no fancy 3D plots or maps ..just Spectra w/ Calibrated Y axis vs Frequency X axis

Save the IFavg data & plot in Excel ( or equiv )

Alex Pettit

[Marko Cebokli]

Here is a table of reflective properties of various metals at 2GHz:

https://ssi.org/wp-content/fbs/sps-wifi-usdc-1980/22/#zoom=true

so, no need to loose any sleep over a steel dish.

Just for fun, I did a simple measurement. I connected an X band coax to waveguide adaptor to my HP8720, and measured the reflection, when covering the WG flange with various metals. (Copper-unetched PCB material, aluminium-just a machined box that was handy, steel-a (slightly rusty) hacksaw). The difference was less than 0.05dB, probably mostly due to non-ideal surface contact. NOTE - to do such a measurement, you need to tighten all of the connectors to the prescribed torque, and fix the adaptor in a vise, so that the coax cable does not move during measurement. Otherwise, the measurement will "dance" tenths of a dB.

Andy's dish looks quite warped in one of the photos - but there it is already lying on the ground, so the warp could be a result of a rapid disassembly...

BTW Satellite TV is in fact more critical about RF losses, because the digital demodulators have a very non-linear, threshold type behavior. A small loss can cause a big increase in BER (Bit Error Rate), a few dB can be the difference between a clean picture and no picture at all. A radio telescope is a linear device - a dB lost at RF will be the same dB on the graph, no more.

Marko Cebokli

16.06.2026 12:25, je Marko Cebokli napisal

To view this discussion visit https://groups.google.com/d/msgid/sara-list/bc16bc6b0d90d8377ec4c4f9c16a84d7%40hamradio.si.

[Marcus D. Leech]

On 2026-06-16 10:22, Marko Cebokli wrote:
>
> Here is a table of reflective properties of various metals at 2GHz:
>
> https://ssi.org/wp-content/fbs/sps-wifi-usdc-1980/22/#zoom=true
>
> so, no need to loose any sleep over a steel dish.
>

Thanks, this is consistent both with my experience and with other
articles I've read in the past.

If you look at the reflectance loss for Al and Fe alloys, it *looks*
like a 38% reduction in reflectivity, *relative to Aluminum*, however,
in absolute terms, they're
  both negligible.  It's a bit like comparing medical-condition risks
for things where the risk is already very very low.    A 30% increase in
risk against a baseline
  risk that's, let's say, 1.5e-5, means very little on an individual
basis...

[andrew....@googlemail.com]

So, this means that a dish steel is nearly as good as an aluminium dish? So the problems with my solar cooker RT were nothing to do with the material it was made of?
Andy

-----Original Message-----
From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Marcus D. Leech
Sent: 16 June 2026 17:07
To: sara...@googlegroups.com
Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

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[Robert Meade]

Yes, there's nothing significantly wrong with a steel dish from a material perspective. I would strongly expect a dish shaping issue and ground noise spillage. Did you try the discovery feed with this dish and get similarly bad results? 

To view this discussion visit https://groups.google.com/d/msgid/sara-list/000001dcfdb9%246fd35450%244f79fcf0%24%40googlemail.com.

[andrew....@googlemail.com]

I didn’t try it.

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[Don Latham]

Yup.

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

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[Andrew Thornett]

I am very happy swapping out the solar cooker as I have a far better communications dish I can use. I do have an unused Discovery H-Line feed ao I am going to see if I can use that with the new dish.

Andy

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From: 'Don Latham' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Tuesday, 16 June 2026 22:23:39
To: sara...@googlegroups.com <sara...@googlegroups.com>

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[Don Latham]

what they said

------------
Don Latham
PO Box 404,
Frenchtown, MT, 59846
406-626-4304

-----Original Message-----
From: Marcus D. Leech <patchv...@gmail.com>
To: sara-list <sara...@googlegroups.com>

Date: Tuesday, 16 June 2026 10:06 AM MDT
Subject: Re: [SARA] Death of the LRO-H2 Solar Cooker Radio Telescope

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[Robert Meade]

I wonder if you tried simulating the feed you used and what surface shape you think the dish had what theoretical ground temp spillage temp would be. Maybe the cantenna feed was spilling over way too much. I had that issue at first with my solar cooker dishes.

I was able to verify +6dB performance on GOES reception moving from discovery dish to the solar cooker with the same feed though. So I doubt the aperture was that badly shaped in my case. Theoretical diff should be 6.6 dB improvement. 

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[Stephen Arbogast]

Sorry  I  caused  a stir.    Yes  the difference between aluminum and  steel  is insignificant for  Engineering.

[Marko Cebokli]

The main advantage of the discovery feed is the built in LNA, avoiding the connector and cable losses. Also possible mismatch losses in a homemade feed, made without suitable test equipment. Otherwise, a dipole feed is not that great, its main advantage being a small shadow, which is important on a small dish.

Marko Cebokli

16.06.2026 22:28, je andrew.thornett via Society of Amateur Radio Astronomers napisal

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[Andrew Thornett]

I tell you what - my wife is MUCH happier with this new dish and feed, and that matters when you have 4 radio telescopes in the garden not including meteor antennas etc......

Amdy

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From: sara...@googlegroups.com <sara...@googlegroups.com> on behalf of Marko Cebokli <s57...@hamradio.si>
Sent: Wednesday, 17 June 2026 06:04:09
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[andrew....@googlemail.com]

I presume, Robert, that the solar cooker dish was significantly larger than the Discovery Dish: 70cm à 150cm ?? You said the feed was the same – ie the Discovery feed ??

Also, out of interest, when you put the Discovery feed on the solar cooker dish, what distance did you set up from where the stalk hits centre of dish to other end of stalk?

Andy

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[andrew....@googlemail.com]

I don’t have any simulation software – what do you use? Is it expensive?

Andy

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[Robert Meade]

Yes. You have the sizes correct. The 25cm 1.25" PVC placement is with the end of the pipe flush against the end of the 3d printed plastic component backside chamfers. Then the DD feed was at I think the 160cm mark for 1.68 GHz GOES reception and 140cm for HI line aligned to the top edge of the 1.25" to 20mm pipe adapter small diameter side. Those were both distances I empirically optimized for max SNR on the signals of interest. 

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[Robert Meade]

Try Ticra tools student edition for this application. Py Physical Optics could also work (PyPO) but has a much steeper learning curve. Thus likely won't work well for a dipole feed vice horn/waveguide.

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[andrew....@googlemail.com]

This has been a very interesting conversation – thanks to everybody who has contributed to it.

Andy

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[Marcus D. Leech]

On 2026-06-17 18:17, andrew.thornett via Society of Amateur Radio Astronomers wrote:

This has been a very interesting conversation – thanks to everybody who has contributed to it.

Andy

A couple more points.   The focal point of a parabolic reflector, measured from the vertex, is:

d*d/16*D

Where 'd' is the diameter and 'D' is the depth.

Now, as far as I know, a parabola like that will have a focal point, per se, that is largely independent of frequency.  But what *DOES* change is that any given
  feed antenna, and any given frequency, will have a phase-center that moves around with both frequency and antenna design.   So, that can give the impression
  that the dish focal point is moving around, depending on frequency.   It's the feed--the phase center of the feed antenna has to intersect the focal point for
  best performance.

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