Lunar Rover Antenna Feed ?

[Alex P]

Can anyone identify the design of the Feed on this ?

[Steve Hallman]

This is the comm antenna on the Apollo lunar rover ...

https://airandspace.si.edu/collection-objects/lunar-roving-vehicle-qualification-test-unit/nasm_A19760746000

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On Thu, Mar 19, 2026, 3:17 PM 'Alex P' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

Can anyone identify the design of the Feed on this ?

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[b alex pettit jr]

I understand that .. Is the top plate a reflector  ?

[flavio camacho]

Looks interesting, maybe a protector for heavy radiation or some sort of heat sync or cold plate. 

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[flavio camacho]

Or maybe an assembly and deploy retainer. 

[Steve Hallman]

I think the top plate is a retaining bracket for the reflector when it's stowed ... There are 10 indentations around it's circumference, one for each of the 10 support ribs in the reflector.

Steve

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On Thu, Mar 19, 2026, 4:19 PM flavio camacho <flavioc...@gmail.com> wrote:

Or maybe an assembly and deploy retainer. 

On Thursday, March 19, 2026, flavio camacho <flavioc...@gmail.com> wrote:

Looks interesting, maybe a protector for heavy radiation or some sort of heat sync or cold plate. 

On Thursday, March 19, 2026, 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

I understand that .. Is the top plate a reflector  ?

On Thursday, March 19, 2026 at 06:43:19 PM EDT, Steve Hallman <1sal...@gmail.com> wrote:

This is the comm antenna on the Apollo lunar rover ...

https://airandspace.si.edu/collection-objects/lunar-roving-vehicle-qualification-test-unit/nasm_A19760746000

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[flavio camacho]

Copy the numbers tells the story. 

On Thursday, March 19, 2026, Steve Hallman <1sal...@gmail.com> wrote:

I think the top plate is a retaining bracket for the reflector when it's stowed ... There are 10 indentations around it's circumference, one for each of the 10 support ribs in the reflector.

Steve

Miracles of Science... Benefiting all Humanity

On Thu, Mar 19, 2026, 4:19 PM flavio camacho <flavioc...@gmail.com> wrote:

Or maybe an assembly and deploy retainer. 

On Thursday, March 19, 2026, flavio camacho <flavioc...@gmail.com> wrote:

Looks interesting, maybe a protector for heavy radiation or some sort of heat sync or cold plate. 

On Thursday, March 19, 2026, 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

I understand that .. Is the top plate a reflector  ?

On Thursday, March 19, 2026 at 06:43:19 PM EDT, Steve Hallman <1sal...@gmail.com> wrote:

This is the comm antenna on the Apollo lunar rover ...

https://airandspace.si.edu/collection-objects/lunar-roving-vehicle-qualification-test-unit/nasm_A19760746000

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[b alex pettit jr]

THAT is probably the purpose !

I posted this that it might be a useful mod for RA .. not so.

Thanks Steve.

- Alex

[Steve Hallman]

Your welcome Alex ...

You're one of the SARA people who has inspired me to explore Radio Astronomy with your focus on experimentation and measurement ... thank you

Steve

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[b alex pettit jr]

Thanks  :)

glad to assist ...

My career was in instrumentation & analysis of aerospace systems .. 

Attention to the small details was the key to success.

Alex P

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

[Steve Hallman]

Alex

Sounds like we may have similar backgrounds ... 

Keep up the good work ... I've been following your loop feed efforts with great interest 

Steve

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[b alex pettit jr]

Hi Steve,

Are you familiar with this collection of  RA info ?

https://github.com/AP-HLine-3D/HLine3D

If I can assist, just Ask .

Alex

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

FYI : I compared the performance of the Loop Feed vs Cantenna ...

They each work fine .. just need TLC in tuning & careful dish<>feed positioning 

Alex

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

[Steve Hallman]

Hi Alex;

I have only seen your multiple YouTube videos, but I have been using SDR# w/ IF Avg.

Your Yagi antenna was quite interesting, and I spent several week studying how they work ... Good Fun

I settled on calibrating a small Discovery Dish, measuring it's Beam FWHM, Responsivity (to convert IF Avg output into Brightness Temperature), and measuring it's noise level in RMS Kelvin.

Are you still working on loop antenna feeds ?

Thanks Steve

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[b alex pettit jr]

Hello Steve,

The Loop_Feed is optimally defined. I've made many of them.

Have you seen this PPT of my eval of the DiscoFeed W/ Nooelec 1m x 0.66m Dish ?

https://github.com/AP-HLine-3D/HLine3D/blob/main/21cm_Step1b_KrakenDiscoveryFeed_Eval_05.pdf

Its performance Significantly exceeds the Nooelec H1 Dipole & Dish  [ current Scope in a Box ] .

Alex

[flavio camacho]

Hello may I interrupt and kindly ask how to construct a feed loop for a 6 feet disk. Thanks. 

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[fasleitung3]

There is a youtube video which exactly demonstrates this purpose: https://www.youtube.com/watch?v=Gbc2rGrbeek

..and BTW, it was used in S-Band.

Wolfgang

[flavio camacho]

Thank you much. 

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[b alex pettit jr]

Hello Flavio,

Here is the basic concept for small dishes  w/ LNAs having SMA input connectors

At 6 ft dia, you could consider a cantenna w/ choke ring for better performance with ( I presume ) a higher f/D dish

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

Alex Pettit

[flavio camacho]

Ok I will review all carefully. I noted you mention a higher f/D. If I remember that the dimensions to set the loop feed at the focus. 

On Friday, March 20, 2026, 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

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[b alex pettit jr]

Yes , But Also 

1) Yes, the dimensions do determine the focal location

2)  The higher the f/D the smaller angle it subtends at focus and the need for a more narrow beam-width feed 

f/D = 0.25

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

f/D = 0.50

Alex

[flavio camacho]

Hooray, got it. Thanks. 

On Friday, March 20, 2026, 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:

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