Discovery Dish Enhancement Test

[Alex P]

This would be an interesting experiment:

Test the increase in performance of the Kraken Discovery Dish 

by Extending the perimeter 15cm 

This changes the f/D ratio from 0.35 to 0.25 which should

1) Provide added RFI Shielding

2) Reduce the Ground Noise Spillover improving the S/N

3) Slightly narrow the Beam Pattern ..

Aluminum window screen would work.

Use some software which can generate calibrated plots such as SDR# & IF_Avg for

comparisons. 

[andrew....@googlemail.com]

Hi Alex,

 

How important would it for people following this suggestion to ensure that the additional “dish” followed the parabola of the original dish, or is it OK at edges like this to simply add a flat panel?

 

What sized holes in the chicken mesh can be accepted for H-Line/ I am sure that was discussed in past on this mailing list but I can’t find it(!)(….Sorry!)

 

Andy

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[b alex pettit jr]

Hello Andrew,

Good Questions 

1) Any shape which  extends  the sides to "shield the feed' should have the most noted improvement

as Ground Noise Spillover is probably the most detrimental issue.

2) Mesh ?  Max maybe 1/20th of the wavelength = 10mm

3) A more accurate approximation of the parabola will improve the beam-width, but that is the least significant parameter.  #1 is Spillover 

4) Reduction in RFI may be another benefit, but that is entirely related to the direction of the signal wrt the positioning of the dish

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

On my WiFi, I  'followed the curve' on the long axis, but just extended the short sides without particular regard to the shape.( just made it look nice )

I've yet to see another system match the performance.  The main benefit of this was Ground Noise Reduction.

In this instance : Perfection is Not Required   

              Alex

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

[b alex pettit jr]

From my 2022 Presentation

( Notice the Reduction in Ground Noise Level, the Increase in H Line Amplitude, and the Reduction of Noise on the Signal )

Alex

[Andrew Thornett]

Does that mean, Alex, that any larger dish will give the improved ground noise effect, or that it requires a dish to be enlarged beyond it's original design specs?

Andy

Sent from Outlook for Android

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From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Sent: Wednesday, December 3, 2025 11:04:23 AM
To: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] Discovery Dish Enhancement Test

 

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[b alex pettit jr]

Its related to the Feed Beam Pattern and the Shape ( f/D Depth ) of the dish.

"All" f/D 0.35 dishes perform similarly regardless of diameter

When it is impractical to install a large choked cylindrical Feed to narrow the beam, 

the next option is to DEEPEN the dish as a Shield.

Look at the Depth of this 12 meter dish  !! Looks like it was build as an f/D 0.25 

Alex

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

[b alex pettit jr]

[Andrew Thornett]

Thanks for clarifying all that.

Sent from Outlook for Android

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From: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>

Sent: Wednesday, December 3, 2025 12:21:49 PM

To: 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: Re: [SARA] Discovery Dish Enhancement Test

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[b alex pettit jr]

Not sure that posted properly