Scope-in-a-box antenna shape
Conrad Cardano
Alex P
Conrad Cardano
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Andrew Thornett
Sent: Friday, March 6, 2026 2:23:47 PM
To: Society of Amateur Radio Astronomers <sara...@googlegroups.com>
Subject: [SARA] Scope-in-a-box antenna shape
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b alex pettit jr
Conrad Cardano
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andrew....@googlemail.com
Alex makes excellent points – I hadn’t thought of the long access along the slots on the mesh dish, and Alex has previously in his experiments demonstrated that reducing ground noise spillover (radio waves bouncing onto dish from ground/trees/adjacent house and out-buildings, your car parked close by, etc.) is one of the best improvements that ana amateur can make – I have myself just taken delivery of some aluminium mesh for this exact purpose.
Andy
From: sara...@googlegroups.com <sara...@googlegroups.com> On Behalf Of Conrad Cardano
Sent: 06 March 2026 21:58
To: sara...@googlegroups.com
Subject: Re: [SARA] Scope-in-a-box antenna shape
Thank you all.
I appreciate your advise and helpful comments!
Conrad
On Friday, March 6, 2026, 'b alex pettit jr' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:
Extending of the narrow dimension reduces Ground Noise Spillover ( S/N degradation )
As the slots are 28cm in one axis, this is another source of Ground Noise Feed-Through
Covering the slotted dish surface with Aluminum Screen is also beneficial.
Alex
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On Friday, March 6, 2026 at 02:09:14 PM EST, 'Andrew Thornett' via Society of Amateur Radio Astronomers <sara...@googlegroups.com> wrote:
We use drift scanning when we use these antennas. This is where the antenna is pointed in a direction and left there for at least 24 hours but could be much longer. As the Earth rotates, the software extracts each data point on the 360 degree azimuth circle. As long as the long axis of the antenna is directed east-west, then the resolution of the antenna reflects that length.
Completing the circle of the antenna increases detection area which increases signal amount detected in given time, but does not increase resolution, as long as the long axis is orientated east-west during drift scans.
The size of the holes in the grid is not a problem as long as they are << wavelength, traditionally we say fine as long as < 1/10 wavelength, so on this case < 2cm - although I don't know whether that rule of thumb can be more accurately defined.
Andy
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