[Moon] Fwd: [Moon-Net] What to expect for 2.8M dish 1296 for Sun noise/Cold sky noise?

[DW Harms (Dick)]

Forwarding my answer to Steve, as it may be of interest to others.

73, Dick PA2DW

Verstuurd vanaf mijn iPad

Begin doorgestuurd bericht:

> Van: "DW Harms (Dick)" <qtc at kpnmail.nl>
> Datum: 17 juni 2019 09:06:00 CEST
> Aan: SteveB <eagle572 at comcast.net>
> Onderwerp: Antw.: [Moon-Net] What to expect for 2.8M dish 1296 for Sun noise/Cold sky noise?
> 
> Hi Steve,
> 
> The sun noise is very much depending on the solar activity, thus the measured level can vary from day to day. 
> A good way to calculate the sunnoise that you can expect, is to use the fenominal software that Doug VK3UM (SK) developed. Though Doug sadly passed, his software is still being maintained. Check http://www.vk3um.com/
> It looks complicated at first glance, but you dont need all parameters. During the recent EME-meeting in Orebro/Sweden, Peter G3LTF presented a good way to simplify the use of the programm. The presentation can be found on www.moonbouncers.org
> 
> If you still have lower noise than VK3UM predicted, you have to start suspecting your feed and cables. Most likely the feed, positioning and performance. Start by measuring return loss and check illumination by pointing to the sun and see if the noise varies if you shift a plate of 40 by 40 aluminium plate over the edge of the dish. If you see variations in noise, you are overilluminating. Else you might not illuminating the whole surface, so do a thorough check of the feed position.
> 
> Wish you succes!
> 
> 73, Dick PA2DW
> 
> Groet, Dick
> 
> Verstuurd vanaf mijn iPad
> 
>> Op 17 jun. 2019 om 06:19 heeft SteveB via Moon-net <moon-net at mailman.pe1itr.com> het volgende geschreven:
>> 
>> Today, I tried to see if my repaired 1296 2.8M dish system would show a reasonable amount of sun noise.
>> 
>> A (General Radio 1216 meter) measurement used an external  down converter to 28 MHz from the 1296 IF frequency of 144 MHz.
>> 
>> The measurements showed a  relative difference between sun (+8dB) and cold sky( +3 dB) = 5 dB difference. A hot load (termination) showed +4.2 dB above cold sky.
>> 
>> Today's 1296 adjusted SFU was 42, and the 10. cm Flux was 66 (a quiet sun). The sun was in front of Taurus-A, which should have contributed only a small amount of noise to the sun measurement.
>> 
>> For 3M dishes, I have seen recently published sun noise numbers from 8 to 12 dB during this quiet sun interval.
>> 
>> Question: Since my dish is 2.8M, why won't it  show much more than the 5 dB measured today? The dish pointing was verified by a vidcam with sun filter and the AZ and EL positioning was peaked using the GenRad 1216 meter deflection.
>> 
>> Clueless in Tucson DM42
>> 
>> Steve Bell KJ7OG
>> 
>> 
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