[amsat-bb] Re: sun noise and other natural noise sources

Michael Heim kd0ar at sbcglobal.net
Thu Sep 4 15:15:13 PDT 2008

Thank you, Domenico for the information,

A lot of reading and study on this is in order.  I'm probably different from many microwave ops, as I started high and am working down in frequency, hi.  well, sort of, as I was on 1296 before I was on 10 GHz.   I used the sun noise calculations that you gave, Domenico, as referred to me by another microwave op (for 10 GHz).  Basically he directed me to a website, of which I do not remember, but you were quite correct, I measured 5-6 dB on 10 GHz using my 60 cm offset fed dish.  I am still relatively new to 10 GHz, being only active since last summer.

Without doing a lot of study, (of which I plan to do anyway, when I get the time to do so), you answered my question, and that is no, I will not see enough of a change in the noise floor (when aimed at the sun) with the antenna gain that I am using to be able to measure, however I should see an increase in the noise floor when aiming at a warm body, ie the earth, or perhaps some object such as a tree, building, etc.

Anyway, that's what I was looking for, a way to test what I have using simple means (and my not having a calibrated signal source).

I HAVE checked the converters using a signal source at a friend's shack, but the unit with the antenna attached  we couldnt, of course make a meaningful measurement.  So I know the frequency is correct, not an image, and the LO is calibrated well enough that I shouldnt have any problem finding the bird once it comes online in mode S.

So I will consider that if I point from cold sky to earth, if I see a change in background noise, things are probably working.

 Michael Heim
Chief Engineer, Forever Broadcasting
New Castle PA
Chapter Chair, SBE-122

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