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Re: High Noise Levels on UO14 and SO-50



> Noticed high noise levels on UO14 and SO-50 again today.

Now THAT is something that individual AMSAT members can do to help the
cubesat designers.  That is, we need a "gouge sheet for receiver noise
power on various satelite bands" in different areas.

Since AMSAT members can frequently hear down to the noise floor, we need
to use thse receivers to establish what is the common noise floor in a
suburban environment.  Particularly, I am interested in 10m and 2m since
these bands are the most vulnerable to extrnal noise, and at the same time
have the least "path loss" to omni antenna receivers.

Reading the literature can suggest noise levels of thousands of degrees,
and there is great fluctuation on 10m depending on the ionosphere.  When I
have asked these questiosn before, I get lots of opinions, but little
measurable quantifiable numbers.

What Id like to see is a useful table comparing atmospheric noise with
the thermal noise floor in dBm at 300K and 3 KHz bandwidth:

BAND  Thermal Worst Typical least
----  ------- ----- ------- -----
70cm  -141
 2 m  -141      ?      ?      ?
10 m  -141      ?      ?      ?

Since 2m has 9 dB less path loss than 70cm and 10m has 14 dB less path
loss than 2m (to OMNI antnenas), the advantages of the lower bands for
lower powered cubesats are obvious, but ONLY if all that gain is not lost
in higher atomspheric noise power.

I'm sure someone has studied this, and it would be nice to have real
figures from measured conditions, rather that basing it on the wide
variables I have seen in the literature...  I do not count man-made noise
as that can be orders of magnitude variance and does not afect everyone at
every location.

bob


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