Re: [amsat-bb] Re: Why preference for mode J?

[tlang@xxxxxxxxxxxxxxxxxxxx (Tony Langdon)]

Hello Bob.

30 Jul 00 00:07, you wrote to All:

 BB> About 9 dB to an omni receive antenna.  This is why it is so much
 BB> easier to receive a satelltie mobile or at home with an omni antenna
 BB> if the weak downlink is on 2 meters.  There is a 9 dB advantage.  This
 BB> is why we are advocating a 2m downlink for our mobile statellite APRS
 BB> system.

Yes, this is true.  Also, 2m antenna systems on most (terrestrial equipped)
fixed stations tend to have a broader main lobe, as they are usually lower gain
than their 70cm counterparts.

 BB>
 >> receiving 435 MHz here in the Los Angeles is much easier than 2M due
 >> to the much lower noise floor.
 BB>
 BB> Conversly, of course, if you are going to track the satelite in AZ and
 BB> EL anyway, then it is easier to have a gain antenna on UHF then on
 BB> 2 meters...  So it all depends on the mission...

Indeed.  I've found that 2m gives consistently stronger reception, though 70cm
gains more improvemt from the use of a beam antenna, whoch is as expected.

Tony

.. ! Air Glue: Just the thing for broken wind!
--
|Fidonet:  Tony Langdon 3:633/284.18
|Internet: tlang@freeway.apana.org.au
|
| Standard disclaimer: The views of this user are strictly his own.


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