Re: [amsat-bb] sattiquette/ Mode B and the human factor

[Bob Bruninga <bruninga@xxxxxxxx>]

On Sat, 13 Apr 2002, Drew Glasbrenner wrote:

> I ... do not think this new LEO is the desire or in the best interest of
> the general membership or the future of Amsat-NA. If someone thinks it is,
> I'd like to hear your reasoning.

The problem with mode J FM easysats as you mention is that the uplink is
20 dB easier than the downlink.  Thus any LID can hit it (and jam
everyone on the uplink)  while not having a clue what he is doing because
he can't hear it!  The uplink is the "easy" part.  The downlink isnt!

If you flip it over and do mode B easysats, however, then the downlink is
9dB stronger and the uplinks are about equal.  Any idiot can hear it and
should at least hear the damage he is doing...

Here is where the 20dB comes from:
1) To omni antennas, UHF has 9 dB greater path loss than 2m
2) Satellites can rarely afford over about 4 watts for the downlink
3) Users easily have 50 watts.

So for mode J:
   VHF uplink  50W. (+11dB)  Path loss   X -0dB
   UHF Downlink 4W. (  0dB)  Path loss   X -9dB
   --------------------
   Uplink to downlink difference 20 dB!

Mode B:
   UHF uplink  50W  (+11dB)  Path loss   x -9dB
   VHF downlink 4W  (  0dB)  Path loss   x -0dB

   Uplink to downlink difference  2 dB! and is 9 dB stronger!

So in my opinion, EZsats should be mode B.

de WB4APR, Bob


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