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Thoughts on future "FM birds" (was: proposal for maximizing fm leo contacts)



> >> As the FM LEO satellites are used by many to simply say hi to their
> >> friends and there are many that do not care for collecting 
> grid squares,
> 
> How many times in a day do two people need to say,
> 
> "Hi Joe.  How you doing."
> "Fine Jim.  Just fine.  How's the gout?"

Good point. :)

> Seriously, there are some people that say hi to the same 
> folks nearly every
> pass.    They should really be asked to rag chew on a different bird.
> Perhaps we need more than a single channel FM bird if people 
> really want to
> limit their satellite contacts to FM.

Well, ideally, the linear birds are better suited to longer ragchews, as
they have inherently greater traffic capacity, but perhaps more FM
transponder space might be a good idea.  Only trouble is that there are only
so many channels, especially in the 2 metre band), that too many birds
floating around up there might cause all sorts of traffic conflicts.
Already, there are occasional conflicts between UO-14 and some of the
digital birds on the 2m uplinks.  70cm is pretty right, we have 3 MHz of
space to play with, but the lower bands have narrower satellite segments
(typically 200 kHz, or 1/15th of the space available on 70cm).

Perhaps we need to investigate other possibilities.  I'll throw a couple of
ideas into the ring.

1.  23cm uplinks.  - This would make it difficult for portable stations, due
to the higher Doppler shift, increased free space losses (but 23cm antennas
can have a heap of gain to compensate), and the low Tx power of most (all?)
HTs up there (typically 1W).  However, my gut feeling is that this is quite
feasible, if one takes the time to build a decent Yagi for the band.  

2.  Cross-mode satellites.  For example, 70cm FM up, 10m SSB down.  Combines
the ease of use of FM on the uplink with the spectral efficiency of SSB on
the downlink.  As these would be single channel birds, sofficient power
could be achieced to hear the downlinks on handheld 10m gear (like those
"pirate CBs" that are now on the market).  Actually, I can clearly hear the
beacon of RS-13 clearly on a Dragon SS-201 10m HT (in USB mode) and a 2 foot
whip.  A moderately powered (say 5W) SSB signal should be clearly audible on
the ground with this setup.  Many stations should have capabilities for 70cm
FM / 10m SSB, so this could be a popular mode.  The Doppler should be pretty
easy to tune as well, with 70cm being non critical, and the 10m side having
only around +/- 600 Hz. 

2a.  A similar technique could be used with a 2m downlink, and an FT-290R or
similar utilised on the 2m SSB link, or perhaps "Mode JX" (X for cross
mode), 2m SSB up, 70cm FM down...

3.  Other wierd and wonderful bands, like 13cm downlinks are another
possibility, but this would require the development of a low cost, easily
reproducible converter kit to attract a large number of operators.  Let's
see what Mode L/S on P3D brings. :)
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