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RE: Thoughts on future "FM birds" (was: proposal for maximizing fm le o contacts)



> True, but there are some subtle but significant differences between
> existing mode A and what I am proposing especially realtive to
> satellite power and getting more people and newcomers involved in
> satellites.
> 
> 1) SSB uplink on 10m needs only a Radio Shack 10m transceiver ($139).
>    Mode A needs an all mode 2m rig ($700?)

Here, it's possible to buy secondhand 2m transverters for $70 or less (about
$40 US), so cost is a moot point, though the availablity of cheap 10m gear
is much greater.  Here, we have a choice of several "pirate CBs", which
would be suited to such a 10m uplink.

> 2) Using 2m as the SSB downlink requires only a 2m to 10m 
> converter ($49)
>    Mode A requires both the 2m SSB transmitter and 10m HF 
> receiver ($139).

The costs are actually similar, if transverters are used for Mode A.  
 
> 3) 2m down is quieter and requires less satellite power.  
> Mode A's weak
>    downlink must compete with higher atmospheric and man made noise.

No argument there.  However, OTOH, 10m requires a more efficient antenna for
Tx, where as a Mode A downlink could be received on a shorter antenna, as
long as the antenna was capable of bringing the noise floor up above the Rx
noise floor.  So Mode A is potentially more practical for portable stations.
I will do more tests on this with RS-13 while I'm on leave, but I can hear
RS-13's beacon _very_ clearly on my Dragon 10m HT (which is capable of SSB).

> Yes, but still, the doppler tuning of mode A transmitter is 5 times
> greater than doing the same on a 10m uplink.  Yes, the 
> combined up/down
> total is the same, but with 10m up, the smaller shift is on 
> the uplink,
> so everyone in the passband retains their relative position 
> about 5 times
> better and the whole group then moves greater relative to any 
> particular
> receiver.  Thus a 5 times reduction in the "sliding QSO" problem...

In the case of inexperienced ops, yes.  If people follow the general
guidelines of satellite operation, they would be tuning their uplinks on
Mode A, and therefore, only drifting the same +/- 600 Hz.

> 
> But you are right that it requires a proper license to transmit on
> the 10m uplink.

Here, it requires Intermediate or Full call to Tx there (which are now
equivalemt, since we went to 5 WPM max CW).  I'm OK, I already have my
Intermediate. :-)

I still think it's an interesting idea, and one that is worth investigating
more.  Just pointing out that even conventional Mode A isn't a bad choice.
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