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Multi channel FM birds



At 11:02 7/23/02 -0700, you wrote:
>At 09:11 AM 7/23/2002 -0400, Bob Bruninga wrote:
>>We are working on an idea to put 4 FM channels on a single payload
>>with downlinks on 2m FM (Mode B) and are thinking of the 15 KHz splits
>
>Would you also use 15 kHz channel spacing on the uplink? If so, you are 
>putting a heavy burden on the operators to do Doppler compensation 
>correctly. If they don't compensate or compensate incorrectly, they are 
>very likely to interfere with adjacent channels.
>73  -Paul
>kb5mu@amsat.org
>
	*************************************************************
								24 July 2002
	KB5MU de G3BVU/W1  BT
	Paul,

	Your point is well taken. 

	However this looks like an excellent application for Uni_Trac 2000. 

	As you know, Uni_Trac 2000 will calculate both the UPLINK (transmit)
Doppler frequency as well as the DOWNLINK (receive) Doppler frequency and
apply these correcting functions to the tuning circuits of modern (computer
controlled) radios.

	The frequency step size of the tuning correction terms can be selected to
be as small as a few 10s of Hertz.

	To the best of my knowledge, Uni_Trac 2000 is the only hardware/software
system that will automatically compensate Doppler frequency changes on the
UPLINK (transmit) path. There are several systems available that compensate
Doppler frequency changes on (only) the DOWNLINK receive signal path.

	Uni_Trac 2000 will maintain the UPLINK signal at a (nominal) fixed
frequency in the satellite's passband.

	Perhaps Bob is planning to use Uni_Trac 2000.

	73s,    John  G3BVU/W1.
		

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