[eagle] Re: Eagle 10 MHz Clock

Lyle Johnson kk7p at wavecable.com
Mon Apr 9 20:55:17 PDT 2007


Hello Bill!

My recollections of "oral history":

> 1) What is the reason for requiring all LO's to be locked to a 10 MHz 
> satellite system clock or are they?

Earlier transponders often had frequency uncertainties of many kHz.  For 
some applications (I seem to recall ranging early in the life of the 
spacecraft as we're trying to stabilize it and change its orbit) knowing 
the frequency is important.  For general QSOs it is less so, especially 
with CAT interfaces to radios what can compensate for transponder errors 
as well as local offsets.

Also, the oscillators so referenced should be able to operate as well as 
past transponders in the absence of the 10 MHz reference.

Some of this desire may have been driven by the P5A requirements, which 
don't apply to Eagle. Doing 5 bps DBPSK signaling at S band requires 
some pretty amazing stability and phase noise characteristics, or so I'm 
told!

> 2) Have the performance specifications for the 10 MHz clock been 
> developed and what are they (in particular phase noise, frequency 
> stability, susceptibility to digital hash, and power level available to 
> each using subsystem - to name a few)?

For Eagle, not to my knowledge.

73,

Lyle KK7P



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