If you have tried to make contact through two independently varying systems such as a receiver with it's LO and a transmitter with it's LO. You would not need any additional justification.
AO-40 was a very difficult satellite to use for that very reason. The U band receiver local oscillator had it's drifting characteristic and the S band Tx had its own LO. Between the two you never knew exactly what the transfer function would be. With a common reference oscillator hopefully closely controlled the transfer function will be much better known.
With a common clock at least everything drifts together. With the higher frequencies of the C band system it will be even more important.

Lou McFadin
W5DID
[email protected]


On Apr 9, 2007, at 11:06 PM, Jim Sanford wrote:

Bill et al:
The requirement for the 10MHz reference descends from the July 2004
meeting in Orlando.As far as I know, it was never thoroughly
justified, it was stated and made sense at the time.Still does, to me,
tho I could be convinced on a case basis that we might not need it.

73,
jim
[email protected]


Bill Ress wrote:

Some very good dialog has been taking place, lead by Juan Rivera as he
heads up the prototype U Receiver build and test project.

Several very important questions have been raised but I'd like to
address just one with this post.

I've volunteered to design and build the S2 Receiver and the C
Transmitter and support microwave component efforts on the phased array
for each. I am finishing efforts on a "prototype" single channel
(assuming there might be several) S2 downconverter.

I fully recognize than "many" system design parameters have not yet been
defined but I'm trying to get that "definition" effort moving along.

This is the first one I'd like to address.

In the coarse of designing the LO for the "prototype" S2 downconverter I
have not been too concerned with use of the 10 MHz satellite clock. But
I think it's time for "system" project guidelines to be developed for
this issue since it can affect the design of all LO's. I have looked for
guidance on the subject in Eaglepedia and have come up short. Point me
in the right direction if it's there (and I just couldn't find it).

I hope I'm not rehashing old discussions (I've only been on the team
since last October) but here are my questions:

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

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)?

My apologies for sending to the entire Eagle list but I'm not sure who
has the responsibility for the clock.

Probably more questions to follow!!!

Regards...Bill - N6GHz



_______________________________________________
Via the Eagle mailing list courtesy of AMSAT-NA
[email protected]
http://amsat.org/mailman/listinfo/eagle



_______________________________________________
Via the Eagle mailing list courtesy of AMSAT-NA
[email protected]
http://amsat.org/mailman/listinfo/eagle