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 w5did@mac.com
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 wb4gcs@amsat.org
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:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
- 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 Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle