[eagle] Re: Eagle 10 MHz Clock

Louis McFadin w5did at amsat.org
Mon Apr 9 21:03:34 PDT 2007


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 at 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 at 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:
>>
>> 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
>> Eagle at amsat.org
>> http://amsat.org/mailman/listinfo/eagle
>>
>>
>>
> _______________________________________________
> Via the Eagle mailing list courtesy of AMSAT-NA
> Eagle at amsat.org
> http://amsat.org/mailman/listinfo/eagle

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