[eagle] Re: Eagle 10 MHz Clock

Bill Ress bill at hsmicrowave.com
Tue Apr 10 12:29:11 PDT 2007


Thanks Tom and to all who responded to my question regarding the 10 MHz 
satellite clock. Most helpful.

Tom, when you refer to "s/c ranging" are you referring to the S2 and C 
transponders?

 From the comments received, it appears that the 10 MHz clock is another 
"system" issue that really needs defining early on and I will endeavor 
to do just that with the help of all who have inputs.

But before that can be done we need to know the certainly or uncertainty 
and the timing for the USO you referenced Tom. It sounds like a worthy 
goal if you can pull it off.

If indeed the clock is used by all LO's it is important that the LO 
designers know the reference's characteristics so that synthesis schemes 
and loop bandwidths can be better defined.

With that in mind, can you Tom, 1) determine what the specs of the 
$ystem USO might be (or point me to a place when I might deduce them), 
and 2) what's a realistic time frame for deciding if that $ugar 
daddy/mommy comes through with a commitment? We not only have to get a 
handle on the 10 MHz oscillator but the RF distribution circuitry after it.

In regards to the RF distribution circuitry, I count 8 users of the 10 
Mhz clock. Help me out here if I missed one....

1) V Transmitter
2) U Receiver (maybe two?)
3) L Receivers (two)
4) S Transmitter
5) S2 Receiver
6) C Transmitter
7) IHU
8) Spare (for X or K beacon or a "contributing" customer)

Again comments are "graciously" appreciated...Bill - N6GHz

Tom Clark, K3IO wrote:
> Bill Ress wrote:
>   
>> 1) What is the reason for requiring all LO's to be locked to a 10 MHz 
>> satellite system clock or are they?
>>
>>   
>>     
> That requirement comes from me. It is my fervent hope that we will be
> able to use the transponders for accurate coherent s/c ranging;
> therefore we want the TX and RX LOs to be related to a common (high
> stability) reference. There are also some (undocumented) desires (that
> may re$ult in $ome project $upport) to use the microwave transponders
> for high accuracy, intercontinental time & frequency synchronization.
>   
>> 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 desire, if it can be promoted (from unnamed $ource$), to use what is
> often called an Ultra-Stable Oscillator (USO) of the type carried on a
> number of interplanetary s/c. I envision us being able to tweak the
> frequency slightly under ground command (i.e. a D/A converter built into
> the USO).
>   
>> My apologies for sending to the entire Eagle list but I'm not sure who 
>> has the responsibility for the clock.
>>
>>   
>>     
> System level responsibilities are up for grabs AFAIK. So far, my
> contribution has been to say "It would tremendously augment capabilities
> if ...".
>
> Please keep asking these questions!    73, Tom
>
>
>   



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