[time-nuts] Lucent RFTGm-II-XO / Lucent RFTGm-II-Rb / NT BW50AA

[Magnus Danielson]

Hi Jim,

On 2019-02-13 14:24, jimlux wrote:
> On 2/12/19 6:31 PM, Bob kb8tq wrote:
>> Hi
>>
>> The normal approach as you head from HF up through stages to 
>> microwaves is to stop
>> at various points along the way. Just where depends on the actual 
>> noise you measure on
>> the sources you have. (Yes you have to measure them yourself).
>>
>> Once you have your noise plots, you can pick likely crossover points 
>> for a PLL. You then
>> design the PLL to hit those targets. After that you measure the 
>> result to see how close you
>> got to your target. Then it’s off to teak this or that to improve 
>> things.
>>
>> The step by step process continues through VHF to UHF to microwaves 
>> as you move through
>> various steps. Indeed you may change your plan once you see what your 
>> measurements tell
>> you about each design iteration.
>>
>> A lot also depends on just what your target actually is. Running PSK 
>> 32 at 22 GHz is a bit
>> different than running WBFM HDTV at 5 GHz. What works for one may not 
>> be ideal (or even
>> close) for the other.
>>
>> So yes, it’s a great way to spend a couple of years fiddling around …..
>>
>> Bob
>>
>
> Decades -
> This is what people who design deep space transponders (particularly 
> for radio science measurements) spend their time on.
>
> One set of requirements says "we want to make carrier only 
> measurements with ADEV <1E-15 at tau=1000 seconds with Doppler"
> Another set of requirements says "we want to send data at rates 
> between 10 bps and 10 Mbps"

Also, you want to maintain link capability for up to 4 decades or so, so 
stability of equipment needs to be long term stable in that environment 
for that context.

Reading up on these systems is really interesting in their system 
design. I really enjoyed reading up on the self-stabilization and 
orientation routines to re-establish home-link and orientation in space 
if lost.

Cheers,
Magnus