[time-nuts] ADEV

[jimlux]

>>
>> And, on the one hand, it's frustrating being the orphan child of the RF
>> user community: you can't get off the shelf test equipment. On the other
>> hand, it's cool, because then you have to *build* your test equipment.
> 
> Hmm. Should do more of that.

Well, one *does* have to convince someone to pay you to do it..

> 
>> To the Ku-band downconverters.. They're pretty crummy (but have a decent
>> SNR to work with).. however, I've seen that there are two kinds.. a
>> vanilla LNB and ones described as "crystal locked"... both are cheap
>> ($20-30 for the former, maybe twice that for the latter)... what's the
>> difference? And, getting into time-nuts territory here, where's the
>> reference for the "locked" variety coming from? Up the coax? inside the
>> LNB? And, can it be retrofitted from a much quieter oscillator? I was
>> thinking that one could build a radio camera with a small array of
>> Ku-band dishes, if you could lock all the receivers together. They *are*
>> pretty low noise (20-30K)
> 
> The key seek-term to add is "external reference" and it seems that 10 
> MHz sine seems to be the standard external reference frequency for LNBs 
> with external reference. I know it will be a tricky frequency for you to 
> score, but the things you do for science.


Browsing the aisles of the local electronics mega-mart... I don't think 
I've ever seen "external reference" in the commodity units.  I figure 
that the "crystal locked" units have a crystal in the LNB (as opposed to 
just running the DRO open loop)..

But, presumably, one could modify the LNB to drive the reference with 
something external (and somehow, I doubt it will be 10 MHz.. but anyone 
able to modify LNBs will be able to make whatever is needed)