[time-nuts] Re: Commercial solution - 122.88 MHz low noise source

[ed breya]

I was curious and looked up this Red Pitaya SDR thing (which I had never 
heard of - I would have guessed a poisonous snake, without the 
internet), and the Abracom TCXO. It's getting a little confusing to keep 
up with what's going on.

First, does the installed TCXO have EFC capability, or not? Jeff 
apparently says not, while Gerhard says yes. According to the datasheet, 
the ABLNO can be an XO only (no suffix), or a VCXO ("V" suffix). Jeff 
should be able to tell which, by inspection.

It appears now that 125 MHz won't work, unless maybe the internal SW 
allows enough frequency offset to be set - TBD, I guess.

A current option seems to be putting the "same" kind of TCXO in a 
separate box to insulate it somewhat from ambient changes. After seeing 
what all the pieces look like, this makes sense, but why not be sure to 
get the ABLNO-V VCXO version, which would allow for PLLing if the 
thermal stuff is not satisfactory, or just because? You may decide to 
forget about the thermal stuff and just do a PLL anyway, with more 
confidence in the result.

If it turns out that the already installed TCXO is VC, then of course 
you could just leave it in, and (carefully) tap off some output for the 
PLL, and add an EFC line back. I think that was one of the possible 
scenarios mentioned in discussion. By the looks of it, it seems like 
trying to remove or replace the installed part, or doing any major mods, 
would be risky to the board.

Ed