http://elecraft.85.s1.nabble.com/K3S-XREF-GPSDO-recommendation-needed-tp7641686p7641729.html
I just went back and read the Bodnar specs again, and it does in fact use a TCXO and NOT an OCXO which is used in most commercial units. My bad. Should have realized that given its small size. It’s holdover characteristics won’t be as good as a unit with an ovenized oscillator.
Nonetheless if holdover periods are few and far between, it may not be much of an issue. In any case, I’ll stick with my Trimble as long as it doesn’t smoke the room up :-)
> On Jun 5, 2018, at 6:57 PM, Grant Youngman <
[hidden email]> wrote:
>
> GPSDO “Holdover” mode (loss of GPS sync) runs typically better than 1x10 (to the) -9 ppm per day. These devices use the last control values and historical data to manage the OCXO (or rubidium, or cesium standard) during periods without GPS sync. They don’t just default to some nominal frequency or run at random. Outside of the occasional times I’ve had to disconnect the GPS antenna to move things around, I’ve never observed any of the GPSDOs I’ve used go into holdover mode on their own. I used to have logs monitoring the old HP standards when I had them, but no longer do that — since it was like monitoring the location of a period on a page :-)
>
> The K3 will retain the last Ref Cal frequency if you unplug the GPSDO altogether. Which nominally, should be the Ref Cal setting you would get if you went through a manual cal and set it at the current rig temperature.
>
> Which is kind of the point. Without the external sync, if you cal the radio after it’s been warming up for 30 minutes, and then start running RTTY or FT8 or some other mode that’s going to heat the radio up, the cal will go to h*ll in a hand basket — if a few Hz or 10s of Hz is a hand basket. Well not in any practical sense, necessarily, but it will change. The GPSDO “nudges” it back into place and is not dependent on the temp of the internal K3 standard.
>
> It’s an compulsive disorder, and not very much of a practical thing, in any case :-)
>
> Grant NQ5T
> K3 #2091, KX3 #8342
>
>>
>> If GPS lock is lost on the Bodnar device it reverts to a TCXO that is likely no better than the one in the K3, assuming the high stability option. (Note: I haven't pursued all of the relevant specs, this is just gut feel.)
>>
>