[time-nuts] About HP10544A

Esa Heikkinen scifiscifi at sci.fi
Sat Mar 7 21:57:04 UTC 2009

I also doubt that there could be something wrong with emitter follower 
so I also did some tests with "capacitive coupler" build on bottom PCB 
of the HP10544:
(1 kohm. terminaton is not visible on the picture)

Generally it's just a wire going over 10 MHz trace on the PCB and then 
it's connected to the spectrum. By this way it's possible to measure the 
output without loading it with any galvanic connection. Of course there 
is almost 30 dB of loss but it's not any trouble with spectrum analyzer 
having over -145 dBm noise floor.

But with that kind of measure the output specrum looks like this:

So there's less harmonics but 2nd and 3rd are still high if compared 
with other OCXO's. Hard to say anything of higher harmonics because that 
kind of coupler takes in all background noise like FM broadcasts etc. so 
I wouldn't trust these measurements too much (and because of that I 
didn't even mention them at first).


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