[time-nuts] About HP10544A

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Mar 7 22:04:10 UTC 2009

Esa Heikkinen wrote:
>> The capacitance of the 1x probe is too high.
> So I have to check that also: it shows 46 pF on 1x mode and 10.6 pF in 
> 10x mode.
> Ok so the main question is that what kind of amplifier I should use with 
> 10544A to get a clean signal, if it can't stand even an oscilloscope 
> without distortion on it's output? And what do that kind of amplifier 
> cost - more than HP10811, for example?
> Many other OCXO's (like thunderbolt's) can be connected directly to the 
> 50 ohms. load without any trouble with harmonics.

You can easily construct a suitable buffer amplifier using inexpensive
and readily available parts.
It was an early design, intended to drive a 1k load located very close
to the connector terminals.

The buffer design depends on what reverse isolation you require and what
output signal level.

The venerable LH0033C has been used as a buffer to drive a 50 ohm load.
However it is relatively expensive if its even available.
Since this is RF you dont need the low offset voltage and drift of such
a device.


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