[time-nuts] Which HP Frequency Counter?

Dan Rae danrae at verizon.net
Sat Mar 8 12:35:33 EST 2008


Jean-Christophe Deschamps wrote:

>Dear group,
>
>I consider buying a used lab frequency counter / timer --preferably 
>HP/Agilent-- covering from few mHz to perhaps 400 MHz.  I'm worried 
>that models handling high frequencies seem to be limited to under 100 
>mV input signal max. I don't want to destroy an input channel each 
>other day when calibrating/repairing some instrument.  Also are there 
>instruments with high impedance input? 50 Ohm is not quite right for 
>investigation in the guts of most designs.
>
Jean-Christophe,

I know you said HP, but the one instrument that I have on my bench and 
use all the time that is not by HP is a Racal-Dana 1992 counter.

It has three inputs, the A input can be set to 1 MegOhm impedance and 
will count up to 160 MHz at good sensitivity, 50 Ohm loads and 
attenuators and filters also available.  The C input goes to 1.3 GHz, 50 
Ohm only.  The A and B inputs can be used for phase comparisons.  Most 
of them have a very good quality Ovened timebase, Option 04E.

There are a lot available in the US and not so many in Europe, prices 
for what they are seem very reasonable; in the US $200 to $300, working.

Some have trouble with the push button switches, these can be replaced, 
but it is a big job to do, there are a lot.  Apart from that I know of 
no other common failure modes.  Not a lot of other components inside 
that cannot be found easily enough.

Manuals are freely available.  And it is quiet.  No fan noise.  My HP 
counter sits in the garage...

Good luck, 

Dan






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