[time-nuts] HP5370A vs B version

[Bob kb8tq]

Hi

If you are buying them on eBay, it is not at all clear which OCXO your A or B will show up 
with. The 10811’s get swapped back and forth with earlier units in a lot of used gear. One
might *think* it’s a one way exchange, but I’ve seen it go both ways. 

If you lock the counter to an external standard, it really does not matter a lot which OCXO
is in it. 

Bob

> On Jul 20, 2019, at 4:21 AM, Frank Stellmach <frank.stellmach at freenet.de> wrote:
> 
> Hi Mr. Taka Kamiya,
> 
> the B version has a 500MHz front end, copied from the HP5345A, with a matched pair of amplifier / Schmitt trigger hybrids.
> The A version has separate amplifier and Schmitt trigger ICs.
> 
> There were also changes on the trigger circuit.
> 
> Then the B version has a simplified µP board, has the OCXO (10811-60111), which is a must for absolute T.I. and frequency measurements.
> 
> Maybe the firmware was also improved a bit, I think mainly concerning the GPIB steering of the trigger circuit.
> 
> This T.I. counter is supposed to be superior over others of that era, because this special time interpolator was more linear.
> 
> I really love mine, so I don't want to sell it.
> 
> Frank
> 
> 
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