[time-nuts] HP5065A C-field current is temperature sensitive
John Ackermann N8UR
jra at febo.com
Mon Aug 31 20:13:44 EDT 2015
Attached is a frequency plot of my 5065A vs. GPS (via PPS) over about 6
months. Note the changed freq and slope between about MJD 57205 and
57235. That correlates to the month we were out of town on vacation,
with the air conditioning set about 6 degrees higher than normal.
(There was probably less differential than that in the basement lab vs.
the thermostat upstairs, so don't try to do any absolute measurements
On 08/31/2015 02:32 AM, Poul-Henning Kamp wrote:
> In message <A1A54F1F-926F-42A9-8AEC-F83BCAF4E58D at n1k.org>, Bob Camp writes:
>> As we go joyously bashing the poor guys that designed this beast,
>> it’s worth noting just how old the design is. 741 op amps were
>> indeed “modern” [...]
> I don't think chip op-amps appear until the 5065 is a toddler, later
> revs use a couple of them.
> The only thing I feel like beating them up about, is that appearantly
> they didn't consider the tempco of the R10||R11 pair (or maybe it is
> just R10 - not sure yet).
> Either way: If any of you have a non-amazing HP5065, Measure the
> A15CR5 voltage, multiply it by 76, and replace R10||R11 with something
> of that value and better than 5PPM tempco.
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