[volt-nuts] HP3458A SCAL hardware

[Poul-Henning Kamp]

In message <52474.15137.qm at web57705.mail.re3.yahoo.com>, Randy Scott writes:

>> I tested it with my HP3577A, and the results are not discouraging:
>> The flatness from 100kHz to 2MHz is close to spec, but I loose
>> about 0.1dB from 2MHz to 8MHz.
>
>Is this with or without the attenuation from your circuit?

Pretty much the same in all three states (3v,1v,0.1v)

>The difference in attenuation between 300 kHz and 10 MHz is 0.03
>dB, nearly double the amount of error allowed.

Yes, after starting to play with this problem, I have become quite
suspicious of any dB number with two decimals :-)

I am not trying to meet the spec here, I think that is pretty much
impossibly by any means other than thermal converters.  I am just
trying to see how good I can do this, with moderate means.

I have been told that even with thermal converters, people soon learn
to put a box over the TC to stabilize airflow, in order to meet the
0.2% spec.

>I've been on the look-out for the thermal converters, but they
>seem quite difficult to find (for the prices I'm willing to pay,
>anyway).

Indeed.  I have been lucky and picked up a 10V and 2V Fluke A55
a couple of weeks ago, and have been having a lot of fun with them
since.

I can't help wondering how HP did this in production, quite a lot of
their RF relays don't meed the 0.2% spec for insertion loss...

Poul-Henning

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