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HP 478 A? Thermistor mounts

 

Re HP 478 A? Thermistor mounts? could someone –please direct me to a listing of the different options? for example? ?HP 478 A - H75?

also interested in any one that uses the H75 option

Regards Paul?
 

Here are the 478A options listed in the 1994 options list, that is on the web somewhere.
?
?
David
 

Hi David? Thank you found the information so made a new file HP 478A? and put the information in there?
Regards :Paul?
 

I have, as listed in the 1994 Options List, an HP-478A-H63, which is spec'd to operate from 100 KHz to 1 GHz and it really does respond that low and lower. It belonged to HP Division 4 (does anyone know that division?) and was last calibrated in 1981, according to the cal sticker. It works very well and is great for calibrating RF voltmeters that operate in the "less than 1 GHz" range such as my HP-411A RF Millivoltmeter.

Jeremy
N6WFO
?

On Tue, Mar 4, 2025 at 3:04?PM Paul Bicknell via <admin=bicknells.f2s.com@groups.io> wrote:
Hi David? Thank you found the information so made a new file HP 478A? and put the information in there?
Regards :Paul?
 

Jeremy,? Maybe Div 4 is Standford Park.? ?I think they were the cal lab the service centers (when there were about 5 or 6 of them) used.? ? ? ?I remember using the 432A/478 to test the 50 MHz references in the power meters plus the 435 (K05 maybe) dual power reference.? The 432A's meter movement itself wasn't used but the DC outputs were measured and the power was calculated from those voltages.? Having checked many of these power references I can't remember any of them being out of spec.? ??
 

Thanks! The primary method of ruining a thermistor mount is to put too much power into it. Consequently, some users keep a 10dB attenuator permanently attached to it.?

Jeremy?
N6WFO?



On Wed, Mar 5, 2025 at 2:48 PM WB2UAQ via <pschuch=rochester.rr.com@groups.io> wrote:
Jeremy,? Maybe Div 4 is Standford Park.? ?I think they were the cal lab the service centers (when there were about 5 or 6 of them) used.? ? ? ?I remember using the 432A/478 to test the 50 MHz references in the power meters plus the 435 (K05 maybe) dual power reference.? The 432A's meter movement itself wasn't used but the DC outputs were measured and the power was calculated from those voltages.? Having checked many of these power references I can't remember any of them being out of spec.? ??

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