Bob,
I have a pair of HP-3551A's*. I'm very familiar with making
transmission lines measurements, and it seems that measuring power
supply noise would be the same, except that you want to block the DC
from the input of the instrument. What has your procedure been and
what numbers have you come up with? Since these instruments read in
dBm0, do you reference from the supply's voltage and then convert to
mV (difference)?
* One that I picked up off eBay for $75.00 looks new and came with
the complete manual, and the battery will run it most of the day.
Thanks,
Burt, K6OQK
Subject: Re: [time-nuts] Low noise power supplies?
A non-standard but repeatable way to measure power supply noise is
to use a Transmission Impairment Measuring Set (TIMS) such as the
HP3945(6)A or 3551
(2)A. These were intended for use in pairs to assess analog
telephone lines for data use. As well as an AF generator, frequency
counter, amplifier, monitor speaker and level meter they will
measure broadband noise. Being designed for POTS they will also
withstand at least 50V DC at the input while measuring the noise.
You can also apply internal filters if required. The last digit
designates a North American? (BELL) or European (CCITT) standard
unit, but broadband noise is the same. They can be picked up really
cheaply now (list was$3000-$5000) and make a nice compact audio test set.
Robert G8RPI.
Burt I. Weiner Associates
Broadcast Technical Services
Glendale, California U.S.A.
[email protected]
www.biwa.cc
K6OQK
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