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From: firstname.lastname@example.org (Dale Chisholm)
Subject: Re: Wideband gain measurement
Date: 8 Oct 2002 16:08:35 -0700
NNTP-Posting-Date: 8 Oct 2002 23:08:35 GMT
It's been decades since I had hands-on experience in this area. 2%
impresses me as fairly tight for RF measurements - 1% is roughly
equivalent to 0.1 dB amplitude as I recall. Instrument-grade
attenuators can have that kind of accuracy so if you can use them as
the basis for your measurements that may be the best way to go.
Do you also need to know phase to 2%? If not, a piece of telecom test
gear called a "Selective Level Meter" may help you out. It's
essentially a calibrated (both sensitivity and bandwidth) radio
receiver. Some had provision for automated coupling to a tracking
generator so they could do swept measurements without a lot of
operator intervention. The two model numbers that come to mind are
"Sierra 128" and "Hewlett Packard 3591", but both of these were
obsolete 20 years ago so I doubt that you'll find either one in prime
(calibrated) condition today.
The other instrument that hasn't been mentioned is a "Phase-angle
Voltmeter". Can't tell you much about them, except that the
instrument lab at a place I worked many incarnations ago used
phase-angle voltmeters to calibrate both loss and delay of coaxial
delay lines used at low VHF frequencies.
"John C. Price" wrote in message news:...
> I have a measurement problem that I have not encountered before. I want to
> measure the gain vs. freq. of an amplifier that works from 1 Hz to 1 MHz,
> and I want measurements accurate to 2%. The thing has a nominal gain of 50
> and the input impedance is 8 pF in parallel with more than a G-Ohm. How do
> I do it? No problem making rough measurements with a scope but I doubt that
> 2% is possible. Should I get an HP 3400? I have an FFT spectrum analyzer
> that seems to do the job below 25 kHz, but what about above that?
> Thanks for any suggestions,
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