Products > Test Equipment
Anyone (else) using a vector voltmeter?
coppercone2:
maybe a modern high quality connector can handle it in a mod. But differential connectors are fairly alien to me. They do keep saying connector technology moved forward.
But the manufacturing precision for connectors is seriously impressive. Those RF connectors are like +-500nm tolerance for center drilling in the microwave connector area.
I wonder what connector would work here.
something along the lines of this, but this is data
https://www.rosenberger.com/products/connectors-adaptors/data-connectors/
G0HZU:
Here's a link to an old HP document that lists some typical applications for the HP 8405A.
https://www.hpmemoryproject.org/an/pdf/an_91.pdf
Here's some info in the link below about testing crystals with the HP 8405A and an HP 8640B sig gen.
https://www.hpmemoryproject.org/an/pdf/an_171-1.pdf
The short term frequency stability and (very) close to carrier phase noise and jitter of the old HP 8640B sig gen will be poor compared to a modern synthesised sig gen and I think this is why the app note uses the LPF and the FM input of the 8640B. This is probably there to clean up the close to carrier jitter and noise of the 8640B sig gen and it may also help with tuning it reliably and easily in small increments of a few Hz.
A modern synthesised sig gen will be much cleaner and more stable (with minimal jitter) compared to the old 8640B at frequencies 'very' close to the carrier. It will also be much easier to tune up and down by just a few Hz compared to the 8640B. So it won't need the LPF at the phase recorder output. The modern sig gen would need to be able to tune in steps of 1Hz or less but this is usually not a problem. I have used this crystal measuring technique with my 8405A and a modern sig gen several times now. I have a few homebrew test fixtures for this stuff. It is very rewarding to do it this way when compared to trying to do it with a modern VNA.
paul@yahrprobert.com:
Back in the 90's I worked in a plasma lab where we did high power RF plasma heating. The big problem was impedance matching to the plasma, which was a difficult load. We had matching networks made out of big vacuum variable capacitors and fixed inductors. The key was to measure the complex voltages from well calibrated directional couplers, then using computer programs and models of the matching network and antenna to adjust the capacitors. We used an HP 8508 vector voltmeter to calibrate the DC's, and then built our own multichannel fast vector voltmeters to measure the load when the plasma formed. We were working in the range 7 to 20 MHz. I've always wondered why nobody seems to make a good vector voltmeter these days. All you can buy is an expensive vector signal analyzer that gives you only one channel.
coppercone2:
that is very interesting
Bud:
The home made N2PK VNA (DDS based) has a Vector Voltmeter mode with a fraction of a degree and amplitude resolution.
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