On Sun, 12 Jan 2020 19:59:52 -0800, Jeff Liebermann
wrote:
Bad idea. The Tek 2232 has both digital and analog storage:
https://www.tek.com/datasheet/2232-digital-and-analog-oscillscope
I suggest you use it as a conventional analog scope for the
untriggered horizontal sweep. If the frequency of the glitch source
is stable, you should be able to "tune" it in by adjusting the
horizontal sweep (with the trigger turned off). That works much
better in analog mode than in digital. Better yet, go back to using
your analog Tek 2465A for looking at the VCO control voltage.
I'm afraid I don't have that option at the moment. The 2465A blew up a
couple of days ago and has now joined my pile of "awaiting attention"
junk.
I didn't blow it up, by the way; it managed it all by itself.
Incidentally, I just noticed that you screwed up in your original
posting. You provided most of the details, a few of the numbers, but
failed to describe the "weird problem with the network analyzer" and
what "spurious spikes in the frequency domain on the RF output" might
be. Is that like a spurious RF signal appearing on the SA swept
display?
I think you may have missed the clarification I posted. Here it is
again:
"I could have put it better I guess. What I mean is I'm seeing thin
spikes in the RF output spectrum of the VNA at other frequencies than
the desired one. I'm guessing these spikes are the result of unwanted
transient voltage spikes present on the DC VCO control voltage which
sweeps the RF output frequency from 4Mhz through to 1.3Ghz."
If so, are you picking up some junk from nearby radio or TV
stations? If you can see it, what's the frequency on the SA? I can
also imagine that your test setup or cabling may be causing these
problems. A probe on the VCO line could easily pickup RF junk from
everywhere.
I think that's a very valuable point there. One possible 'infection
vector' for noise is the method I'm using for sniffing the VNA. As you
may know, spectrum analyzers of this vintage were very intolerant of
DC on the input socket. There doesn't even seem to be a margin of
error! So any DC riding on the signal you're trying to obtain a
spectrum for and you blow up the front end. And I have a bit of a
complex when it comes to blowing up test equipment. I'm very, very
cautious these days, so I've just used a few turns of wire to couple
the signal from the VNA to the SA. This removes the DC risk, but does
mean there's no shielding around the sniffer coil. And right next to
these items there's my linear power supply powering up my Yaesu 857d.
Now the linear supply should be fine, being linear, but I'm just
wondering if the Yaesu, even in receive mode, might be generating some
stray spurious that the SA is picking up somehow. I'll switch those
items off when I try it again. My working practices are a bit slapdash
I must admit, but no worse than the average hobbyist I would imagine.
--
No deal? No problem! :-D