On Tue, 14 Jan 2020 17:42:04 +0000, Cursitor Doom
wrote:
I've now uploaded 3 photos of what I'm seeing. The most obvious noise
(apart from being obvious) is the 'comb' across the screen. I'm
getting the most spurii at the lowest 'fundamental' (around 5Mhz) but
as I sweep up in frequency the number of spurs declines markedly so by
200Mhz there are only 4 spurs remaining and they're much wider apart.
The other form of noise I mentioned in an earlier post is the more
attenuated and spread out one visible just to the right of the
centre-frequency line. This noise, unlike the 'comb' is constantly
flickering and random.
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Sorry for the late reply, but I had to waste the last few days dealing
with the California Dept of Motor Vehicles to renew my drivers license
and obtain a Real-ID endorsement. I passed both but am still
recovering and might need a few more days to calm down.
Interesting spectrum analyzer display and description. The most
interesting part is how you managed to produce the photo, without
bothering to mention the:
1. Network analyzer test Frequency
2. SA (spectrum analyzer) horizontal MHz/div.
3. SA vertical full scale, dBm per division, and dBm full scale.
4. Whether you were misusing a scope probe (again) or feeding it
with 50 ohms. Also, any attenuators or couplers in the RF path.
5. Did you remember to turn of the 1, 10, 50Mhz markers on the
HP8754A?
6. Any other numbers which might be useful, especially those you
previously mention, but which I'm too lazy to dig through your old
postings to find.
Had you supplied some numbers, I would have dived into the HP8754A
network analyzer service manual, and determined the frequencies of the
two oscillators (3.6 - 4.3GHz minus 3.6 - 3.0GHz) used to produce your
unspecified output frequency. I would then compare the possible
intermodulation mixes of these two frequencies, with the mess on your
spectrum analyzer screen, and see if any of the spurs are the result
of oscillator feedthrough, intermod mixing, or overdriving the
spectrum analyzer and creating the spurs in the SA. However, since
your photos were not accompanied by any numbers, I can't do this for
you. Incidentally, you might want to ask in one of the HP test
equipment forums for what a working HP8754A RF output looks like on a
spectrum analyzer. I would not be surprised if the mess on your
screen is quite normal.
Incidentally, if you download and read the HP8754A service manual,
you'll find a large number of Performance Tests. Performed properly
in the manner specified, you should get a better idea if your network
analyzer is functioning as expected.
Also, this is your second warning about providing insufficient
information and numbers. Provide numbers with your problems or
prepare thyself for the wrath of the radio gods. The recent failure
of your Tek 2645A scope was a poorly aimed warning shot (I was aiming
for your Tek 2232A scope) and a hint of things to come.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558