On Mon, 13 Jan 2020 00:18:13 +0000, Cursitor Doom
wrote:
On Sun, 12 Jan 2020 17:17:04 -0500, Phil Hobbs
wrote:
Frequency domain glitch? You mean a discrete spur?
A glitch is a transient time-domain animal.
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.
I would guess(tm) that they are mixer spurs produced by the two
oscillators used to produce the network analyzer RF output signal. A
clue as to their relative amplitude compared to the RF output would be
helpful.
Look at the spurious stuff coming out of the network analyzer. Now,
vary the network analyzer frequency and see how they move. You can
tell the order (harmonic number) of the spurious components by how
much they move. For example, if you change the network analyzer 1 MHz
and the spur moves 3 MHz, than you are dealing with the 3rd harmonic
of one of the two input signals to the mixer in the network analyzer.
I also suspect that you might be picking up RF from nearby radio and
TV broadcast stations. Install a small antenna into the RF IN port of
your spectrum analyzer and see if there are signals at the same
frequencies that you are seeing them on the network analyzer RF
output. If so, you might check the shielding and grounding in the
network analyzer.
A DSO can save a single
instance, or (with averaging) ignore the noise and asynchronous
background and just reproduce the glitch itself.
Well, Jeff has posted some advice for me on that aspect which I intend
to try out tomorrow using my Tek DSO which is probably much better
suited to the task than the analogue one I've hithertofore been
using..
Yep. Failure to observe my advice will result in divine retribution.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558