For those of you who use the EMCO wide-band horns I thought I would
mention that they have modified the design somewhat from the original
Fairchild "Boxey" design to something with more elegance.
http://www.atsemc.com/3117_rev_b.pdf
It is still mostly for use from 2-18 GHz, with the designed sweet
spot being from 7.5 GHz upwards. You can use it below 2 GHz when on a
sweep, but you would be better served using a log periodic below 2
GHz... and filter, filter, filter because that 1.7-1.9 GHz band (in
the U.S.) is going to seriously put the hurt on your measurements.
You can also use this horn above 18 GHz, and could squeeze it to
maybe 22 or 26.5 Ghz but you would do better with a second horn for
18 to 26 GHz, and then a third for 26.5 to 40 GHz (with dedicated
amps and filters of course).
Some sweep folks use these to drive a diode detector for broadband
detection and they do a rather remarkable job of hunting down
wide-band signals with them using a 1 GHz bandwidth Oscilloscope and
an good amplifier, but you often need a 2.5 or 3 GHz high pass filter
to clean things up once you clear the 2.4 GHz ISM bands. You can also
use the diode detector/amplifier to push a line/pulse stretcher that
triggers the sweep on your spectrum analyzer or receiver. With modern
spectrum analyzers you end up dumping all the traces into RAM or HDD
so you can correlate the data in memory to the signal that triggered
it with ease without all the line/pulse stretching and delays lines
that were previously required (PSA, ESA, RSA, RTSA, 30x6, etc).
Excuse my ramblings, but I would love to see someone come out with a
search receiver/spectrum analyzer that gave you a half dozen inputs
instead of just one so you went directly from the antenna of the band
of interest into the analyzer instead of amplifier, filtering,
switching and then going to the SA. If you need three or more horns
to cover from 2 GHz to 40 GHz why not just add an extra mixer card to
the SA and dedicate a given channel to a given antenna. I mean, hey,
we are already doing this manually or quasi manually... why not just
built it into the instrument. DOn';t give the instruments a switch...
given it a whole channel and give each channel it's own independent
processor and signal processing so that all the mainframe is only
going is give you the graphical interface and mass storage.
The real magic of this would be with some of the newer real time
spectrum analyses that are totally modular like the 3066, 3086, PSA,
RTSA and so on where all you have to do to add the extra channel is
drop in a some cards and tweak the software. Six channels would
suffice, but give each channel both an RF input and a dedicated trigger input.
-jma
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Received on Sat Mar 02 2024 - 00:57:28 CST