Yes. The comparison is between lab equipment costing tens/hundreds of
thousands of dollars and a very decent ham-produced unit that we can
currently buy for less than $600.
And I've had no difficulty calibrating my VNWA 3e for 2-port
measurements to several different measurement planes. One of those
produced the data for this report.
http://k9yc.com/BandpassFilterSurvey.pdf ; Screen plots of all the
measured data are here.
http://audiosystemsgroup.com/BandpassFilterData.htm
Most of the time, my VNWA 3e has a 3m cable attached to its output and a
1m cable to it's input. The 3m cable is a convenient length to reach
connectors for antennas entering my shack. I have several master
calibrations for this measurement plane, and several more for a special
test jig that W6GJB built for me to measure chokes. That test jig places
the choke in series between input and output, S21 is measured, and the
math function in VNWA software solves the voltage divider equation and
plots Zmag, Rs, and Xs vs frequency.
73, Jim K9YC
On 12/5/2018 11:34 AM, Wes Stewart wrote:
Rick,
With all due respect, I'm not terribly surprised with your comments,
considering that you worked for HP. When I worked for Hughes, I
remember several occasions where I took an airplane ride from Tucson
to our sister facility in Conoga Park, CA just to use their network
analyzer to measure something or the other. It took me several years
to get a capital equipment proposal approved by upper management to
purchase an HP8510. As I recall, with all of the ancillary equipment,
software, cal kits, etc, the cost was in the neighborhood of
$200,000. And it was still buggy and did require support.
The VNWA software may not be as user friendly as you would like, but
it's remarkably free. As I said, it will run the FA-VA5 and I didn't
mention it but it will even run the old N2PK. There are automatic
selection options for the clock multipliers. I suspect that a request
to Tom, might get an option to move the center frequency to the marker
written into a revision. (I'm not speaking for him.)
Wes N7WS
On 12/5/2018 9:13 AM, Richard (Rick) Karlquist wrote:
On 12/5/2018 7:21 AM, Wes Stewart wrote:
2) Short of an HP-8510, 8753 or 3577 the gold standard for hobbyist
use IMHO is the SDR-Kits, DG8SAQ designed VNWA.
(https://www.sdr-kits.net/introducing-DG8SAQ-VNWA3) This is also a
two-port vector analyzer. The VNWA software is *very* powerful, with
a commensurate learning curve, and is well supported by the author
Dr.Tom Baier as well as some very knowledgeable users. A bit
difficult to operate in the field because it's tethered to a
computer, but I have done it. This is a lab grade instrument. Uses
SMA connectors.
I would somewhat argue about the software being very powerful.
Especially compared the the HP analyzers you mentioned. It
is not even close in terms of user productivity. For example,
AFAIK, there is no command to set the center frequency to the
marker frequency. The user would have to make a note of the
marker frequency and then manually enter the new center
frequency. Just one of many limitations. The user is also expected
to set the multiplication factors for RF and LO depending on the
measurement frequency. This is very poorly documented.
It is not clear if you can do full 2 port calibration. This
is probably covered under the learning curve comment. If it
is possible, it isn't obvious or straightforward.
It is good that the VNWA is well supported but the HP analyzers you
cited are intuitively obvious to use and don't require any
support in most cases.
(I have owned a VNWA for a few years).
Rick N6RK
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