A big HP system is totally impractical for the average guy. I have a
rack of the old stuff here so i'm not saying it's got no place, rather
when you are out in the rain and the mud, you need something that's not
going to take a cart to pull around, a bunch of power and does not weigh
100 lbs / box.
The VNWA is a nice unit but it's WAY WAY WAY to delicate for serious
field work. The newest variation with the micro USB is a step back
because that connector is far more fragile than the old hunk-square type
A USB connector. Guys who use them "all the time" in the field are
apparently much more disciplined than I am. The other issue is that it
requires a computer to work. So it's workable on the ground, but if you
have to go up the tower, then it's a problem. And the software is a
long way from intuitive - but it does work fine once you figure out how
to use it.
The myVNA software used with the N2PK requires virtually zero learning
curve. I love the GUI and the N2PK but this is even more non-portable
in that my N2PK requires a parallel port to drive it as well as the
computer. So it's attracted to the bench and never goes for a field trip.
The MFJ has a weakness for local BC stations but the reason a zillion of
those were sold is that they are reasonably accurate, self contained,
rugged and don't have tiny parts that are easy to break. No wonder it's
the average ham's most used go-to analyzer.
Because of the BC station problem, I bought a Rig Expert 55 Zoom and
really like it. As with the MFJ, it's 100% self-contained, rugged, has
a plastic case which helps keep rain and field crud out of it, and
performs basic VNA-type stuff that I had to do previously with my VNWA.
The RE also has the VNA-type ability to calibrate at the end of a hunk
of coax.
I'm sure there are other gadgets out there that would do a fine job but
to my eye the Rig Expert is the best all around most utilitarian device
for the "antenna analyzer" job assignment, with the MFJ259 a distant 2nd.
73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com
On 05-Dec-18 2:16 PM, Jim Brown wrote:
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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|