[TowerTalk] Antenna Analyzers

Wed Dec 5 19:42:16 EST 2018

Last year I had a need for a very small, compact analyzer for a trip to Central America. 
I ended up buying one of these:

https://www.mfjenterprises.com/Product.php?productid=MFJ-223
It worked great for what I needed it for, charges with a USB wall charger, and is very compact.
I don't have a problem with broadcast transmitters nearby so I  can't comment on how it will work on topband. 
Was also very handy for FD.

73,
Gary K9GS
-------- Original message --------From: Jeff Blaine <KeepWalking188 at ac0c.com> Date: 12/5/18  5:23 PM  (GMT-06:00) To: towertalk at contesting.com Subject: Re: [TowerTalk] Antenna Analyzers 
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
>>>
>>
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