Re: Topband: Handheld Impedance Analyzer

[Jim Brown]

On Tue,3/29/2016 7:40 AM, Mike Waters wrote:

Interesting! I had no idea that anything was available with that capability.


And the AIM2180 is not even the best (or the cheapest) of the units that 
do it. The winner, by far, is the VNWA 3e. Less than $700 with shipping 
cables, case, and calibration loads (priced in British Pounds), goes to 
1.3 GHz, self-powers from the USB port of the computer that runs it. And 
it has all the software transformational capabilities of the AIM boxes, 
including AC6LA's Excel spreadsheets (which is what the AIM boxes use). 
Well supported both by the designer, DG8SAQ, and SDR-Kits, the small 
group of British hams who build and sell it. Both are active on a Yahoo 
group. The VNWA writes the Touchstone files needed for export to other 
software (like SimSmith) directly; those produced by the AIM 4170 must 
be translated to Touchstone by AC6LA's Zplots.


http://sdr-kits.net/VNWA3_Description.html

Several years ago, N0AX was writing a rave review of it for QST (along 
with other VNAs), but WX0B killed it by threatening a patent fight. So 
most US hams don't know about it.


73, Jim K9YC
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Re: Topband: Handheld Impedance Analyzer

[Mike Waters]

Interesting! I had no idea that anything was available with that capability.

73, Mike
www.w0btu.com

On Tue, Mar 29, 2016 at 8:49 AM, Guy Olinger K2AV 
wrote:

> THIS is the way that you do it. The newer graphing boxes (most of them
> since AIM4170)  will allow you to pre-calibrate a transmission line, and
> then see all results as if you were really up there.
>
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Re: Topband: Handheld Impedance Analyzer

[Guy Olinger K2AV]

THIS is the way that you do it. The newer graphing boxes (most of them
since AIM4170)  will allow you to pre-calibrate a transmission line, and
then see all results as if you were really up there.

Get an instrument (they are getting less and less expensive) that will
graph R and X (both below and above the horizontal graph axis) and see what
is really going on. Trying to extend SWR as a prime instrument is
ultimately doomed. SWR is around because in ancient days it was all that
could be afforded and built from junk box parts. Since embedded CPU's are
in everything from gas grills to washing machines to telephones to little
kid's toys, the programs and the IC chips to make the essential math really
simple have become very cheap.

Resonance is where the graph line for X crosses zero. Just use your SWR
like the oil pressure lamp in your car. Let it tell you where out of bounds
for your amp is, tell you when something got broke in your antenna because
it is not the same any more, etc. Don't try and use it for the deep stuff
or initial adjustment.

We do not have to use our hammers to fix our Swiss watch any more. Having
the box tell you the R and X values at the FAR end of a transmission is a
gift way, way too good not to be the first analytical line of attack.

73, Guy K2AV

On Tue, Mar 29, 2016 at 2:07 AM, Jim Brown 
wrote:

> On Mon,3/28/2016 10:29 PM, Henk PA5KT wrote:
>
>> You can calibrate it with your feedline connected so you do real antenna
>> measurement.
>>
>
> One point of clarification. If you make a measurement that accurately
> provides magnitude and phase, including the SIGN of the phase, then
> accurately determine the electrical length of the feedline and subtract it
> out with correct math, that measurement is just as "real" as if you took
> your analyzer to the antenna and measured there with a zero length cable.
> In other words, there is nothing "better" about measuring at the antenna if
> you made the "in the shack" measurement correctly and transformed it
> correctly.
>
> I've done it both ways -- W6GJB was on my tower working on a monoband Yagi
> for me, I set up my VNWA at the base of the tower, calibrated it to a piece
> of coax long enough to reach Glen on the tower, and measured the antenna.
> Later, I measured from the shack with a much shorter piece of coax to the
> line, and transformed the measurement up to the antenna. I got the same
> data for the antenna from both measurements.
>
> 73, Jim K9YC
>
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Re: Topband: Handheld Impedance Analyzer

[Jim Brown]

On Mon,3/28/2016 10:29 PM, Henk PA5KT wrote:
You can calibrate it with your feedline connected so you do real 
antenna measurement. 


One point of clarification. If you make a measurement that accurately 
provides magnitude and phase, including the SIGN of the phase, then 
accurately determine the electrical length of the feedline and subtract 
it out with correct math, that measurement is just as "real" as if you 
took your analyzer to the antenna and measured there with a zero length 
cable. In other words, there is nothing "better" about measuring at the 
antenna if you made the "in the shack" measurement correctly and 
transformed it correctly.


I've done it both ways -- W6GJB was on my tower working on a monoband 
Yagi for me, I set up my VNWA at the base of the tower, calibrated it to 
a piece of coax long enough to reach Glen on the tower, and measured the 
antenna. Later, I measured from the shack with a much shorter piece of 
coax to the line, and transformed the measurement up to the antenna. I 
got the same data for the antenna from both measurements.


73, Jim K9YC
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Re: Topband: Handheld Impedance Analyzer

[Henk PA5KT]

Hi,

I use a miniVNA pro with bluetooth Bluevna software to my Android 
smartphone or tablet.


You can calibrate it with your feedline connected so you do real antenna 
measurement.


73 Henk PA5KT

Op 3/27/2016 om 21:08 schreef dick.bingham:

Greetings All

I am getting fed up with multiple trips between new antenna matching stations 
and the
tx-source/VSWR and not converging on a good match in quick order !

Please send me - OFF LINE - your recommendation for a handheld impedance 
measuring tool that covers 400KHz to at least 150MHz. I looked at the RigExpert 
AA-220 in the latest QST and it looks like a decent tool.

I certainly do not want to restart this topic but new stuff is becoming 
available and I don't want to settle for second best if 'best' is not 2X more 
costly!

73 Dick/w7wkr CN97uj
-


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Re: Topband: Handheld Impedance Analyzer

[shristov]

 "Richard (Rick) Karlquist"  wrote:

> I don't believe the above assertion.
 
> Can anyone give a specific example of an antenna having
> an SWR at the resonant frequency, (where X=0), that is higher than
> the SWR at frequencies slightly above or below the resonant frequency?
 
> I submit that a local minimum in the SWR will always coincide
> with X=0.  This is easily proved on a Smith chart, where X=0
> corresponds to the X-axis.  Adding reactance or susceptance moves
> the impedance farther from the origin in all cases, meaning SWR goes up.


It would be exactly so if the real part of the antenna
input impedance did not change with frequency.

The real part of dipole impedance rises quite a bit with frequency, so the 
resonant
frequency as defined by X=0 will be different from the minimum SWR frequency.
With multi-element beams, R may change with frequency in more complex ways.

But for a given coax impedance, what should be aimed for is the lowest
maximum SWR in the working frequency range (subject to preferences).
The resonant frequency itself, defined as X=0 or otherwise, is irrelevant.

73,

Sinisa  YT1NT, VE3EA







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Re: Topband: Handheld Impedance Analyzer

[Richard (Rick) Karlquist]

On 3/28/2016 9:14 AM, Jim Brown wrote:

On Mon,3/28/2016 4:37 AM, KE1F Lou wrote:

Is the lowest SWR is the resonant frequency?
 Resonant frequency is when Xl=Xc.
When Xl=Xc is not necessarily the lowest SWR.


Exactly right. If, for example, the antenna's feedpoint impedance at
resonance is different from the feedline impedance, or if the analyzer
impedance does not match the feedline impedance, the lowest MEASURED SWR

73, Jim K9YC
_


I don't believe the above assertion.

Can anyone give a specific example of an antenna having
an SWR at the resonant frequency, (where X=0), that is higher than
the SWR at frequencies slightly above or below the resonant frequency?

I submit that a local minimum in the SWR will always coincide
with X=0.  This is easily proved on a Smith chart, where X=0
corresponds to the X-axis.  Adding reactance or susceptance moves
the impedance farther from the origin in all cases, meaning
SWR goes up.

Rick N6RK
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Re: Topband: Handheld Impedance Analyzer

[Matt Murphy]

I recently purchased an MFJ 225 two port handheld mini VNA for $269.

http://www.mfjenterprises.com/Product.php?productid=MFJ-225

I do not own more expensive gear to test its calibration against, but so
far it appears accurate both for measuring Xl and Xc, SWR and also doing
frequency sweeps for testing filters.

I'd vowed not to buy another MFJ product after my 259B turned out to have a
faulty tuning capacitor, but this one seems to have improved build quality
and uses encoders behind the knobs.

The unit is compatible with the IG-miniVNA software which runs under
Windows.  At some point once I have a chance to verify the unit's
calibration I will post a review. My needs at this time are mostly to learn
how to use a two-port VNA and potentially justify the purchase of a higher
quality unit.

73,
Matt NQ6N


On Mon, Mar 28, 2016 at 11:14 AM, Jim Brown 
wrote:

> On Mon,3/28/2016 4:37 AM, KE1F Lou wrote:
>
>> Is the lowest SWR is the resonant frequency?
>>  Resonant frequency is when Xl=Xc.
>> When Xl=Xc is not necessarily the lowest SWR.
>>
>
> Exactly right. If, for example, the antenna's feedpoint impedance at
> resonance is different from the feedline impedance, or if the analyzer
> impedance does not match the feedline impedance, the lowest MEASURED SWR
> will be different from the resonant frequency. This happens with lots of
> antennas, including most dipoles, and with most ground-mounted verticals.
> For example, this causes the minimum SWRof my 80 dipole,as measured in the
> shack by a 50 ohm analyzer, to be about 100 kHz below its actual resonant
> frequency.
>
> This is why swept impedance measurements made by an instrument that can
> produce a file that can be transformed by "subtracting out the feedline" is
> so important.
>
> The feedpoint Z of my high dipoles for 80 and 40 is in the range of 85
> ohms, so I feed them with RG11. This minimizes the ACTUAL SWR in the
> feedline (because SWR is determined by the LOAD, NOT the match to the
> transmitter), so it minimizes feedline loss. It does, of course, require
> matching to the rig or power amp in the shack so that the output stage is
> happy, and to minimize distortion in the output stage.
>
> 73, Jim K9YC
>
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Re: Topband: Handheld Impedance Analyzer

[Jim Brown]

On Mon,3/28/2016 4:37 AM, KE1F Lou wrote:

Is the lowest SWR is the resonant frequency?
 Resonant frequency is when Xl=Xc.
When Xl=Xc is not necessarily the lowest SWR.


Exactly right. If, for example, the antenna's feedpoint impedance at 
resonance is different from the feedline impedance, or if the analyzer 
impedance does not match the feedline impedance, the lowest MEASURED SWR 
will be different from the resonant frequency. This happens with lots of 
antennas, including most dipoles, and with most ground-mounted 
verticals. For example, this causes the minimum SWRof my 80 dipole,as 
measured in the shack by a 50 ohm analyzer, to be about 100 kHz below 
its actual resonant frequency.


This is why swept impedance measurements made by an instrument that can 
produce a file that can be transformed by "subtracting out the feedline" 
is so important.


The feedpoint Z of my high dipoles for 80 and 40 is in the range of 85 
ohms, so I feed them with RG11. This minimizes the ACTUAL SWR in the 
feedline (because SWR is determined by the LOAD, NOT the match to the 
transmitter), so it minimizes feedline loss. It does, of course, require 
matching to the rig or power amp in the shack so that the output stage 
is happy, and to minimize distortion in the output stage.


73, Jim K9YC
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Re: Topband: Handheld Impedance Analyzer

[KE1F Lou]

Is the lowest SWR is the resonant frequency?
 Resonant frequency is when Xl=Xc.
When Xl=Xc is not necessarily the lowest SWR.

73 Lou  KE1F


On 3/27/2016 8:30 PM, Robert Harmon wrote:

Maybe a dumb question but how can you tell the resonant freq with
the AA-54.   I have one and can do the graph and see where it dips to 
the lowest
but havent figured out how to find the resonant freq other than 
entering freqs in the
close by range and find on that has the lowest SWR.   I have the 
MFJ-259B also and
it is no match for the AA-54 but at least when I scan I can find the 
lowest swr point

and then read the frequency.

Bob
K6UJ

On 3/27/16 4:24 PM, Stan Stockton wrote:

I also have AA-54 analyzers.  There is no comparing the MFJ-259B to the
AA-54.  The rig expert unit runs circles around the MFJ in so many ways.
Once you use an AA-54 I will guarantee that you will never ever want 
to use

an MFJ analyzer again.

73...Stan, K5GO

On Sun, Mar 27, 2016 at 4:45 PM, <donov...@starpower.net> wrote:


Hi Dick,


I have an AA-54 and its the best hand held antenna analyzer I've
ever owned.


73
Frank
W3LPL

- Original Message -

From: "dick.bingham" <dick.bing...@gmail.com>
To: topband@contesting.com
Sent: Sunday, March 27, 2016 7:08:09 PM
Subject: Topband: Handheld Impedance Analyzer

Greetings All

I am getting fed up with multiple trips between new antenna matching
stations and the
tx-source/VSWR and not converging on a good match in quick order !

Please send me - OFF LINE - your recommendation for a handheld 
impedance

measuring tool that covers 400KHz to at least 150MHz. I looked at the
RigExpert AA-220 in the latest QST and it looks like a decent tool.

I certainly do not want to restart this topic but new stuff is becoming
available and I don't want to settle for second best if 'best' is 
not 2X

more costly!

73 Dick/w7wkr CN97uj

- 




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Re: Topband: Handheld Impedance Analyzer

[Guy Olinger K2AV]

Grant has a good list of possibilities in his post. Some newer ones I
haven't tried yet.

SWR is an extremely limited measurement to analyze antennas. I have had
many correspondences with hams led off on a wild goose chase by SWR
measurements. With their MFJ 259's etc, I have them create graphs of X and
R by frequency so they can see what is happening. That's a lot of trouble,
and the MFJ doesn't tell you the sign of the X value. But the graphs
usually turn on the lights in Georgia.

The best tools for analyzing antenna issues are instruments that produces a
graph of R vs frequency overlaid by X vs frequency. Resonance is where the
X graph crosses zero. Capacitive reactance should be a negative value.

The other useful trick is many analyzers' ability to show impedance
presented at the far end of a transmission line. This is done in a software
or firmware program after saving characteristics of the transmission line
with a calibration procedure of one sort or other. The conversion is a math
exercise.

There is a tendency to assume that the measurement in the shack is the same
as the measurement at the antenna. This is just about never true over
bandwidth and the effect of an unfortunate length of transmission line can
cause changes in SWR at the shack to apparently run backward from component
changes at the antenna creating enormous confusion and waste of time.
Having the instrument convert values based on it's calibration of a
feedline completely eliminates this kind of confusion.

And there are most excellent NON-resonant antennas that simply cannot be
setup properly with SWR readings.

Beyond that, the "transmission line" can contain a filter for highpass,
lowpass, or bandpass to remove unwanted signals from overloading an
instrument. The calibration of the transmission line is made with the
filter in line and that calibration data and the program math will correct
for the impedance changes caused by the filter as well as the coax. This is
extremely handy with BC stations nearby. My AIM 4170 has this feature and
has paid for the cost of the instrument many times over, being able to
obtain clean graphs regardless of any high level crap RF around.

Once you realize what you are seeing with graphs of R and X vs frequency,
you will realize that SWR tells you about the same as an oil pressure lamp
in your car. All you know is that it's changed from what you had before.
But to analyze and chase troubles, you will immediately go for the R and X
graphs.

SWR is grotesquely over-valued as an indicator. It can be a flat liar for
some trouble shooting and can make an antenna gone really bad look good.
Just remember that the best dummy load has a really great SWR.

It will cost you some money, especially if you get to realizing how useful
TWO port devices really are. But those too are coming down in price, and if
you really want to know what is going on with wires and matching networks,
you will get the good stuff, and put away the toys.

73 and good luck
Guy K2AV

On Sun, Mar 27, 2016 at 8:45 PM, Grant Saviers  wrote:

> My 2c, having owned MFJ269, AIM4170, VNWA2.3 & 3, AA54, SARK110, old noise
> bridges, and used a friends FG-01 on a DXpedition.
>
> The MFJ is old, not all that accurate and really useless in the presence
> of other strong RF, eg BCB.  Sold it.  I'd call it obsolete vs current
> competition.
>
> AIM4170 (old serial port) was next, still own it and use it, the separate
> DC power and PC is a pain for "handheld" but done that, nice graphics,
> accurate, PC output, full calibration capabilities, it's a full S11
> analyzer + TDR.
>
> VNWA 2.3 then upgraded to VNWA 3, full 2 port network analyzers, these are
> in a league of $$$ bench instruments, rarely used for antennas, but most
> heavily used of all.
>
> AA54 bought as real "handheld" for on tower or at antenna, no PC needed,
> funky menu system, simple B graphics, no auto find capability, but did
> what I needed in the yard and on DXpeditions, SO239 connector and rugged
> case make it pretty sturdy.
>
> SARK110 is the latest,  fits in shirt pocket, much better color graphics
> and PC output than AA54, a real S11 analyzer, TDR, signal gen, etc.  Most
> bang for the buck.  Cal capabilities. Fragile connector.  Several auto
> modes that are useful when tuning. Rechargable battery, decent life.  The
> winner for me.
>
> You Kits FG-01 (now FG-011), smallest, does the swr measuring job, easy to
> navigate, cheapest
>
> Caution:  Experience (bad) shows the SARK110 and FG-01 won't handle much
> RF, you can blow the front ends if tuning an antenna while another nearby
> is transmitting which can happen on DXpeditions. Probably true for all of
> the others, but so far avoided with the AA54.  The others stayed home.
>
> Big antennas can sometimes hear enough RF to make these handheld units
> yield ambiguous results.  There really aren't the bandpass filtering and
> bullet proof front end needed that you find in R, Agilent, etc.  

Re: Topband: Handheld Impedance Analyzer

[Robert Harmon]

Maybe a dumb question but how can you tell the resonant freq with
the AA-54.   I have one and can do the graph and see where it dips to 
the lowest
but havent figured out how to find the resonant freq other than entering 
freqs in the
close by range and find on that has the lowest SWR.   I have the 
MFJ-259B also and
it is no match for the AA-54 but at least when I scan I can find the 
lowest swr point

and then read the frequency.

Bob
K6UJ

On 3/27/16 4:24 PM, Stan Stockton wrote:

I also have AA-54 analyzers.  There is no comparing the MFJ-259B to the
AA-54.  The rig expert unit runs circles around the MFJ in so many ways.
Once you use an AA-54 I will guarantee that you will never ever want to use
an MFJ analyzer again.

73...Stan, K5GO

On Sun, Mar 27, 2016 at 4:45 PM, <donov...@starpower.net> wrote:


Hi Dick,


I have an AA-54 and its the best hand held antenna analyzer I've
ever owned.


73
Frank
W3LPL

- Original Message -

From: "dick.bingham" <dick.bing...@gmail.com>
To: topband@contesting.com
Sent: Sunday, March 27, 2016 7:08:09 PM
Subject: Topband: Handheld Impedance Analyzer

Greetings All

I am getting fed up with multiple trips between new antenna matching
stations and the
tx-source/VSWR and not converging on a good match in quick order !

Please send me - OFF LINE - your recommendation for a handheld impedance
measuring tool that covers 400KHz to at least 150MHz. I looked at the
RigExpert AA-220 in the latest QST and it looks like a decent tool.

I certainly do not want to restart this topic but new stuff is becoming
available and I don't want to settle for second best if 'best' is not 2X
more costly!

73 Dick/w7wkr CN97uj

-


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Re: Topband: Handheld Impedance Analyzer

[Stan Stockton]

I also have AA-54 analyzers.  There is no comparing the MFJ-259B to the
AA-54.  The rig expert unit runs circles around the MFJ in so many ways.
Once you use an AA-54 I will guarantee that you will never ever want to use
an MFJ analyzer again.

73...Stan, K5GO

On Sun, Mar 27, 2016 at 4:45 PM, <donov...@starpower.net> wrote:

> Hi Dick,
>
>
> I have an AA-54 and its the best hand held antenna analyzer I've
> ever owned.
>
>
> 73
> Frank
> W3LPL
>
> - Original Message -
>
> From: "dick.bingham" <dick.bing...@gmail.com>
> To: topband@contesting.com
> Sent: Sunday, March 27, 2016 7:08:09 PM
> Subject: Topband: Handheld Impedance Analyzer
>
> Greetings All
>
> I am getting fed up with multiple trips between new antenna matching
> stations and the
> tx-source/VSWR and not converging on a good match in quick order !
>
> Please send me - OFF LINE - your recommendation for a handheld impedance
> measuring tool that covers 400KHz to at least 150MHz. I looked at the
> RigExpert AA-220 in the latest QST and it looks like a decent tool.
>
> I certainly do not want to restart this topic but new stuff is becoming
> available and I don't want to settle for second best if 'best' is not 2X
> more costly!
>
> 73 Dick/w7wkr CN97uj
>
> -
>
>
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Re: Topband: Handheld Impedance Analyzer

[Martin Kratoska]

Try SARK-110
http://www.sark110.com/home

beats others mostly hands down.

73,
Martin, OK1RR

Dne 27.3.2016 v 21:08 dick.bingham napsal(a):

Greetings All

I am getting fed up with multiple trips between new antenna matching stations 
and the
tx-source/VSWR and not converging on a good match in quick order !

Please send me - OFF LINE - your recommendation for a handheld impedance 
measuring tool that covers 400KHz to at least 150MHz. I looked at the RigExpert 
AA-220 in the latest QST and it looks like a decent tool.

I certainly do not want to restart this topic but new stuff is becoming 
available and I don't want to settle for second best if 'best' is not 2X more 
costly!

73 Dick/w7wkr CN97uj
-


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Re: Topband: Handheld Impedance Analyzer

[Richard (Rick) Karlquist]

On 3/27/2016 12:08 PM, dick.bingham wrote:


73 Dick/w7wkr CN97uj


Most or all of these devices are intolerant of
strong AM BCB signals.  If you have BCB stations
within 10 or 15 miles, try to borrow one to see
if it works for your situation before buying
one.  If you buy one, try to get return priveleges.
You cannot add a BCB reject filter to help,
unless the unit can do "calibration".  All handhelds
I am aware of don't have this capability.
If you don't have any nearby BCB stations, then
you can disregard this warning.

Rick N6RK
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Re: Topband: Handheld Impedance Analyzer

[donovanf]

Hi Dick, 


I have an AA-54 and its the best hand held antenna analyzer I've 
ever owned. 


73 
Frank 
W3LPL 

- Original Message -

From: "dick.bingham" <dick.bing...@gmail.com> 
To: topband@contesting.com 
Sent: Sunday, March 27, 2016 7:08:09 PM 
Subject: Topband: Handheld Impedance Analyzer 

Greetings All 

I am getting fed up with multiple trips between new antenna matching stations 
and the 
tx-source/VSWR and not converging on a good match in quick order ! 

Please send me - OFF LINE - your recommendation for a handheld impedance 
measuring tool that covers 400KHz to at least 150MHz. I looked at the RigExpert 
AA-220 in the latest QST and it looks like a decent tool. 

I certainly do not want to restart this topic but new stuff is becoming 
available and I don't want to settle for second best if 'best' is not 2X more 
costly! 

73 Dick/w7wkr CN97uj 
-
 


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Re: Topband: Handheld Impedance Analyzer

[Mike Waters]

On Sun, Mar 27, 2016 at 2:40 PM, Jim Brown 
wrote:

> I don't have time to write off-list replies to questions that have general
> interest, so I'm responding on the list.


Same here. :-)

My "quick and dirty antenna analyzer is still a 10+ year old MFJ-259B. I
> also own an even older AEA sweep analyzer that can be jumpered for 75 ohms,
> and I have it set that way to measure 75 ohm feedlines.
>

I was also going to suggest an MFJ-259B (what I use), but it doesn't cover
the entire freq range specified.
It works for 75 ohms, if you use the digital display rather than the analog
SWR meter and (of course) connect it directly to the feedpoint with a 6"
piece of coax.

Jim just gave you very good advice. It depends on what you are willing to
pay.

73, Mike
www.w0btu.com
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Re: Topband: Handheld Impedance Analyzer

[Jim Brown]

On Sun,3/27/2016 12:08 PM, dick.bingham wrote:

I certainly do not want to restart this topic but new stuff is becoming 
available and I don't want to settle for second best if 'best' is not 2X more 
costly!


I don't have time to write off-list replies to questions that have 
general interest, so I'm responding on the list. I suspect that the 
solution to your problem is a combination of 1) better understanding of 
your antenna design, which is generally aided by study of books like the 
ARRL Antenna Book and the ON4UN book; 2) decent measurement hardware; 
and 3) comparing measured results with the model, using free software 
like AE6TY's SimSmith and AC6LA's ZPlots (a freeware Excel spreadsheet 
that runs only in Excel, not in freeware clones).


My "quick and dirty antenna analyzer is still a 10+ year old MFJ-259B. I 
also own an even older AEA sweep analyzer that can be jumpered for 75 
ohms, and I have it set that way to measure 75 ohm feedlines.


My really good one is the VNWA 3e, designed by German prof DG8SAQ, built 
and sold by hams in the UK. All the heavy lifting is done in a laptop 
connected via USB, and the VNWA is USB powered. The VNWA software links 
to ZPlots, which can transform a measurement made in the shack to one 
made at the antenna itself. And the VNWA can do a TDR of the line to 
tell ZPlots how long the line is that must be transformed, and can 
measure to very good precision Vf, Zo, and attenuation vs frequency of a 
sample of the coax in use. For those who may have slept through 
Transmission Lines, Vf, Zo, and attenuation all vary with frequency, and 
the variation is greatest at lower frequencies. This is all predicted by 
the transmission lines equations. I paid about $750 for my VNWA three 
years ago, including a calibration kit, a cheesy carrying case, and 
shipping to my door in W6.


The VNWA, like most serious vector analyzers, can generate data files 
for export to programs like SimSmith and ZPlots, which can then be used 
to design matching networks, stubs, etc. And the VNWA is well supported 
both by a Yahoo Group that is monitored daily by DG8SAQ, the hams who 
sell the unit, and a fair number of smart and helpful users.


http://sdr-kits.net/VNWA3_Description.html

73, Jim K9YC
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Topband Reflector Archives - http://www.contesting.com/_topband

Topband: Handheld Impedance Analyzer

[dick.bingham]

Greetings All

I am getting fed up with multiple trips between new antenna matching stations 
and the 
tx-source/VSWR and not converging on a good match in quick order ! 

Please send me - OFF LINE - your recommendation for a handheld impedance 
measuring tool that covers 400KHz to at least 150MHz. I looked at the RigExpert 
AA-220 in the latest QST and it looks like a decent tool.

I certainly do not want to restart this topic but new stuff is becoming 
available and I don't want to settle for second best if 'best' is not 2X more 
costly!

73 Dick/w7wkr CN97uj 
-
 


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Topband Reflector Archives - http://www.contesting.com/_topband