On Jun 4, 11:30*am, Cecil Moore wrote:

That is a trivial problem. What configuration?
What does the schematic look like?

The auto tuner is a simple LC network (series inductor, shunt
capacitor) Cecil. It reports the inductor and capacitor values and the
side of the network the shunt capacitor is on (transmitter or
antenna). Of course it reports final SWR as well.

For instance, at 28.7Mhz it matched with an inductor value of 0.17
microhenries and 0 pF at an SWR of 1.0 (1:1).

My MFJ-259B reported 25-j11 at 28.7 Mhz which obviously is not in
agreement with the auto

Thanks Cecil

Dykes AD5VS

On Jun 4, 11:09*am, Jim Lux wrote:

you can do it with an Excel Spreadsheet..

A spreadsheet like XLZIZL does it in a flash.

Thanks Jim. I found and downloaded XLZIZL

73
Dykes AD5VS

On Jun 4, 12:18*pm, Richard Clark wrote:
On Thu, 04 Jun 2009 11:47:31 -0700, Jim Lux
wrote:

By the way, the assumption that the run of the mill ham rig has a 50 ohm
resistive output impedance is not necessarily valid.

By the way, this comment above is another assumption in that it lacks
a quantifiable. *I find it offered quite often as a negative assertion
to which the several many posters who offer them never provide an
actual value to prove what the run of the mill ham rig is, much less
is "not."

Actually, I did a casual search for such data, but couldn't find any
for the "run of the mill" solidstate 100W ham rig . There is a fair
amount of data for one tube rig or another). There is some data in
the Moto Ap notes by Granberg, etc, that's reasonably representative,
but it doesn't include the effect of the inevitable LPF on the output.

So, looking at things with which I have practical experience and
measurements.. MMIC amps tend to be be pretty flat over octave
bandwidths, but I don't think they're representative of ham rigs with
either FET or Bipolar output stages (which have to cover multiple
octaves, in any case). Hot microwave FET amps have output impedances
that are anything but 50 ohms, and designing the output networks keeps
lots of RF engineers employed, especially over temperature and device
parameter variation.

I'd love to see some real data for ham rigs.



*Rarer, indeed, is any effort put forward by those posters
to show they have attempted to quantify their own equipment.

Perhaps that's because this is, after all, "rec. radio", as in, nobody
is paying people to comment here, and unless you have a particular
need to know the output Z, it's not worth it to spend the time to
measure it. As previously commented, either you're in the "no tuner"
category, and you tolerate whatever mismatch there is on both ends of
the transmission line, or you have a tuner, and you tune for "best
match", with whatever the output Z is.

For all we know, the folks that complain about not getting a good
match on a Brand X antenna, when everyone else does, have a rig with a
bad match on the output.


As there are posters here who have performed this work, shown their
data, and such data follows conventional design considerations (which
is easily revealed within the page cited athttp://www.wy2u.com/);

Indeed? I'd love to see the data.


then these assumptions dressed in denial are rather unprofound proofs.
As this topic has been visited many times, and as it quickly descends
into equally unsupported claims (although often annotated with vague
references and citations that are quickly demolished); I doubt
anything said here is going to sway those assumptions.


My original contention is that if you're going to measure Antenna Z by
using an autotuner and seeing where it tunes, one of the underlying
assumptions is that the other side of the tuner is 50 ohms.

In reality, having actually done this (e.g. use LDG AT200PC tuners to
measure the mutual impedance matrix of an array), I think the
resolution/step size of the tuner is a bigger problem with the
technique. Given the availability of low cost VNAs for the ham
market, that's a MUCH better solution to measuring antenna impedances.

As an amusing exercise (I anticipate none will tread down this path),
the page athttp://www.wy2u.com/offers a means to test your own rig's
Source Z - if, in fact, you can cope with translating your tuner's
settings into picofarads and nanohenries, and if you can obtain a
known mismatch. *These impediments are Herculean to most,
unfortunately.

Looking at that page, I don't see an obvious link.

Measuring the output Z of the transmitter would be an interesting
exercise.. for microwave circuits, one uses a load-pull setup..

The challenge is, of course, that the amplifier is an active device,
so the output Z probably changes depending on the load. It's not like
an antenna, where the feedpoint Z at a given frequency is pretty much
constant, regardless of the incident power.



73's
Richard Clark, KB7QHC

dykesc wrote in
:

On Jun 4, 4:33*pm, Owen Duffy wrote:

I have thought about this in the past, mainly the prospect of a relay
switched autotuner that reported a calculated load Z based on the
found matching solution, but I concluded that it was not likely to be
of reasonable accuracy over the tuner range.

Probably would be as accurate as any other gear we can afford Owen.

I doubt it. Again it relates to the loss characterisation of the
components. If you could do that, the device could also calculate its own
efficiency... now that would be a feature that would kill the market!!!

I'm going to suggest that MFJ make that a feature on an auto tuner. I

See above.

....

There is at least one instrument for the
ham market that purports to make such measurements at normal
transmitter power. IIRC, R&S used make a commercial product, but it
wouldn't have come cheap.

I looked on the R&S site. The only thing I found was a "Field Fox"
analyzer selling for $7,599.00. It is the cat's meow, but guess I'll
have to stick with my 259B.

http://www.telepostinc.com/ for a ham instrument (LP-100).



There is at least one other low level antenna analyser that
represents that it is less affected by interference than the '259B.

Which one Owen.


http://w5big.com/ AIM4170.

The operative word in my statement was "represents". As to whether it is
actually better, and whether it is adequate, you will need to depend on
owners. The badging of the instrument as AS doesn't add value for me.

Problem is that many of the people using these things see them as a magic
bullet and don't actually understand transmission line fundamentals,
which questions their opinion of the performance of the instrument.


That has become very obvious to me.

We haven't dispensed with the need for a good reflectometer in capable
hands, or is it just that we haven't dispensed with the need for capable
hands?

BTW, for referring measurements at one place to another, TLLC at
http://www.vk1od.net/calc/tl/tllc.php may be of interest. It would be a
challenge to incorporate those calcs in a small 8 bit microcontroller,
their capacity and performance on logs, hyperbolic cosines, etc is the
issue. Probably why most of the tools that do this, use a client on a PC
to do the calcs and presentation.

Owen

"dykesc" wrote in message
...
On Jun 4, 12:29 pm, "Jerry" wrote:

I may be missing something. But, if the objective it to learn if the
local 105 MHz signal is actually introducing error into your impedance
measurement, only a few Smith Chart Polts are needed. You know the path
(on
the Chart) the shunt reactance will have taken while being adjusted to
make
a "match". You also know the path the series reactance took. Start from
the Chart center and move the impedance along the circles of constant
resistance for the series reactor. Move along the circles of constant
admittance for the shunt reactance. When the Xc and Xl are both known, and
you know which is closest to the "transmitter", it seems that a "program"
is
unnecessary. What am I mising?

Jerry KD6JDJ

Thanks Jerry. No you aren't missing anything other than the fact that
my familiarity with Smith Chart analysis is limited to working through
a few exercises in the last chapter of the ARRL Antenna book. I will
be looking for more Smith Chart tutorial info on the web and am
certain I can get myself up to speed enough to start working with
conductance, suseptance, admittance, etc.

Thanks again. From your post it appears it will be a straight forward
exercise once I get my head around it.

73
Dykes AD5VS

Hi Dykes

As you may already know, the Smith Chart is simply a plot that shows *all*
impedances with a real resistance. Smith displays the impedances so the
user can quickly see how any given impedance can be adjusted by adding any
series or parallel resistances and/or reactances. Series inductance moves
the impedance "upward" along the circles of constant Resistance. Shunt
inductance will move an impedance along the circles of constant conductance.

Jerry KD6JDJ

On Thu, 4 Jun 2009 22:05:00 -0700 (PDT), wrote:

On Jun 4, 12:18*pm, Richard Clark wrote:
On Thu, 04 Jun 2009 11:47:31 -0700, Jim Lux
wrote:

By the way, the assumption that the run of the mill ham rig has a 50 ohm
resistive output impedance is not necessarily valid.

By the way, this comment above is another assumption in that it lacks
a quantifiable. *I find it offered quite often as a negative assertion
to which the several many posters who offer them never provide an
actual value to prove what the run of the mill ham rig is, much less
is "not."

Actually, I did a casual search for such data, but couldn't find any
for the "run of the mill" solidstate 100W ham rig . There is a fair
amount of data for one tube rig or another).

Hi Jim,

Searching and measuring are worlds apart.

There is some data in
the Moto Ap notes by Granberg, etc, that's reasonably representative,
but it doesn't include the effect of the inevitable LPF on the output.

Now, this is the most curious statement of them all. Every LPF that
is mounted in any Ham grade HF rig is designed with both a 50 Ohm
input Z and a 50 Ohm output Z. This is easily verified through the
same page that does the calculations, or through trivial math for the
individual components' Z.

So, looking at things with which I have practical experience and
measurements.. MMIC amps tend to be be pretty flat over octave
bandwidths, but I don't think they're representative of ham rigs with
either FET or Bipolar output stages (which have to cover multiple
octaves, in any case).

Why not? Those same HF rigs have switched LPFs for each octave. This
has been a staple of solid state design for 30+ years. Consult a
schematic.

Hot microwave FET amps have output impedances
that are anything but 50 ohms, and designing the output networks keeps
lots of RF engineers employed, especially over temperature and device
parameter variation.

And for those same 30+ years of HF solid state rigs, their power
transistors have had (and still do) output "native" Z of several Ohms.
This is not a remarkable deviation by the progression to FET, the FET
is simply a different "native" Z with a different transform to get to
the same 50 Ohms. Consult any schematic where the Z transform in the
output transformer is clearly in a Z step-up in the proper ratio. This
stuff has been slam-dunk for decades.

I'd love to see some real data for ham rigs.

Mine (Drake TR-7 and Kenwood TS-430s) exhibit values that vary around
50 Ohms with a low of 35 Ohms and a high of 70 Ohms in the margins.
Those rigs also suffer in those margins. Measurements were done by
pull, by substitution, by looking into the antenna connector with an
RF Bridge and all confirmed by simple reverse design principles.
Variations between any method rarely departed from one another, and
never from the values above. Walt Maxwell has reported his own data
(tube set albeit, but the principles of transformation and exhibited
Source Z are not dependant upon technology).

*Rarer, indeed, is any effort put forward by those posters
to show they have attempted to quantify their own equipment.

Perhaps that's because this is, after all, "rec. radio", as in, nobody
is paying people to comment here, and unless you have a particular
need to know the output Z, it's not worth it to spend the time to
measure it.

This apology condemns the hobby to the lowest common denominator. If
it were meaningful, we would be reading yet another miracle antenna
claim without hint of skeptical enquiry braced with theory, hammered
with models and test gear behind it.

As previously commented, either you're in the "no tuner"
category, and you tolerate whatever mismatch there is on both ends of
the transmission line, or you have a tuner, and you tune for "best
match", with whatever the output Z is.

Every problem is reduced to those two options?

For all we know, the folks that complain about not getting a good
match on a Brand X antenna, when everyone else does, have a rig with a
bad match on the output.

That is arguably so, and my experience described above about operation
in the margins would suggest so. But it would be a very atrocious
Source Z that would lead one to that observation. My experience was
noted only by close examination, not a smoking finals deck. The
complainants experience would argue that the rig is flat out broken
with the drivers pushing 5 or 10 W through incapacitated finals.

More likely the complaining is related to issues outside of the rig.

As there are posters here who have performed this work, shown their
data, and such data follows conventional design considerations (which
is easily revealed within the page cited athttp://www.wy2u.com/);

Indeed? I'd love to see the data.

Op. Cit.

then these assumptions dressed in denial are rather unprofound proofs.
As this topic has been visited many times, and as it quickly descends
into equally unsupported claims (although often annotated with vague
references and citations that are quickly demolished); I doubt
anything said here is going to sway those assumptions.


My original contention is that if you're going to measure Antenna Z by
using an autotuner and seeing where it tunes, one of the underlying
assumptions is that the other side of the tuner is 50 ohms.

In reality, having actually done this (e.g. use LDG AT200PC tuners to
measure the mutual impedance matrix of an array), I think the
resolution/step size of the tuner is a bigger problem with the
technique. Given the availability of low cost VNAs for the ham
market, that's a MUCH better solution to measuring antenna impedances.

As an amusing exercise (I anticipate none will tread down this path),
the page athttp://www.wy2u.com/offers a means to test your own rig's
Source Z - if, in fact, you can cope with translating your tuner's
settings into picofarads and nanohenries, and if you can obtain a
known mismatch. *These impediments are Herculean to most,
unfortunately.

Looking at that page, I don't see an obvious link.

Can you supply a known mismatch? It is inputable at that page;
Can you supply a known C from a tuner that has matched that load? It
is inputable at that page;
Can you supply a known L from a tuner that has matched that load? It
is inputable at that page;
Can you adjust the source Z when the tuner has matched that load? It
is inputable at that page.

This is a substitution method.

These steps reveal the common design criteria for building an LPF for
an output stage. Consult "Filters, Image-Parameter Design" in any
copy of "Reference Data for Radio Engineers." Consult, further,
"Filters, Modern-Network-Theory Design" in the same source. Read the
caption of Fig. 2 in that section:
"The Generator and Load must be considered part of the filter."
In the supporting text:
"The generator and load resistors can be assigned any value
between zero and infinity."
Fig. 25 shows the mathematical impact of Source Z (as R or G) to the
Network response. It also shows the Load Z as a mirror R or G in
symmetry to the source. These commonplace considerations are repeated
in Fig. 27, 28, and 29.

Consult Fig. 34 where both ends can be "interchanged." And repeated
out through Fig. 56.

In the section entitled "Low-Impedance Generator and Load" observe:
"A low impedance generator and/or load may be used with
the above filter by ... an effective turns ratio that transforms
the low impedance to the value required..."

Measuring the output Z of the transmitter would be an interesting
exercise.. for microwave circuits, one uses a load-pull setup..

The challenge is, of course, that the amplifier is an active device,
so the output Z probably changes depending on the load.

I've heard that platitude far too many times. Of course it is an
active device. Of course the output Z changes with load. Do you have
anything more to offer than simple qualitative musings? One could as
easily dream that output Z varies with room temperature, with
humidity, with time of day, with elevation, and if the total of those
variations were capped off with a quantitative measurement of an
accumulated ±10%, then the whole list of objections would get hooted
off the stage. Give me a metric instead of looking under the bed for
spooks.

It's not like
an antenna, where the feedpoint Z at a given frequency is pretty much
constant, regardless of the incident power.

It is also not like a resistor, or a capacitor, or an inductor. Nor
is it like an audio amp or its speaker. The output Z is not like so
many things that to start this list only leads into an infinity of
trivial comparisons that wander the landscape.

So, the output Z is not like the load Z. What significance does that
bring?

On the other hand, I have worked with high power Transistor circuits
that have acted exactly as resistors, inductors, and capacitors and
output Z was exactly like an antenna at a given frequency (or rather
input Z, as one design was an active 100W load).

73's
Richard Clark, KB7QHC

"Jerry" wrote in
:

....
As you may already know, the Smith Chart is simply a plot that shows
*all*
impedances with a real resistance. Smith displays the impedances so
the user can quickly see how any given impedance can be adjusted by
adding any series or parallel resistances and/or reactances. Series
inductance moves the impedance "upward" along the circles of constant
Resistance. Shunt inductance will move an impedance along the circles
of constant conductance.

There are a range of formats for plotting "*all* impedances with a real
resistance", and Philip Smith found some of them in his quest for what is
now known as the Smith chart. It is not simply a plot of R and X, but in
fact a plot of the complex voltage reflection coefficient and it can have
R and X scales overlaid (along with a bunch of TL related radial scales),
and because of the behaviour of transmission lines, G and B scales. The
R, X, G, B scales are a consequence of the plot of the voltage reflection
coefficient, an overlay, and not the fundamental quantity plotted.

The magic that underlies the Smith chart is the Telegrapher's Equation
(or a lossless form for most applications).

Owen

"Roger D Johnson" wrote in message
...
dykesc wrote:
I am trying to validate impedance values I am measuring with my
MFJ-259B. I want to do this by using my MFJ-993B auto tuner. The tuner
uses a simple L network to create the conjugate match. I want to take
the final inductance, capacitance and swr values from the auto tuner
digital display after matching is completed and back calculate the
impedance that the tuner is seeing. Is there an online calculator that
will do this?

Many thanks for replys.

Yes! It's called RevLoad and is available free from Tonne Software.

http://tonnesoftware.com/

73, Roger

Thanks Roger Thats a great program.

Jerry KD6JDJ

On Jun 4, 10:30*pm, Owen Duffy wrote:

I doubt it. Again it relates to the loss characterisation of the
components. If you could do that, the device could also calculate its own
efficiency... now that would be a feature that would kill the market!!!


Actually, you could probably do this with a series of lookup table. A
tuner mfr has a fairly good idea (or can get a fairly good idea, with
some time to do appropriate measurements) of the loss properties of
the tuner components. Based on measuring some AT200PCs with a TenTec
VNA, there is *some* interaction between the components, so it's not a
perfect linear scaling as you step through the values. The tuner knows
the frequency, it knows the L and C, and it knows the parasitic Rs,
and it knows that it's "matched", so it should be able to calculate
currents and voltages, and figure out loss.

Whether you could do it in a tiny PIC... I don't know.



I'm going to suggest that MFJ make that a feature on an auto tuner. I

See above.

BTW, for referring measurements at one place to another, TLLC athttp://www.vk1od.net/calc/tl/tllc.phpmay be of interest. It would be a
challenge to incorporate those calcs in a small 8 bit microcontroller,
their capacity and performance on logs, hyperbolic cosines, etc is the
issue. Probably why most of the tools that do this, use a client on a PC
to do the calcs and presentation.


You'd be surprised.. the question is whether someone is motivated
enough to try and do it. There's not much commercial market, so it
would be a labor of love, and that requires a somewhat bizarre
intersection of someone who takes pride in putting complex math (in
both senses of complex) into a limited processor AND someone who is
familiar with the relevant equations and their use.

In any case, given that folks have done this sort of thing on
Z80/8085/6502 class processors... It doesn't have to be fast.. 10
seconds is a LOT of CPU clock cycles.
jim

On Jun 5, 12:00*am, Richard Clark wrote:
On Thu, 4 Jun 2009 22:05:00 -0700 (PDT), wrote:
On Jun 4, 12:18*pm, Richard Clark wrote:

Hi Jim,

Searching and measuring are worlds apart.

In the context of discussing on a newsgroup, I'm willing to spend a
few minutes searching. I'm not willing to spend hours measuring.
Others might. I seem to have recalled seeing some data a few years
ago, but I couldn't find it with google.



There is some data in
the Moto Ap notes by Granberg, etc, that's reasonably representative,
but it doesn't include the effect of the inevitable LPF on the output.

Now, this is the most curious statement of them all. *Every LPF that
is mounted in any Ham grade HF rig is designed with both a 50 Ohm
input Z and a 50 Ohm output Z. *This is easily verified through the
same page that does the calculations, or through trivial math for the
individual components' Z.

Uh huh... and all manufacturers use high precision components, and the
impedance at one end of the filter isn't affected by the impedance at
the other end?

My original point is that, barring measurement, you don't KNOW.
(which is sort of your argument too, eh?)



So, looking at things with which I have practical experience and
measurements.. MMIC amps tend to be be pretty flat over octave
bandwidths, but I don't think they're representative of ham rigs with
either FET or Bipolar output stages (which have to cover multiple
octaves, in any case). *

Why not? *

Because the MMICs are a totally different design model. To start
with, they're also Class A, while most ham rigs run Class AB. They
also tend to be "detuned" for broadbanding, at the expense of
efficiency. (not all MMICs are this way.. I'm talking about the MAR-n
series, for instance)

Hot microwave FET amps have output impedances
that are anything but 50 ohms, and designing the output networks keeps
lots of RF engineers employed, especially over temperature and device
parameter variation.

And for those same 30+ years of HF solid state rigs, their power
transistors have had (and still do) output "native" Z of several Ohms.

Would that the active device has a Z that is constant, but it's not.
Sure, the MRF454 data sheet says the output Z is 1+.2j ohms (or
something like that) at 30MHz, but is it still that at 1MHz?

Looking at a more modern power FET for amplifier use, the IXZ210N50L..
There's a whole page of S parameters, and S22 goes from 0.88@-51deg at
2MHz to at 14.32 MHz to at 30 MHz... that's
at Ids =200mA.. bump Ids to 500mA, and the magnitudes stay about the
same, but the phases change, by tens of degrees.

Having actually worked on an amplifier design with similar parts, I
can also say that the datasheet is only a "get you in the ballpark for
the design" tool. The "real parts" (especially when packaged on a
board and attached to the heat sink) are substantially different.

No simple transformer is going to make that look like a constant 50
ohms.

I'd love to see some real data for ham rigs.

Mine (Drake TR-7 and Kenwood TS-430s) exhibit values that vary around
50 Ohms with a low of 35 Ohms and a high of 70 Ohms in the margins.
Those rigs also suffer in those margins. *

so the VSWR looking back from the tuner into your transmitter is
1.4:1? A return loss of around 15dB... what's that work out to... an
error of about 10-15% in the "measuring impedance with a tuner"
technique... not bad, but not great, either, especially stacked up
with the other uncertainties..

Good enough to give a "cross check" on another measurement? Maybe...
if the tuner technique showed I had a load Z of 100+50j, and the MFJ
gave a result of 90 + 40j.. yeah, I'd say it is consistent.



Measurements were done by
pull, by substitution, by looking into the antenna connector with an
RF Bridge and all confirmed by simple reverse design principles.
Variations between any method rarely departed from one another, and
never from the values above. *

Although you have to admit that a 2:1 impedance variation isn't a
particularly outstanding "constant impedance load"


*Rarer, indeed, is any effort put forward by those posters
to show they have attempted to quantify their own equipment.

Perhaps that's because this is, after all, "rec. radio", as in, nobody
is paying people to comment here, and unless you have a particular
need to know the output Z, it's not worth it to spend the time to
measure it. *

This apology condemns the hobby to the lowest common denominator. If
it were meaningful, we would be reading yet another miracle antenna
claim without hint of skeptical enquiry braced with theory, hammered
with models and test gear behind it. *

Not at all.. just because *I* don't want to spend the time measuring
it doesn't mean that the information is of no value to the community.
I would venture that of all the data that hams, collectively, could
measure, this is actually not as useful as some other data.. It just
doesn't have that much impact on day to day operation. Very few hams
adjust their tuner by calculating L and C based on measured data, or
else there wouldn't be a plethora of articles and posts about
"tuning", "pruning", "trimming" and the techniques for doing this, and
arguments about whether a Brand X meter is better than a Brand Y
meter, etc.

Hams, by and large, adjust their tuners by minimizing the reflected
power, and don't much care what the actual component values are. (e.g.
what ham tuner actually has accurate dial calibrations in pF or uH? )

Professionals, on the other hand, do CARE, and do make the
measurements, particularly if they're doing phased arrays, or
designing circuits for mass production, or have to document that their
system will work over wide ranges of temperatures, aging, and other
effects. But, because they're getting *paid* to do it, they're more
than happy to do so. It makes the rest of the job easier.



As previously commented, either you're in the "no tuner"
category, and you tolerate whatever mismatch there is on both ends of
the transmission line, or you have a tuner, and you tune for "best
match", with whatever the output Z is.

Every problem is reduced to those two options?

Obviously not, but I'll bet that it covers over 90% of hamdom (and a
lower percentage of the folks reading this thread).


Looking at that page, I don't see an obvious link.

Can you supply a known mismatch? *It is inputable at that page;

This is a substitution method.

Ahh.. I misunderstood.. I thought you were pointing to process for
doing the measurement and/or some measured data. The cited page is
just the calculator for part of the problem.




Measuring the output Z of the transmitter would be an interesting
exercise.. for microwave circuits, one uses a load-pull setup..

The challenge is, of course, that the amplifier is an active device,
so the output Z probably changes depending on the load. *

I've heard that platitude far too many times. *Of course it is an
active device. *Of course the output Z changes with load. *Do you have
anything more to offer than simple qualitative musings?

Sure.. check out the Ixys data sheet. Plenty of grist for "Z varies
with load and frequency"
Phase of S22 varies 40-50 degrees with Ids. That's in your 10%
ballpark
On the other hand, I have worked with high power Transistor circuits
that have acted exactly as resistors, inductors, and capacitors and
output Z was exactly like an antenna at a given frequency (or rather
input Z, as one design was an active 100W load).


Yes.. but were those run-of-the-mill amateur transceivers? (the
original question).. I have no doubt that it is possible to build
amplifiers with constant Z (to any degree of constancy desired.. heck,
a 1000W amp and a 60db pad gives you a 1mW amplifier with very good
output Z, regardless of what the amp does).

But, does a "designed for mass production and cost target" transmitter
fall into that category?
It's not a published spec
ARRL doesn't measure it when they review rigs

So it's left to someone who cares to do so.