"Walter Maxwell" wrote
... I have explained many times that even though the PA source
upstream of the tank circuit is non-linear (and no one's saying it isn't),
the energy storage in the tank makes the output of the tank a linear
source, no matter what the shape of the current wave form may be
at the input. The output of the tank is proved linear because the
voltage/current ratio at the output is non-varying and the shape of
the voltage and current wave forms are essentially sine waves.
Consequently, the output circuit can be represented by a Thevenin
source that supports both a conjugate match and the maximum
power transfer theorem.
______________

If this statement about the tank circuit being ~ a linear source is valid,
does that mean that any load-reflected power that appears across the output
terminals of the tx stops at the tank circuit, and never sees the
non-linear, non-matching Z of the active PA?

And if so, would that also mean that such a tx would not be prone to
producing r-f intermodulation components when external signals are fed back
into the tx from co-sited r-f systems?

Yet experience shows that this is not the case for ~closely spaced
interfering signals. The only mitigation for this for a PA with a tank
circuit is the rejection of that tank circuit to those off-freq, external
signals, and to the resulting IM products generated by mixing with the main
tx signal in the active (and non-linear) PA stage of that tx.

And the tank has VERY low rejection to load reflections of the signal
bandwidth to which it is tuned.

Also to be considered are the modern broadband (88-108MHz) FM broadcast
transmitters, which have no tank circuits, but except for some designs
incorporating balanced 3 dB hybrid combiners are affected by load
reflections about the same as a tx with a tuned tank circuit.

RF

On Tue, 20 Mar 2007 19:19:26 -0500, "Richard Fry" wrote:

"Walter Maxwell" wrote
... I have explained many times that even though the PA source
upstream of the tank circuit is non-linear (and no one's saying it isn't),
the energy storage in the tank makes the output of the tank a linear
source, no matter what the shape of the current wave form may be
at the input. The output of the tank is proved linear because the
voltage/current ratio at the output is non-varying and the shape of
the voltage and current wave forms are essentially sine waves.
Consequently, the output circuit can be represented by a Thevenin
source that supports both a conjugate match and the maximum
power transfer theorem.
______________

If this statement about the tank circuit being ~ a linear source is valid,
does that mean that any load-reflected power that appears across the output
terminals of the tx stops at the tank circuit, and never sees the
non-linear, non-matching Z of the active PA?

Richard, my earlier treatise considers only tube-type PA's with pi-network output coupling circuits used in
the Amateur Service, such as the Kenwood TS-830S on which my measurements were made. It was not intended to
consider PA's used in the tv service. Sorry, I didn't make this distinction earlier.

And if so, would that also mean that such a tx would not be prone to
producing r-f intermodulation components when external signals are fed back
into the tx from co-sited r-f systems?

This issue is irrelevant, because the signals arriving from a co-sited system would not be coherent with the
local source signals, while load-reflected signals are coherent. The destructive and constructive interference
that occurs at the output of a correctly loaded and tuned PA requires coherence of the source and reflected
waves to achieve the total re-reflection of the reflected waves back into the direction toward the load.

Yet experience shows that this is not the case for ~closely spaced
interfering signals. The only mitigation for this for a PA with a tank
circuit is the rejection of that tank circuit to those off-freq, external
signals, and to the resulting IM products generated by mixing with the main
tx signal in the active (and non-linear) PA stage of that tx.

Again, Richard, this condition is irrelevant to the re-reflection of the waves reflected by the load, because
the relevant signals are not coherent.

And the tank has VERY low rejection to load reflections of the signal
bandwidth to which it is tuned.

This may be true for PAs with bandwidths wider than those occurring in ham tx. However, the destructive and
constructive interference between the reflected and source waves in a correctly loaded and tuned ham tx
results in total re-reflection of the reflected waves.

Also to be considered are the modern broadband (88-108MHz) FM broadcast
transmitters, which have no tank circuits, but except for some designs
incorporating balanced 3 dB hybrid combiners are affected by load
reflections about the same as a tx with a tuned tank circuit.

And still further, Richard, the FM transmitters you refer to above are not in the same category as those used
in tube rigs used by hams.

Incidentally, Richard, have you really reviewed the report of my TS-830S experiment?

Walt

"Walter Maxwell" wrote
(RF): And if so, would that also mean that such a tx would not be prone
to producing r-f intermodulation components when external signals
are fed back into the tx from co-sited r-f systems?

This issue is irrelevant, because the signals arriving from a co-sited
system would not be coherent with the local source signals, while load-
reflected signals are coherent. The destructive and constructive
interference that occurs at the output of a correctly loaded and tuned
PA requires coherence of the source and reflected waves to achieve
the total re-reflection of the reflected waves back into the direction
toward the load.

But even for coherent reflections, if the PA tank circuit has very low loss
for incident power (which it does), why does it not have ~ equally low loss
for load reflections of that power? Such would mean that load reflections
would pass through the tank to appear at the output element of the PA, where
they can add to its normal power dissipation.

Also, does not the result of combining the incident and reflected waves in
the tx depend in large part on the r-f phase of the reflection there
relative to the r-f phase of the incident wave? And the r-f phase of the
reflection is governed mostly by the number of electrical wavelengths of
transmission line between the load reflection and the plane of
interest/concern -- which is independent of how the tx has been
tuned/loaded.

If the ham transmitter designs that your paper applies to produce a total
re-reflection of reverse power seen at their output tank circuits, then
there would be no particular need for "VSWR foldback" circuits to protect
them. Yet I believe these circuits are fairly common in ham transmitters,
aren't they? They certainly are universal in modern AM/FM/TV broadcast
transmitters, and are the result of early field experience where PA tubes,
tx output networks, and the transmission line between the tx and the antenna
could arc over and/or melt when reflected power was sufficiently high.

RF

On Wed, 21 Mar 2007 08:18:14 -0500, "Richard Fry" wrote:

"Walter Maxwell" wrote
(RF): And if so, would that also mean that such a tx would not be prone
to producing r-f intermodulation components when external signals
are fed back into the tx from co-sited r-f systems?

This issue is irrelevant, because the signals arriving from a co-sited
system would not be coherent with the local source signals, while load-
reflected signals are coherent. The destructive and constructive
interference that occurs at the output of a correctly loaded and tuned
PA requires coherence of the source and reflected waves to achieve
the total re-reflection of the reflected waves back into the direction
toward the load.

But even for coherent reflections, if the PA tank circuit has very low loss
for incident power (which it does), why does it not have ~ equally low loss
for load reflections of that power? Such would mean that load reflections
would pass through the tank to appear at the output element of the PA, where
they can add to its normal power dissipation.

Also, does not the result of combining the incident and reflected waves in
the tx depend in large part on the r-f phase of the reflection there
relative to the r-f phase of the incident wave? And the r-f phase of the
reflection is governed mostly by the number of electrical wavelengths of
transmission line between the load reflection and the plane of
interest/concern -- which is independent of how the tx has been
tuned/loaded.

If the ham transmitter designs that your paper applies to produce a total
re-reflection of reverse power seen at their output tank circuits, then
there would be no particular need for "VSWR foldback" circuits to protect
them. Yet I believe these circuits are fairly common in ham transmitters,
aren't they? They certainly are universal in modern AM/FM/TV broadcast
transmitters, and are the result of early field experience where PA tubes,
tx output networks, and the transmission line between the tx and the antenna
could arc over and/or melt when reflected power was sufficiently high.

RF
Richard, your statement above begs the question, "Are you aware of the phase relationships between forward and
reflected voltages and between forward and reflected currrents that accomplish the impedance-matching effect
at matching points such as with stub matching and also with antenna tuners?

When the matching is accomplished the phase relationship between the foward and reflected voltages can become
either 0° or 180°, resulting in a total re-reflection of the voltage. If the resultant voltage is 0°, then the
resultant current is 180°, thus voltage sees a virtual open circuit and the current sees a virtual short
circuit. The result is that the reflected voltage and current are totally re-reflected IN PHASE with the
source voltage and current. This is the reason the forward power in the line is greater than the source power
when the line is mismatched at the load, but where the matching device has re-reflected the reflected waves.

This phenomenon occurs in all tube transmitters in the ham world when the tank circuit is adjusted for
delivering all available power at a given drive level. When this condition occurs the adjustment of the
pi-network has caused the relationship between the forward and reflected voltages to be either 0° or 180° and
vice versa for currents, as explained above. When this condition occurs, destructive interference between the
forward and reflected voltages, as well as between the forward and reflected currents, causes the reflected
voltage and current to cancel. However, due to the conservation of energy, the reflected voltage and current
cannot just disappear, so the resulting constructive interference following immediately, causes the reflected
voltage and current to be reversed in direction, now going in the foward direction along with and in phase
with the forward voltage and current.

In transmitters with tubes and a pi-network output coupling circuit there is no 'fold back' circuitry to
protect the amp, because none is needed, due to the total re-reflection of the reflected power. It is only in
solid-state transmitters that have no circuitry to achieve destructive and constructive interference that
requires fold back to protect the output transistors.

This has been a quick and dirty explanation of the phase relations that accomplish impedance matching.
However, I have explained it in much more detail in my book "Reflections--Transmission Lines and Antennas."
Yes, I know the book has been sold out and now unavailable, but I have put several chapters on my web page
avaliable for downloading. The pertinent chapters covering this issue are Chapters 3, 4, and 23, available at
www.w2du.com. I hope that reviewing these chapters will be helpful in clearing up some of the
misunderstandings that are clearly evident in some of the postings on this thread.

Walt, W2DU

Walter Maxwell wrote:
In transmitters with tubes and a pi-network output coupling circuit there is no 'fold back' circuitry to
protect the amp, because none is needed, due to the total re-reflection of the reflected power. It is only in
solid-state transmitters that have no circuitry to achieve destructive and constructive interference that
requires fold back to protect the output transistors.

One can illustrate the destructive and constructive
interference with a solid-state transmitter and
no tuner. Consider the following example using
S-parameter terms.

100W--50 ohm line--+--1/2WL 300 ohm line--50 ohms
a1-- --a2
--b1 b2--

Since there is zero reflected power on the 50 ohm
line, we know that "total destructive interference"
(as described by Hecht in "Optics", 4th edition, page
388) exists toward the source at point '+'.
s11 = (300-50)/(300+50) = 0.7143 = -s12
b1 = (s11)(a1) + (s12)(a2) = 0

Note that given a1, s11, and s12, we can calculate the
magnitude and phase of a2 needed to make b1=0. That
is the Z0-match condition.

The conservation of energy principle says that, (in
a transmission line with only two directions) "total
constructive interference" must exist in the opposite
direction to the "total destructive interference" and
that they must be of equal magnitudes. That tells us
what *must* happen to the energy associated with the
a2 reflected wave.

All of the energy incident upon point '+' from both
directions, |a1|^2 + |a2|^2, is directed toward the
load by the interference patterns at the Z0-match
point '+'. We hams commonly refer to that condition
as being 100% re-reflected.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
All of the energy incident upon point '+' from both
directions, |a1|^2 + |a2|^2, is directed toward the
load by the interference patterns at the Z0-match
point '+'. We hams commonly refer to that condition
as being 100% re-reflected.

The above is true in the special case of a Z0-match.
In general, |a1|^2 + |a2|^2 = |b1|^2 + |b2|^2
and since |b1|^2 = 0, the above expression is
correct.

*Quoting from HP Ap Note 95-1*:

|a1|^2 = Power incident on the input of the network
(i.e. Forward power on the 50 ohm line)

|a2|^2 = Power reflected from the load
(i.e. Reflected power on the 300 ohm line)

|b1|^2 = Power reflected from the input port of the network
(i.e. Reflected power on the 50 ohm line)

|b2|^2 = Power incident on the load
(i.e. Forward power on the 300 ohm line)

end quote from HP Ap Note 95-1
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote in
:

....
s11 = (300-50)/(300+50) = 0.7143 = -s12
b1 = (s11)(a1) + (s12)(a2) = 0

Cecil,

I see you are back to using S parameters to disguise the fact you are using
about Vf and Vr in trying to support your "power wave" explanation of what
happens on the transmission line.

S parameters are ratios of Vf and Vr.

Owen

Owen Duffy wrote:
I see you are back to using S parameters to disguise the fact you are using
about Vf and Vr in trying to support your "power wave" explanation of what
happens on the transmission line.

Others use the term "power wave", Owen, but *I DO NOT*
so please stop accusing me of something of which I am
not guilty. I use the term "EM RF energy wave" for
the traveling waves under discussion.

When anyone can prove that RF energy waves don't exist
or are not associated with EM energy or don't move at
the speed of light, I will retire from the argument.
Good luck on that one.

S parameters are ratios of Vf and Vr.

Exactly! No disguise intended - it's just additional
support from the well respected field of S-parameter
analysis for the distributed network wave reflection
model. The only difference is that the S-parameter
Vf and Vr values are normalized to Z0 so when they
are squared they indeed do yield watts.

Your tone seems to reject the S-Parameter analysis
as a valid model of reality. Any model that has to
resort to rejecting the S-Parameter analysis as well
as the distributed network wave reflection model is
certainly suspect. Did you ever see the movie, "One
Bridge Too Far"? This "reflected wave energy doesn't
exist" argument reminds me of that movie.
--
73, Cecil http://www.w5dxp.com

On Thu, 22 Mar 2007 15:55:40 GMT, Walter Maxwell
wrote:

On Wed, 21 Mar 2007 08:18:14 -0500, "Richard Fry" wrote:

"Walter Maxwell" wrote
(RF): And if so, would that also mean that such a tx would not be prone
to producing r-f intermodulation components when external signals
are fed back into the tx from co-sited r-f systems?

This issue is irrelevant, because the signals arriving from a co-sited
system would not be coherent with the local source signals, while load-
reflected signals are coherent. The destructive and constructive
interference that occurs at the output of a correctly loaded and tuned
PA requires coherence of the source and reflected waves to achieve
the total re-reflection of the reflected waves back into the direction
toward the load.

Hi Walt,

It is not irrelevant, merely illustrative of the concept of reflection
that is consistent with a coherent source.

Your points of phase are the sine non quo to the discussion, but all
too often arguers only take the half of the 360 degrees available to
argue a total solution. Even more often, they take only one or two
degrees of the 360.

But even for coherent reflections, if the PA tank circuit has very low loss
for incident power (which it does), why does it not have ~ equally low loss
for load reflections of that power? Such would mean that load reflections
would pass through the tank to appear at the output element of the PA, where
they can add to its normal power dissipation.

This is the symmetry of the illustration of external signals. You
used external signals yourself as part of your case study; hence the
relevance has been made by you.

Also, does not the result of combining the incident and reflected waves in
the tx depend in large part on the r-f phase of the reflection there
relative to the r-f phase of the incident wave? And the r-f phase of the
reflection is governed mostly by the number of electrical wavelengths of
transmission line between the load reflection and the plane of
interest/concern -- which is independent of how the tx has been
tuned/loaded.

And we return to the sine non quo for the discussion: phase.

If the ham transmitter designs that your paper applies to produce a total
re-reflection of reverse power seen at their output tank circuits, then
there would be no particular need for "VSWR foldback" circuits to protect
them. Yet I believe these circuits are fairly common in ham transmitters,
aren't they? They certainly are universal in modern AM/FM/TV broadcast
transmitters, and are the result of early field experience where PA tubes,
tx output networks, and the transmission line between the tx and the antenna
could arc over and/or melt when reflected power was sufficiently high.

RF

Richard, your statement above begs the question, "Are you aware of the phase relationships between forward and
reflected voltages and between forward and reflected currrents that accomplish the impedance-matching effect
at matching points such as with stub matching and also with antenna tuners?

It seems he is on the face of it, doesn't it? Afterall, he is quite
explicit to this in the statement you are challenging.

When the matching is accomplished the phase relationship between the foward and reflected voltages can become
either 0° or 180°, resulting in a total re-reflection of the voltage. If the resultant voltage is 0°, then the
resultant current is 180°, thus voltage sees a virtual open circuit and the current sees a virtual short
circuit. The result is that the reflected voltage and current are totally re-reflected IN PHASE with the
source voltage and current. This is the reason the forward power in the line is greater than the source power
when the line is mismatched at the load, but where the matching device has re-reflected the reflected waves.

Nothing here contradicts anything either of you have to say.

This phenomenon occurs in all tube transmitters in the ham world when the tank circuit is adjusted for
delivering all available power at a given drive level.

This introduces the two concepts of the "need for match" and the
"match obtained." They are related only through an action that spans
from one condition to the other. They do not describe the same
condition, otherwise no one would ever need to perform the match:

When this condition occurs the adjustment of the
pi-network has caused the relationship between the forward and reflected voltages to be either 0° or 180° and
vice versa for currents, as explained above. When this condition occurs, destructive interference between the
forward and reflected voltages, as well as between the forward and reflected currents, causes the reflected
voltage and current to cancel. However, due to the conservation of energy, the reflected voltage and current
cannot just disappear, so the resulting constructive interference following immediately, causes the reflected
voltage and current to be reversed in direction, now going in the foward direction along with and in phase
with the forward voltage and current.

If a tree were to fall onto the antenna, a new mismatch would occur.
Would the transmitter faithfully meet the expectations of the Ham
unaware of the accident? No, reflected (0-179 degrees) energy would
undoubtedly offer a 50% chance of excitement in the shack. The
consequences of dissipation would be quite evident on that occasion.
For the other 180 (180-359) degrees of benign combination; then
perhaps not.

In transmitters with tubes and a pi-network output coupling circuit there is no 'fold back' circuitry to
protect the amp, because none is needed, due to the total re-reflection of the reflected power.

That would more probably be due to cost averse buying habits of the
Amateur community, and the explicit assumption of risk by them to
react appropriately in the face of mismatch. Tubes were far more
resilient to these incidents than transistors of yore.

It is only in
solid-state transmitters that have no circuitry to achieve destructive and constructive interference that
requires fold back to protect the output transistors.

They too have access to the services of a transmatch that is probably
more flexible than the tubes' final. If they didn't use a tuner, then
the foldback would render many opportunistic antennas as useless.
Again, as a cost item, this solution (fold-back) is dirt cheap and was
driven by the market economies of a more onerous and costly repair
through a lengthy bench time to replace the transistor (which has an
exceedingly high probability of a quicker failure for a poor job).

73's
Richard Clark, KB7QHC

On Thu, 22 Mar 2007 12:59:20 -0800, Richard Clark wrote:

On Thu, 22 Mar 2007 15:55:40 GMT, Walter Maxwell
wrote:

On Wed, 21 Mar 2007 08:18:14 -0500, "Richard Fry" wrote:

"Walter Maxwell" wrote
(RF): And if so, would that also mean that such a tx would not be prone
to producing r-f intermodulation components when external signals
are fed back into the tx from co-sited r-f systems?

This issue is irrelevant, because the signals arriving from a co-sited
system would not be coherent with the local source signals, while load-
reflected signals are coherent. The destructive and constructive
interference that occurs at the output of a correctly loaded and tuned
PA requires coherence of the source and reflected waves to achieve
the total re-reflection of the reflected waves back into the direction
toward the load.

Hi Walt,

It is not irrelevant, merely illustrative of the concept of reflection
that is consistent with a coherent source.

Your points of phase are the sine non quo to the discussion, but all
too often arguers only take the half of the 360 degrees available to
argue a total solution. Even more often, they take only one or two
degrees of the 360.

Richard, it's been my observation that many of those who argue are clueless concerning the phase relationships
required to obtain the destructive and constructive interference that achieves the re-reflection of the
reflected waves. A reflection resulting from a discontinuity in the path of a signal delivered by a souce is
guaranteed to be coherent with the source wave. If there is no coherence between the reflected wave and the
source wave there may be an interference, but none of the type that results in total destructive and
constructive interference relevant to impedance matching. I don't understand what you mean by 'taking only one
of two degrees of the 360.'

But even for coherent reflections, if the PA tank circuit has very low loss
for incident power (which it does), why does it not have ~ equally low loss
for load reflections of that power? Such would mean that load reflections
would pass through the tank to appear at the output element of the PA, where
they can add to its normal power dissipation.

The paragraph above seems to me to imply that RF doesn't understand the destructive and constructive
interference phenomena involved with re-reflection.

This is the symmetry of the illustration of external signals. You
used external signals yourself as part of your case study; hence the
relevance has been made by you.

Whoa, Richard! You'll have to point out where I've discussed external signals in any case study involving
phase relationships between forward and reflected waves. I've never done so knowingly.

Also, does not the result of combining the incident and reflected waves in
the tx depend in large part on the r-f phase of the reflection there
relative to the r-f phase of the incident wave? And the r-f phase of the
reflection is governed mostly by the number of electrical wavelengths of
transmission line between the load reflection and the plane of
interest/concern -- which is independent of how the tx has been
tuned/loaded.

And we return to the sine non quo for the discussion: phase.

That's true, but although RF apparently realizes that the phase relationship is relevant, he doesn't seem to
understand the details of the phase requirements that achieve the necessary interferences that accomplish the
impedance matching.

If the ham transmitter designs that your paper applies to produce a total
re-reflection of reverse power seen at their output tank circuits, then
there would be no particular need for "VSWR foldback" circuits to protect
them. Yet I believe these circuits are fairly common in ham transmitters,
aren't they? They certainly are universal in modern AM/FM/TV broadcast
transmitters, and are the result of early field experience where PA tubes,
tx output networks, and the transmission line between the tx and the antenna
could arc over and/or melt when reflected power was sufficiently high.

RF

Richard, your statement above begs the question, "Are you aware of the phase relationships between forward and
reflected voltages and between forward and reflected currrents that accomplish the impedance-matching effect
at matching points such as with stub matching and also with antenna tuners?

It seems he is on the face of it, doesn't it? Afterall, he is quite
explicit to this in the statement you are challenging.

No Richard, I don't believe he is. I don't see the 'explicitness' you seem to find. It's the complete lack of
the explicitness that makes me believe he doesn't quite get it.

When the matching is accomplished the phase relationship between the foward and reflected voltages can become
either 0° or 180°, resulting in a total re-reflection of the voltage. If the resultant voltage is 0°, then the
resultant current is 180°, thus voltage sees a virtual open circuit and the current sees a virtual short
circuit. The result is that the reflected voltage and current are totally re-reflected IN PHASE with the
source voltage and current. This is the reason the forward power in the line is greater than the source power
when the line is mismatched at the load, but where the matching device has re-reflected the reflected waves.

Nothing here contradicts anything either of you have to say.

True, but RF just hasn't said it all, because, as I said above, I don't believe he understands the details of
the phase requirements to achieve the match.

This phenomenon occurs in all tube transmitters in the ham world when the tank circuit is adjusted for
delivering all available power at a given drive level.

This introduces the two concepts of the "need for match" and the
"match obtained." They are related only through an action that spans
from one condition to the other. They do not describe the same
condition, otherwise no one would ever need to perform the match:

I don't comprehend your statements in the paragraph above.

When this condition occurs the adjustment of the
pi-network has caused the relationship between the forward and reflected voltages to be either 0° or 180° and
vice versa for currents, as explained above. When this condition occurs, destructive interference between the
forward and reflected voltages, as well as between the forward and reflected currents, causes the reflected
voltage and current to cancel. However, due to the conservation of energy, the reflected voltage and current
cannot just disappear, so the resulting constructive interference following immediately, causes the reflected
voltage and current to be reversed in direction, now going in the foward direction along with and in phase
with the forward voltage and current.

If a tree were to fall onto the antenna, a new mismatch would occur.
Would the transmitter faithfully meet the expectations of the Ham
unaware of the accident? No, reflected (0-179 degrees) energy would
undoubtedly offer a 50% chance of excitement in the shack. The
consequences of dissipation would be quite evident on that occasion.
For the other 180 (180-359) degrees of benign combination; then
perhaps not.

If a tree were to fall onto the antenna the new mismatch would surely detune the transmitter, causing unwanted
dissipation, of course, but only a lid would fail to retune the transmitter before removing the tree.

In transmitters with tubes and a pi-network output coupling circuit there is no 'fold back' circuitry to
protect the amp, because none is needed, due to the total re-reflection of the reflected power.

That would more probably be due to cost averse buying habits of the
Amateur community, and the explicit assumption of risk by them to
react appropriately in the face of mismatch. Tubes were far more
resilient to these incidents than transistors of yore.

It is only in
solid-state transmitters that have no circuitry to achieve destructive and constructive interference that
requires fold back to protect the output transistors.

They too have access to the services of a transmatch that is probably
more flexible than the tubes' final. If they didn't use a tuner, then
the foldback would render many opportunistic antennas as useless.
Again, as a cost item, this solution (fold-back) is dirt cheap and was
driven by the market economies of a more onerous and costly repair
through a lengthy bench time to replace the transistor (which has an
exceedingly high probability of a quicker failure for a poor job).

IMHO, Richard, the mfgrs of solid-state rigs with no means of matching the output to a load other than 50
ohms short changed the ham, thus requiring him to be satisfied with the power fold back, or buy an antenna
tuner.

Walt, W2DU