About all that anyone needs to know about an amateur radio amplifier
(transmitter) in order to use it properly is the output power level and the
required load resistance. The latter is usually 50 ohms for a variety of
reasons, most of which relate to convenience, availability of coax cables,
test equipment impedance environment, etc. Beyond those values, there is
nothing about the amplifier design which is used in designing and adjusting
the remainder of the tuner, transmission line and antenna system. The power
level is of importance only in telling us how much voltage and current is
involved in various parts of the system.

The result is the ultimate in convenience. We need have no intimate
knowledge of "what is in the black box" in order to use it properly. In
fact, even if we had full knowledge of all the particulars of the design, we
would still use only its required load resistance and power levels
associated with it modulation waveforms, etc.

Our modern amateur transmitters and amplifiers even have a convenient meter
on the front panel that tells us when we have met our obligation to provide
a 50+j0 ohm load. It may be labeled "SWR" and calibrated in an unusual
scale, but the important thing is that when it reads 0 or "1:1 SWR" that
tells us that we have met the load resistance obligation - nothing more or
less.

I think that a great deal of confusion over this whole issue comes from two
sources:

1. vague efforts to apply the infamous "Maximum Power Transfer Theorem" from
the early days in undergrad EE school; and

2. confusing an r-f transmitter output stage with the classical "signal
generator" with a dissipative 50-ohm internal resistance.

Forget both of those irritants and concentrate on the required load for the
transmitter, which the designer will provide and insist upon, and then
adjust the antenna system to provide that load and all will be well.

At no point will anyone, including the r-f amp designer in all likelihood,
know or even care what the so-called "internal resistance" of the amplifier
happens to be. He demands only one thing: the specified load resistance.
Given that, his design will deliver the required power, efficiency, heat
load, harmonic content, distortion levels, etc. etc.

I know of no instance in the design of everything connected to the output
port of the transmitter where there is need to know anything other than the
required load resistance for the amplifier and the power levels (average,
peak, etc.).

Why do folks make this so complicated, Ian?

73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"






----- Original Message -----
From: "Ian White, G3SEK"
Newsgroups: rec.radio.amateur.antenna
Sent: Thursday, August 14, 2003 1:42 AM
Subject: Length of Coax Affecting Incident Power to Meter?


Dr. Slick wrote:

As Roy says, the equations relating any one of these parameters to any
other are all well known. NONE of them ever involves source impedance.

Assuming the source impedance is 50 ohms, which it usually isn't
with most PAs.

NO - and this is the central point.

When Roy and I are saying:
NONE of them ever involves source impedance.
- that is exactly what we mean.

We didn't mean there is a hidden assumption about what the source
impedance is - we meant what we said: it isn't there at all, in any of
the equations we're talking about.

Look them up; and then go deeper and look at how they are derived. They
involve only the load impedance and Z0. That's "only", as in "no hidden
additives."


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

On Fri, 15 Aug 2003 07:45:32 GMT, "George, W5YR"
wrote:

About all that anyone needs to know about an amateur radio amplifier
(transmitter) in order to use it properly is the output power level and the
required load resistance.

Hi George,

And us folk need never worry about what is beneath the hood as long as
we don't need a mechanic. Sheesh, haven't you learned to turn the
knob until the meter is full scale? All you have to really remember
to push the button before you talk!

The latter is usually 50 ohms for a variety of
reasons, most of which relate to convenience, availability of coax cables,
test equipment impedance environment, etc.

For which us same folk STILL don't give a fig. Are you some sort of
salesman? Who uses coax when telephone wire is free? You got stock
in this cable stuff? I got satellite and I don't need it.

Beyond those values, there is
nothing about the amplifier design which is used in designing and adjusting
the remainder of the tuner, transmission line and antenna system.

What are you talking about designing? Is your charge card void? Do
the sales clerks ignore you? Have you consider stitching your own
semaphore flags for a hobby instead? At least no one would laugh as
much for all the arm waving.

The power
level is of importance only in telling us how much voltage and current is
involved in various parts of the system.

None of us folk even think of voltage or current, this impotence is
not needed to make a contact. What's the point?


The result is the ultimate in convenience.

Something that us folk take for granted and never give a thought to
because it is exactly that: convenient. Are you writing a magazine
article no one reads? I hope you include lots of pictures. I prefer
Reader's Dogma myself.

We need have no intimate
knowledge of "what is in the black box" in order to use it properly.

Us folk would ask "what is in the black box? What are YOU talking
about?" My boxes are brown like any from the liquor store. The only
black box I've seen was at the cemetery. I don't think I will worry
how to use THAT properly - thank you!

In
fact, even if we had full knowledge of all the particulars of the design, we
would still use only its required load resistance and power levels
associated with it modulation waveforms, etc.

WE? You don't talk like one of us folk!


Our modern amateur transmitters and amplifiers even have a convenient meter
on the front panel that tells us when we have met our obligation to provide
a 50+j0 ohm load. It may be labeled "SWR" and calibrated in an unusual
scale, but the important thing is that when it reads 0 or "1:1 SWR" that
tells us that we have met the load resistance obligation - nothing more or
less.

Who looks at that - are you one of those goggle-eyed professors that
try to 'splain the meaning of life? You missed that by a country mile
and still don't seem to have learned about what knobs are for. Twist
one and push buttons until someone talks back. Your black box
obviously has none of the modern conveniences, is it a telegraph?


I think that a great deal of confusion over this whole issue comes from two
sources:

1. vague efforts to apply the infamous "Maximum Power Transfer Theorem" from
the early days in undergrad EE school; and

Us folk never went to this underground school, nothing to be confused
about at all. Are your problems from being a squinty-eyed miner?
Maybe that's why you can't read these meters. Pull the blinds and
take a load off your peepers.


2. confusing an r-f transmitter output stage with the classical "signal
generator" with a dissipative 50-ohm internal resistance.

What language are you trying to talk?

Forget both of those irritants and concentrate on the required load for the
transmitter, which the designer will provide and insist upon, and then
adjust the antenna system to provide that load and all will be well.

Gawd this is complexity for its own sake, you white coated pencil
necked geeks need to get a life. If you are looking for the good
times, pop the cap off a cold long-neck. I hope you don't need a
glass, you would strangle fun out of TV.


At no point will anyone, including the r-f amp designer in all likelihood,
know or even care what the so-called "internal resistance" of the amplifier
happens to be. He demands only one thing: the specified load resistance.
Given that, his design will deliver the required power, efficiency, heat
load, harmonic content, distortion levels, etc. etc.

Infernal resistance is right. distortion is what I don't want to hear
and what you are spouting on about is rattling the cone on my speaker.


I know of no instance in the design of everything connected to the output
port of the transmitter where there is need to know anything other than the
required load resistance for the amplifier and the power levels (average,
peak, etc.).

Is this bragging or complaining? Talk to your chaplain for relief.


Why do folks make this so complicated, Ian?

73/72, George

Oh! a philosopher hmm? About the only complication is the broken
lever of my Lazy Boy. Do you have a screw driver? Drink it college
boy, but don't ralph on the couch when you pass out.

73's
The mythical lurker.... ;-)

Well said, George.

Roy Lewallen, W7EL

I agree with every word, George.

Why do folks make this so complicated, Ian?

Mostly by insisting on asking questions that may not even *have* an
answer!

The US Constitution guarantees every citizen's right to ask whatever
questions they wish - but the Universe does not guarantee there'll be
any answers.

--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

Ian White, G3SEK wrote:



I agree with every word, George.

Why do folks make this so complicated, Ian?


Mostly by insisting on asking questions that may not even *have* an answer!


The problem is that finding the output impedance
analytically is usually very difficult.

Measurement methods (usually questionable) have
been proposed that "estimate" the output
impedance. These tests can often be manipulated to
get some desired result (for example 50 ohms).

The value of output impedance depends especially
on signal level and also several other parameters,
such as negative feedback.

Is the value of output impedance important?
Sometimes in critical situations it can be. For
example, a lowpass filter connected to the output
of the PA may not be exactly correctly terminated
at the input end. The error slightly affects the
filter response, especially at the filter cutoff
frequency. The passband ripple can also be
affected. Most lowpass filter types can be
designed for unequal values of generator and load
impedances.

If the PA is broadband solid-state a sweep method
can be used to optimize the filter design.

Usually these errors are unimportant, especially
in typical Ham Radio.

Bill W0IYH

"George, W5YR" wrote in message ...
....
I think that a great deal of confusion over this whole issue comes from two
sources:

1. vague efforts to apply the infamous "Maximum Power Transfer Theorem" from
the early days in undergrad EE school; and

2. confusing an r-f transmitter output stage with the classical "signal
generator" with a dissipative 50-ohm internal resistance.

Forget both of those irritants and concentrate on the required load for the
transmitter, which the designer will provide and insist upon, and then
adjust the antenna system to provide that load and all will be well.

Those of us who _do_ have to worry, in intimate detail, about
generator source impedances, are most thankful that we do NOT when we
put loads on our ham rigs. Thanks for a great posting that nicely
summarizes what a lot of us have been saying for a long time. Perhaps
Reg is right. Perhaps we SHOULD quit calling it an SWR meter and
instead call it a "Transmitter Load Indicator" (or perhaps transmitter
load error indicator).

When you plug an appliance into the mains, do you worry about what the
mains source impedance is, so long as it's low enough to maintain the
proper voltage? When you connect speakers to an amplifier, do you
worry about what the source impedance is, so long as it's low enough
to not materially affect damping? If not, why would you worry about
transmitter source impedance? Why would you not worry instead about
proving the proper load so the amplifier can do it's job right?

Cheers,
Tom

proper voltage? When you connect speakers to an amplifier, do you
worry about what the source impedance is, so long as it's low enough
to not materially affect damping? If not, why would you worry about

I would not go there on the audio . The speakers do need to match the design
of the amp just as the load on a transmitter needs to match the design
impedance. Most power output devices are designed to produce maximum power
and /or minimum distortion into a specific load.

"Ralph Mowery" wrote:
proper voltage? When you connect speakers to an amplifier, do you
worry about what the source impedance is, so long as it's low enough
to not materially affect damping? If not, why would you worry about

I would not go there on the audio . The speakers do need to match the design
of the amp just as the load on a transmitter needs to match the design
impedance. Most power output devices are designed to produce maximum power
and /or minimum distortion into a specific load.

Virtually all "HiFi" audio amplifiers are designed to have
"damping" factor of something significantly more than 10.
Damping factor is the ratio of the load impedance to the
amplifier's output impedance. You might even find a few (more
expensive units) that have ratios greater than 1000, which is to
say that the output impedance of the amp (designed to drive
speakers in the range of 4 to 16 Ohms), has an output impedance
of 4/1000 of an Ohm).

Just as with RF, the output impedance has little to do with the
power delivered to the load impedance. The amplifier can
generate a maximum voltage by design, and how much power is
actually delivered depends solely on the impedance of the load.
Hence the same amplifier can deliver twice the power to a 4 Ohm
speaker as it can to an 8 Ohm speaker, and that is twice what it
will deliver to a 16 Ohm speaker. And it also works just fine to
drive a 600 Ohm headset, with significantly less power.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Richard,

It always astounds me how the technically challenged are wont to launch ad
hominem attacks instantly when matters evidently beyond their understanding,
or perhaps in disagreement with their preconceived notions and prejudices,
are brought to light.

I note that not a single statement that I made in my posting is either
declared incorrect or is replaced by your version of "truth."

All I read is a lot of disconnected, poorly conceived and worded "slams" at
me for posting the piece in the first place.

The note was addressed to Ian who points out that he agrees totally with
everything that I said. Why not select him as a target as well ? Double your
pleasure with two targets! And, of course, appear the fool twice for making
such an inane posting in the first place.

Further to the point, no one has offered a single word of disagreement with
the factual content of the posting. Only you have felt compelled to take
your valuable time to post nonsense mouthings having nothing to do with the
subject matter.

Richard, in the past I have had a small degree of respect for your postings
and your viewpoints, but if this is the best you can do now, then clearly
it is time for you to resume your meds.

Historically, you seldom if ever contribute anything of substance to a
discussion but rather tend to sit on the sidelines making learned comments
about the abilities of the participants to present their material and the
degree to which they fail to meet your high standards for discourse.

Yep, time for the meds . . .

Or, perhaps you could actually contribute something of value by telling us
where my posting is in error in *fact*, not in error for having been posted.
I presume that you feel capable of tackling that chore.

But, you are right about one thing: if you are an example of "us folks" then
I am definitely not one of you, and very proud of it.

73/72, George
Amateur Radio W5YR - the Yellow Rose of Texas
Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
"In the 57th year and it just keeps getting better!"








"Richard Clark" wrote in message
news
On Fri, 15 Aug 2003 07:45:32 GMT, "George, W5YR"
wrote:

About all that anyone needs to know about an amateur radio amplifier
(transmitter) in order to use it properly is the output power level and
the
required load resistance.

Hi George,

And us folk need never worry about what is beneath the hood as long as
we don't need a mechanic. Sheesh, haven't you learned to turn the
knob until the meter is full scale? All you have to really remember
to push the button before you talk!

The latter is usually 50 ohms for a variety of
reasons, most of which relate to convenience, availability of coax
cables,
test equipment impedance environment, etc.

For which us same folk STILL don't give a fig. Are you some sort of
salesman? Who uses coax when telephone wire is free? You got stock
in this cable stuff? I got satellite and I don't need it.

Beyond those values, there is
nothing about the amplifier design which is used in designing and
adjusting
the remainder of the tuner, transmission line and antenna system.

What are you talking about designing? Is your charge card void? Do
the sales clerks ignore you? Have you consider stitching your own
semaphore flags for a hobby instead? At least no one would laugh as
much for all the arm waving.

The power
level is of importance only in telling us how much voltage and current is
involved in various parts of the system.

None of us folk even think of voltage or current, this impotence is
not needed to make a contact. What's the point?


The result is the ultimate in convenience.

Something that us folk take for granted and never give a thought to
because it is exactly that: convenient. Are you writing a magazine
article no one reads? I hope you include lots of pictures. I prefer
Reader's Dogma myself.

We need have no intimate
knowledge of "what is in the black box" in order to use it properly.

Us folk would ask "what is in the black box? What are YOU talking
about?" My boxes are brown like any from the liquor store. The only
black box I've seen was at the cemetery. I don't think I will worry
how to use THAT properly - thank you!

In
fact, even if we had full knowledge of all the particulars of the design,
we
would still use only its required load resistance and power levels
associated with it modulation waveforms, etc.

WE? You don't talk like one of us folk!


Our modern amateur transmitters and amplifiers even have a convenient
meter
on the front panel that tells us when we have met our obligation to
provide
a 50+j0 ohm load. It may be labeled "SWR" and calibrated in an unusual
scale, but the important thing is that when it reads 0 or "1:1 SWR" that
tells us that we have met the load resistance obligation - nothing more
or
less.

Who looks at that - are you one of those goggle-eyed professors that
try to 'splain the meaning of life? You missed that by a country mile
and still don't seem to have learned about what knobs are for. Twist
one and push buttons until someone talks back. Your black box
obviously has none of the modern conveniences, is it a telegraph?


I think that a great deal of confusion over this whole issue comes from
two
sources:

1. vague efforts to apply the infamous "Maximum Power Transfer Theorem"
from
the early days in undergrad EE school; and

Us folk never went to this underground school, nothing to be confused
about at all. Are your problems from being a squinty-eyed miner?
Maybe that's why you can't read these meters. Pull the blinds and
take a load off your peepers.


2. confusing an r-f transmitter output stage with the classical "signal
generator" with a dissipative 50-ohm internal resistance.

What language are you trying to talk?

Forget both of those irritants and concentrate on the required load for
the
transmitter, which the designer will provide and insist upon, and then
adjust the antenna system to provide that load and all will be well.

Gawd this is complexity for its own sake, you white coated pencil
necked geeks need to get a life. If you are looking for the good
times, pop the cap off a cold long-neck. I hope you don't need a
glass, you would strangle fun out of TV.


At no point will anyone, including the r-f amp designer in all
likelihood,
know or even care what the so-called "internal resistance" of the
amplifier
happens to be. He demands only one thing: the specified load resistance.
Given that, his design will deliver the required power, efficiency, heat
load, harmonic content, distortion levels, etc. etc.

Infernal resistance is right. distortion is what I don't want to hear
and what you are spouting on about is rattling the cone on my speaker.


I know of no instance in the design of everything connected to the output
port of the transmitter where there is need to know anything other than
the
required load resistance for the amplifier and the power levels (average,
peak, etc.).

Is this bragging or complaining? Talk to your chaplain for relief.


Why do folks make this so complicated, Ian?

73/72, George

Oh! a philosopher hmm? About the only complication is the broken
lever of my Lazy Boy. Do you have a screw driver? Drink it college
boy, but don't ralph on the couch when you pass out.

73's
The mythical lurker.... ;-)

On Sat, 16 Aug 2003 07:07:16 GMT, "George, W5YR"
wrote:

Richard,

It always astounds me how the technically challenged are wont to launch ad
hominem attacks instantly

Do you accept that yours similarly deflates your credentials? It
would at least place us on equal footing - in the gutter I suppose,
but I brought my snorkel. ;-)


73/72, George

Hi George,

If you suffer the heat of taking a stand, so much for a test of faith.
I have not seen you respond to the chain of evidence I have supplied
to these matters. I will offer that this body of work long preceded
my missive. You might or might not find that work
interesting/correct/or worthy of your attention, but that does not
erase if from the archive nor detract its intrinsic merit in desired
measure to bruised ego.

Pick any ONE of your cherished notions that I so soiled and put it up
for a clear and concise examination.

OR

Let me head that off with a very simple question that most dodge; and
in fact lies at the very heart of your subject line:
Given the premise that the amateur's rig output Z is NOT 50 Ohms, what
value does it have (cite any assembly of conditions)?

You will no doubt get many thumps on the back from well-wishers who
spit in my direction. How many will offer a numeric response to that
technical enquiry? I can forecast that will stand at the current
exchange rate of 0. I will also forecast there will be either total
silence, or scattered muttering about why they wouldn't engage such a
scurvy fellow as me. And yet the absence of that number from the
discussion under this subject line mocks the charter of this group
more than my humor did you.

Is it lower than 50? Higher than 50? How much? The stunned silence
in response to such simple, forced speculation is more a result of
intellectual catatonia than moral indignation.

Those who have offered numbers (I count among them), who have revealed
methods of their derivation (I count among them), who performed actual
bench work (I count among them), who offer rationale as to the
subject's correlation to other observables (I count among them) is
notable in contrast to those who have nothing to show but the shallow
rhetoric of impotent denial.

73's
Richard Clark, KB7QHC