John Woodgate wrote:

I read in sci.electronics.design that Tom Ring
wrote (in ) about '1/4 vs
1/2 wavelength antenna', on Thu, 3 Mar 2005:


He forgot to mention that for that output impedance to be relevant, you
need superconducting wire to the speakers as well as superconducting
voice coils.


See the last sentence, about the effect of an **8 ohm** source impedance
on damping.

Get a sense of humor. Or maybe more ice and mixer.

tom
K0TAR

John Woodgate wrote:

I read in sci.electronics.design that Tom Ring
wrote (in ) about '1/4 vs
1/2 wavelength antenna', on Thu, 3 Mar 2005:


He forgot to mention that for that output impedance to be relevant, you
need superconducting wire to the speakers as well as superconducting
voice coils.


See the last sentence, about the effect of an **8 ohm** source impedance
on damping.

Oh, and going from 8 ohms output impedance to 10e-7 (unless I
miscounted) would take the damping factor from 1 to 8e7, which is a bit
more than 2. Ignoring the speaker wires of course.

tom
K0TAR

On Fri, 4 Mar 2005 16:11:50 -0600, "Richard Fry"
wrote:

"Richard Clark" wrote regarding Harris "Z" FM broadcast transmitters:
"For even greater reliability, any
PA module can be used as an IPA module,
with absolutely no modification."

It is quite obvious that as an IPA, that in the lower wattage systems
it represents overkill at 845W to generate drive to final PAs to 2.2
KW output. Hence the lower total efficiency. On the other hand,
an IPA driving 845W to generate 22KW obviously makes better
efficiency sense and is found in the overall 64.5% figure.

Yet another case where you write with guesswork, not knowing the facts.

Hi OM,

How amusing. :-)

Obviously you do not understand the architecture of this line of
transmitters, even though what I am about to write is available on the
Harris website.

Yes it is, isn't it. What that has to do with MY intimate knowledge
of them is hardly the point when I asked YOU for details. But this
posting only gets better.

The PA and IPA modules are the same,

As already noted in my direct quote above.

and consist of two, independent amps--each amp capable of 425W output.

Not being particularly knowledgeable, and taking your advice about the
information's availability (seeing that I provided the link, not you):
"Each module is conservatively rated to produce
850W of power into a system VSWR of 1.5:11"

AH! there we are with that errant SWR again. I wonder how you
explained that without noting this other egregious error of 850W?
What is even more amusing is that either way (425/850) it has
absolutely no impact on the outcome. But this gets better, after the
snooze that follows:

Their actual output
power depends on the tx they are installed in, and the power level required
from it. The only thing they have in common is a heat sink. An IPA at any
power level uses only one of these amps per 5kW (or less) block of PA amps.

How boringly trivial. Does the recitation of irrelevant facts bear
on some point being drawn here?

The other amp of the IPA remains unpowered and in reserve, and autoswitches
on line if the active one fails.

Op. Cit.

The lower AC input to RF output efficiency of the lower powered transmitters
arises from the fixed overhead in all units for losses OTHER than in the RF
amplifiers, i.e., power supply losses, exciter and controller power, RF
combiner and harmonic filter losses, and cooling power--the AC consumption
for which in low power units is a larger proportion of the total.

I said as much in the top section. However, if you enjoy your own
words that's fine, but it is becoming repetitive barring any obvious
point. (Both my and your entry could have as easily been left out -
did you say you were an editor?)

NOW, if the PA finals, accounting for 22KW are 80% efficient, that
must mean that they only consume 27.5KW of power to do so, and that
with a power input rating of 31KW then leaves the IPA (an identical
80% efficiency module) and control circuitry to absorb 3.5KW to
deliver the drive of .845KW.
It follows that for an 80% efficient IPA, it accounts for 1KW power
consumption. This remainder is easily attributable to power supply
losses (if we simply assign an industrial average efficiency of 95%
for power conversion) otherwise the system TTL circuits and LCD meters
suck down 2.5KW on their own.

Your analytical skills are seriously wanting. Please re-read my response
above.

Let's see, I have offered an analysis that supports your thesis that
the efficiency of this transmitters elements are ballpark 80% and you
say I am WRONG?

What a hoot!

I can only wonder why you can't offer your own numbers to show my
error. :-)

I originally wondered why you couldn't offer your own numbers and
carry your own water. Go figure....

Like I said, this has been one wild ride.

It is quite evident that such transmitters are no where
near these vaunted examples - but few dare venture into these
dissections.

It is "evident" only to those who don't understand the subject. Others have
not dared to venture into these dissections probably because THEY know
better.

I cannot say that I have enjoyed a more droll posting from your hand.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote:
and consist of two, independent amps--each amp capable of 425W output.
Not being particularly knowledgeable, and taking your advice about the
information's availability (seeing that I provided the link, not you):
"Each module is conservatively rated to produce
850W of power into a system VSWR of 1.5:11"

And so it is when operating as a PA output module, when both sides of the
module are active. In IPA service only one side is active. The words on
the website say so.

Let's see, I have offered an analysis that supports your thesis that
the efficiency of this transmitters elements are ballpark 80% and you
say I am WRONG? What a hoot!

Only by an absurd conclusion that to get there "the IPA (an identical 80%
efficiency module) and control circuitry to absorb 3.5KW to deliver the
drive of .845KW." Note also your incorrect value for IPA output power. It
is never more than 425W per 5kW (or less) block of PAs. If more PAs are
used in that power level tx, another IPA and PA block are added. Of course,
you would know that if you took the time to read and absorb the website
data.

I can only wonder why you can't offer your own numbers to show my
error. :-) I originally wondered why you couldn't offer your own
numbers and carry your own water. Go figure....

Honestly, given your penchant to ridicule and intimidate people in this
newsgroup, I have little motivation to carry your water. There is much data
about these txs on the Harris website, free for the reading. I am through
trying to set you straight.

It is incredible how you, as someone with barely a perfunctory understanding
of this transmitter system, feels qualified to argue about it here with
someone who has been part of its development team. "Go figure..."

RF

I read in sci.electronics.design that Tom Ring
wrote (in ) about '1/4 vs
1/2 wavelength antenna', on Fri, 4 Mar 2005:
John Woodgate wrote:

I read in sci.electronics.design that Tom Ring
wrote (in ) about '1/4 vs
1/2 wavelength antenna', on Thu, 3 Mar 2005:


He forgot to mention that for that output impedance to be relevant, you
need superconducting wire to the speakers as well as superconducting
voice coils.


See the last sentence, about the effect of an **8 ohm** source impedance
on damping.

Oh, and going from 8 ohms output impedance to 10e-7 (unless I
miscounted) would take the damping factor from 1 to 8e7, which is a bit
more than 2. Ignoring the speaker wires of course.

Also ignoring the ***voice-coil resistance***. If that is included, as
it must be for a correct analysis, you get 2.

F Langford-Smith 'invented' the concept of damping factor, and around
1949 accepted the point made by James Moir that, by not properly taking
into account the effect of the voice-coil resistance, it was a seriously
misleading concept. Yes, 60 years later, people are still being misled.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

How can a filter filter correctly when its input is terminated in
an indeterminate impedance?

============================

No problem! The frequency response of a filter, input to output terminals,
is independent of the source resistance.

John Woodgate wrote:

I read in sci.electronics.design that Tom Ring
wrote (in ) about '1/4 vs
1/2 wavelength antenna', on Fri, 4 Mar 2005:

Also ignoring the ***voice-coil resistance***. If that is included, as
it must be for a correct analysis, you get 2.

F Langford-Smith 'invented' the concept of damping factor, and around
1949 accepted the point made by James Moir that, by not properly taking
into account the effect of the voice-coil resistance, it was a seriously
misleading concept. Yes, 60 years later, people are still being misled.

Good point. I stand corrected.

The only nit I would pick would be that impedance be used, since you
need to measure it at the frequency(ies) in question, not DC. And then
there is that pesky crossover in most systems. Personally I like biamping.

tom
K0TAR

"gwhite" wrote in message
...
Richard Clark wrote:

On Wed, 23 Feb 2005 19:08:20 GMT, gwhite wrote:

RF transmitters are not ....

Sorry OM,

This was all nonsense.

Nice articulation. I don't know who OM is, but RF transmitter power amps
are
not "impedance matched." Neither are audio power amps for that matter.

'OM' is radio ham speak for 'Old man'. 8-)

Leon
--
Leon Heller, G1HSM
http://www.geocities.com/leon_heller

I read in sci.electronics.design that Tom Ring
wrote (in ) about '1/4 vs
1/2 wavelength antenna', on Sat, 5 Mar 2005:
Personally I like
biamping.

So do I.
--
Regards, John Woodgate, OOO - Own Opinions Only.
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Reg Edwards wrote:
How can a filter filter correctly when its input is terminated in
an indeterminate impedance?


============================

No problem! The frequency response of a filter, input to output terminals,
is independent of the source resistance.



That may be true in the Danelaw where you live, Reg, but not in the
rest of the universe. Imagine a circuit consisting of a voltage source
in series with a source resistance followed by a shunt capacitance in
parallel with a load resistor. Write the output voltage equation for this
circuit. Now, replace the source resistance with a short. Write the
output equation for _this_ circuit. Compare the two equations.
Are the frequency responses the same? Now use an indeterminate
impedance for the source resistance. Can you tell what the voltage output
of this circuit is?
73,
Tom Donaly, KA6RUH