On Fri, 4 Mar 2005 11:11:32 -0600, (Richard
Harrison) wrote:
"Physics is not application-selsctive."
True. The laws of physics are inviolable.
....
I would be surprised if some final filter were not used to guarantee
compliance with the rules.

Hi Richard,

Yes, that would be the technical marvel of the ages, but just like our
rigs, even the biggest FM transmitters bend to the necessity for
output filtering:
http://www.broadcast.harris.com/prod...%20Bro%2DB.pdf

There is an amusing claim, however, for their power module(s)
"Each module is conservatively rated to produce
850W of power into a system VSWR of 1.5:11."

Not a very good copy editing job is my guess.

Looking at the "efficiency" side of the equation is simple here too:
Power Consumption (nominal)
• Z2CD: 4.0kW at 2.2kW output power
55%
• Z3.5CD: 6.1kW at 3.75kW output power
61%
• Z5CD: 7.9kW at 5kW output power
63%
• Z7.5CD:11.7kW at 7.5kW output power
64%
• Z10CD: 15.3kW at 10kW output power
65%
• ZD20CD:31kW at 20kW output power
65%

73's
Richard Clark, KB7QHC

"Richard Clark" wrote:
Looking at the "efficiency" side of the equation is simple here too:
Power Consumption (nominal)
(clip)
_________________

Another case of writing without knowing, I see.

The power consumptions you cite are the TOTAL values for those transmitters,
not of the RF power amplifiers alone. The total value includes the exciter,
driver(s), power supply losses, control circuits, and RF combining losses,
as well as power for the internal cooling fans. The PA modules have 80% or
better efficiency, by themselves.

The reason I know is that I was the author of those specs.

RF

On Fri, 4 Mar 2005 12:42:47 -0600, "Richard Fry"
wrote:

"Richard Clark" wrote:
Looking at the "efficiency" side of the equation is simple here too:
Power Consumption (nominal)
(clip)
_________________

Another case of writing without knowing, I see.

Hi OM,

Yes, I do recall your claims that contradicted Mendenhall's explicit
efficiency computations. So I see no need to pursue undocumented
claims you offer. Unless you can supply specific references from
Harris about this 80% efficiency, then such comments remain as suspect
as before.

The reason I know is that I was the author of those specs.

I am still wondering about the odd entry of:
"Each module is conservatively rated to produce
850W of power into a system VSWR of 1.5:11."

I notice you passed on discussion to this particular point of
accuracy. 11s can be explained by hitting 1 too many times, or 80 by
hitting an errant 0 too many. One of those things that escape the
notice of a spell-checker.

73's
Richard Clark, KB7QHC

"Richard Clark" wrote:
Unless you can supply specific references from Harris
about this 80% efficiency, then such comments remain
as suspect as before.

You may take what I wrote as being "from Harris," because I was part of
Harris FM Product Management for those transmitters before my retirement in
1999 (after 19 years there). I was responsible for documenting all
performance features and parameters published for the product line, using
numbers generated and approved by Engineering.

If the PAs alone were as (in)efficient as you imply with your calculations,
power consumption for the entire transmitter would be considerably higher.
Common sense should tell you that PA module efficiency would have to be much
higher than the efficiency calculations you posted in order for total power
consumption to be as stated on the Harris spec sheets.

I am still wondering about the odd entry of:
"Each module is conservatively rated to produce
850W of power into a system VSWR of 1.5:11."

Yes, that is a "typo," as you noted. Very good. It should read
"...VSWR of 1.5:1."

RF

On Fri, 4 Mar 2005 13:41:50 -0600, "Richard Fry"
wrote:

If the PAs alone were as (in)efficient as you imply with your calculations,
power consumption for the entire transmitter would be considerably higher.

The implication is drawn by and from your inertia.

Common sense should tell you that PA module efficiency would have to be much
higher than the efficiency calculations you posted in order for total power
consumption to be as stated on the Harris spec sheets.

Hi OM,

It is tedious to have to carry your water for you. I had to chase
down your Mendenhall references, this seems to be a consistent trait.
Claims are generous in this group and heavily discounted due to the
paucity of facts. Such facts as may be drawn out, but could have had
been as easily offered by you:

"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.

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.

This, as you put it (but fail to evidence), would quickly subdue
suspicion. And an equal treatment to more conventional, retail
Amateur Radio Transmitters also reveals efficiencies through the same
exercise. It is quite evident that such transmitters are no where
near these vaunted examples - but few dare venture into these
dissections.

73's
Richard Clark, KB7QHC

"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.

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. The PA and IPA modules are the same, and consist of two,
independent amps--each amp capable of 425W output. 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.
The other amp of the IPA remains unpowered and in reserve, and autoswitches
on line if the active one fails.

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.

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.

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.

RF

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:
"There is an amusing claim, however, for their power module(s) "Each
module is conservatively rated to produce 850W of power into a system
VSWR of 1,5:11."
Not a very good copy editing job is my guess."

Richard must be right. I guess a finger was left too long on the no.1
key and nobody caught it in time.

I admire Gates` scheme of paralleling many relatively low powered
amplifiers. If one fails, you can continue almost as if nothing
happened. Very nice.

Best regards, Richard Harrison, KB5WZI