On Mon, 6 Sep 2004 10:01:15 +0000 (UTC), "Reg Edwards"
wrote:


"Walter Maxwell" wrote
If you question my statements above see the data from my measurements
using
professional grade instruments in either QEX, May/Jun 2001, Chapter 19 in
Reflections II,

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

The accuracy of measurements depends on who uses the instruments rather than
on what the manufacturer says in his sales catalogue. I'd much prefer just
to take your word for it, Walt. The manufacturer's type number is
superfluous - it sounds like a gratuitous advert.
----
Reg, G4FGQ

Thanks for the compliment, Reg, that you prefer to take my word for it. However,
the reason we include the manufacturer is not as a gratuitutous advert, but to
distinguish between the Cadillacs (Hewlett-Packard and General Radio, among a
few others) and the non-descripts. The Cadillacs are professional, precision
instruments, which, when used by knowledgeable people, provide data that can be
relied upon.

Without knowledge of the quality of the measuring device the reader is
justifiably suspicious of the data.

Walt

On Mon, 6 Sep 2004 14:44:03 +0000 (UTC), "Reg Edwards"
wrote:


"Richard Harrison" wrote
I`d design for a conjugate match at the rated load and include overload
protection for an output short circuit or near short. For solid-state
I`d provide overvoltage protection.in addition to overcurrent
protection.

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

To obtain a conjugate match it is first necessary to know what the source
impedamce is. How or from where is that elusive figure obtained?

It is not given in a transmitting tube manufacturer's data sheets. Perhaps
it doesn't matter what it is - not needed?
----
Reg, G4FGQ

I guess I'll have to repeat it for emphasis, Reg, but if the drive level is set
so that when the tuning and loading of the pi-network is adjusted to deliver the
maximum available power is within the normal operating range, there is a
conjugate match. In this condition the source and load impedances are equal.
This condition is by definition and proved by measurements.

If you like I'll send you a copy of the test procedure and the data.

Walt

On Mon, 6 Sep 2004 06:51:01 -0500, "Richard Fry" wrote:

"Walter Maxwell"
When I bought the tx for new BC stn WCEN in 1948
it was from Gates Radio in Quincy. Is it possible that
Geoff's business is a spinoff from Gates?

Yes, Harris-Intertype (later just "Harris Corp") bought Gates Radio, lock,
stock and barrel -- not a spinoff.

Don Peterson, developing the use of TDR for finding discontinuities
in RF feed lines for TV. He developed a kit for use in the field for
locating ghost problems in the lines connecting the tx to the antenna.
Were you aware of Don's work in this area?

Vaguely. My primary contact and mentor was Dr Matti Siukola, lead engineer
at RCA's antenna lab and test range at Gibbsboro, NJ. Under his direction I
was responsible for updating and improving the VHF and UHF RF pulse test
sets used by RCA Field Service.

RF

At the RCA Labs antenna lab Dr. Siulola's name was held in reverence, but I
never had the opportunity to meet him. After initially being at the RCA Labs
antenna lab I originated the antenna lab at the new RCA Labs spinoff division,
the Astro-Electronics Div, which produced the world's first weather satellite,
TIROS 1, of which I developed the entire antenna system. However, I began that
development at the RCA Labs antenna lab prior to the AED spinoff. I was working
there along with Jess Epstein, of the Brown, Lewis, and Epstein group who
performed the ground radial experiment that set the FCC standards for radials
that still exist today.

I also spent time at the Moorestown antenna lab, working on the development of
the Lunar Rover dish antennas. On its finish I performed all the final pattern,
gain, and ellipticity measurements prior to shipping them to NASA.

Walt

On Mon, 6 Sep 2004 10:39:54 -0400, "Tam/WB2TT" wrote:

Hi Roy,

Going back to the Slick discussions of last winter, Was that you who made
the statement that you can have 100% re reflection from a transmitter, even
if it has a 50 Ohm output impedance? At first I thought this was all wet,
but after making some low power experiments, I am convinced it is true.

Tam/WB2TT

Yep , Tam, it's correct. The internal resistance in Class B and C amps has two
parts, 1) the cathode-to-plate resistance, which is dissipative, and 2) the
non-dissipative resistance established by the V/I ratio within the pi-network
tank circuit--a high resistance at the input and a low resistance at the output.
The V/I ratio also establishes the slope of the load line. Consequently, the
reflected power reaching the network output is not absorbed, but instead adds to
the power delivered by the generator. Although powers are not generally
considered to add, they do in this case, because their respective voltage and
current phasors add. If the reflected voltage and current phasors are not in
phase with those from he source, the only result is that the source is
mismatched to the load and reduces its delivery of power. Readjusting the tuning
and loading controls brings the out-of-phase phasors in phase, establishes a
conjugate match and the source again delivers the maximum available power.

Walt, W2DU

On Mon, 6 Sep 2004 10:39:54 -0400, "Tam/WB2TT" wrote:

Tam, would you please send me your email address? I want to send you a copy of
two new chapters from Reflections III. I have reason to suspect your email shown
above is not correct for email.

Walt

On Mon, 06 Sep 2004 18:41:37 GMT, Walter Maxwell wrote:

[snip]
|Thanks for the compliment, Reg, that you prefer to take my word for it. However,
|the reason we include the manufacturer is not as a gratuitutous advert, but to
|distinguish between the Cadillacs (Hewlett-Packard and General Radio, among a
|few others) and the non-descripts. The Cadillacs are professional, precision
|instruments, which, when used by knowledgeable people, provide data that can be
|relied upon.
|
|Without knowledge of the quality of the measuring device the reader is
|justifiably suspicious of the data.

Careful Walt. Reg is an Englishman, he doesn't know what at Cadillac
is, other than an American automobile, which makes it suspect.

You should use Jaguar for comparison. Uh oh, better not, that is an
American company (Ford).

Alright, how about Aston Martin. Darn, another Ford.

I've got it; Rolls-Royce! Nope, that's a German car (BMW).

Okay maybe a Bentley. Nooo. That's a Volkswagon.

Surely a Land Rover. Not again! Another Ford.

You're right. HP and GR were the Cadillacs of the industry. [g]

On Mon, 6 Sep 2004 06:20:23 -0500, "Richard Fry"
wrote:

How do I know? I was the author of all of the brochures and technical data
sheets for Harris' entire FM product line for the ten years before I
retired. That any published value of impedance applied to the load
impedance expected was/is universal across the product lines: AM/FM/TV.

Hi OM,

If you simply follow the reference trail of those trade publications
(the design guides used by the engineers who did the actual work) you
would find PLENTY of source Z discussion:

from Harris White Paper:
"High Linearity RF Amplifier Design"
referencing
"Advances in AM Modulation Techniques to Improve Digital
Transmission of HD Radio and DRM"

"The poor antenna match will create a significant ripple in the
transfer characteristic of the main power amplifier. If that
amplifier itself has a poor output match to 50 Ohms
[the succeeding discussion gets into the inability of feed
forward correction to accommodate to this condition and the
introduction of an expensive isolator and lowered efficiency]
.... Alternatively, the amplifier itself could be modified to
improve its output match."

From Harris White Paper:
"Improving Efficiency With Split-Level Combining"
referencing
"High-Linearity RF Amplifier Design" (op. cit.)
and
"RF Power Amplifiers for Wireless Communications"
ppg. 31-32, 110
Discussion of load pulling to determine the "source impedance."
pg. 99-103 , Figures 4.21 & 4.23
Discussion of the source transformation from source Z 4 Ohms to
load Z 50 Ohms. Amplifier exhibits an 78% efficiency.
and
"Feed Forward Linear Amplifiers"
"Frequency ripple is one of the principle factors that limit broad
band signal cancellation and hence feed forward performance."
....
"As previously discussed, to prevent loss of power due to
impedance mismatches the input and output impedance of a device
should be equal to the characteristic impedance (e.g. 50 Ohms)
of the source and load to which it is connected."

From Harris White Paper:
"REDUCING FM IBOC TRANSMISSION COSTS WITH THE PROPER
CONFIGURATION AND LINEARIZATION TECHNIQUES"
referencing
"Feed Forward Linear Amplifiers" (op. cit.)
and
"RF Power Amplifiers for Wireless Communications" (op. cit.)
and
So on and so on and so on (no deviance from commonplace
design considerations that have been described for generations).

73's
Richard Clark, KB7QHC

Install a matching network that achieves a quasi-conjugate
match between the network and the load. That's what I do. :-)
--
73, Cecil
======================

My dear Cecil,

99% of the contributors to this newsgroup, particularly the professionals,
should make appointments to see a shrink. Problem? - the inabilty to grasp
what is staring them in the face.

It's a sad reflection on the present state of electrical engineering
educational facilities in the Western world. Never mind, there's still
hope, the Chinese, Vietamese, Hindu's, Indianesians, etc., will help us to
sort out such trivial matters as vswr. The problem of sharing energy
resources will take a little longer.

I have just opened a bottle of Chilean, Isla Negra, Cabernet Sauvignon. I
can't read what else it says on the label. But we musn't neglect our good
(South) American near-neighbours and friends.

I am listening to the BBC. The World's finest educational facility although
it sounds more like the VOA than the VOA.

It seems that a very large proportion of the Virginian forefathers were of
the criminal classes, convicts, conveyed in chains, who shared there lives
on arrival with negro slaves. Life expectancy in Baltimore and Maryland was
about 7 years. Between 50,000 and 100,000 convicts were exported to the Land
of the Free. They were present at the Alamo and assisted at many other
places to rid the land of the original inhabitants. Is this proudly recorded
in your children's history books?

Shot any rattlers lately?

From a sincere European friend of all USA citizens, descendents of convicts,
SWR worshippers, conjugal-match adherents, voters even for Bush, or
otherwise.

Reply not needed.
----
Punchinello, G4FGQ

On Mon, 6 Sep 2004 20:24:44 +0000 (UTC), "Reg Edwards"
wrote:

make appointments to see a shrink

Good advice.

Does yours offer refunds? I doubt if there are any measureables that
Lord Kelvinator could use to derive a cost/benefit ratio - hence your
shrink's depostis are secure.

Stick with the wine, at least you know where your money is going, and
it keeps you out of the mud. ;-)

73's
Richard Clark, KB7QHC

On Mon, 6 Sep 2004 20:24:44 +0000 (UTC), "Reg Edwards"
wrote:


Install a matching network that achieves a quasi-conjugate
match between the network and the load. That's what I do. :-)
--
73, Cecil
======================

My dear Cecil,

99% of the contributors to this newsgroup, particularly the professionals,
should make appointments to see a shrink. Problem? - the inabilty to grasp
what is staring them in the face.

It's a sad reflection on the present state of electrical engineering
educational facilities in the Western world. Never mind, there's still
hope, the Chinese, Vietamese, Hindu's, Indianesians, etc., will help us to
sort out such trivial matters as vswr. The problem of sharing energy
resources will take a little longer.

I have just opened a bottle of Chilean, Isla Negra, Cabernet Sauvignon. I
can't read what else it says on the label. But we musn't neglect our good
(South) American near-neighbours and friends.

I am listening to the BBC. The World's finest educational facility although
it sounds more like the VOA than the VOA.

It seems that a very large proportion of the Virginian forefathers were of
the criminal classes, convicts, conveyed in chains, who shared there lives
on arrival with negro slaves. Life expectancy in Baltimore and Maryland was
about 7 years. Between 50,000 and 100,000 convicts were exported to the Land
of the Free. They were present at the Alamo and assisted at many other
places to rid the land of the original inhabitants. Is this proudly recorded
in your children's history books?

Shot any rattlers lately?

From a sincere European friend of all USA citizens, descendents of convicts,
SWR worshippers, conjugal-match adherents, voters even for Bush, or
otherwise.

Reply not needed.
----
Punchinello, G4FGQ

Hello All,

Reg's post above just gave away his cover as an undersea transmission-line
engineer that renders his failure to comprehend SWR, conjugate match, oops, I
mean conjugal match, completely comprehensible.

I know his relevation was totally inadvertant, but it's evident to this SWR
worshipper that he's really a situp comedian empowered with an overdose of, what
did he call it, Kavurnay Sawvignun? He admitted he couldn't read what was
printed on the bottle.

So let's all take pity on this sensitive guy who's beyond his depth in trying to
fathom our attempts to bring him up to speed on the vocabulary required for
speaking intelligently on the vital engineering issues we discuss on this
important media of understanding.

God bless the Cween.

Walt