I could never disagree with Bill Orr; he was an icon, even in his own
time. Whatever he didn't know, he would know who to ask.
I went to visit (at my employer's expense) Eimac at least 4 times during
our transmitter design efforts, measuring things and meeting Bill Orr;
and twice when he visited RF Communications. I wonder if the W6WRT-Bill
and I ever met at San Jose.
==========
From: "Bill, W6WRT" <dezrat1242@yahoo.com>
ORIGINAL MESSAGE:
On Wed, 22 Jul 2009 22:04:59 -0500, "Gary Schafer" <garyschafer@comcast.net>
wrote:
> >You disagree with Bill Orr?
REPLY:
If Bill Orr is recommending a resistor to "swamp out" load variations
over the
RF cycle in a tube's input circuit, then yes, I disagree.
A resistor can not store energy during the high impedance part of the RF
cycle
and then return it during the low impedance part. A parallel resonant LC
circuit
can, given sufficient Q. The circuit can be either a pi-net or a simple LC
parallel resonant circuit.
73, Bill W6WRT
Herzog admits and agree's with W6wrt (We got too many Bills and Wills
around.) But extends the whole idea to the economics of not having the
tuned circuit for economic reasons, for the case of my ten kilowatt
design, and then for performance magic in the transistor driver to
grounded tube cases.
I noted that the RF wave on oscilloscope seemed to get extra output
from the tube at the peak of the cycle. And the transistor driver
seemed to be clipping the peaks of the cycle as it saturated. The
combination of the two distortions helps cancel them out.
------------------------------
Herzog also agree with Gary below: and note the big "IF".
Warren Amphar, from Collins, who challenges Warren Bruene, and I have
argued much about the meaning and use of this mythical driver
input/output impedance; to no useful end; ending with me championing
neither. It is all in their semantics. Warren Brune was famous for his
forward-reverse measurement bridge, AND made most all of the famous
Collins transmitter high power designs. He became infamous for his
clout with ARRL/QST to keep another writer's articles opinions about
this topic from getting any press. This is a useless and endless point
to argue.
===============
From: "Gary Schafer" <garyschafer@comcast.net>
You misunderstand Bill. We are not talking about a tuned circuit at the
input of the grounded grid amp. We are talking about what effects the
varying load has on the driver. If [NOTE THIS BIG IF} the driving source
has a low enough
impedance as seen by the amplifier then the varying load provided by the
amplifier will have less effect on the driver. The load change is then a
smaller percentage change for the driver.
I did not imply that swamping the exciter was better than a tuned circuit at
the input of the amp.
73
Gary K4FMX
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