On Sun, 05 Jun 2005 21:58:06 GMT, "Henry Kolesnik"
wrote:

In TV broadcasting reflections from the antenna back to the transmitter will
be reflected by the transmitter to the antenna and the signal will be
rebroadcast albeit at somewhat less power.

Hi Hank,

That would pretty much reveal the SWR if we knew, wouldn't it? If
"somewhat less power" was in 1.2:1 ratio, we wouldn't care so much,
but how would the viewer feel about such service?

Then depending on the length of
transmission line the viewer may see ghosting.

I think we, or another correspondent and I have dealt with that at one
time. At the time I believe it was called "fringing," not "ghosts."
The difference being that what were called ghosts at the dawn of the
TV era were separated by fractions of an inch rather than fractions of
a mm. As such, ghosts couldn't have been originated by anything
shorter than mile length transmission lines that were poorly
terminated at both ends. Instead, ghosts were actually transmission
path length differentials in a multipath situation.

In audio I don't know why and I have run my Collins 30S-1 into ladder line
with a 14 to SWR with no one except me knowing!

Well, if this is meant to be analogous to fringing/ghosting, I suppose
its because a microsecond blur at AF is entirely inaudible. Or are we
speaking of SSTV? However, this begs the question, How did you know?
All the Collins equipment I taught at school didn't come with a SWR
meter. It was wholly unnecessary if you performed the standard
tune-up. Matter of fact, back then the only SWR meter I saw was for
Ham gear. The finals' tank performed every function of matching as
any tuner.

However, with the KWT-6, we did use an external tuner, 180-V1
(although I may have this mixed up with another model), for coax
feedlines. This was more for its automatic feature where the
transmitter could be tuned up with a 50 Ohm load, and the automatic
tuner simply did the job of presenting it with the transformed load.

However, returning to the point of a transmitter rereflecting a
reflection; I know the bare KWT-6 into ladder line employs its tank to
protect its final tubes. Without that safeguard, I have seen plates
melt - something no one here wants to call dissipation lest it be
evidence of an internal resistance. The bare tubes with their native
very hi Z would rereflect like nothing else - and this begs the
observation - how could you get original any power out of them, past
the tremendous mismatch? The tuner/final tank comes back into the
equation, and rereflection goes out the window as a property of the
transmitter and returns to the domain of matching.

If anyone wants to constrain the entire crusade of the rereflecting
transmitter to the tube set feeding ladder line - then feel free to do
so. However, I don't think I've ever seen a mobile tube rig feeding
ladder line - no doubt one day I will. We will probably talk about
efficiency. :-)

73's
Richard Clark, KB7QHC