[TenTec] Station setup

[Jim Reid]

Dan wrote,  in part:

> I still don't see no matter how much people try to come up 
> with reasons to explain it that it could possibly improve 
> things at the antenna itself.  

Dan,  The answer is the conjugate match.  To understand
the conjugate match takes a bit of study.  Try the latest
issue of QEX I referenced;  or,  if you can find one,  a
copy of Walt Maxwell's first edition of "Reflections",
published by the ARRL.  The conjugate match is also
written up in most recent earlier editions of the ARRL
"Antenna Book".  For example,  Chap. 25,  "Coupling the
Transmitter to the Line",  up to at least the 17th edition and 
a few ahead of that one.  I don't have newer editions,  but
presume it is in them (it?) as well,  hi.

In your example,  the water that couldn't get in the hose,
falls to the ground.  If all the power which is put out by the
rig,  to use your analogy, is not radiated by the antenna,  or
 is not lost by heating lossy conductors in the tuner or in the 
transmission line, where would you say it goes?   Even
as little as 30 watts dissipated within your tuner or
transmission line could cause problems!  Ever accidentally
touch an Ungar 30 watt soldering iron?

It certainly does not stay in the transmission line,  else the
line would get very hot,  very quickly;  the solder within
the coax connectors would soon melt,  hi.  All the power,
then,  which is not lost to heat in the tuner and line HAS
to be input into the antenna input terminals and RADIATED!
The power also does not get sent back into the rig,  where
it would also soon cause havoc;  my linear purrs along just
fine when my tuner is feeding full legal limit into a line
which has around 3:1 vswr at the output of the tuner
at the top end of the band.  Why,  because even with that
vswr,  caused by the Z mismatch at the line/antenna terminals,
that system is "conjugately matched", and all the incident power
from the rig enters the antenna terminals

Where things can get warm,  is trying to feed a short
vertical,  real short,  as when the vswr is 8:1 as Steve
Best uses in his analytic work on this topic.  And yes,
it pays to get your antenna to within at least 3:1 or so
at the band edges.  With much higher vswr and full power
out,   it would be wise to have a fan in the tuner to blow air 
across the inductor to keep from melting something there.  

I managed to melt the plastic coil form within an MFJ tuner 
once trying to center feed an 80 meter dipole while operating 
on 160 meters at full gallon output!  Not a wise thing to attempt; 
to center feed a 1/4 wavelength antenna element,  hi.  But,
I thought I was desperate and could get away with it--not
so.

I know these ideas are not intuitively that obvious;  I first
struggled with them when studying RF transmission lines
and circuits when back in engineering school,  decades ago;
but the conjugate match theorem was even being taught
back in the 1950's,  hi.  Was even taught to the AC power
engineering students;  the only way to get all the power
from the power house down into the homes/factories of the
folks of the city within the neighborhoods  where even
60 Hz  Z mismatches can happen,  hi.  Why do you suppose
you see banks of capacitors atop some power poles within
neighborhoods?  Used to adjust the power systems "power
factor";  that is,  performing an impedance match within
the distribution system!  The problem occurs as many 
homes/factories present way to reactive a load,  too
high inductance,  or high positive reactance: comes from
all the motors we use.  So to match the load to the power
distribution grid,  the source rig and distribution system
must be impedance matched to all that distributed
inductive reactance with the addition of those capacitor
banks.  Then,  the water flows into the load just fine,
even when it is very inductively,  positively reactive
and not pure R at all.  The load and the source generators
have been "conjugately matched".

Hope this explanation helps a little in understanding the
concept.

73,  Jim,  KH7M


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