[TowerTalk] Reflections, Tuners and Antenna Forum Talks

DavidC DavidC" <eDoc@netzero.net
Wed, 10 May 2000 21:30:27 -0400

> 6.  Final step and measurement.  Move the Bird to
> the output of the Palstar tuner to measure the
> indicated forward and reverse powers with all
> set up and operating as in  4.  above.  Will the indicated
> forward  power,  less the indicated reflected power
> show the 1000 watts, as Walt Maxwell's writings
> assert?  We will see.
> 6.1 Forward indicated power on the Bird,  using the
> 2500 watt full scale "slug" shows 1150 to 1200 watts,
> again wind varying.
> 6.2 Reflected power at the output terminals of the AT4K,
> about 230 to 300 watts on the 500  watt slug in the reverse
> position.
> So,  within the tolerances of the measuring apparatus,
> sure enough,  the forward power indicated less the
> indicated reflected power,  does sum to the 1000 watts
> at the output of the amplifier.
> This seems to validate Walt Maxwell's view that the
> forward power into a line/antenna system on the output
> side of an antenna tuner,  when used,  would be the
> sum of the "true" amp output power plus the re-reflected
> mismatch power, in this case of some 230 to 360 watts from
> the mismatch up at the dipole antenna.
> 73,  Jim,  KH7M

Do I have this correct?

OUTPUT = 1150-1200 watts
REFLECTED = 250-300 watts
DIFFERENCE = 900 watts
BIRD ERROR =  +/- 5% or 50 watts @ 1000 watts
HENRY OUTPUT = 1000 watts continuous, ON or OFF, with the Palstar
keeping output even by matching whatever it "saw" on the line to the 50 ohm
output requirements of the Henry.

Somewhere between 50 and 150 watts of the RF that the Henry shipped out
though the Palstar tuner was eventually lost in the coax or tuner?

(It seems apparent that the antenna "refused" to radiate it since it was
*continually* reflected according to your Bird readings.)

Or is the proposition that  50-150 watts of the 1000 "cycles" back and forth
and when the amp stops sending power that "cycling" 50-150 watts then is
radiated?  If so, why wasn't it radiated, and not reflected, in the first

(It *is* a percentage and not an absolute since a 100 watt rig would see
5-15 watts reflected, not 50-150 watts.)

I'm *still* missing a piece of this equation and since Walt's book is on
hold a
reliable reference is elusive!

Any chance you can put that Bird out at the antenna terminals and get some

(Eliminating guess-work as to what may be happening in the coax.)

Any chance you can set up a RF field meter and see how the levels of
antenna-radiated power varied, if at all?

(Documenting the capacity of the antenna to accept all or part of the
radiated power.)

- Thanks! & 73, DavidC  K1YP in Hudson, FL

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