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[AMPS] Reading Reflected and True (?) Power

To: <amps@contesting.com>
Subject: [AMPS] Reading Reflected and True (?) Power
From: jreid@aloha.net (Jim Reid)
Date: Fri, 1 Oct 1999 16:55:39 -1000
Hi again,  to continue:

> Jim Reid wrote:
>
> >And I really wonder why less drive power is required into
> >the matched system than into the dummy load for the
> >same indicated forward power.....

Jon replied:

>  As to why your matched antenna with the tuner requires less drive power
> than the dummy load, I have no idea! .....

Well,  today I proceeded with more care.  Borrowed another Bird
43 from KH6FMT,  who must have purchased it close to 45 years
ago!  It certainly looks it,  S/N 15794;  mine, only a few months
old is S/N 277093 !

I put John's meter in the line ahead of the linear to get a more
accurate look at drive power;  I was concerned that the load
on the exciter might be different when going into the linear
from when going to either the dummy load or the antenna
system.

Result,  drive powers for the same power from the linear
into the dummy load or the matched (using the tuner) antenna
system are,  in fact, the same!  So that clears away that puzzle
from yesterday.

> Unless the Henry has a roller inductor (does it?).....

Yes,  in the Henry Ultra there are two roller inductors:
the pi network inductor is a roller, L107 of the circuit,
and the output L network inductor,  L104 is also a roller.
These two rollers are ganged together,  and are the
tuning control for the amplifier.

The load capacitor is a vacuum variable, a Jennings 5kv
465 pf unit in my amplifier.

> What happens if you use the tuner to match the dummy load to the amp?  It
> sounds silly, but give it a try and tune for maximum output.

After the above measurement result,  I didn't try this,  hi.

> Using my tuner, I can easily adjust maximum power output even though the
> SWR is 1:1, what I am doing is changing the input impedance to match the
> amplifier.

Yes,  from here on I will be using my tuner all the time.

Thanks to all for your contributions and the discussion.  Topic
should now be QRT.

73,  Jim,  KH7M



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