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; especially since there
>is zero, or close to it, reflected power when the
>Bird resistor is the load ?
Jim,
Thanks for all your experiments. It is enlightening to see what happens.
As to why your matched antenna with the tuner requires less drive power
than the dummy load, I have no idea! I would think they would be the
same. The only thing I can think of is that your amplifier tank may not
be able to tune to 50+j0 Ohms (assume a perfect dummy load) directly on
the output. Unless the Henry has a roller inductor (does it?), you may
not be able to "exactly" match it on every frequency. A tapped inductor
is a compromise for the particular band. The tuner on the other hand may
act as an additional impedance transformer to help better match the
output of the tube. As you adjust the tuner and play with the caps and
inductor, you not only change the output impedance but the input
impedance as well. So you are probably matching it better.
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.
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.
I most certainly prefer to operate with my tuner is my antenna is not a
good match. My power meters read more accurately, my amp dissipates less
and I know that everything is properly tuned up. Since I have plenty of
umph from the amp and transceiver, I don't really care about the losses
in the tuner.
You results about tuning the amp into an unmatched antenna directly vs.
using a tuner are what I would expect.
Nice job!
73,
Jon
KE9NA
--------------------------------------------------------------------------
The Second Amendment is NOT about duck hunting!
Jon Ogden
jono@enteract.com
www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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