"Art Unwin" wrote in message
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On Sep 28, 9:27 am, "JB" wrote:
Many out there don't"John Smith" wrote in
message

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Frank wrote:

You are probably correct concerning a 3:1 SWR. Transmitters
usually have to meet full output into a 2:1 SWR, all phases, with no
sign of oscillation. In this case I had assumed that a matching
network
would be used between the PA and coaxial input.

Frank

Everything I have ever ran can handle 2:1 quite nicely, with
transistors, I worry about exceeding that ... or, how big is your
heatsink/fan?

Regards,
JS

If you put a FSM out and start fiddling, you find that some radios don't
do
their best above 1.5:1 and many start shutting back past 2:1 and the
internal tuners are only spec'd at being able to match 3:1 or better. Even
after that, there is sufficient loss, that your 100 watt radio is now an
80
watt radio. It may be a neat portable feature, but since you have to get
the antenna down below 3:1 anyway. Might just as well do it right from the
beginning or at least get a big tuner. We didn't worry about these things
with the Pi-net tuning.
JB
Things are gettung side tracked here. When I am experimenting I
measure capacitance, inductance
and resistance against frequency where the totally resistive ponts are
of interest.
The standard resonant points will be low resistance and the
anti resonance points can range from 50 ohms to 300 ohms and I plot
these against frequency,.
So a poster took issue with the 300 oghms with the suggestion that I
advocated the use of 300 ohms
connected to 50 ohms for transmission. That was a comment to bait and
people started to bite at it
especially when it was mentioned that 3/4 of the power would be lost.
When all the data is compiled it then becomes useful
with respect to antenna design. For measuring purposes it is only
important that the anti resonant pont is resistive since there are so
many factors that
t
can change the ohmic value in its final environment. It is then that
you become concerned about the matching
The poster mentioned a" system "in his evaluation which has no
relavence to the project at hand, he only posted
for baiting purposes and frankly his supplied figures was just a hoax
or just a plain error that had no connection
to the post I made.
Art

How are you determining the resistance values of a theoretical antenna? Are
you using known resistance of various materials and assuming various
resistive losses?

Or are you using resistive terminations?