R: [AMPS] Have Cake & Eat it too

[Maurizio Panicara]

Nothing strange, any voltage power meter reads a voltage on the
line and indicates the correlated power at a stated impedance.
In case the load is not purely resistive or higher than the nominal
impedance the power reading is incorrect and bigger.

As already reported by others, in the case of high SWR the sum
of the direct and the reflected voltage will rise the power reading.
A bit semplicistically (roughly) Direct power minus Reflected power
approximates something that's not too far from the real power.
No wonder what you read.

In any case, it's never raccomandable to tune an amplifier peaking
the SWR reading. Although SWR it's a voltage ratio and doesn't
change with applied power levels, the amplifier PI network, when
matching a strange impedance, could work in a bad condition where
the second or third harmonic rise and SWR increases because of
that (the antenna SWR is frequency dependent). In such a case,
tuning on highest SWR can be the tuning for worst harmonic
suppression rather than the best energy transfer to the antenna.

73,
Mauri I4JMY


-----Messaggio Originale-----
Da: Jonathan Kaplan <jonk@jskent.com>
A: <Amps@contesting.com>
Data invio: giovedì 9 settembre 1999 15.51
Oggetto: [AMPS] Have Cake & Eat it too


>
> Hi All,
> I've been slowly putting on line my tower installation with a
> TH7DX and a M2 40 mtr dipole atop a 55ft crankup. I've noticed
> a strange behavior since switching from a tuned dipole. My
> Clipperton L amp will tune either for power or SWR on all bands
> but 15mtrs, but not for both. In other words, when I tune the AMP
> the power meter (a RS model) will either show greater power at
> a high SWR or low power at low SWR. But not high power at low
> SWR!  What does this mean is wrong? Does it neccessarily
> mean the final output into the air is limited, and that the antenna
> system is out of tune?
>
> I just need confirmation of that theory and how to test it.
>
> Thanks for any help.
> 73
> Jonathan KO6XS
>
>
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>






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