> I'm trying to find some sort of published graphic that displays the
> relationship between SWR and apparent power, as measured
> by a standard RF power meter, such as the VFD. Put another
> way, if the meter says my SWR is 1.8:1 and my power is
> 1440 watts, I want to be able to apply a factor to
> know my real forward power level.
Hi Pete,
I have both the VFD and the older R.F.Apps. P-3000 meter.
The P-3000 had the ability to display either forward (including
the added re-reflected power), the "True"/real forward power
or just the reflected power or the voltage on the line.
It is my understanding that the "new" VFD reads only the "True"
forward power, or as you call it the real forward power.
The true forward power would be the power going forward
on the output side of your tuner, if you are using one, less
the reflected power which is re-reflected back up the line
by your tuner. As you know, a power meter on the antenna
side of your tuner will NOT be reading the radiated power,
but the sum of the radiated power plus the reflected power
resulting from the Z mismatch which has caused the vswr.
With a tuner adjusting the transmitter input side of the tuner to
1:1 vswr, the VFD installed on the same input side of the
tuner ought to read true forward power anyway, as there
ought not be any reflected power there, if your vswr
meter is accurate anyway, hi. Some folks have put
a Bird meter, or other power meter on the output, or
antenna side of their tuner and found significantly higher
indicated forward power! Of course, as now you are
reading out there the true or real forward power plus the
reflected power which has been re-reflected from the
tuner, and is doomed to be re-reflected again, less line
loss when it again reaches the antenna "terminals".
Anyway, you knew all that already, hi. I think the VFD
is set to read real/true forward power as could their
original P-3000 instrument.
73, Jim KH7M
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