Ron wrote:
> > <snip>
> > I don't think that is right. I did another test with the same setup but this
> > time I used only a 1000 ohm resistor for a load and no capacitor.
> >
> > Transmitter--watt meter--tuner--drake watt meter-- 1000 ohm load resistor.
> >
> > By adjusting the tuner for zero reflected power on the first watt meter that
> > leaves the drake watt meter and a 1000 ohm resistive load that should have
> > no reflected power.
> >
> > With 20 watts indicated on the first watt meter the drake watt meter showed
> > about 100 watts forward and about 80 watts reflected. The difference in
> > forward and reflected readings is the power delivered to the load. But there
> > should be no reactive component in the load in this setup. There should not
> > be any reflected power from the load. There should be no "apparent power".
> >
> > The reading of high forward and high reflected power on the meter has to be
> > meter error when not operating at the design impedance.
> >
> > This brings us back to the question of how do we determine how much
> > reflected power we have, if any, when looking at a watt meter?
> >
> > In this case with the 1000 ohm resistor there should be no reflected power
> > in the circuit. This indicates a gross error in the meter reading.
> >
> > 73
> > Gary K4FMX
> >
>
> Hi Gary.
> The output side of the tuner looking into the resistive load is reactive and
> is
> determined by the line length , velocity factor and frequency.
> If you have a reference on Smith Charts, you will see that one can transform
> an
> impedance using a length of transmission line.
> One can also cancel the reactive component of an antenna by using the same
> technique and change the impedance into a pure resistance.
> If the line impedance were 1000 ohms (and the resistor is non-inductive), then
> there would be a resistive load at the tuner , all frequencies , all line
> lenghts.
> If it is any other impedance , then there are standing waves on the line and
> the
> impedance at the tuner revolves around a circle on the Smith Chart known as a
> Circle of constant SWR and is determined by the position of the line length to
> the tuner. It repeats itself every electrical wavelength and is purely
> resistive at two positions only.
>
> Voltage magnitude times Current Magnitude is Apparent power and is composed of
> Real Power (Watts)and Reactive Power (VARS) . The real power is Includes the
> phase angle between I and V . Reactive is whatever is left.
> ---
> Ron
>
>
Hi Ron,
Yes I would agree with you if there was a transmission line involved. But in
this
test the load resistor is connected directly to the watt meter no line involved.
Between the tuner and the watt meter I first had about 3 feet of line. I then
eliminated that and connected the watt meter directly to the tuner. No line. The
watt meter read the same with or without the 3 feet of line from the tuner.
Slight
adjustment of the tuner without the line. I tried this on 20 meters and on 80
meters with the same readings on both bands. I first used a 5 watt 1000 ohm
metal
film resistor for the load. I then replaced it with 3 parallel carbon resistors
to
make 1000 ohms. The readings were the same. There may be a small amount of
reactance in my connections but the fact that I get the same readings on 80 and
20 I
would think pretty much eliminate any reactance being a factor.
73
Gary K4FMX
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