>>PEP from the FT101EX could be as much as 150 watts. That
>>means the FL2100 needs to be fully loaded at 150 watts of
>>CW carrier drive, and that is just too much. You'd need
>>an attenuator pad between the amp and rig or really watch
>>your control settings.
>
> Why can't I just reduce the drive on the '101 to 25 watts
> and drive the amp with that?
25 watts carrier? That's 100 watts PEP if you watch the peak
envelope power and use the controls properly to maintain
that peak level.
You'd need a good PEP reading meter. The Ameritron PEP meter
is a very good one for this application since it even reads
extremely short peaks accurately and holds the level on the
meter, and it also reads pretty close on avarage power. The
key will be a good meter.
> From brief experience:
>
> It looks like if I drive the amp with 25 watts, I get
> around 125 -130 watts out of the
> amp. Four times that (PEP) is 520 watts, well below the
> 1200 watts PEP rating
> of the amp.
Well, in order to be LINEAR amplifier carrier efficiency has
to be about half or less the efficiency on full power peaks.
Let's assume the 2100 makes 60% efficiency at full drive.
That means 30% or less efficiency on carrier, so we'll guess
25% to be safe.
At 25% carrier efficiency four times the power would be the
input power, or 130 watts times four or 520 watts. That
means the anode heat is 520-130 or 390 watts. The tubes are
rated at 160 watts each, so you are 35 watts over each
tube's dissipation limit.
If you are NOT over each tube's dissipation limit at 130
watts carrier, the amplifier is almost certainly mistuned
for linear AM service.
Now if you wanted to run the 572's at 2/3 of rated
dissipation on AM, you have 320*.666 = 213 watts
dissipation available. With 213 watts dissipation you have
284 watts input available, 213 watts of heat, and 71 watts
of carrier.
Now you don't have to run the amp that way, but that's
probably a reasonable value for AM. The tubes won't melt and
it would be linear. You also would not have high voltages on
the tank circuit on audio peaks.
Linear amplifiers on AM are generally heat limited, not peak
power limited, when properly tuned.
73 Tom
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