> Anyhoo....the second time I used it, the bandswitch arced
> and
> burnt to a crisp! Maybe I'm not tuning it up properly?
Maybe. Maybe not.
Since the PEP for normal 100% sine-wave modulated AM is 4
times the carrier power, and the FT101 can distort the audio
and make it eight times or more the carrier, it easily could
be you tuned wrong.
You actually should load that FL2100 at full Yeasu drive,
but that would be too much for the little FL2100 for very
much time. The FL2100 is a terrible AM linear for the FT101.
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.
> My desire is to use it on 40 meter AM.....yep! AM!!! I
> want
> to run about 150-175 watts of carrier, driving the amp
> with an
> FT-101EX through a Dentron MT-3000A to a W9INN dipole
> (which
> is resonant on 7290).
Let's see if your numbers make sense.
175 watts of carrier. To be linear, the FL2100 would
typically have less than 25% carrier efficiency. That means
tube dissipation under carrier conditions would be 525
watts. You'd have:
700 watts dc input
175 watts carrier output
525 watts heat in anodes capable of dissipating 320 watts
1400 watts PEP with 100% sine wave modulation
700 watts PEP output with 100% sine wave modulation
That amplifier is far too small for the power level you
expect on **clean** AM operation. It would have to be tuned
at 1400 watts of plate input power or sligthtly more. That
would be 600 watts or so dissipation out of 320 watts
available.
Now you see why people never ran many linears with AM...at
least until CB came along.
> How do I do this without burning up the bandswitch again,
> assuming it was my fault in the first place???
Load the amp heavy enough to handle peaks without saturating
or over-dissipating the tubes. To do that safely, you will
need to add two more tubes.
73 Tom
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