*I will try to explain AM Transmitting while using an Amplifier designed
for SSB, as taught to me by my old Elmer((( SK. )))*
* Since SSB only outputs power when you
speak into the microphone. The SSB mode of operation averages out to be
about 30% Duty Cycle where the Tubes and Power Supply are concerned. This
allows an Amplifier built for SSB Service to employ a much lighter duty
power supply. And also the Power Rating for the Tubes and The Cooling
System, can be much higher. BUT, AM operation with Full Carrier is 100%
duty Cycle. Running an Amplifier in AM at Full Carrier Output will soon
kill the tubes and power supply. When I run my SB-220 Amplifier on AM. All
I want is about a 200 to 250 Watt Carrier at most. This is done by reducing
the drive on the radio. With a 200-250 Watt Carrier from an Amp rated for
an easy 1000 Watts you will now say..... what's the use? Well, when you
modulate an AM signal, the sidebands go up to 4 times the carrier output.
You are effectively going from 200 Watts to about 800 Watts PEP ((( Peak
Envelope Power ))) ...... The reason I chose 200 Watts carrier from a 1000
Watt amplifier is that this works out to about 20% duty cycle. Then the
100% Modulated AM Signal does the real work. We can't speak as to Alpha
and Ten Tec Amps but would bet that this rule still applies. An RMS type
Meter will not show this power increase but a Peak Reading Watt Meter will.
*
* My Friend, there are people here with more
Degrees than a Thermometer. While I only have the 2 years of College to
fall back on. But, I have worked on some of the Biggest and Smallest
Transmitters in the World. So, if I am wrong about this in my tried and
true simple explanation. There will be others onboard soon to correct me.
This is however the way we run our equipment. *
* 73 for now from Wade/KJ4WS*
On Sat, Aug 2, 2014 at 11:03 AM, Brian Carling <bcarling@cfl.rr.com> wrote:
> Yes they can. At least they did this morning in a FB QSO on 7293 KHz from
> FL to KY.
> Omni VII and a mighty 422 Centurion.
>
> Best regards - Bry Carling, AF4K
>
>
>
> > On Aug 1, 2014, at 8:46 PM, Barry N1EU <barry.n1eu@gmail.com> wrote:
> >
> > On Sat, Aug 2, 2014 at 12:28 AM, george fritkin via TenTec <
> > tentec@contesting.com> wrote:
> >
> >> 200 to 250 watts AM results in 800 to 1000 watts PEP at 100% modulation.
> >> Three 811 tubes can not handle that power.
> >
> > How about two 3-500Z's?
> >
> > 73, Barry N1EU
> > _______________________________________________
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> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
> _______________________________________________
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