I have read this through twice and still can't figure out what the point is
that you are making
- sorry - my bad!
I also have the two year AEET degree. Thanks to Georgia Tech. I haven't worked
on very
many commercial AM broadcast transmitters, but I understand a number of them
use
modulation methods that the expert hams find anathema, such as screen grid mod
or low
level mod. with a linear amplifier.
The transmitters don't worry about some 3 dB loss or other, they just do their
job, and are not
smart enough to go around looking worried! Hence my 422 is still not
complaining to me.
On 2 Aug 2014 at 11:55, Wade Staggs wrote:
> *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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> >
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