[TenTec] Centurion and AM

[Wade Staggs]

*Many of the newer Shortwave transmitters produce very little Carrier. They
have always placed a much smaller LSB signal on the air and really punch
the USB side hard. Instead of using Modulation Transformers..... They now
use Digital Pulse Modulation where the VCC (( for clarity )) of the PA
Section is controlled by (( varied )) by Very Large and High Power
Switching Devices at Audio Frequencies. By doing this they save Tons of
money on their Power Bills. Which as you can imagine is quite expensive. I
know that I could not afford any kind of... 100 Kilowatt at a 24/7  rate
....Power Bill. We are trying to explain the process in simple terms. Even
though Miss Brenda, Burns me up each Winter and Freezes me all Summer....
Why do some women do that?*
*
Wade/KJ4WS*


On Sat, Aug 2, 2014 at 3:43 PM, <bcarling at cfl.rr.com> wrote:

> 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 at 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 at gmail.com> wrote:
> > > >
> > > > On Sat, Aug 2, 2014 at 12:28 AM, george fritkin via TenTec <
> > > > tentec at 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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