*AM Receivers don't need much Carrier to properly Demodulate the signal.
And here is a fact that most folks have not thought about. The Sound
Sub-Carrier in the older TV Broadcast Transmitters was Frequency Modulated.
But the Video information was Vestigial Sideband. The older TV Broadcast
System had a Band Width of around Six (( 6 )) MHZ. That's correct folks MHZ
and not KHZ ... This is why the TV Broadcast Transmitters in the old Analog
Format had to have a ERP (( effective radiated power )) into the Mega Watt
range to cover a 50 to 90 mile service area. Can you just imagine what kind
of RF Footprint we would have with a One Mega Watt ERP on 40 meter SSB and
then reimagine that on a narrow bandwidth Digital Mode and CW, which is the
Original Digital Mode......*
* Wade/KJ4WS*
On Sat, Aug 2, 2014 at 1:50 PM, k6jek <k6jek@comcast.net> wrote:
> Pretty good explanation, Wade. Go to AMfone.net to meet and talk with
> people who live and breathe AM and who might have a more nuanced view of
> things like PEP. The advice, though, is the same, divide by four as a rule
> of thumb.
>
> Jon
>
>
> On Aug 2, 2014, at 9:55 AM, 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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>
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