Re: [Amps] Centurion cooling improvement ideas for AM service

[Gary Schafer <garyschafer@comcast.net>]

Not really so in either case.

A 1200 watt pep out amp with 60% efficiency will have an input power of 
2000 watts. That will burn 800 watts in heat with full carrier.

That same amp with an AM signal applied and transmitting 300 watts of 
carrier with no modulation will have an efficiency of 33% for the 
carrier. That means the input power will be 909 watts with 300 watts out 
and no modulation. That will burn 609 watts in heat. With modulation 
added the efficiency goes up but so does the power. The efficiency at 
the carrier level still remains at 33% and will still waste 909 watts on 
its own. Add the side band power of the AM signal to that and the amount 
of heat only increases.

The amp is tuned and operated the same for AM as it is for SSB. If tuned 
for 1200 watts pep out, (SSB or AM) The efficiency on SSB at 300 watts 
out is exactly the same as it is for AM at 300 watts out. The efficiency 
at the 1200 watt level is also the same for the AM peaks as it is for 
the SSB peaks.

The only difference is that the AM signal has a higher duty cycle than 
the SSB signal. That raises the average dissipation higher for the AM 
signal.

73
Gary  K4FMX



Joe Isabella wrote:
> But that's only if you transmit a full power CW carrier.  A keyed amp with no 
> drive at all
> dissapates less than an amp putting out 300W carrier (DC input power), and less 
> than an amp
> putting out 1200W PEP, regardless of mode.
>
> Joe,
> N3JI
>
> --- "Rob Atkinson, K5UJ" <k5uj@hotmail.com> wrote:
>
> > > > SNIP<<< 
> > AM isn't so simple, and there are some paradoxes for those familiar with SSB 
> > operation only.
> > One is that an amp in AM service actually runs cooler when the driving 
> > carrier is modulated and the
> > amp is boosting sidebands and the carrier; it runs a bit hotter when you are 
> > not saying anything and it's keyed and txing carrier only.  since it's tuned 
> > for 4x carrier power, efficiency is higher and heat dissipation less when 
> > getting full voice.  So, don't shut up!  Dead air = meltdown hi hi.
> >
> > Rob/K5UJ
> >
> > _________________________________________________________________
> > Is your PC infected? Get a FREE online computer virus scan from McAfee® 
> > Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963
> >
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
>
>
>
>
>                 
> _______________________________
> Do you Yahoo!?
> Win 1 of 4,000 free domain names from Yahoo! Enter now.
> http://promotions.yahoo.com/goldrush
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps



_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps