[AMRadio] AM Amps


Bob Bruhns bbruhns at erols.com
Fri Jan 14 11:51:07 EST 2005


Nice amp!  670 watts dissipation, 1430 watts out means 1430 + 670
watts input, or 2100W input.  (This agrees with the plate voltage
and plate current.)  Efficiency would be 1430/2100 = 0.681 or 68.1%,
which is quite good for a linear amplifier at maximum output.

In linear operation, an amplifier's efficiency is proportional to
its output.  At full power output, you get maximum efficiency.  That
means 1430 watts is the maximum output for the particular tuning
adjustment of the amp.  So an AM signal passed through this
amplifier set up as described would produce positive peaks up to
1430 watts.  For faithful reproduction of AM with 100% positive
modulation, this would correspond to 1430/4 = 357.5 watts carrier.
So somehow the driver power would have to be reduced for proper AM
operation.  Your mileage may vary.


----- Original Message ----- 
From: "James M. Walker" <chejmw at acsu.buffalo.edu>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Thursday, January 13, 2005 11:48 AM
Subject: Re: [AMRadio] AM Amps


> Hum,
> 4-1000A G.G. amplifier, 3000 VDC plate, 700 MA Plate I, 500 MA
> Grid I, with 125 Watts out of DX-100 running apprx 2100 W input
and
> dissipating 670 watts plate = approximately 1430 watts output!
>
> While the carrier level into 50 ohm dummy load is 1400 watts
measured
> and a really NICE orange glow! This is with a 200 cfm blower, air
system
> socket and chimney.
>
> Jim
> WB2FCN
>
> ----- Original Message -----
> From: "Jim candela" <jcandela at prodigy.net>
> To: "Discussion of AM Radio" <amradio at mailman.qth.net>
> Sent: Wednesday, January 12, 2005 7:07 PM
> Subject: RE: [AMRadio] AM Amps
>
>
> >
> > Darrell,
> >
> > That amp you built with the 4-1000 was a "killer" in more ways
than one!
> > Time for a confession..
> >
> > Regards,
> > Jim
> > WD5JKO
> >
> > -----Original Message-----
> > From: amradio-bounces at mailman.qth.net
> > [mailto:amradio-bounces at mailman.qth.net]On Behalf Of Darrell,
WA5VGO
> > Sent: Tuesday, January 11, 2005 6:04 PM
> > To: Discussion of AM Radio
> > Subject: Re: [AMRadio] AM Amps
> >
> >
> > At 04:21 PM 1/11/2005 -0500, you wrote:
> >
> > >In a message dated 1/11/05 12:14:43 PM,
ronnie.hull at glowbugs.com writes:
> > >
> > >
> > > > well all I can say is it works.. works well as a matter of
fact, and
> has
> > > > been for 6 years :)
> > > > I typically run between 350 and 400 watts of carrier every
day. It
> looks
> > > > great on the scope. Modulation envelope is perfect. 100%
modulation.
> In
> > 6
> > > > years Ive only lost one tube, and I accidently broke that
one.
> > > >
> > > >
> > >
> > >I have to agree with Gary.   You're seeing 1600 watts PEP and
400W of
> > carrier
> > >OUT with a pair of GG 813s???   Does not compute!   Just
curious, are you
> > >talking about 400W INPUT power to the linear under carrier only
condx
> > >maybe?   If
> > >so, this would work out to about 133W carrier OUT and each 813
> dissipating
> > >about 133W which would make more sense.
> > >
> > >Dennis D. W7QHO
> > >Glendale, CA
> >
> >
> > I'm with Dennis and Gary. To run a linear amplifier at 375 watts
of
> carrier
> > and 100% modulation, you will need around 800 watts of plate
dissipation.
> > For a short time a number of years ago, I tried running an AF-68
and a
> > 4-1000A linear amplifier. I could never get more than around 450
watts of
> > carrier and stay linear............I didn't need a heater in the
shack
> > either.
> >
> > 73,
> > Darrell, WA5VGO
> >
> >
> >
> > 73,
> > Darrell, WA5VGO
> >
> >
> >
> >
> > ______________________________________________________________
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