[AMRadio] AM Amps


James M. Walker chejmw at acsu.buffalo.edu
Fri Jan 14 12:37:21 EST 2005


Bob,
This amplifier was built as a "test fixture" to proof out the circuitry
from the Engineers Handbook. The original was spec'ed out in Class
"C" mode and ran with 3500 VDC at 1 amp Plate current. There is a
proviso at the end of the description, that " Although we understand this
power level exceeds Authorized Amateur levels" it gives a good idea of
what can be accomplished with good engineering practices. I built it to
run AFSK a long time ago, it still works great, and with the original Eimac
4-1000A, purchased in 1978. Power supply is 4700 VDC at 1.5 amperes
continuous. Sits in a six-foot rack with wheels and warms a corner of the
building.
Jim

----- Original Message -----
From: "Bob Bruhns" <bbruhns at erols.com>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Friday, January 14, 2005 11:51 AM
Subject: Re: [AMRadio] AM Amps


> 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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