[AMRadio] AM Amps


James M. Walker chejmw at acsu.buffalo.edu
Fri Jan 14 12:47:56 EST 2005


Yep,
that is what the meters showed approximately 67% by my reckoning,
the 5KW dummy load gets warm only when you turn it up. There is
not enough drive from the DX-100 on AM to run it at the 3.5KW level
mentioned in the article. Ah, I might also mention that the article rig is
continuous tuning from 3.5 to 21 Mhz. Whereas this unit is 1.6 to 30 Mhz.
with subsequent heavier components. Or following the Harris philosophy
"Go Big, or Stay Home".

The monitor scope only required that I put a one turn loop on the end of
the 10X probe to monitor the waveform, cool!
Jim
WB2FCN

----- Original Message ----- 
From: "Bob Bruhns" <bbruhns at erols.com>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Friday, January 14, 2005 12:10 PM
Subject: Re: [AMRadio] AM Amps


> Come to think of it - since it is a grounded grid amp, some of the
> driver power is appearing in the output, so actual efficiency is
> really a bit below 68%. Still quite good. The output AM carrier
> power ratio holds; for faithful reproduction of AM with 100%
> positive modulation, the carrier power will be 357.5 watts.
> 
> ----- 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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