[Boatanchors] AM linear question

[Bry Carling AF4K]

Guys always says these things about the inefficiency of AM linear mode, and they 
could be right. I can sure tell a difference on received signals though when a guy running low 
power AM kicks one in though!

YMMV

73 de AF4K

On 8 Dec 2015 at 11:43, Gary Schafer wrote:

> I wouldn't talk too long with 150 watts output on AM with a 30L1. you will
> be exceeding the plate dissipation of the tubes.
> 
> If the amp is tuned up for 600 watts output as you normally would, you then
> reduce the drive to produce a carrier of 150 watts (25% of output)for AM. 
> 
> At 600 watts output the efficiency of the amp will be around 60%. At 150
> watts carrier output the efficiency will be around 30%. This is normal
> operation for a linear amp on AM. 
> 
> At 30% efficiency and 150 watts output the input power will be around 500
> watts. 500 watts - 150 watts leave 350 watts of plate dissipation!
> 811A's as I remember have a plate dissipation of only 65 watts each. For
> four of them that is 260 watts so you are exceeding the plate dissipation of
> the tubes by 90 watts in this mode of operation.
> 
> On SSB the average power of the amp is much lower that it is on AM so the
> tubes are not stressed so much unless you hold the carrier on at tune up or
> run very heavy processing.
> 
> By the way if everything is set up properly the plate current shouldn't
> increase with modulation. It should just wiggle around a little.
> 
> 73
> Gary  K4FMX
> 
> > -----Original Message-----
> > From: Boatanchors [mailto:boatanchors-bounces at mailman.qth.net] On Behalf
> > Of D C _Mac_ Macdonald
> > Sent: Monday, December 07, 2015 9:35 PM
> > To: RAY FRIESS
> > Cc: boatanchors at mailman.qth.net
> > Subject: Re: [Boatanchors] AM linear question
> > 
> > If you set the exciter rig's output to hold the AM carrier output of the
> > 30L-1 to 30% of the "normal" CW output, you should be safe.  Keep the
> > exciter's modulation down to the point where the 30L-1 current
> > "flickers" upward about 30% more than its idle current with RF drive but
> > NO modulation and I think that you should be safe.
> > 
> > * * * * * * * * * * *
> > * 73 - Mac, K2GKK/5 *
> > * (Since 30 Nov 53) *
> > * k2gkk hotmail com *
> > * Oklahoma City, OK *
> > * USAF & FAA (Ret.) *
> > * * * * * * * * * * *
> > 
> > 
> > > From: rayfrijr at msn.com
> > > To: boatanchors at mailman.qth.net
> > > Date: Mon, 7 Dec 2015 19:33:12 -0700
> > > Subject: [Boatanchors] AM linear question
> > >
> > > Having been a ham for nearly 50 years now, I should know this, but I
> > wanted to get input from
> > > some of the other old timers ... perhaps from Glenn.
> > >
> > > I have two 30L-1 linears and I'm curious as to whether or not I
> > could/should use them on AM, and if
> > > so, should they be run at reduced power or with other restrictions.
> > >
> > > Thanks guys...
> > 
> > 
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