[Heathkit] Heath Warrior as an AM amplifier

[James M. Walker]

Yes indeed,
Pretty much my reduced version. If Ya want a "Big Rig"
Buy one or build one, Modifying a Warrior to do something 
it was never intended for, for all practical purposes is a "Waste of time"
or as we used to say, "Left as an exercise for the STUDENT"!
YMMV
Jim
"Go Big or Stay HOME!!"
WB2FCN
http://eshop1.chem.buffalo.edu/


----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: <heathkit at mailman.qth.net>
Sent: Tuesday, January 17, 2012 11:52 AM
Subject: Re: [Heathkit] Heath Warrior as an AM amplifier


> 
> ----- Original Message ----- 
> From: "James M. Walker" <chejmw at buffalo.edu>
> To: <heathkit at mailman.qth.net>
> Sent: Tuesday, January 17, 2012 7:11 AM
> Subject: Re: [Heathkit] Heath Warrior as an AM amplifier
> 
> 
>> Or a classic case of "YOU CAN'T GET THERE FROM HERE" !
>> Strange!
>> Jim
>> WB2FCN
> 
>    Linear amplfiers were used for many years by broadcast 
> stations. One characteristic of these transmitters is low 
> plate efficiency. A Class-B linear will have, in principle, 
> no plate current in its quiescent state, i.e. no signal, and 
> about 66% with maximum signal. When used for AM the carrier 
> is there all the time and is well below the maximum output 
> of the amplifier so its efficiency for the carrier is quite 
> low. Since even processed speech and music has a high ratio 
> of peak to average level the average or "all day" efficiency 
> of AM linear amplfiers was not much better than the 
> efficiency for the carrier only. While these transmitters 
> had good signal quality the low efficiency made them 
> expensive to operate especially since most high power 
> transmitters required lower level linear amplifiers as 
> drivers. There began to be a demand for something better. 
> One answer was the Dougherty circuit of Western Electric, 
> which had something like 65% all-day efficiency but was hard 
> to keep tuned up and had rather high distortion. Other 
> manufacturers began to offer plate modulated transmitters. 
> These had fairly high efficiency but required expensive 
> modulation transformers. There were modifications of the 
> original Dougherty circuit that substantially improved its 
> performance, particularly the ones patented by James O. 
> Weldon, of Contenental Electronics. Transmitters of this 
> type are currently made. Another approach was the pulse 
> modulated transmitter (forgotten the inventor), capable of 
> very high efficiency, this is the basis of the transmitters 
> made by Harris, and I think now by others. There were some 
> other approaches but amateurs has switched to SSB before 
> these became available. The high efficiency linears have no 
> advantage for carrier suppressed signals so are not found in 
> ham gear.
>     Using a linear amp for AM is a throwback to the 1930s. 
> A good deal of technical literature of the time covers 
> broadcast transmitters using them and may be of interest.
> 
> 
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com 
> 
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