[AMRadio] power ratings

Bob Macklin macklinbob at msn.com
Tue Jul 12 20:44:19 EDT 2005

A comment about AM transmitters. A plate modulated AM transmitter requires a
modulator of 50% of the power of the final to produce 100% modulation. These
transmitters like the Johnson Ranger produce better audo than the screen
modulation units like the small Heaths. Only the Heath DX-100 and TX-1
(Apachee) used plate modulation.

But most of the airborne military transmitters used screen modulation to
reduce the weight and power requirment. These all produce very good
comunication audio.

But if you want broadcast quality audio you need a real plate modulated rig.

Bob Macklin
Seattle, Wa.


----- Original Message ----- 
From: "kenw2dtc" <kenw2dtc at comcast.net>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Tuesday, July 12, 2005 5:30 PM
Subject: Re: [AMRadio] power ratings

> "Ken, as I read the rules, we are only allowed to run 375 watts carrier.
> With 100% modulation this will give us 1500 watts pep which is the max
> output allowed."
> *******Don, You are correct about the 1500 watts PEP.  It could also be
> derived by 600 watts of carrier with much less than 100% modulation.
> are also schemes where the carrier is almost 1000 watts and it is
> downward at nearly 100% and still get the 1500 watts PEP.  Another comment
> about linears in AM service.  Those who do the math and run an SSB linear
> with the PEP equal to 4 times the carrier sometimes miss the calculation
> the male voice which will usually modulate higher than 100% unless limited
> in the audio section.  Thus many SSB amps do not have the headroom for
> AM.
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