[AMRadio] AM Linear Operation

Ed Swynar gswynar at durham.net
Sat Mar 18 07:32:20 EST 2006

Hi Mike,

I'm sure it's been all hashed --- and re-hashed! --- here before, but a good
rule of them is this: to determine the (safe!) carrier output capability of
your linear amplifier in the AM mode, take note of the plate dissipation of
your tube(s) from the tube manual, then divide by two...

Example --- I have a pair of 813's in parallel here: a single 813 can
dissipate 125-watts, so that's 62+ watts of dissipation, times two, equals
125-watts in total. Adjust your drive accordingly so as not to exceed this
value, all the while monitoring RF output on a watt meter. When speaking,
it's always advisable to monitor your signal on a scope, too...I use a
Heathkit SB-610 monitorscope here, in the trapezoidal position...

Works for me!

~73~ Eddy VE3CUI - VE3XZ

----- Original Message -----
From: "Mike Duke, K5XU" <k5xu at jam.rr.com>
To: "Discussion of AM Radio" <amradio at mailman.qth.net>
Sent: Friday, March 17, 2006 11:21 PM
Subject: [AMRadio] AM Linear Operation

> I've been reading this AM linear thread with great interest.
> I currently run a TS570 which gives me no more than 25 watts of carrier,
> plus a bit more on modulation peaks. I have an unmodified DX60 that I
> to put back in service later this summer after a shack painting project is
> finished. (No need to move it twice!)
> Because I enjoy operating, and would like to do so with enough signal to
> heard reasonably well on 80 and 40 meters, I too have been considering
> linear to run on AM.
> This discussion of linears on AM has caused me to reason that there is no
> exact magic combination of carrier drive level and audio level which is
> guaranteed to produce a cleanly amplified AM signal. For me, at least,
> apparent fact is most unfortunate indeed. My signature will give you a
> of the usefulness of a scope in my shack.
> So, do I sit on my hands and wait for better propogation on the higher
> bands, or do I continue serving as the pin-drop test for all those
> 75A4's, HQ170's etc?
> Mike Duke, K5XU
> American Council of Blind Radio Amateurs
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