[Johnson] Why amplifiers v. plate mod?

Tue, 28 May 2002 22:26:35 -0400

Considering that 750 watts OUTPUT AM carrier isn't legal any more with
100% modulation, or alternatively that the Johnson 500 now has the
maximum allowable output carrier, an amplifier like the AL-1200 or
such with an actual 750 watt brick on the key (RTTY) rating, can
easily deal with 375 watts carrier and 1500 watts pep from a 100%
modulated signal.

That's just about a perfect match to my Ranger running AM. Need about
25-30 watts AM out to drive the AL-1200 to 375 watts carrier plus 100%
modulation.

Johnson Pedestal ain't strictly legal any more, unless it's throttled
back. (Though I doubt seriously that bothers anyone that owns one.)

----- Original Message -----
From: "Roy Morgan" <[email protected]>
To: "Cal Eustaquio" <[email protected]>;
<[email protected]>
Sent: Tuesday, May 28, 2002 7:21 PM
Subject: Re: [Johnson] Why amplifiers v. plate mod?

> At 04:02 PM 5/28/02 -0700, Cal Eustaquio wrote:
> >All:
> >I think I already know this but I wanted your opinion. I keep
hearing
> >about hams juicing up their normally SSB linears to amplify AM. Is
> >this supposed to be better than running a plate modulated rig of
the
> >same power class?
>
>
> Depends on what you mean by "juicing up" and also on what you or
they mean
> by "better"
>
> The "juicing up" normally needed to be done in the  power supply.
> The "better" may be from the idea that running a linear amplifier
you
> HAVE  on AM is cheaper than buying or building a new transmitter or
final
> stage.
>
> Facts about this:
>   1)  Most/many linear amplifier power supplies meant for SSB
service would
> not support steady state use in AM serivice.
>   2)  Many hams did/do not understand the use of Linears in am
service.
>   3)  The linear has a maximum carrier power it can deliver (still
being
> linear).
>   4)  The principles and engineering factors involved have been
clearly and
> repeatedly explained.
>   5) Measuring "efficiency" of a linear amplifier used in AM service
> normally leads to unimpressive numbers.
>   6) Running a linear amplifier properly with a clean AM input
signal
> produces a stronger AM signal that sounds just fine.
>   7) The TMC company built transmitters operating on with these
conditions
> for years. You can hear some today by tuning to 5.0, 10.0, 15.0 or
20.0 mc.
> (WWV)
>
> Roy
>
>
>
> >  For some reason, I think AM done in this manner
> >wastes more power than a similarly plate modulated rig. What gives?
> >Thanks.
> >
> >Cal, N6KYR.
> >
> >_______________________________________________
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>
> - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> 7130 Panorama Drive, Derwood MD 20855
> Home: 301-330-8828 Work: Voice: 301-975-3254,  Fax: 301-948-6213
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>
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