A long accepted rule of thumb to approximate the sweet spot for linearity is
to load to maximum CW output and then increase loading (less C) until the
output decreases 3-5%. Having a scope is nice if you want to be exact and
is how I set up my AM transmitter.
Carl
KM1H
----- Original Message -----
From: "Bryan Swadener" <bswadener@yahoo.com>
To: <amps@contesting.com>
Sent: Thursday, September 27, 2007 2:22 AM
Subject: Re: [Amps] Amplifier Linearity
> --- Edwin Karl wrote:
>> Does anyone besides me still use a 'scope in
>> trapezoid pattern looking
>> at input vs. output linearity?
>>
>> Seems like we're getting into "flat topping" tubes,
>> etc just to get the max.
>> output level etc.
>>
>> All the "it can't happen here" talk is really
>> counter productive. If a guy
>> says
>> he can do it for heaven's sake let it go. Please
>> don't try and prove how
>> clever you
>> are. It just doesn't impress me and wastes my time.
>>
>> Thanks
>>
>> 73
>>
>> ed K0KL
>
> Hi Ed,
>
> You can count me as one who saw the light in the 70s.
> I had purchased my used SB220 and (at first) adjusted
> it for maximum CW/single-tone output before operating
> in the SSB mode. It was shortly afterward that I
> acquired the Heathkit 'twins' (SB-610 & SB-620)
> monitor scopes, and learned from a 2-tone/trapezoid
> test that I was NOWHERE near the linear region. More
> loading was the cure. Until I have a peak limiter
> installed ahead of the mic input, I monitor in
> real-time with the scope in envelope mode.
>
> I understand the gadget du jour is some CW key-line
> pulser. I have yet to read anything as to how it can
> ensure linear operation (without the use of an
> oscilloscope of any kind). So far, I'm unimpressed.
> Vy 73,
> Bryan WA7PRC
>
>
>
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