[AMRadio] AM power

[Bob Macklin]

"what you're not getting, Gary, with the proper voltage and everything
running the way it should on my rig, when I DO hit the same point on
positive voice peaks as the single-tone, the negative peaks aren't
anywhere -near- the baseline of the carrier.  That is -not- 100% 
modulation."

Sounds like you have a modulator problem.

A properly deigned AM PLATE modulator will produce very clean 100% upward 
and downward modulation on a single tone. If it doesn't you have distortion 
in your audio system.

This stuff can only be measured with a tone because the human voice does not 
produce symmetrical waveforms!

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"


----- Original Message ----- 
From: "Geoff Edmonson" <w5omr at att.net>
To: "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Saturday, June 18, 2011 8:07 PM
Subject: Re: [AMRadio] AM power


> On 06/18/2011 09:55 PM, Gary Schafer wrote:
>> Jeff,
>
> My name is Geoff.  With a G e o f f.
>
>> An easy way to prove this to yourself: set your scope on the output of 
>> your
>> transmitter for say 2 divisions of carrier.
>
> Seems I'm the one that told you I -did- this.  That's why I KNOW I've
> got a voice with an SR of 4, when there's proper voltage on the 
> modulators.
> 250TH's, in Class B,  like ~3000VDC.  I run about half that and 0 bias.
> At that level, there's 220mA of resting current.  There's not enough
> voltage to properly modulate the final - the positive peaks are kinda
> rounded off, they don't reach, but with an SR down to 3 (instead of 4) I
> can run the carrier up to around 200w.
>
>
>> Then modulate it with a single
>> tone until the voltage on the scope doubles (4 divisions). That is 100%
>> modulation I am sure that you would agree.
>>
>> Now remove the single tone and modulate with your voice until the voice
>> peaks hit the same 4 divisions on the scope. You are now modulating 100%
>
> what you're not getting, Gary, with the proper voltage and everything
> running the way it should on my rig, when I DO hit the same point on
> positive voice peaks as the single-tone, the negative peaks aren't
> anywhere -near- the baseline of the carrier.  That is -not- 100% 
> modulation.
>
>
>
>
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