I am not an expert on Bird 43 wattmeters, but I am using one to
upgrade a DX100 with improved audio, new modulator pentodes. It has
the peak reading mode, so i tried it out yesterday, while talking,
with carrier running 125 watts on the non-peak reading mode
(standard) using a 250 watt slug. I switched to a 1 kW slug, and the
transmitter was making around 400 watts peak reading, a little higher
(up to 500) on significant positive modulation peaks of my voice. I
had an audio processor limiting the negative to <100% during this.
Yes, I was curious as to why it was typically 3X and not 4X as
modulation theory would predict, for 100% sinewave modulation too. Do
tell.
John
K5PRO
>
> Why is it that a Bird 43 with a calibrated peak reading kit only reads
>THREE times the power for a peak reading of a 100% modulated AM
>waveform, instead
>of FOUR times the power as the textbooks all say it should?
>
> Is it because the 43 is responding to a Half wave rectified signal but
>'calibrated' to read as though it was responding to something else?
>
> I believe I have an answer, and it is directly related to both threads, but
>I was hoping for some open discussion of the subject to see where it goes,
>and if it goes in the direction of my solution or not...
>
> Hint: It is a mathematical relationship between the average response of the
>43's analog meter movement and the FCC's definition of power output.
>
>Regards,
>
>Dennis O.
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