[Amps] peak reading with AM signals tspa

[John T. M. Lyles]

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.