Hi Jim... Hmm, it came from my sometimes flakey memory... I'm pretty sure there was a 0.25 second spec for the metering somewhere... maybe it was simply assumed that the meter time constant would be about 0.25 seconds. I suppose that if someone came up with a very slow meter, they could get away with huge SSB PEP, so it makes sense that the time constant of meter should be specified at least approximately.
In any event, the FCC proceeded as though the DC volts multiplied by the DC amps gave the average power input - which was not true for AM. This Dc metering ignored the real power increase during modulation, permitting the upside down tube loophole. Now if guys like me had just kept their mouths shut about it, maybe the FCC wouldn't ever have caught on. But no, we had to throw it in the sidebanders' faces. I plead extreme youth at the time. Bacon, WA3WDR ----- Original Message ----- From: "Jim Wilhite" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" <amradio@mailman.qth.net> Sent: Saturday, February 18, 2006 7:28 PM Subject: Re: [AMRadio] AM Transmitter Advice?? > Bacon, not trying to be contrite, but where in the old rules did the .25 > second time constant appear? I have a copy of the old rules and don't see > it. It says only that "have the means". > > 73 Jim > W5JO > > > At that time, plate power input to an AM > > transmitter was measured by the reaings of DC meters > > with approximately 0.25 second time constant. That > > time constant would make the meters read average > > voltage and current, which smoothed out SSB and > > controlled carrier signals. But on plate-modulated AM > > it did not read true power during modulation, because > > it was looking at average voltage and average current > > separately, while in AM the voltage and current are not > > separate, but they increase and decrease together, > > resulting in higher power input during modulation. > > > _______________________________________________________ _______ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:AMRadio@mailman.qth.net > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
