For unprocessed speech, the CCIR long ago established an 8 dB peak/average
ratio.
This may be on the low side, as I have seen 9 and even 10 dB ratios in
literature about
FDM carrier system loading.
Using unprocessed speech and the 1 kW average input limit, it would have been
possible to run > 3 kW PEP output,
from a typical SSB transmitter, but since communications effectivity is
dependent of averaged signal/noise ratios,
this would have been quite pointless.
Regarding the 0.25 s plate meter time constant, it was found in the amateur
radio regulations
of many countries, including Sweden. I have also wondered about the
"enforceability" of such a rule.
73/
Karl-Arne
SM0AOM
----- Original Message -----
From: "Tom W8JI" <w8ji@w8ji.com>
To: "Gary Schafer" <garyschafer@comcast.net>; "'AMPS'" <amps@contesting.com>
Sent: Sunday, October 15, 2006 11:17 AM
Subject: Re: [Amps] "10 Meter Ban" to be lifted ...
> > There was no limit on the peak envelope power we were
> > allowed to run; only a
> > limit on the average power as read on the plate meters.
> >
> > Peak envelope power can range from 5 to 10 times or
> > greater than the average
> > power we see on the plate meter with voice.
>
> OK, I see your point. Good point Gary and one that almost
> everyone misses.
>
> Conventional thought is the peak to average power ratio is
> only about 2:1. While that may be true for processed speech
> (even through ALC), it isn't true for unprocessed speech.
>
> So technically, using the meter response dictated by early
> FCC rules, we could run 10kW PEP input or more on occasional
> voice waveform peaks without making the meter exceed the
> legal 1000 watts indicated input on suppressed carrier phone
> transmissions.
>
> While the FCC increased carrier mode power like RTTY, FM,
> and CW it decreased peak power and average power of AM and
> peak power of unprocessed or lightly processed SSB.
>
> My only addition to that is the very short duration peak
> doesn't mean much for communications, so we didn't lose much
> in that way (except on AM). Anyone using processing already
> restricted the peak-to-average ratio (which also increases
> communications effectiveness) and would not have seen such a
> dramatic reduction in peak power. In other words the peak
> didn't mean that much anyway when the speech was processed
> to improve communications effectiveness.
>
> Good point Gary.
>
> 73 Tom
>
>
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