[Amps] "10 Meter Ban" to be lifted ...

Karl-Arne Markström sm0aom at telia.com
Sun Oct 15 07:00:06 EDT 2006


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 at w8ji.com>
To: "Gary Schafer" <garyschafer at comcast.net>; "'AMPS'" <amps at 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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