[BC] Re: SUPER MODULATION & AM STANDARDS

[Lamar Owen]

On Thursday 12 May 2005 07:20, DHultsman5 at aol.com wrote:
> Were  there actually any confirmed and documented cases
> of harmful interference  that resulted from stations
> modulating above 125% positive?  In other  words, was a
> new FCC rule really needed to protect  innocent
> bystanders?  Or was this, in fact, only a response to
> some  politically-connected 50 kW operators crying foul
> because the "hot-rodded"  5 kW guys were beating them
> in loudness?

My original elmer years ago, John Randolph (who died in 1992) mentioned a 
station he worked at in DC that had a 10kW capable 5kW transmitter that 
modulated to 250% positive.  Since modulation percentage directly impacts AM 
coverage, this effectively sidesteps the 5kW power level protection limits.  
So it's not really an interference issue in the positive modulation 
direction; it's a sidestepping of coverage limits.  You raise the sidebands 
up and you get more distance to effective reception.  And you walk on your 
co-channels' sidebands, as well as you first adjacents' carriers.

Unfortunately I have forgotten many of the details; perhaps it was WEEM?  That 
doesn't sound exactly right.

I mentioned this on the RT list several years back and someone on the list 
remembered the incident, but I can't seem to find it in my RT archive.

This would have been in the 60's.
-- 
Lamar Owen
Director of Information Technology
Pisgah Astronomical Research Institute
1 PARI Drive
Rosman, NC  28772
(828)862-5554
www.pari.edu