[BC] Decluttering AM ... and whither AMS?

[Kevin Tekel]

R.J. Carpenter wrote:
> In the unlikely scenario of all 1 kW Class C stations going to 50 kW,
> their cochannel desired to undesired ratio would be exactly the same
> as it is today.  Sure there is a diurnal variation in the ratio, but
> the ratios would remain just as they are today at any given moment.

OK, but does this argument take into consideration the co-channel beats
caused by each station having a slightly different carrier frequency?
That's what greatly exaggerates the overcrowding on the "graveyard
channels" at night -- you might have a perfect daytime signal from a
Class C station in your area, but as the skywaves start rolling in around
sunset, the signal becomes more and more choppy from all the fluttering
and warbling caused by co-channel signals, until the point where the
"desired" signal becomes unintelligible because of all the interference.

This is where a technology like Advanced Modulation System (AMS) could
have a great benefit: to allow AM stations to increase their modulation
level, and therefore their effective signal coverage, without increasing
their carrier power level.  Unfortunately, AMS was held up by patent
issues in 2003, and nothing has been heard about it since.  Nonetheless,
here are some write-ups about AMS, from when it was first presented in
2002 by Mike Dorrough:

http://www.rwonline.com/reference-room/special-report/01_rw_ams_1.shtml

http://beradio.com/currents/radio_currents_12/





	
		
__________________________________ 
Yahoo! Mail - PC Magazine Editors' Choice 2005 
http://mail.yahoo.com