Re: [IRCA] More IBOC In Philly

[Barry McLarnon <bdm@xxxxxxxxxx>]

On Friday 23 September 2005 11:53, David Gleason wrote:
> I don't think a 0.5 contour is primary. The primary is 5 mvm, I believe
> and the city grade is 25 mvm if I remember the definitions correctly. In
> most urban areas, a 5 mvm contour will not produce much listening;
> consensus is that it takes about 10 mv/m or better to generate AM
> listening.

Quoting from the FCC regulations (47CFR73.182, "Engineering Standards of 
Allocation"):

"The groundwave signal strength required to render primary service is
2 mV/m for communities with populations of 2,500 or more and 0.5 mV/m
for communities with populations of less than 2,500."

If you can provide a reference showing a consensus that 10 mV/m is 
required, I'd love to see it.  This may be true for downtown Los Angeles, 
but it certainly isn't true in general.

If you haven't already done so, I urge everyone to read the 2002 report 
about the Clear Channel tests with WTOP and WARK in the DC area.
It's an easy read, just a few pages.  You can get it at
http://www.nrscstandards.org/DAB/doccitedinamiboc.asp - it's the
first document listed on the page.

In their tests, they had good reception of WARK on a variety of radios with 
a field strength of only 0.2 mV/m, even with a much stronger first 
adjacent signal present from WTOP (0.8 mV/m) - provided that WTOP wasn't 
running IBOC, of course.  The report also says "listening is quite 
acceptable on an average car radio well beyond the 0.5 mV/m contour".
Then, of course, there's the concluding remarks about AM IBOC being 
"profoundly deleterious".

Clear Channel would probably like to disown this report now, but it's out 
there, and it speaks the truth: that AM IBOC is an appalling travesty.

Barry

-- 
Barry McLarnon VE3JF  Ottawa, ON

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