[BC] Poor Reception Areas

[Barry McLarnon]

On Tuesday 23 February 2010 08:15:06 Urban, Brian L wrote:
> The engineering charts in 73.333 are used to predict received signal
>  strength; F(50,50) for desired signals, F(50,10) for interfering signals.
> 
>      The F(50,50) chart gives the estimated 50% field strengths exceeded
>    at 50% of the locations in dB above 1 uV/m. The chart is based on an
>    effective power radiated from a half-wave dipole antenna in free space,
>    that produces an unattenuated field strength at 1 kilometer of about
>    107 dB above 1 uV/m (221.4 mV/m).
> 
> The F(50,10) interfering signal curves are 50% of locations 10% of the
>  time.  Those curves are based on actual measurements made in the early
>  days of radio.  If you have ever tried to take FM field strength
>  measurements, you know what a crock of bull those curves actually
>  are.  See 73.314 for the accepted procedure.  Check your credulity at the
>  door.

Right you are, Brian... and here's the kicker: the formula for determining 
permissible FM HD power increases, as concocted by NPR and recently rubber-
stamped by the FCC, is based upon that very same "crock of bull".  I'm sure 
the folks at NPR Labs know it's a crock (after all, all of their previously 
published analyses of potential interference used sophisticated propagation 
prediction tools, not the bogus FCC curves) but in this case, good 
engineering once again gave way to political pressure.

Barry

-- 
Barry McLarnon VE3JF  Ottawa, ON