[BC] Poor Reception Areas

[Dippel, Don]

Hello All and thank you for your input. I think Dana has it right about the interference factor being the most important.

I have been running V-soft's Probe for years and know about the contours, especially using Longley-Rice.

What started my thoughts was the NPR survey. They said 75% of listeners were in the 60 Dbu contour. 12% in the 50 dbu, 6% out to 40 dbu and 6% beyond the 40. But my question was, is it safe to assume the average home could get reception if it was within the 50? Or may the 54? Maybe there is no reasonable answer.

I do appreciate the responses because they help me to think this through.

Don Dippel
Chief Operator WPCS
RBN Engineer

 

-----Original Message-----
  From: Urban, Brian L

70 dBu (dB above 1 uV) = 3.16 mV/m
60 dBu (dB above 1 uV) = 1 mV/m
57 dBu (dB above 1 uV) = 0.7 mV/m
54 dBu (dB above 1 uV) = 0.5 mV/m

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.

--
Brian Urban
Chief Operator
KUT Radio
TEL 512-471-1085

On 2/22/10 4:19 PM, "Jason R. at KGVL - KIKT" <jyrussell at academicplanet.com> wrote:

>45-50+ is pretty low, and you'll start getting trash and picket fencing 
>45-50+ as
>you drive along.
>60+ works, but you'll start noticing some noise in the signal.
>I *think* 70 dbU is a city - grade.  Gets inside most businesses with a 
>useful signal.
>80+ ish oughta sound pretty decent.
>90+ should drive a receiver into quieting.