[BC] Poor Reception Areas

[Mark Humphrey]

Warren took the words right out of my keyboard.  Taking measurements
in the field can be a very enlightening experience which I would
recommend to anyone with the time and equipment.  You'll gain a very
good understanding on the effects of terrain, buildings, and foliage
on mobile reception, and the relationship between receive antenna
height and signal strength.

Based on measurements in the hilly, heavily-wooded Philadelphia area,
I came up with a rough "fudge factor" to estimate the input signal to
a car radio.   Take the FCC predicted contour, subtract about 14 dB to
account for the reduction in height from 9 to 2 meters and another 6
dB to correct for antenna factor, assuming a standard quarter-wave
whip.   So, a predicted field strength of 1000 microvolts/meter (60
dBu) corresponds to around 100 microvolts at the receiver input, and
54 dBu will give you 50 microvolts, which is still adequate for
blended/mono reception.

Out in open farm country, the situation improves; 48 dBu is usually
enough to provide satisfactory rural service (in the absence of
interference, as Dana points out.)

A rooftop yagi mounted  30 feet AGL doesn't require much of a fudge
factor; this should deliver at least 50 microvolts to a receiver in a
area with an actual field strength of 50 uV/m or 34 dBu.

Mark