[BC] KDKA

[Richard Fry]

Chuck Leavens wrote:
> Parts of Pittsburgh lose the signal and the south hills
> are not a strong signal area for them either. Go figure.
Peter Haas answered:
> KDKA generates 431 mV/m/kW at 1 km for 280 degrees,
> whereas WHO, only 20 KHz higher (which is actually irrelevant),
> generates 471 mV/m/kW at 1 km for 300 degrees.
> That's 70,800 W out for 50,000 W in for KDKA and 84,000 watts
> out for 50,000 W in for WHO.
________________

For a given MW freq, propagation path, and ground conductivity, the 
difference in distant, groundwave field strength between 70,800 watts ERP 
and 84,000 watts ERP is only 0.74 dB.  This value should hardly be 
detectable at the receiver.

KDKA's reported signal problems in parts of Pittsburgh and the south hills 
probably are related to the terrain and other propagation conditions along 
the paths between them and KDKA's tx site.  Proof of that would be to 
measure KDKA's field along a radial toward a problem zone, but at 
unobstructed locations closer to the tower.  Most likely the fields at 
unobstructed locations fall on or near the FCC curve for KDKA's freq, 
radiator efficiency, and the conductivity for that radial.  If that is true, 
and more distant fields are well below that curve, the reason must be 
related to the overall path and propagation conditions, and not to the 
design/efficiency of KDKA's radiator.

Probably the field strength in KDKA's problem zones wouldn't change 
significantly even if it was using an exact electrical copy of the WHO 
antenna.

RF