[BC] Overcrowding & noise floor on AM

[Johnson, Richard]

On Tue, 20 Mar 2007, PeterH5322 wrote:

>
>> For many years, I would lunch with a fellow, in his 90s, who started in
>> broadcasting in the 1930s.  (He retired in the mid-1990s)  He told me about
>> working at a 100 W station that was on a frequency in the 1300s on the dial.
>> (I don't remember the exact frequency)  They would often sign on after
>> midnight for external frequency measurements.  They got QSLs from as far
>> away as Australia.
>
> 0.1 kW was a legit power for Class IV stations (1230, 1230, 1340, 1400,
> 1450 and 1490, after 1941; 1200, 1210, 1310, 1420 and 1500 before 1941),
> and for the  two "Class IV stations operating on a Class III frequency".
>
> In the 1960s, 0.1 kW was banished for all Class IVs except those on Class
> III requencies, and all Class IVs moved to 0.25 kW nights, and 1 kW days,
> using a DA days, if required.
>
> In the extended L.A. area, we had two Class IVs which had DA-Ds ... 1400
> in Santa Paula, and 1450 in Ventura.
>
> It was 1340 in Mojave which ran 0.1 kW into the 1960s. Probably 0.25 kW
> days/0.1 kW nights.
>

Agreed that the noise-floor has radically increased since I was in
the radio industry (25-30 years). In Massachusetts, WBZ, 50 kW,
clear channel, one of the first such stations (KDKA claims first),
is not usable within much of its service area. Much of the noise
seems to have a 60 Hz modulation so it is probably because the
power companies upped their transmission voltages without improving
their insulation and wiring. This was not 'caught' by the FCC as
it would have been in the days where we had FCC Field Offices
and local FCC Engineers in charge of the radio district. Nathan
Hallenstein of the Boston Office comes to mind. He was also the
guy who administered the FCC license tests. Anything that
interfered in his radio district would be investigated and
possibly "written up." He would never stand for such abuse
of the spectrum.

When I used to turn on WACE during the experimental period I
got QSL card requests from all over the world! In the nighttime
I could hear everybody in the universe all over the dial on
my car radio. Of course they don't make sensitive car radios
anymore because all they would receive is noise. Note that
there is a slime-tide that wants to put Internet connectivity
on the power-lines as well! Go figure!

As I recall, the FCC rules required that a station put 3.16 mV/m
at the post office in the town they were licensed to cover. Such
a signal would be barely usable on a Bose auto radio nowadays!

Cheers,

Richard B. Johnson
Project Engineer
Analogic Corporation


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