14 Dec
2011
14 Dec
'11
4:40 p.m.
On 14 Dec 2011, at 3:49 PM, David Riley wrote:
Our VHF channels go from 2 to 13 (I don't remember
the story behind why channel 1 is missing) and UHF covers 4 to... 68? Most of time the 3
major networks ran on VHF, because it reached further; we always had a harder time
receiving the UHF channels at home when I was growing up.
The original (1938 - 1940) allocation was 18 channels with channel one at 44-50MHz and 19
at 288-294MHz. Channel 19 vanished in the 1940-1946 allocation with the remaining
frequencies shifting around; channels 14 and up vanished in the 1946-1948 allocation
(which again saw frequencies juggled about). In the '46-'48 period things started
to go sideways; the existing channels (save for channel six) were shared with fixed and
land mobile services; to mitigate interference the FCC had depended on VHF frequencies
not propagating over the horizon but in practice they did so readily; in addition
responding to pressure for more stations the FCC had reduced the separation distance
between stations to 80 miles. In May 1949 the FCC ruled that television could no longer
share frequencies with fixed and mobile services and that the 72 to 76 MHz band could be
used only for fixed radio services, all of which lead to the issue of where the mobile
services could go -- which ended up being one of the existing television channels.
While the television industry was none to thrilled to lose a channel they felt that 12
clear channels were preferable to 12 shared channels. The ARRL had actually proposed that
channel two be dropped so that the second harmonic of the 28-29.7MHz amateur band
wouldn't cause interference, but the industry elected to ditch channel one because FCC
regs held that channel one could only be used for community service with a 1KW restriction
while other channels were permitted 50KW.
--
Dr. Christian Kennedy
chris at mainecoon.com AF6AP
http://www.mainecoon.com PGP KeyID 108DAB97
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