faint signals

[Rick Levy <Radiowaves@CompuServe.COM>]

>>Does channel 62 have a another transmitter on channel 47 somewhere?  I've
been picking up the same "Shop At Home" programming on both, though faintly
 on 47.<< 

That's an "image" generated within the receiver.  You should be able to
find a  number of other picture images, all 15 channels below the incoming
signal, when the latter is strong enough.  I suspect that ch. 62 is one of
the strongest of your incoming signals in Cambridge.

The FCC rules impose a minimum geographical separation of 74.5 miles
between sites of UHF stations 15 channels apart to minimize potential
interference.  Fifteen channels on UHF is 90 MHz spacing, twice the
intermediate frequency used internally by many (if not all) sets based on
the superhetrodyne principle pioneered by Major Armstrong.  Receivers vary
in their ability to reject image frequency pickup.  

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