Posted by Steve Green on November 05, 2009 at 10:27:20:
In Reply to: Re: Re: Get Your News Seven Seconds Faster At NewsRadio 450.5125 MHz posted by Cal Stymes on November 05, 2009 at 09:46:22:
Some places in Queens, even on some great DX radios (American Bosch, Atwater Kent), also got WCBS on 850. It was the product of 2 times 880 (1760) minus 2 times the IF of 455 (910), which came out to a steady 850.
There was no such effect, at least on the AM dial, with co-tower WNBC. Their 'spur', or whatever the term, would have come in below the AM dial, on 410 kHz.
My flawed math would put that double-IF spur on the actual AM dial just for closeby stations between 720 and 1300 ..... Such a WGN spur would come in on 530, and a WAVZ spur theoretically would occupy 1690.
A more 'honest' 910 spur, again, if 'spur' is the right word, would be the AM station's actual frequency minus 910. I must've heard a half dozen 1490 stations putting a broad, swell signal (albeit beset with whitsles) on 580. Of course, the effect isn't the station putting out a signal on 580 but the circuitry of the radio making it seem that way. That effect mathematically would limit reception of such spurs to stations with parent frequencies between 1540 and 1700.
I suppose, LOL, that the ultimate 'spur' would be for stations licensed to 910. Two times 910, minus 910, equals 910! Even though it's the circuitry effect of the radio, some 910 stations must have *some* sort of whistle problem in their coverage areas away from the immediate transmitter site, no?
On another image/harmonic/spur note:
Has anyone checked to see if 770 WABC also comes in repectably well on 1540 near their Lodi tower? The so-called ground erosion may have changed that reception over the years. For a while it was a goofy treat to punch up 1540 and hear 77.