Plate F wrote:That was a city police transmission captured on a railroad frequency with the interference tone. So what happened was that the police signal was too strong and pried into the railroad frequency? But why is it only on THAT particular frequency I ever hear the noise or even the wrong broadcast for that fact?
A radio "listens" to frequencies both above and below the local oscillator frequency, the local oscillator runs at either plus or minus the radios IF... That is what an image is, [some people call 'em 'intermods, which means intermodulation products' (or just mixing products)also at various multiples of the local oscillator frequency. These are real signals.. Real radios have preselection to filter these signals out, scanners, being broadbanded, escentially do not. These signals are another reason why an external preamplifier can cause more trouble than it is worth. These signals are real and can cause all kinds of problems, the reason why one is better off with an amateur two meter radio or RR freq only radio over a wide band scanner..... Elsie Kay