tell@oscar.cs.unc.edu (Stephen Tell) (02/19/91)
> Broadcast band FM receivers ordinarily use an >IF of 10.7 MHz, TV receivers use a picture IF of 45.75 MHz and a >sound IF which is 4.5 MHz below that, at 41.25 MHz. TV receivers built >before 1950 or so use a picture IF of 25.75 MHz. Broadcast AM receivers >use 455 kHz as the IF freq. Just out of curiosity, what services are licensed in the bands where all these common IF frequencies fall and thereby get all the interference from cheaply-designed consumer junk? I suppose emmissions of these frequencies are regulated just like noise from computer gear; are the limits the same? -------------------------------------------------------------------- Steve Tell tell@cs.unc.edu H: +1 919 968 1792 #5L Estes Park apts CS Grad Student, UNC Chapel Hill. W: +1 919 962 1845 Carrboro NC 27510
dana@locus.com (Dana H. Myers) (02/20/91)
In article <1687@borg.cs.unc.edu> tell@oscar.cs.unc.edu (Stephen Tell) writes: > >> Broadcast band FM receivers ordinarily use an >>IF of 10.7 MHz, TV receivers use a picture IF of 45.75 MHz and a >>sound IF which is 4.5 MHz below that, at 41.25 MHz. TV receivers built >>before 1950 or so use a picture IF of 25.75 MHz. Broadcast AM receivers >>use 455 kHz as the IF freq. > >Just out of curiosity, what services are licensed in the bands where >all these common IF frequencies fall and thereby get all the interference >from cheaply-designed consumer junk? 455khz is directly below the AM band; I recall this may be used for radio navigation beacons (usually located at airports). I don't know what services are at 10.7 Mhz; however, I do know that any signal transmitted there has the potential for world-wide propagation, even at relatively low power levels. I can tell you this; I can detect no RF at all from any of my receivers using a Yaesu general coverage receiver. Nothing at 10.7MHz, nothing at 455kHz, even the cheap radios don't emit anything. Keep in mind, in the IF strip, the power levels are quite low and the circuitry quite compact; very litle potential for unwanted radiation. -- * Dana H. Myers KK6JQ | Views expressed here are * * (213) 337-5136 | mine and do not necessarily * * dana@locus.com | reflect those of my employer *