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January 02, 2013

Comments

Gary

Actually, tuning in single sideband (SSB) will work as well or better than synchronous detection for rejecting adjacent channel interference, as long as the tuning is stable (i.e., doesn't drift). SSB is much more sensitive to drift than AM mode is, and inexpensive portables tend to drift more than tabletop communication receivers.

herculodge

I'll get my CCrane SW out of the garage and see if that works for 1090. My CCrane CCR does not get it.

Tim

I've found the AM/SW selectivity on the Sony ICF-7600GR to be on the poor side, even when using the synchronous detection. The sync works well for preventing SW fading, but not for removing adjacent signal interference. I find the above-mentioned technique of switching on SSB to be preferable.

Mark Roberts

If KNX is transmitting IBOC -- and the iBiquity website indicates that it does -- then I don't think you're going to have much luck. Take a look at http://www.nrscstandards.org/Reports%20ref%20docs/iBiquityAM%20test%20data%20report/Appendixarev02am.pdf, page 18, diagram at the top of the page. The upper primary digital sideband for KNX extends from 1080 to 1085 kHz. So you are going to be fighting noise - at just about the transmission level of the main 1070 kHz signal - originating from the first adjacent channel to 1090. A synchronous detector might help, if you can tune the station in such a way as to use only the upper (analog) sideband of the 1090 signal. But I think you would have to combine it with a very narrow IF filter, 2 or 3 kHz at most. I don't think being in Torrance makes it more challenging, particularly; I suspect any location in much of the city of Los Angeles is going to have the same challenge. You certainly might get overload from the 1070 signal, but I don't think it would show up at 1090 unless you had an equally strong signal close-by at 1050, and the FCC simply wouldn't have allocated that, because it has required a minimum separation of 30 kHz between stations in the same general area.

KDIS, Radio Disney at 1110, is likely to be a challenge for people in the Pasadena area, and it, too, utilizes IBOC, as do most Radio Disney stations.

Keep in mind also that the days of protected clear channels and protected nighttime coverage areas are increasingly over. It's just another nail in AM's already well-fastened coffin.

Drive-In-Freak

Nothing will kill off IBOC hash. It's not a matter of bandwidth or spillover, but the station actually transmitting 10KHz above AND below their assigned frequency. Instead of taking up the normal 10KHz of spectrum they take up 30KHz.

Drive-In-Freak

IBOC bandwidth:
http://www.hfunderground.com/wiki/Reporting_Interference#Interference_by_IBOC_.28digital.29_signals

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