Re: CC Skywave for Christmas

Bruce Conti

On Fri, Feb 26, 2016 at 12:32 AM, 'G Vance URL' gvance11@... [ultralightdx] <ultralightdx@...> wrote:
  I have better luck defeating IBOC hash when I lean into the offending station.  When I tune further away from the IBOC station, I hear only more hash...

Yes.  The most significant digital signals are +/- 10 to 15 kHz from the center frequency.  Take a look at the RF spectrum FFT of WBZ HD here...  The image is annotated to make it easier to understand.  You'll see the carrier center frequency of 1030 kHz, the analog content covering +/- 5 kHz from the center frequency, and then the strongest digital content covering +/- 10 to 15 kHz from the center frequency.  There is additional low-level digital content covering the 'empty' space between the analog and digital, but it's insignificant and only a nuisance if close to the transmitter site.

The biggest problem is when two radio stations 20 kHz apart are transmitting HD digital.  My worst frequency is 1070 kHz because it gets digital interference from 1060 KYW HD on the upper side and 1080 WTIC HD on the lower side.  On an ultralight, some combination of off-frequency tuning and using the directional antenna to null interference is required in this case.

Bruce Conti
B.A.Conti Photography

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