"Bob Dobbs" wrote in message
news:49eb5ac5.4793609@chupacabra...
dave wrote:
Telamon wrote:


Well, how about analog? I have some hiss in there all the time and often
times warbling rumble kind of noise. It's very annoying and I wish they
would turn that HD crap off.


The IBOC signal is either side of the AM carrier. Each IBOC sideband is
identical but out-of-phase with the other. The theory is the IBOC
sidebands cancel each other out in your receiver. But if one sideband
propagates better than the other (which is always the case once you get
a few miles from the transmitter) the cancellation is not complete.
This is when you hear the digital hash and the wubba-wubba sound.

For those of us using a radio with selectable sideband synchronous
detection, but unable to choose USB and LSB at the same time (like my
Drake SW2) we are forced to listen in plain AM.



The theory doesn't even work well within the local signal area, since almost
no radios use a detector that detects both sides of the envelope. Therefore,
you have only one sideband being detected, and the IBOC hash will be present
under the analog program material if the radio is sufficiently broadband
(more than about 8 KHz).