Re: [IRCA] Stopping HD Radio

[Barry McLarnon <bdm@xxxxxxxxxx>]

On Thursday 27 September 2007 10:13, Powell E. Way III W4OPW wrote:
> Well stations aren't broadcasting FOR your DX'ing
> pleasure. Skywave was  / is there and won't go away.
> It can also be an aggravation close in to the station
> because of groundwave / skywave cancellation.  I don't
> care for HD as it really is an outdated and data bit
> starved / reduced mode, and even under perfect
> condtions it isn't as good as analog. Right now power
> levels are 1% of analog, but with the modulation cycle
> even wiith no audio is 100%. That's why it creates
> such a mess. The laughable thing is on the
> clears...the adjacents IBOC prevents each others IBOC
> from decoding at night. I guess THAT is poetic
> justice.

That's not quite right - the digital sidebands of adjacent channel
do not overlap, so it is not IBOC killing IBOC.  IBOC stations will have
lousy digital coverage at night regardless of whether their adjacent
channel neighbors are running IBOC at night or not, because it is the adjacent
channel analog signals that are killing the digital sidebands.  OTOH, it's the
analog coverage that gets degraded by IBOC on the adjacents.

So, you get lousy digital coverage (out to the 20 mV/m contour, if you're 
lucky), and if you have strong IBOC on an adjacent, your analog signal gets
all hissed up beyond that contour.  Great system!
A good real world illustration of this came from someone near Chicago.  See
http://lists.radiolists.net/pipermail/broadcast/2007-September/060480.html
for more gory details.

Barry

-- 
Barry McLarnon  VE3JF  Ottawa, ON

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