FCC approves nighttime IBOC for AM

Aaron Read readaaron@friedbagels.com
Fri Mar 23 12:24:47 EST 2007

 >>Thus, if I aim my antenna at Boston and tune to 91.9, WMWM on 91.7
 >>keeps me from receiving WUMB in HD.

Larry - HD signals are generally not receivable much beyond the 60dBu 
contour area at best.  The concept of "fringe reception" is going to 
rapidly disappear if FM ever goes "all digital" which actually could 
hurt smaller stations like WUMB.

Anyways, if you're in north Salem you are *well* outside WUMB's 60dBu 
range...which gets to about Winthrop or so, maybe south Revere.  Granted 
if you're on Nahant or the south side of Marblehead, you might catch a 
break across the water, but that's it.  But the rest of Marblehead and 
Salem is probably too far away to get the HD carriers of WUMB.  Remember 
- they're only 6.6 watts of digital!

FWIW, the digital carriers of HD Radio are largely redundant but not 
entirely.  The point is that you can, in theory, blow away either the 
upper or lower carrier entirely due to adjacent channel 
interference...and the HD signal will still be perfectly receivable. 
The problem is that now you're entirely reliant on that remaining 
digital carrier so if there's any disruption to it at all - the radio 
can't fall back on the other carrier.  So yes, a strong 1st adjacent 
will cause problems for HD Radio reception.

However, in your case I suspect it has more to do with your distance to 
WUMB than your proximity to WMWM.

Of course, WUMB could purchase an HD Radio installation for WMWM in 
exchange for WMWM rebroadcasting WUMB on the HD2 channel!  ;-)  Come to 
think of it, I think WUMB would probably be better off trying to do 
something like that with WXRV; the 60dBu limit means that stations with 
lower ERP (like WUMB, or WMWM) really have limited options in multicasting.


Aaron Read
Boston, MA 02446-2204


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