[BC] New $99 HD Radio

[Mark Humphrey]

I've found that the first-adjacent channel selectivity of the FM
sections of most digital receivers is very good, especially when both
adjacent stations transmit analog-only.  This is probably due to the
DSP IF section used in IBOC radios.

But if a local station is transmitting HD and a distant neighbor is
analog, then the "apparent" selectivity will seem poor. This isn't the
receiver's fault, it's the stronger station's digital carrier "noise"
masking the weaker first- adjacent analog signal, and it sounds very
similar to fading.

A good example can be heard along I-95 as Baltimore is approached from
the northeast.  The 104.1 in Waldorf, MD (I forget what the callsign
is this week) is quite listenable around Havre de Grace, but quickly
gets clobbered by digital interference from 104.3 in Baltimore.  The
problem doesn't really clear up until you get past BWI airport.  There
are a couple more cases like this near Baltimore and Washington.

Mark

On 4/13/07, RichardBJohnson at comcast.net <RichardBJohnson at comcast.net> wrote:
> I sent them a message asking them to publish some technical
> specifications such as sensitivity and selectivity. As many know,
> most modern radios don't have any <grin>. It would be useful to know
> if any radio manufactuters supply radios that can receive signals
> with amplitudes less than 10 millivolts per meter anymore especially
> considering that the FCC thinks that 3.16 millivolts per meter
> represents a primary service contour.
>