Re: How will the US local area stations commerate the end of System-M?

In article 
<25ff7c5a-647f-4882-b659-6a5368b96958@[EMAIL PROTECTED]
>,
 Albert Manfredi <bert22306@[EMAIL PROTECTED]
> wrote:

> On May 1, 9:26 pm, Bruce Tomlin <bruce#fanboy....@[EMAIL PROTECTED]
> wrote:
> 
> > I'm wondering if this is a coincidence, or if an adjacent analog
channel
> > (even from the same antenna farm) really does make an ATSC station
hard
> > to tune in.
> >
> > If this is true, then the shut-off can't come any too soon for me.
> 
> Yup. It's not a coincidence. Analog stations tend to transmit at much
> higher ERP than their digital counterparts, and this was especially
> true in the early days of the transition. So what happens is that
> receivers with less than ideal selectivity, as many of the older
> models are, will detect the strong analog adjacent channel and clamp
> down their AGC. This will then cause the much weaker digital station
> you're tuned to disappear in the noise level.

Ah, AGC. I'm not too strong on radio technology, but I do seem to recall 
that AGC is what can cause volume to flutter on radio signals. And 
crappy AGC is also what makes Macrovision possible. That would certainly 
correspond with one of my situations, channel 30 (analog 29) in San 
Antonio being good and bad in a constant 1 or 2 second cycle.

> Anyway, I've noticed things improving over time, mostly because
> broadcasters have either increased the power of the digital signal, or
> improved the digital antenna location on the tower, or both. And since
> adjacent digital stations don't seem to cause any problem, even with
> my two older receivers, I can't help but believe that shutting off
> analog will help matters.

Maybe that's the _real_ reason why Bob wants to see the analog cutoff 
delayed... :-)