Anthony,

Ironically, all the RF pollution is the reason why it won't work.  So much 
of the man-made noise in the AM broadcast band consists of pulses of one 
sort or another, and those pulses wreak havoc with digital encoding.  FM 
filters out the pulses, and so the digital stuff survives.  Most engineers 
I've talked to are pessimistic about HD radio's viability on the AM band.

Steve

----- Original Message ----- 
From: "Anthony Vece" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, April 06, 2007 17:55
Subject: Re: Fw: [NYDXA-List] FCC Approves IBOC Go Ahead


> Hi Steve;
>
> I'd like to see the digital part of it work for AM.
>
> With the increasing numbers of routers and other devices that generate =
> RF, I find I get a lot of interference and heterodynes on AM.
>
> 73 De Anthony W2AJV
> [log in to unmask]
> ECHOLINK NODE NUMBER: 74389
>
>  ----- Original Message -----=20
>  From: Steve Dresser=20
>  To: [log in to unmask]
>  Sent: Friday, April 06, 2007 2:14 PM
>  Subject: Re: [BLIND-HAMS] Fw: [NYDXA-List] FCC Approves IBOC Go Ahead
>
>
>  Colin,
>
>  Based on my experience with two different HD radios, it's a pretty =
> fragile=20
>  mode on AM.  In my area, broadcasters are still turning off HD at =
> night, so=20
>  I can't speak to such things as selective fading, but during the day, =
> I can=20
>  only get two stations with any reliability.  Just about any kind of =
> static=20
>  or noise sends the radios back into analog mode.  Maybe some day there =
> will=20
>  be better circuitry for coping with noise, but it's not there at the =
> moment.
>
>  Steve
>
>  ----- Original Message -----=20
>  From: "Colin McDonald" <[log in to unmask]>
>  To: <[log in to unmask]>
>  Sent: Thursday, April 05, 2007 18:21
>  Subject: Re: Fw: [NYDXA-List] FCC Approves IBOC Go Ahead
>
>
>  > So, i suspect that high gain AM antennas with built in preamps will =
> become
>  > much cheaper and will be recommended.
>  > I can just imagine the advertizing for them now.
>  > The whole debate around weather you will need a good signal all the =
> time
>  > strikes me as a bit odd, since, even though it is A M, the digital =
> signal
>  > won't have to be nearly as strong to be decoded when compared to an =
> audio
>  > signal.
>  > I also expect there are noise cancelling circuits built into the =
> iboc=20
>  > radios
>  > to attempt to eliminate noise from outside the pass band that the =
> digital
>  > signal will need.
>  > I don't know allot about the type of digital signal it is, but if it =
> is=20
>  > like
>  > most digital streams, it will only take up a certain segment of the =
> audio
>  > band and everything else can be blanked out.
>  > So, phase shifting and fading may have already been compensated for.
>  > Am i totally wrong about all this?
>  > It seems to me that engineers designing iboc and those intending to =
> use=20
>  > it,
>  > aren't a bunch of intelectually challenged morons who don't know the =
> first
>  > thing about RF communications.  I am posative much of the problems =
> brought
>  > up here have been addressed and worked out already.
>  > 73 Colin, V A6BKX
>  > ----- Original Message -----=20
>  > From: "Steve Dresser" <[log in to unmask]>
>  > To: <[log in to unmask]>
>  > Sent: Thursday, April 05, 2007 11:22 AM
>  > Subject: Re: Fw: [NYDXA-List] FCC Approves IBOC Go Ahead
>  >
>  >
>  >> Steve,
>  >>
>  >> I've had two HD radios for about a month now, and from what I've =
> seen,=20
>  >> you
>  >> need a pretty noise-free signal to make it work reliably, and =
> that's
>  >> especially true for AM where, ironically, there's more noise.  On =
> FM, it
>  >> works quite well with my tuner, but that's because I have a =
> 9-element=20
>  >> beam
>  >> up on the roof.  If I didn't have that antenna, digital radio would =
>
>  >> hardly
>  >> be worth considering because I'd have a hard time even with many =
> local
>  >> stations.  Let's face it, you can't get away from the noise unless =
> the
>  >> antenna is outside, and noise is the enemy here.
>  >>
>  >> Steve
>  >>
>  >> ----- Original Message -----=20
>  >> From: "Steve" <[log in to unmask]>
>  >> To: <[log in to unmask]>
>  >> Sent: Thursday, April 05, 2007 11:18
>  >> Subject: Re: Fw: [NYDXA-List] FCC Approves IBOC Go Ahead
>  >>
>  >>
>  >> > From what I recall, from an older article in one of the hifi =
> mags, =3D
>  >> > digital AM doesn't have nearly the range of a standard AM signal. =
> =3D
>  >> > Also,, I suspect the adjacent channel interference will mean that =
> a =3D
>  >> > digital stream will need to be fairly strong to work.
>  >> >
>  >> > Steve, K8SP
>  >> >
>  >> >
>  >> >
>  >>
>  >>
>  >> --=20
>  >> No virus found in this incoming message.
>  >> Checked by AVG Free Edition.
>  >> Version: 7.5.446 / Virus Database: 268.18.26/746 - Release Date: =
> 4/4/2007
>  > 1:09 PM
>  >>
>  >>
>  >
>  >
>  >
>
>
>