Hi Colin.
Noise is only half of the equation though. It is true that digital AM will
hear much less noise, but what digital does have a problem with is
multi-path which will be a serious problem with AM. Also, AM as it
currently exists does not have a capture effect like FM, so a momentary
interfereing signal means you hear two signals, and the human ear filters a
bit of that as long as it doesn't go on too long. Digital will have
capture, so your signal will need to always be strong enough to capture the
receiver, and multi-path and selective fading in all of its forms will be
the bane of AM's existence with respect to digital AM. The other real
problem with this technology is that they are trying to do it with too
small a bandwidth. That is why interference is such a concern. You don't
hear anyone complaining about interference on FM because the channel
spacing is wide enough to properly support digital up there.
73, de Lou K2LKK
At 04:21 PM 4/5/2007 -0600, you wrote:
>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 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 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 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 -----
>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, 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 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 -----
> > 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, =
> > > digital AM doesn't have nearly the range of a standard AM signal. =
> > > Also,, I suspect the adjacent channel interference will mean that a =
> > > digital stream will need to be fairly strong to work.
> > >
> > > Steve, K8SP
> > >
> > >
> > >
> >
> >
> > --
> > 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
> >
> >
>
>
>
>--
>No virus found in this incoming message.
>Checked by AVG Free Edition.
>Version: 7.5.446 / Virus Database: 268.18.26/748 - Release Date: 4/5/2007
>3:33 PM
Louis Kim Kline
A.R.S. K2LKK
Home e-mail: [log in to unmask]
Work e-mail: [log in to unmask]
Work Telephone: (585) 697-5753
|
