[BC] IBOC "secrets" and my opinions.

[Johnson, Richard]

On Mon, 26 Mar 2007, Rich Wood wrote:

> ------ At 07:06 PM 3/25/2007, Bill Harms wrote: -------
>
>>    I am glad to see that you at least admit the possibility that
>> this technology may not work. I think the issue is when do we
>> determine enough is enough if it is not working. The problem with
>> making effort to make it work is that it may cause damage to what
>> is already there.
>>
>>    In order to find out if this will work or not, it should be
>> treated as an experimental technology.  I see too many people
>> thinking that it is going to happen no matter what. One thing that
>> has not been adequately tested is nighttime operation and its
>> effects.  That needs to be done first before we decide this is what
>> needs to be done.
>
> Ordinarily, this would be the preferred method. However, each
> transmitter installation is different. I don't see a way to duplicate
> all the idiosyncrasies of every installation without having the
> station rollout take as many decades as the receiver rollout will.
>
> I believe broadcasters have to be willing to bite the bullet, knowing
> full well it's live ammunition, and fix the real world problems that
> arise in each situation. If we do it now, when there are very few AMs
> using the system we can learn how to fix each facility before the
> entire audience has gone from adjacent stations. If we wait until
> there are many stations using it, we'll have mutually assured
> destruction. Like DTV, there won't be enough riggers and anti-NIMBY
> lawyers available to handle a large number of stations. By the time
> this stuff winds through the courts the audiences will have found
> alternatives.
>
>>    Perhaps the IBOC nay-sayers are seeing something that some
>> others don't see.
>
> Perhaps the programming folks among us are aware of how quickly an
> audience can be lost and how difficult it is, especially in AM, to
> get them back. It's Bosnian Roulette. We do know that WBZ, Boston,
> wipes out KDKA, Pittsburgh, in Western MA during critical hours. I'm
> well out of both stations' protected contours. However, there are
> closer-in listeners who may be regulars with Arbitron diaries or
> PeopleMeters who will simply disappear in a daypart already hurting
> for listeners for all but the strongest of signals. Please don't tell
> me no one listens to AM at night. Art Bell made some significant
> money for Premiere Radio Networks with an overnight show. So did
> Larry King when he was on Mutual overnight.
>
> I'm completely unwilling to give up any daypart. Even the lowest
> rated contributes to the station's overall numbers and position in the market.
>
> Someone here mentioned that small stations should have taken an
> active role in filing opinions with the FCC. They should have formed
> a group. Some believed that, since they don't intend to use the
> system, it won't affect them. In fact, they'll be the most vulnerable
> victims. It's now too late. Once someone lights up adjacent to them,
> their audiences will be gone. The reason I've been given by many is
> that they'd be ignored when competing with well financed lobbyists
> and political contributors.
>
> Let er rip. Fix the tears and the tears.
>
> Rich
>

I have been investigating some of what has been said on this
list about IBOC on AM. It appears as though it is really a
receiver problem. Don't get me wrong. I'm not advocating
trashing 150 bazillion conventional AM radios so that IBOC
will work. Instead, as I am beginning to understand the
technology, if an AM radio was designed with more modern
technology, digital demodulation of AM with a wall filter,
there would be no buzz. There really is plenty of bandwith
available for IBOC on AM. The feds were not bamboozled.
The problem is that AM radios of conventional design,
superheterodyne with envelope detectors, cannot handle the
adjacent channel IBOC interference at reasonable cost.

What the industry really needs is a decent AM radio using
modern technology. Such a radio would directly digitize
incoming spectra. AM would be demodulated by multiplication
of the digitized data with the selected frequency. The
resulting 'garbage' would be subjected to a FFT, the bins
outside 10 kHz zeroed out, then the inverse FFT would be
taken. The result would be a very clean AM signal with
no response beyond the 10 kHz passband (9 kHz for some
foreign countries), and no intermodulation from out-of-band
responses. The same kind of preselection would be used for
IBOC digital. You just don't demodulate the AM signal to
baseband before digital processing. When I say
"no intermodulation," I am talking 96dB down. Since a
typical S/N of off-the air AM signals seldom exceeds
60dB, the intermodulation is 30 dB below the noise so,
in fact, it is truly "no." Sixteen bits is 65536:1 =
20 log (65536) = 96.32 dB

In the past, such a receiver was incredibly expensive.
Nowadays, we have inexpensive components that can handle
these low bandwidth signals at very low cost. Remember
that "real-time" for AM is 10,000 changes per second --
truly trivial. For accurate replication of the RF
component, you would need to sample something like 10
times over-sampling. This means you need a 20 MHz 16-bit
ADC. These things are now cheap, $35.00/1000. You can
even get a whole development system for $158.00!
Goodle "16-bit DAC 20 MHz" and see for yourself. Once
somebody starts producing a million radios per month
the price would likely drop to the $5.00 range.

So, I think that instead of complaining that the new
technology is not compatible with 85 year-old radio
design, some entrepreneur(s) should take the bull by the
horns and develop a decent radio. They don't actually
need to get such a radio into production. Leave that
for the Pacific rim. What they need to do is generate
the "IP" intellectual property with as much as possible
embedded into a single chip. Then they license this
technology and, perhaps, the chip design. There are
lots of "radio" engineers who are now quite versed
in software. A development kit and some (sometimes
not too) pleasant software debugging time, would
establish the viability of the digital radio approach
for conventional AM. Then you could attract some
investors. All words and ideas presented here are
placed into the Public Domain. Get to work!

In the meantime, read my book:
http://www.AbominableFirebug.com

Cheers,
Dick Johnson

P.S.
Ignore the garbage that follows. I will eventually use
another email address, rather than the work one.

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