Hi John and all,
I agree that David Weinberger has done a poor job on this article.
I don't think that he is confused; he's writing to entertain, not
to inform. IMO, most of his examples have serious flaws:
Sure, if many stations are simultaneously sending "green", a
smart receiver (telescope) can easily separate them. But
optical frequencies are unsuitable for most applications,
because of line-of-sight limitations, effects of weather, etc.
At UHF, such separation is much more difficult.
IMO, if broadcast licenses were free, what's on the air would
not change very much. Broadcasting to a large audience
entails the high costs of real estate, equipment, and energy,
and, depending on what is being transmitted, expensive
content, talent, and/or production. The license is just the
tip of the iceberg.
Much of the value of Caller ID is that it cannot be easily
forged, because it is originated by the network. The Internet
does not now have reliable "Caller ID", which is why hackers
can wreak so much havoc by spoofing IP addresses.
The GNU radio example merely shows the ability to decode and
play two FM broadcast stations simultaneously from one A/D
converter output (contrary to Mr. Weinberger's statement,
the stations must be on different frequencies, ).
However, I do agree with David Reed that smart radios could
improve spectrum utilization by a factor of ten or more. This
could mean that, rather that being a scarce resource auctioned
for obscene prices, spectrum would be available at little or
no cost to those who wanted it. Some techniques to accomplish
this include CDMA, diversity reception, spatial multiplexing,
user terminals as relays, more effective Tx power controls,
and better efficiency of source and channel coding.
There was an article addressing some of these points in
the October 2002 issue of RF Design. See
http://rfdesign.com/ar/radio_designing_mimo_systems_2/index.htm
IMO, the fault is not just with the regulators. IS-95 CDMA
makes much better use of spectrum than GSM. Why is it not
more widely used? Politics, and intellectual property issues.
73,
Stewart KK7KA
----- Original Message -----
From: "John Rabson" <[email protected]>
To: <[email protected]>
Sent: Monday, March 17, 2003 12:00 AM
Subject: LF: Re: The myth of interference ?
The author seems to be confusing "interference" in the sense a physicist
would use the term (that is, interaction between photons or electromagnetic
waves in a fundamental sense) and the sense in which a radio engineer would
use it (disturbance of one radio transmission system by another).
If I have understood him correctly, he seems also to be suggesting that
there is an infinite amount of transmission bandwidth available. Not so in a
strict sense, but if you go to a high enough carrier frequency and cover a
sufficiently limited geographical area you may be able to get enough for
your purposes without disrupting other services.
Or have I totally misunderstood the whole thing?
John Rabson G3PAI
----- Original Message -----
From: "Andre Kesteloot" <[email protected]>
To: "AMRAD Tacos l" <[email protected]>; "lf-amrad" <[email protected]>;
"rsgb_lf_group" <[email protected]>
Sent: Sunday, March 16, 2003 4:09 PM
Subject: LF: The myth of interference ?
>
>
> http://www.salon.com/tech/feature/2003/03/12/spectrum/index.html?x
>
> André N4ICK
>
>
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