On Thu, 2004-11-25 at 08:27, Al Quaglieri wrote:
Doug Smith replied:
Don't really see much demand for spectrum for data on shortwave.
(VHF & especially microwave are a different story!) It's not easy to
reliably transfer significant amounts of data over shortwave; SW
transmission will be very much a last resort.

This is pure speculation on my part, but I can foresee a time when the
VHF/UHF bands become so clogged with highspeed data that less glamorous
operations such as regional/citywide paging, low-rate text messaging,
product ID tagging, water meter transponders, etc., go looking for the
lower frequencies. Without broadcast QRM, a relatively modest paging
transmitter on, say, 6.1 mHz could blanket a 10 mile radius 24 hours with
little of the line-of-sight problems of VHF.

I can see RFID tagging and water-meter transponders operating on SW
frequencies. Maybe with a modest spread-spectrum (over a few hundred
KHz) scheme.

I don't see portable messaging schemes working on SW. The problem is
noise from digital equipment. (computers, mostly) I think you're going
to have a hard time pushing enough RF through modern metal-framed
buildings to overcome computer hash.

--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com