On Sun, 2 Oct 2005 18:29:13 -0400, Ari Silversteinn
wrote:

Crossposted to:

rec.radio.amateur.antenna,rec.radio.amateur.misc, rec,radio.amateur.equipment

Novitiate he

Clearly,

I am learning AM broadcast basics in particular the issues regarding the
geo-targeted broadcasting of alert messages from moving vehicles. Would
most appreciate any assistance.

Nice idea but......

Due to Katrina/Rita, the company I work for has been given the opportunity
to demonstrate a messaging system that would reach out approximately 1 mile
+/- in transmission deliverance. This would be an "overbroadcast" (my term)
in that it would override local AM radio broadcasting to reach into cars,
trucks etc. In particular, we are working with a stationary site (a
chemical spill for instance) and an emergency vehicle that would move back
and forth at and through the site, at up to 70 mph, broadcasting an alert,
voice and tone message.

And what makes you think anyone is going to be listening on AM. I
think the vast majority of radio listenings in urban areas listen to
FM except possibly for drive time shows, 24 hour news stations and the
comparatively few people enamored of talk or religious radio. FM of
course is subject to the capture effect wherein the strongest signal
prevails to the exclusion of others (at least that is the theory).

AM, particularly at night is subject to strong skywaves.

Reading about LPAM, this looks technically possible but one concern I have
is antennae size. A fire truck, for instance, could have an antenna mounted
on its front, and up to 4 feet over the top of its roof, so we might look
at as much as 20 feet of length. I realize this places us over the 3 meter
max so one of the ???? is whether LFAM is realistic.

Am I way off base here, can any antennae, fractal or other, or any AM
antennae technology, be utilized to design an antenna and propagate this
type of signal?

I think the problem here is not the technology, but a fundamental
misconception of what it is you are trying to prove and who is likely
to be your audience. At this point you do not need an engineer, you
need a sociologist.

W3JT

All comments appreciated.