It's Not the Frequencies, Stupid
Roy
-------- Original Message --------
Subject: It's Not the Frequencies, Stupid
Date: Mon, 7 Nov 2005 14:23:18 -0500 (EST)
From: Sean Donelan <se...@donelan.com>
To: na...@merit.edu
http://www.tvtechnology.com/features/Masked-Engineer/f_mario_orazio-10.19.05.shtml
Katrina communications problems were caused by downed towers, power loss,
broken connections, drained batteries, missing generators, and equipment
underwater. Pick one or more. They were not caused by a lack of access to
frequencies used for analog TV.
Bob Vaughan
All the bells and whistles in the world won't do a hoot of good when the
site is underwater, or the tower is a heap of scrap steel lying on the
ground..
Once upon a time, everybody was using conventional (non-trunked) NBFM
systems, and if you were operating in the same band, and had enough channel
slots in your radio, you could setup your radios to talk to your neighbors,
even if the radio sites were smoking holes in the ground. The fire services
understand this, which is why most fire departments use VHF hiband, and
use simplex channels on the fireground.
Originally, this was hard to do, because radios had a very limited number
of channel slots, and a very limited tuning range, but as radios got better,
these problems mostly disappeared. Now, you can have a couple hundred channels
in a wideband radio.
Now, agencies are moving to trunked systems, and digital trunked systems,
which may or may not be compatible with each other, but all of which
depend on central controllers in order to operate.
If your controller disappears, there are various fail-over modes that allow
a limited amount of channels, but the bulk of your system is useless.
You are now limited to the number of RF channels in the system, not the
number of virtual channels created by the trunking system.
If you're using a digital system, that is not APCO-25 compliant, and are
using digital voice, you can't talk to anybody who is not part of your
system, or not using the same type of radios, unless you revert to analog
conventional.
If you're using a EDACS trunking system, you can't use the radios on a
Motorola system. You can talk on simplex channels, or thru a system level
interconnect, but the trunking systems are incompatible.
What really astounds me it the agencies that buy systems that are completely
incompatible with anybody around them. For instance, Oakland bought EDACS,
instead of joining in with the Alameda County system, which is Motorola
system, as are most of the other public safety trunked systems in the bay
area.
A similar situation occured in NOLA, where New Orleans was EDACS, while
everybody else was Motorola. When the New Orleans system died, their radios
were incompatible with the other systems in the area, and could not be used.
Except in certain very congested areas, the cry of "we need more spectrum"
is a myth used by the vendors to push their latest multi-million dollar
systems, which will all have the same problems as any other centrally
controlled systems. In addition, being on completely new frequencies,
everybody will need new radios, and there will be even less compatibility
with existing systems.
--
-- Welcome My Son, Welcome To The Machine --
Bob Vaughan | techie @ tantivy.net |
| P.O. Box 19792, Stanford, Ca 94309 |
-- I am Me, I am only Me, And no one else is Me, What could be simpler? --
Jeff Liebermann
>Interesting article directly applicable to the Bay Area and earthquakes
(...)
>http://www.tvtechnology.com/features/Masked-Engineer/f_mario_orazio-10.19.05.shtml
>
>Katrina communications problems were caused by downed towers, power loss,
>broken connections, drained batteries, missing generators, and equipment
>underwater. Pick one or more. They were not caused by a lack of access to
>frequencies used for analog TV.
Kewl. The article suggests instant towers and aerostats (balloons).
Great idea.
Inflatable tower:
http://www.boschaero.com/tower.htm
Aerostats:
http://www.boschaero.com/aerostat.htm
They're being used in Iraq by our military for something. Probably to
scare the insurgents. The video of the inflatable tower is worth
watching:
http://www.boschaero.com/movies.htm
http://www.boschaero.com/movies/towers.wmv (5.3MB)
Just think of it as a good place to store the hot air coming from the
direction of Washington DC.
Incidentally, I'm building an inflatable antenna for HF out of a 4"
dia dryer duct tubing. I have two models. 8ft and 20ft. Think of it
as an oversized rubber ducky antenna for HF. It works fairly well,
but still needs some work. I'll probably offer it to the FEMA as a
natural disaster proof antenna.
--
Jeff Liebermann je...@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558