[TowerTalk] Tall verticals
Guy Olinger, K2AV
Wed, 10 May 2000 21:26:31 -0400
Emergency communications come in three flavors:
1) your end of the circuit is wasted.
2) the other end of the circuit is wasted
3) both ends of the circuit are wasted.
3) may be treated as 1) for purposes of planning a given site. 1) gives
the most insight.
***Your end of the circuit is wasted by the disaster...
Although 2m is the disaster team's dream, two meter repeaters are always
exposed and subject to being taken out. FEMA disaster scenarios for test
exercises always include taking out the repeaters and telephones. That
is where 80 meters comes in. It carries better locally than point to
point rubber duckies. It also island hops. It will get you out of an
area where the duckies are only working 1 mile radius, and 80 meters is
If you have decided that your emergency antenna is a delicately tuned
top-loaded tower, then any FEMA tester will require that your plan
accounts for crumpled tower and/or shredded beam. There goes the tuning.
Your eighty meter antenna needs to be something you can get back up.
Like 130' of wire to anything left standing and end-fed against a ground
rod. Since your emergency frequency will likely be confined 39xx SSB
most likely, you can use one of these little 300 watt tuners to match
the end against ground, and run coax to the transmitter. Put the tuner
in a plastic cake box and run coax and wires through small holes in the
cover. This will be as good a NVIS antenna as you can construct. A
deliberate NVIS dipole is good, but after the place is wasted, can you
count on good dipole ends? There are scenarios when you do, but you have
to plan for them. Note both of these are HORIZONTALLY polarized, with
minimal ground losses. (Only verticals on a saltwater beach qualify, and
there they are dynamite.)
You may not be subject to FEMA (Federal Emergency Management Authority)
testing, but if you pass anyway, chances are YOUR stuff will be on the
air when everyone else's is down.
***The other end is wasted.
They are using anything they can string, and unless they are on a beach
they will be NVIS for sure (high angle) and HORIZONTALLY polarized. You
will match them best with an NVIS type yourself.
Save the loaded tower for DX.
- - . . . . . . - - . . . . - - . . - . .
Apex, NC, USA
----- Original Message -----
From: DavidC <eDoc@netzero.net>
To: <email@example.com>; <firstname.lastname@example.org>
Sent: Wednesday, May 10, 2000 9:56 AM
Subject: Re: [TowerTalk] Tall verticals
> 80m is far more important to me for emergency communications
> than is 160m. Are there changes in the configuration of the
> tower and antennas that would make it more suitable to 80m
> use? Must I eliminate the side-mounted beam entirely?
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com