I remain puzzled why you guys are discussing compromise antennas in an
emergency communications system. I wonder if the fire department guys built a
compromise VHF/UHF communications system when they spec'd out their
requirements and performance. Did they hide their 154 MHz antennas under the
roof? Did they look for a means to "just get by?" Did they mount a rubber
ducky, with a gutter clip on the backside of the firehouse under the rain
gutter, and connect it with RG-58 to their radio?
If this is a for-real emergency communications solution that the community
desires, and they have asked amateur radio operators to be prepared (that is
truly an honor) then don't we hams owe it to the community and our own
reputation to build them a station, with antenna, that WORKS, that puts out a
solid, dependable signal?

Rick K2XT

After re-reading the original post I see the fire dept system will be
manned by experienced hams and that would allow for more complex but
efficient equipment like antenna tuners and antennas fed with balanced
line, etc. Even a G5RV with a tuner might be something to consider. One
thing I will point out would be the compromise if someone installed a
vertical like an R-7 or GAP Titan or Butternut, etc for regional or
statewide comms. The difference between a T2FD and resonant dipole would
seem like nothing compared to a T2FD over a vertical for this type use.
Bob


Rick wrote:
I remain puzzled why you guys are discussing compromise antennas in an
emergency communications system. I wonder if the fire department guys built a
compromise VHF/UHF communications system when they spec'd out their
requirements and performance. Did they hide their 154 MHz antennas under the
roof? Did they look for a means to "just get by?" Did they mount a rubber
ducky, with a gutter clip on the backside of the firehouse under the rain
gutter, and connect it with RG-58 to their radio?
If this is a for-real emergency communications solution that the community
desires, and they have asked amateur radio operators to be prepared (that is
truly an honor) then don't we hams owe it to the community and our own
reputation to build them a station, with antenna, that WORKS, that puts out a
solid, dependable signal?

Rick K2XT

On Sun, 11 Feb 2007 03:01:13 +0000, Bob wrote:

Even a G5RV with a tuner might be something to consider.

One thing you need to keep in mind is whether even 75 meters will be
sufficient for statewide communications around the clock. I can tell you
that often it is not. Around here, in the wintertime the critical
frequency (the maximum frequency at which a signal arriving straight up
will bounce back) falls to well below the 80 meter band at night. Often
the critical frequency will be around 2.5 MHz, or lower, by around 10 PM.
During those times, your 75-meter NVIS signal will just go sailing off
merrily into space. You have to be on 160 meters during those times, if
you want reliable NVIS communications.

I am a regular participant in a military traffic net (not MARS, but
similar) that operates at 0730 each morning, on a frequency that's not so
very far off the high end of the 75-meter band. The normal net control
station is about 80 miles from here, and in the wintertime, the critical
frequency is often right around our operating frequency and rising fast as
the sun comes up. Very often, I can just barely hear the NCS (or can't
hear it at all) at net starting time of 0730, but by 0745 to 0800 the NCS
has come up in strength to where solid 100 percent copy is easy. Move the
net start time to a half hour earlier and there'd be no way... we'd all be
talking to ourselves.

As for later in the daylight hours, 75 meter signals often get absorbed by
the D and E layers so they never bounce back. During those times 40
meters is your only hope.

So, for an emergency station that has a snowball's chance of being able to
maintain communications 24x7, you need 160, 80, and 40 meter coverage from
an antenna around 30 feet high if you can get it up that high. That would
be the low end of the best height range for 160 meters and the high end of
the best height range for 40 meters.

On Sun, 11 Feb 2007 00:28:56 GMT, (Rick) wrote:

I remain puzzled why you guys are discussing compromise antennas in an
emergency communications system. I wonder if the fire department guys built a
compromise VHF/UHF communications system when they spec'd out their
requirements and performance. Did they hide their 154 MHz antennas under the
roof? Did they look for a means to "just get by?" Did they mount a rubber
ducky, with a gutter clip on the backside of the firehouse under the rain
gutter, and connect it with RG-58 to their radio?
If this is a for-real emergency communications solution that the community
desires, and they have asked amateur radio operators to be prepared (that is
truly an honor) then don't we hams owe it to the community and our own
reputation to build them a station, with antenna, that WORKS, that puts out a
solid, dependable signal?

Rick K2XT

I couldn't agree more. I suggest you go back to fire depatrment and
ask which they would rather have 1) an efficient and good working
communications system or 2) a small non-noticable antenna that
performs poorly. You can't give 'em both.

Danny, K6MHE