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1993-02-21
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68 lines
Field Day Antennas & Kits - part 3
Quick set-up modifications for antennas.
One of biggest problems during an emergency or field day operations
is the assembly and tuning of an antenna. Granted, a whip does not
require much in the line of tuning or assembly, however a yagi would.
As I recommended before, use antennas that are prepared prior to an
emergency or a field day and for emergency use; the simpler the better.
Things to keep in mind are that stations outside the emergency area
are running at full potential with large directional antennas and full
power. Trying to match them while operating in a mud & debris
enviroment, out of the back of a car, may be a large undertaking and
not practical under the situation. You may have walk in serveral miles
carrying 80-lbs of equipment and supplies to reach the emergency site.
As for field day, it's much easier. Preps can be made months in
advance and it's this one factor that can make or break a field day.
============================================================
Lets look at the Yagi, Cubical Quad, Inverted Vee, and Wire Dipole.
These antennas seem to appear at most field days stations I've been to
and I've been to several. Keep in mind that a sloper will have
similar solutions, which is another antenna I've seen at field day
sites.
YAGI: (3 Element mono band, HF, armstrong rotor, gamma match)
{Use the Cushcraft as a model}
Assemble at home per directions. Assemble coax to be used
at field day and be sure to provide enough (ie 70-100 ft).
Test the coax via a dummy load with 100 watts of power CW.
Check the SWR and loss at the desired band for the coax.
When complete, save for antenna testing.
Place the assembled antenna on a mast or tower for tuning.
This height should be the height the antenna is to be used
at during field day. I would recommend here that, if
possible, test the antenna at the site with the support
that is to be used during field day. Adjust the element
lengths and gamma match, with the coax tested before, until
all the 'kinks' are worked out. The SWR should be less than
1.5:1 across the band area you desire to operate in.
Remove the antenna intact and mark the joint fittings of the
tapered elements. Mark the dogbone on both the DE and the
gamma match element. Disassemble the antenna and store in a
PVC 4-in pipe with caps or a wooden box or canvas bag. Coil
the coax and cap the PL-259s. Disassemble the mast or tower.
Bag the hardware and attach to the support.
When Field day or an emergency comes up, you are ready with
premarked and pretested equipment. I have done this for six years
and have found that it saves a bunch of grief. Use the coax you
tested, not some hoser's botch job. And do you own assembly. If it
fails, there is no one but you to blame. This concept can take a
2000 point total to a 4000 point level if done right. In an emergency
situation, it's the difference between a poor signal and a clear
signal. Make it so the tuner is not required.
Continued next posting................ :)