Thursday, August 2, 2012

Simple Antennas for Amateur Radio Operators--a continuing series.

KH6JRM's Amateur Radio Blog

Post #178

Portable antennas

One of the things I like to do when the weather is nice (such as today) is to drive my van up an old sugar plantation road and set up a low-power emergency station at a clearing above Laupahoehoe town.  At an elevation of 1,200 feet on the east slope of Mauna Kea, I have a clear view of the Pacific Ocean off to the northeast and a fairly good shot at Japan over the summit of Hawaii Island's largest mountain.

Once I reach the clearing, I retrieve my homebrew 40-meter helix (see last post), 50-feet of 450-ohm ladder line, a 4:1 balun, the trusty Drake MN-4 tuner, about 10-feet of RG-6 coax, and the venerable Yaesu FT-7 qrp rig, which can be used for both cw and SSB contacts from 80 meters to 10 meters.  The vertical helix is comprised of two, 5-foot schedule 40 pvc pipes, which are joined by a pvc connector.  Sixty-six feet of #22 gauge hookup wire is wound in a spiral to the top of the vertical pole.  A 48-inch "stinger" from an old CB antenna is attached to the spiral to provide some top loading.  At the base of the vertical helix, I attach 8, 33-foot radials to the remaining part of the ladder line.  The radials fan out wherever the geography of the clearing allows.  For a power source I use a deep cycle marine battery and solar cells.  I can run the old Yaesu FT-7 for many hours with the solar array providing a continuous charge to the battery.  I've used automobile batteries in the past, but these batteries are not designed for extended periods of time.  They do work, but they have limitations. 

This arrangement works well and I've enjoyed many hours of low power operation (usually less than 10 watts).  This is the same emergency station I have installed at home.  The "go" kit is portable and can be set up quickly.

I've also used "Ham Stick" antennas with radials attached to achieve some success in stationary portable operations.  I've even resorted to using an old B & W apartment antenna on a picnic table to make enjoyable contacts (mostly cw).  MFJ's model 1622 is a good copy of the B & W design.

My portable station can be stored in the van and is available anytime I'm away from the qth.  Those of you who can't operate a station from your home because of HOAs, CC&Rs, and limited space may want to consider some form of mobile set up for your amateur radio station.  If you are clever, your vehicle might be part of an antenna system you can hook up to your home station.  Of course, this depends on just how nosey your neighbors are.  You can still have an enjoyable amateur radio experience if you let your imagination and creativity take hold of your antenna ideas.  Granted, a tall tower with a 4-element monobander beats anything I might dream up, but you can still run an amateur radio station if you let limitations become possibilities. There are several good books in the marketplace that address stealth and hidden antennas--many of these volumes are published by ARRL, CQ Communications, and the RSGB.  Sometimes, I just enter "stealth antennas" in the Google Search box and see what happens.  Occasionally, you can find some excellent information that can help you get on the air at a modest cost without creating what some neighbors call a "nuisance."

So, investigate the possibilities and take some time to design and build your "stealth" antenna.  You might be surprised at just how good your homebrew skyhook works.  I've built several antennas that have given me hours of enjoyment at almost no cost. 

Until next time,

Aloha es 73 de KH6JRM--BK29jx15