Kele, In some countries south of the US border a few AM stations, where I have
done some work, roof mounted AM antennas are used. Most of them are in the
upper portion of the band around 1600 Khz. Care was taken to bond in every
bit of metal to avoid problems. In one such station in Mexico City the
radials ran horizontal for 40 feet and then vertical down the sides of the 6
story building. Some debate occurred whether or not to earth the radials when
they reached the ground. The setup was meant to replicate a 1/4 wave ground
plane and the FS measurements were acceptable considering the location among
buildings in downtown Mexico City.
For receiving I have become a believer in K6SE's pennant antennas. I have
spent the last week comparing them against a 500 foot beverage, low dipole (60
feet), inverted L 3/8 wave type, a 190 foot snake, and I can only say that
they are a must for any serious low band enthusiast who can't string a
beverage in 6 directions. First of all they are simple to erect, predictable,
very directional, and easy to feed. I put one together ( a 74 foot length of
wire) with some telephone hook up wire, a 1000 ohm resistor, a length of nylon
cord and a rock in about 15 minutes. The feed point was fed with 300 twin
lead (radio shack indoor type) and after 100 feet of twin lead a 50 foot piece
of RG-8X connects to the Receiver antenna selector switch. I presume that the
100 feet of twin lead transformer will give me enough of an impedance boost
to get close to the 900 ohms that is claimed for the pennant. This antenna is
hot and a pre-amp is not required at this location.
All I can say is that the tests are very convincing and the pennant is a
winner.
KV4FZ
P.S. de W4ZV...several have commented that Webpage on pennants is
not working (http://www.angelfire.com/md/k3ky/page37.html) I have tried
it at least 3 times and it worked perfectly every time. It might be that
your Web browser is out of date (no Java?) but it works fine for me.
--
FAQ on WWW: http://www.contesting.com/topband.html
Submissions: topband@contesting.com
Administrative requests: topband-REQUEST@contesting.com
Problems: owner-topband@contesting.com
|