The Totally Tunable Cheap 1/4 wave Ground Plane!
For what it is worth, I just finished building a GP antenna that is very cheap & simple to make. It is totaly tunable! Cost $10.00!
Parts:
(5) Telescoping antennas (like from rabbit ears) 9" to 34". They need to have a swivel base that ends in a screw mount. I found them on the web for $1.50 each (I will look for the name of the supplier).
(1) SO-239 antenna plug with the 4 mounting holes.
(5) Bolts that fit the ends of the telescoping antennas.
Thats IT!
Bolt four of the antennas to the SO-239 base. Then solder the other small bolt to the stub that comes out of the SO-239; bolt the remaining antenna to the last screw. Your done!
The antenna is completely tunable in the 88-108mhz band and then some. I have seen a number of different formulas for figuring length of elements, but the one that seems to work best for me is: 234/Frequency= length in inches (for the antenna-radiator). Add 5% for the ground radials. So, for my freq of 107.9, the radiator is 2' 2" and the 4 radials are 5% longer. You can rasie and lower the radiator when hooked up to a SWR meter to get the lowest reading.
Right now I have it mounted indoors, but I am going to solder into place the radials at a 45 degree angle, and maybe all of the elements so they don't slide around. I am trying to come up with an idea to mount it outside and be more wind resistant. I was thinking of a solid, but somewhat flexable rubber rod or pole that it could be strapped to that would hold it steady and still be able to bend somewhat in a stiff wind. I would love any ideas others may have on the mounting.
Thats it. I hope this helps anyone trying to build an inexpensive antenna.