Cheap antenna tuning notes
After hearing of the problems from the McARCS antenna building project with the WA5VJB Cheap Antennas, I decided to build a few more myself. I have built a number of these antennas for bands from two meters to 1296. I have not had any problem with any of them. I also made a get together day plan with Carl (KB6ZST)..
It seems as tho the major problems were already identified, namely too small of wire, and the insulation left on the wire. While the antenna in this mode was just below the two meter band, it would not tune up.
Carl borrowed Steve’s (KJ6EIF) antenna analyzer and I brought mine also, along with two of the antennas I made. Mine were with one eighth inch bronze rod and were pretty close. Carl found with the analyzer he could play and prune the antenna into the proper range ((see his Nibbling notes on this blog)).
This last week I played with mine at home. One antenna tuned just right for where I wanted it–144.200–and the other was high by about 550 khz. I tried to lengthen the driven element single rod piece with a short section of tubing, but it did not move the resonant frequency swr much. I moved the tubing to one end of the first director and the slightly long now element made the antenna come alive. Easily went to one to one swr at my required frequency. That first director has a REAL BIG effect on the impedance and matching of the antenna. I have read about this before but never really noticed the amount of the effect. Guess I have been very lucky in my past antennas!!
BTW, my antenna showed very close to a one to one at 144.200 ((my design frequency)) and a two to one swr band width of plus/minus one and a half mhz.
Anyway, if you build one of these antennas with the WA5VJB specifications, it should come close. To first check the swr, move the coax connection location slightly. Then maybe try a slight length adjustment of the driven element or the opening/closing of the driven part of the loop. Then you could try a shortening or lengthing of the first director.
Please note that there are differences of length for different sizes of rod!!! This can affect the frequency of operation. Even on two meters there is an adjustment to be made between the ssb/cw and the fm portions of the bands.
Good luck and happy antenna work.