Post by sfi355 aka Billy Bob on Apr 27, 2021 22:08:52 GMT -5
I believe that I have a 1975 ish P500 Penetrator, I had order all the parts from MFJ and I assembled the antenna. Now tested the antenna. And what I getting is that the antenna is resonating at 30.300 to 32.300 MHz the SWR is 1.5 at each end. At 27 MHZ swr is 3.0 and up. Now the base that I got from MFJ didn’t have any holes drilled so that force me to drill through the metal that is molded at the top of the part, so I can put a bolt all the way through to be able to tie the hair pin element to. I have made the center element longer and I still got the same results. Now I made up a much long hair pin and again I got the same results. Does anyone have a clue what this is?
On the Hy-gain 500 there is a stud that goes through the side of the bottom insulator. Inside of that insulator the wire from the center of the coax connector connects to that stud. On the out side of the insulator one end of the gamma match rod and the beta rod connect to the stud. The gamma match rod is supported by the two insulators and the other end is attached to the bolt that holds the vertical element to the top of the insulator. The other end of beta rod connects to one of the bolts that holds one the ground plane elements to the bracket. Since all the element sections of the whole antenna are clamped together and not preset as some antennas are that use screws, it's important to make sure they are all the correct length as stated in the manual. If you have a 1975 it should have 3 sections on the ground plane radials and 2 bolts holding them to the bracket. The later Telex hy-gain used 2 elements for the ground plane radials and 1 bolt to hold the ground plane radials to the bracket. Makes no difference except that it was most likely cheaper to produce that way with lees element tubes and bolts. In 1977 they changed the height of the antenna's vertical radiator measurement from 22' 9 1/2" to 22'6" because of the 40 channels being authorized. The center frequency of the band went from channel 12 to 19 so the antenna had to become shorter. Still an antenna analyzer will be a great help.
Inside a wire is soldered to the center of the antenna connector and the other end of it has a ring terminal that connects to the stud that goes through the side of the insulator. A bolt could be used also with the head inside. The original wire was a small gauge but something like a 12 gauge wire would allow you to run more power without burning up the wire.
Post by sfi355 aka Billy Bob on May 4, 2021 11:47:38 GMT -5
I Toke the antenna down, I took the base apart and this time I took the wire from the center of the SO-239 coax connector and hooked it up to the bolt on that sticks out of the side of the Plastic Base, I put the antenna back together and set it up as per the manual and and now the antenna works as it should. SWR at channel 1 is now 1.4 and at channel 40 it is 1.1. Thanks for your help Air1.