Hi Paul The info I gave you applied to the SD214 series antennas (old SRL210A4 oe 210C4). I am guessing that it would also apply to the cheaper SD2352 series.
Let's hope you don't need to get inside the dipole itself. BTW what is the diameter of the aluminum tubing used on the SD2352? The SD214 uses 3/4in OD. Paul Kelley N1BUG wrote: > Thanks Burt! > > If all the dipoles seem to be OK (not noisy) I am thinking of making > my own harness to use 4 of them. I've constructed several > multiple-antenna EME arrays so I understand the concepts and the > importance of equal lengths, etc. I used an old HP RF impedance bridge to match the harness sections on the antennas I built. It allowed me to match actual electrical lengths to within .01 wavelength. > > My only concern with making my own harness is that the length of > coax attached to each dipole is not long enough to reach a tee > connector on the mast and allow sufficient vertical spacing between > dipoles. (The original configuration had four bays of two side by > side dipoles, so the shorter length was appropriate there.) It will > be easy enough to add on some coax but since the impedance at my 147 > MHz frequency is not exactly 50 ohms and somewhat reactive it will > vary somewhat with the coax length. I don't think it will be enough > to cause major issues. You could try using 3/4 wavelength matching pieces to get the extra length. That should be equivalent to 1/4 wave but will be more sensitive to frequency changes. > > I see that I will need to use some odd multiple of a quarter > wavelength for the 50 ohm coax sections from the array center tee to > each of the outer tees feeding pairs of dipoles. Never having seen one of those antennas (the SD2352) up close, I am not sure of the harness configuration and how it would compare to the SD214 that I am familiar with. > > I need to see if I can figure out what failed and why in the > original configuration before I go investing time and money into a > rebuild though. Its useful service life before becoming too noisy > was less than a year! Figuring out the failure mode is the most important first step. Then you can go from there to possible solutions whether it is harness replacement, repair or dig into the dipoles. Good luck Burt>>> > > Paul N1BUG > >
