Rebuilding the old Diamond X-500 Antenna...

The old Diamond X-500 2m/70cm vertical is finished, reassembled, and up on the test mount. This one had a rough life... Back in 2016, the antenna had quit working. When the tower fell in April '16, the fiberglass portion also got snapped off just above the aluminum mount. I tossed it in the scrap antenna pile until a later date. Fast forward to May of 2018, I finally got to it while rebuilding all the damaged antennas,

The metal base had to be cut away with tubing cutters to gain access to the base loading coil, as the threaded section had become seized. During disassembly, I discovered the series and shunt capacitors in the base were toasted. Closer examination revealed the top part of the fiberglass enclosure was split and the metal cap was smutty black...I'm guessing it had taken a lightning strike. The condensate drain hole was also plugged up with _stuff_, so that was cleaned out for proper drainage. 

The capacitors were originally some low voltage style. I replaced the series cap in the feed with a nice 10pf 2.5 kv version, and fabricated the 1.5pf shunt cap by twisting two pieces of wire with 600v insulation, while reading the value with a capacitance meter. It was all cleaned up, the contaminated foam removed from the coils, the stacking couplers were sanded to remove crud, the top fiberglass section was repaired with fiberglass resin, a pvc sleeve / splice was installed over the broken section at the bottom of the fiberglass enclosure (radome) and 'glassed, and the bottom aluminum section was brazed back together with low temp aluminum brazing rod and a propane torch.

I got it up on the test tower this morning and ran some tests, and all was well. SWR match is good, and some on the air tests proved that it was working pretty good. I'm ready to install the decoupling elements, and get it up on the tower on a sidearm (I'm not top mounting it, these things seem to be lightning magnets when put on top of tall towers!).

 Parts of the antenna are in this pile of scraps...

  Internals out of the radome, partially cleaned up...

 Nasty couplers...

 Damp contaminated foam on the coils had to be removed...

 

 Had to use a tubing cutter to cut the bottom off, to gain access to the base loading coil.

 Yuk... corrosion and ratty looking caps...

 Shunt cap blown apart...

 Shunt cap...

 I split a piece of pvc pipe to stretch over the fiberglass tubing, made clean cuts on the broken fiberglass, wetted the parts with fiberglass resin, and assembled...

 Fiberglass resin applied to all parts...

 

  Fiberglass cloth laid over the splice...

 Fiberglass CSM (chopped strand matte)

  Base cleaned up, ready for reassembly...

 1.5pf cap (dicky) fabricated and installed (in red).

 

  10pf series cap installed... I slipped a piece of thick heat shrink over this assy, before reinserting it into the aluminum housing...

 All reassembled, I used GE silicone caulking to seal all of the joints, and bolted it to the top of the test stand in my back yard. SWR was good, and it seem to work OK. Another antenna resurrected from the scrap pile

Dave WB4IUY
http://www.WB4IUY.net