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!).
10pf
series cap installed... I slipped a piece of thick heat shrink over
this assy, before reinserting it into the aluminum housing...
Dave WB4IUY
http://www.WB4IUY.net
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).
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
