[Antennas] Cushcraft R-7000 or Yaesu watt meter.

[Adam Farson]

Hi John,

Well, I had a similar experience with a Hy-Gain DX-77, in April 2000. The
damp, and frequent rainfall, prevalent in the Pacific Northwest did not help
matters.

At a power level of 1kW PEP (SSB), the tubular capacitor on the 20m trap
arced over, and the end of the capacitor was burnt right off. Fortunately,
there was no equipment damage, as my Yaesu Quadra amplifier detected the
high SWR and shut down.

I replaced the DX-77 with a Cushcraft R8; in September 2000, the 17/20m trap
failed. The point of one of the screws at the insulating base of the trap
shell (which is the outer electrode of the trap capacitor) was too close to
the aluminium centre tube (the inner electrode). An arc developed at 1kW
PEP, and burnt up the Delrin insulator. I contacted Cushcraft, sending them
photos of the damaged area on the trap. They sent me a replacement unit
incorporating some design changes, and the R8 has been working flawlessly on
all bands ever since. Cushcraft were very cooperative and supportive in
resolving this issue.

I have the R8 mounted on a mast attached to the side of my house. The base
of the R8 is 6m above the ground, and the height to the top of the antenna
is 14.7m. The RG-213/U feedline is coiled into a choke just below the R8
base.

I have another Cushcraft vertical, an AV-80 75/80m monobander (not installed
at present). I used it for several years at my previous QTH, running 1kW,
without any problems whatsoever.

Best 73,
Adam, VA7OJ/AB4OJ
North Vancouver, BC, Canada
http://www.qsl.net/ab4oj/