on my WBX last fall. I suspect that part of the reason was that the
antenna I was using (a discone wide-band antenna mounted on the roof) is
not DC grounded and thus can develop a good sized charge.
An anecdote: many years ago I built a ham radio repeater system that was
located on the roof of a dormitory building at school. There was a
short tower on the roof and the 1/4 wave ground plane antenna was
probably about 120 feet above ground. The coax cable went from the
antennas down to our ham shack on the top floor of the building. At the
bottom of the surplus CATV hardline cable was a PL-259 connector with a
"barrel" connector to allow hooking up a flexible jumper. The
dielectric between center and shield in the barrel was a clear plastic.
I was working on the repeater one spring day with the antenna
disconnected. Every minute or so I heard a faint "pop" sound. When I
investigated, I saw blue flashes in the plastic on the barrel connector.
It turned out there was storm activity in the vicinity, and the charge
on the 19 inch long whip built up to a level where it arced across the
3/8 inch or so of dielectric. The storm was far enough away that we
couldn't hear the thunder inside the building.
Since then, I've preferred to use DC-grounded antennas (or at least to
have something in the system that provides a DC path)! Sadly, I didn't
follow my own advice last fall...
John
----
On 4/12/2012 8:11 PM, dave k wrote:
> blew my second WBF front end after 1 day of wonderfull RX. I don't know how it happend. I was using a few different types vhf and uhf omnis and yagi antennas, everything seemed to be working fine. Now it can't hear hardly anything and the typical strong noise signal in the center freq is back. Is it possible that some of the equipment mounted on the antenna mast could be shorting it out? Or is the WBX just so sensitive that a strong signal can blow it up? I have 2 Ubiquiti bulllet2HP's on the roof. One is clamped to the same mast as the UHF omni that was connected the to WBX. They are 24V DC over the unused pairs. Im really bummed out. Any recommendations or similar experiences ?
>
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