Rod,
Sorry to be late replying to this one. My experience has been that solder
joints or anything tinned will not hold up well when directly exposed to the
elements (at least here in NH.) It doesn't take long for that white oxide
stuff to form and compromise the material. I would agree that tinned or
untinned braid can be effective, but the spaces between threads will be a
further source of rapid deterioration. The copper strap sold by Polyphaser
is relatively cheap in short lengths, so that would be the first choice.
If you must use braid, I don't think coating it with solder is the best way
to prevent oxidation. Instead, try painting it with that liquid rubberized
plastic sold in hardware stores for dipping tool handles. A few coats of
that stuff will make a nice, permanent, waterproof seal against the
elements. It's good for dripping on outdoor solder joints, too (like where
you bond the radials for a 4-square, which is where I'm using it.) But as
others have pointed out, solder joints won't stand up to the heat generated
by lightning. Use compression clamps or Cadweld (I found the latter to be
the best way.)
On the separate ground systems, I guess I have heard that at long distances
like 250 feet, the two grounding systems won't see each other. I built a
heavy ground system at the tower (11 rods so far, 12.5 feet apart, connected
with 1/0 wire), and have another rod outside the shack for the common point
ground. There will be at least three other nearby ground rods attached to
the main rod. I connected the tower grounding system to the main rod at the
shack with 250 feet of 1/0 wire direct buried 4 feet deep alongside the PVC
conduits. Although the long distance might have made this unecessary, I
figured that the systems were already connected through the shield braids
and other grounded wires in the PVC, and that the 1/0 might provide a lower
inductance path. Also, since it's direct buried, my hope is that it will act
as one giant 250 foot horizontal ground rod. In retrospect, I might have
been better off opting for 250 feet of copper strap, but the 1/0 was more
easily available locally and much more rugged for direct burial in a deep
trench.
By the way, we had a sudden, unexpected electrical storm the other day (very
late in the year for that). I was in the basement room when it started and
didn't get to the shack until some pretty big strikes happened nearby.
However, with my new ground system with Polyphaser suppressors at both ends,
there was no equipment damage. I also didn't hear the characteristic beep in
the phones that we always get with nearby electrical storms, so I think the
new ground system and surge suppressors on the phone lines have helped
there, too.
The one exposed piece of equipment was my new weather station. The
high-speed wind alarm went off every time the lightning flashed, giving me
ridiculous readings for wind speed. No permenent damage, though. That's the
only wire coming into the shack without surge suppression. This winter, I'll
be trying to figure out a way to fix that. It's a bit complicated by the
fact that you're not supposed to lengthen the cables coming from the sensors
because the instrument has been adjusted to the specific cable lengths. But
there's a junction box where I might install some Polyphaser MOVs if there's
room.
Hope this helps,
73, Dick, WC1M
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