Chuck - AE4CW wrote:
David, Industrial Communications Engineers (I.C.E.) makes a couple of open
wire arrestors that I think are well designed. On both legs of the open
wire they feature a DC short to ground (inductor) on the antenna side that
helps drain static ( and resulting noise) from the antenna, a gas tube to
ground for fast rise-time impulses, a high-voltage capacitor in series
between antenna and Xceiver, and a high resistance to ground on the input.
In my opinion this is about as good as you can get short of disconnecting
and grounding the antenna well away from the shack.
http://www.iceradioproducts.com/impulse1.html#2
http://www.iceradioproducts.com/impulse1.html#2
I've thought about these. One problem is that open-wire lines are often
operated at very high SWRs, so the voltage can be enormous if you pick
the wrong place along the line to install it. Open lines are often used
for multiband antennas, and so the 'right' (low impedance) spot to pick
will vary from band to band!
ICE says that they will work with impedances of 300-600 ohms. Although
the characteristic impedance of a line may be within this range, the
impedance *seen* at a particular point could be very high or low.
Before installing a device like this I would query the manufacturer,
explaining (if this is the case) that you are planning to operate the
line at 10:1 (or whatever) SWR and verifying that it will work properly
in this case. You might need the high-power version for 100 watts.
The other thing to keep in mind is that the effectiveness of any
lightning arrestor depends on the quality of the ground system and the
layout -- that is, you need a single entry point for all antennas, power
lines, phone lines, etc., everything has to be bonded together, etc.
There's a lot to keep in mind and it all needs to be done correctly.
This is why a lot of guys choose to disconnect everything.
Vic
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