On 7/26/2010 8:46 AM, Jim Thomson wrote:
> Date: Mon, 26 Jul 2010 06:21:30 -0400
> From: Pete Smith<firstname.lastname@example.org>
> Subject: [TowerTalk] Gas Tube protection for remote antenna switches;
> shorting coax cables when disconnected
> Yesterday we had a severe thunderstorm episode, with significant
> cloud-to-ground lightning nearby. All my coax and control lines were
> disconnected, but when one particularly close strike occurred, an arc
> jumped across the open SO-239 on my entry panel. No damage in the
> shack, fortunately, but it set me wondering.
> 1. Does it make sense to put a shorting plug at the shack end of a coax
> cable? With my Ameritron RCS-10 relay box, putting a shorted PL-259 in
> position 1 on the relay box has the same effect when the control cable
> is disconnected, except at the tower end. A better idea?
> ## putting a shorted pl-259 in pos #1 just used up pos #1.
and still leaves the other connections/positions open. Not good for
> Why not use a torroid.. like 45 uh... using 10-12 ga magnet wire. Then,
> the center conductor is always at DC grnd. [ on the cable heading towards
> the station.. ie: input side]
> ## does the ameritron grnd, or float the un-used ports ??
"Out of the box" they float, but it's a very simple job to have the
unused connections grounded. Power down and all are grounded. It's a
simple solder bridge between two foils, or for the solder challenged, a
short piece of #12, 14, or 16 can be soldered in place.
> My AS
> box grnds all the unused ant ports. DPDT relays are used, one per
> port. Common goes to ant port, NC goes to grnd buss... and NO
> goes to kw input buss. If lightning present, all Unused ports are grnded.
> If power to control box is shut off, or rotary switch thrown to pos 7-12..
> all ports 1-6 are grnded.
> ## You could also install an ICE arrestor, or similar, at shack end... then
> the center conductor is always DC grnded...plus it has a gas discharge tube
> in parallel with the 12 ga , 35 uh torroid they use. It's also dc
> blocked... and
> the station side of the block caps has series resistors going to grnd.
> You could
> also install a 2nd torroid on the station side of any dc block cap.
> ## I'd also grnd all the braids if all coax cables at the top of the
> then run the coax down the inside of the tower .. and also grnd the braids
> at base of
That's what I've done here.
> Then install the ICE arrestor or eq in the station.
Then the arrestor is mounted on the grounded bulkhead where the cables
enter the shop and house.
> ## IF the yagi uses either a hair pin [floating] or a beta match [
> grnded hair pin] then the
> center conductor is grnded anyway. If no hair pin is used... like on an OWA
> design.... I see no reason
> why a 35-70uh choke couldn't still be used directly across the DE. If
> a remote switch box is used, at least you have
> all the braids grnded at top of tower already.
> 2. Ameritron makes a "lightning-protected" version of the RCS-10,
> called the RCS-10L. From the parts list (no schematic) it appears that
> the only added component is a gas tube, rated at 1500V, 10 KA. I
> presume this is across the output of the relay box coming to the shack.
> Again, good idea?
I have multiple RCS-8s on the tower one for 75 and one for 40. These are
fed from a "six-pack" which allows for two stations to use the system.
> ## sure, that will work. But can u take the box apart to change out the
> gas discharge tube, with no hassle ? On the German Hoffi brand lightning
> arrestor's, it takes no time at all to change out the gas discharge tube.
> deal with the Suhner + also the Spinner brand of lightning arrestor's.
Seems like I read the tube is easy to change in the ice units, but
that's relying on a rather shaky memory.
> ## did Ameritron install the gas tube on the side of the remote box... for
> easy access ?
> 1500 V means the gas tube is good for 20 kw with flat swr... and 10 kw
> with a 3:1 swr.
What about 6 or 7:1?
> Later... Jim VE7RF
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