It may be worthwhile to consider installing a pair (or multiples) of vacuum
relays on the open line, outside the house, to function as a DPST knife switch.
Relay closure is controlled inside the ham shack.
Although I wouldn't consider it, one could supplement the relays with a spark
arrestor and place it in between the relays and the home entrance, keeping it a
reasonably safe distance away from the home.
I use a total of four vacuum relays in two pairs, each pair is separated by 15
ft. along 600-ohm balanced feeders. One set is inside a homebrew ATU. They're
Jennings RS8 vacuum *contactors*, rated at 75-amps and 28 KV, 30KV peak. The
relays engage when my outside tuner is activated from a control box in the ham
shack.
I've found at this point in similar discussions that someone will want to
refute the idea because "lightning traveled miles to strike, and you want to
break it up with relays?" Yes, exactly. My dipole antenna is cut to 80m, and
used on all bands through 10m with an outside, motorized ATU. The relays are
fully floating. No ground reference. Nothing to divert a surge. Nor is it
needed or wanted in this application. The vacuum relays completely allow the
line and antenna to disconnect and float above ground potential.
I've been using my dipole this way for 30+ years in Florida where thunderstorms
develop most summer afternoons.
Now the bad news: Jennings RS8 relays are being sold for $200-$400 ea. Over
the years, I've been able to purchase Hi-pot tested relays for under $50 ea. at
hamfests and through commercial surplus vendors. But, there's nothing
sacrosanct about the RS8. One can mix and match vacuum relays, provided the
coil voltages are alike. My Hi-pot tester is limited to 12KV, but if the
vacuum can hold off 12KV, then odds are good the vacuum isn't compromised.
https://www.rfparts.com/relays/relays-vacuum/relays-vacuum-jennings/rs8-26n138-p.html?srsltid=AfmBOopSTS5L2NUA7UMX-KTujVadlysCRUFnLsSDnnmwFcT5gY8IIkrs
Paul, W9AC
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|