[TowerTalk] Lightning GROUND switch wanted

[K0FF]

In the Ameritron units I just looked into they have some nice big open frame
relays with large contacts and wide spacing. Unknown what material the
insulation is made of but looks substantial.

I was unaware of the type of wiring configuration used, but now see that it
makes good sense,as Tom explained it. Rather than ground the center
conductor of the UHF connectors they are left to float, but the connection
lead length is almost zero, then the armature of the relay is grounded so as
to provide a barrier between the arc path and center conductor. Sort of what
we call a "waveguide beyond cuttof" at UHF, but for lightning.

Keep in mind though that no matter how good the isolation is on the centter
conductor, that the most damage is done by the current on the shield. Many
hams still think of the shield as being "grounded" because somehwere at the
other end it is grounded. It's not grounded any more than the top of the
tower is grounded because the base is.

So if the relay box is at the top of the tower you are still not protecting
the rig or anything else from the lightning on the shield unless you have a
bulkhead plate at the radio end.

73 Geo>K0FF

Geo>K0FF
-----Original Message-----
From: Pete Smith <n4zr@contesting.com>
To: towertalk@contesting.com <towertalk@contesting.com>
Date: Thursday, August 31, 2000 10:33 PM
Subject: Re: [TowerTalk] Lightning GROUND switch wanted


>
>At 08:52 PM 8/31/00 -0400, Tom Rauch wrote:
>...
>>Copy the RCS-8, and it will greatly reduce any possibility of
>>currents flowing inside the cable to the rig. Of course it does
>>nothing for currents on the outside, for that you need to use a very
>>good ground or unscrew the cables and move them away from
>>everything else.
>>
>>By the way, the relay in the RCS-8 is good for well over 6 kW into
>>50 ohms at HF.
>
>Tom makes an interesting point here.  Many of the remote antenna switches,
>stack matches, etc. on the market use a relay (JW1FSN-DC12V, same part #
>from several manufacturers, including NAIS) that is apparently good for
>very high power, but is physically very small and encapsulated, and only
>costs ~$2 each in small quantities.  It would seem that such a relay can't
>offer the sort of protection from lightning that he describes, if only
>because the physical spacing between contacts is very small.
>
>So, the next question is, what relay does Ameritron use in the RCS-8?  Many
>of us might be interested in homebrewing a grounding panel with them, if
>the cost isn't too high.  Tom?
>
>73, Pete Smith N4ZR
>
>The World Contest Station Database
>is back up and running at
>http://www.qsl.net/n4zr
>
>
>
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