[PCR-1000] ZAPTRAP

Fri, 15 Aug 2003 18:54:01 -0400

When I was stationed in Guam, they had a big spark gap on their SW
transmitter HV.  Idea was if the HV got too high, it would arc over and shut
itself down.  Of course, Guam has pretty high humidity....<smile>

We have a large HF broadband antenna, complete thing is isolated from
ground.  Has two silver balls, about 2" diameter for lightning protection
(with a half mile+ of 1.25" hardliner, that probably isolates the
transmitter fairly well).

Thanks for the conversation!  Always good to listen to better ideas...

73 de Tim, AG4QE

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Folke
Sent: Friday, August 15, 2003 6:35 PM
To: [email protected]
Subject: SV: [PCR-1000] ZAPTRAP

The DC-voltage that can apear during certain weather, hailstorms and so
on has a polarity, yes. Which specific polarity
between antenna and earth at the different wheather types and
situations? Sorry I don�t know.
The voltage induced by nearby lightnings are more like AC and with only
one diode only one half periode would be clipped.
Besides diodes VDR:s MOV:s and small neon lamps are used for this
purpose.

/Folke

-----Ursprungligt meddelande-----
Fr�n: [email protected]
[mailto:[email protected]] F�r Tim Tapio
Skickat: den 15 augusti 2003 23:56
Till: [email protected]
�mne: RE: [PCR-1000] ZAPTRAP

I understand the reasoning behind the dual diodes, but I still have the
question as to whether static has polarity.  I don't know the answer.

73 de Tim, AG4QE

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Folke
Sent: Friday, August 15, 2003 11:59 AM
To: [email protected]
Subject: SV: [PCR-1000] ZAPTRAP

The reason for two anti-prallelled diodes is to take care of both
polarities of statics and induced voltage in the antenna. If you get in
contact directly with lightning voltage, please don�t worry about
polarity, any kind of diodes, cables and other stuff use to vaporize any
way.... The weather station doesn�t care about loss of high freqs as a
radio, then it is OK with a power diode. The method of disconnecting and
grounding cables outside the building is the best protection.

/Folke

-----Ursprungligt meddelande-----
Fr�n: [email protected]
[mailto:[email protected]] F�r Tim Tapio
Skickat: den 15 augusti 2003 17:50
Till: [email protected]
�mne: RE: [PCR-1000] ZAPTRAP

Are you sure?  Does static have a positive or negative relationship to
ground?  Lightning flows from ground to cloud, negative to positive (I
don't believe it though).  Someone else mentioned the capacitive effect
of the diodes at higher frequencies, suggested using standard 1N4148
switching diodes.  The stuff in my weather station has a 5 amp diode
(didn't see any
numbers) but that is not RF.

The main importance is a good ground and if it is highly likely for
lightning outside, discount from the radio...and ground it or disconnect
outside.  I run all my coaxes through bulkhead connectors on a 1/4"
copper bar outside with three ground rods attached (12' apart) and #6
wire to connect (small but better than nothing).

73 de Tim, AG4QE

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of [email protected]
Sent: Friday, August 15, 2003 4:43 AM
To: [email protected]
Subject: [PCR-1000] ZAPTRAP

Hi all,

Just for the record, since no-one has mentioned it, you need 2 diodes,
in parallel, one each way, between line and ground.

73, Heath.

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