In a message dated 21/01/05 16:18:13 GMT Standard Time, [EMAIL PROTECTED] writes:
I'm in a very stormy country (Northern Alps) and we have at least once per month a thunderstorm that already cost me one pair of power Xstors (in my TS-130 - $380!!!) so even with $5 each TO220 part, I did not want to loose them, or at least reduce the chance to loose them. So I instaled on the KAT2 control board an RF Chock (1 mH) and an NE2 neon bulb wired between K18-pin 3/8 and ground just to establish a direct lway to ground for static electricity (via the chock) and in case of a virulent one turn on the NE2 and establish a full short to ground. ------------------------------------------------------------------------------ - Hi Robert, It is normal practise to install an RF choke directly across the antenna socket of tube (valve) PA to protect in case of a failure of the coupling capacitors from the tube anode. 2.5kV can be very damaging to your health! Suppose these have ceased to be used since the move to solid state PA's. >From memory 2.5mH was the normal value used in the last one I built in the 1960's. The addition of a neon to hold off the path until the neon strikes should not represent any problem though am not entirely sure that it is necessary not knowing the KAT2 circuitry. In professional communication terminal equipment that is connected to external lines the inclusion of gas or carbon arresters is a standard feature at the point where the external line is connected. In addition all of our telecom distibution frames and even the distibution pedestals had arresters built in as standard. The protection operation point was selected to be higher than the normal operating voltages on the line. A QRP K2 is listed as providing 70 to 80V across 50 ohms and the normal striking voltage of a neon is about 110V, so the neon should not strike. There are however some neons on the market that strike at a lower voltage somewhere in the 60V region and to our cost we found these put a S/C across the phone line when ringing voltage and normal telephone battery were present. These would also operate when the K2 was giving normal PA O/P. Probably the choke on it's own would be entirely sufficient to provide the protection needed as long as the component was able to handle the current required. Bob, G3VVT K2 #4168 _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
