On Sat, 23 Oct 2010 16:07:41 -0500, "Kenneth A. Christiansen" <w...@i29.net> wrote:
Thanks for that information Kenneth. I'll bet it works on Texas spring rain static too! Tom Childers N5GE Antenna 4507 Branchview Drive Arlington, TX 76017 n...@n5ge.com http://www.n5ge.com >40 years ago we had a windy dust storm in Bismarck ND and I lost the RF >amplifier in my new solid state Heathkit receiver three times that day >before I realized the dirt and high winds were putting a static charge >on my antenna. I found there was a capacitor between the antenna and the >RF amp and the static would arc across the capacitor and burn out the >RF amp. Of course tube type receivers did not have this problem. I found >out a 100K resistor from the antenna to ground would prevent this and >not load down the antenna. > >Several years ago my friend I each bought a new IC-746PRO. The first >time we had a blizzard with 50 MPH winds and snow my friend and I both >burned out our new rigs with snow static trying to check into the ND >Weather Net. The K2 survived just fine. The IC-746PROs were both fixed >under warranty but it still cost both of us shipping. I found out the >IC-746PROs did not have any path to discharge the antenna charge from >the snow static. > >I recently installed the KPA100 Upgrade and one of the steps was to >remove R10 the 100uh choke between the antenna jack and ground. There is >no other path to ground and I have read on the reflector about people >having their SWR and Power measuring diodes go bad and it was easy to >see why. I plan to use this rig to check into the ND Weather net this >winter so knew I needed to fix the problem. > >MFJ on my remote tuner uses a 40 K resistor to protect their circuit. >That is less than the 100 K I have used over the years so it should >protect even better. > >I put in the following change to fix my problem. I bought four 10K half >watt resistors in a package from Radio Shack for $1.99. I soldered them >in series and soldered one end to the center pint of the antenna jack J2 >and the other end to ground. I calculate that the resistors would >withstand a 16 to 1 VSWR and I do not think the KPA100 would be able to >put out 100 watts to a 16 to 1 VSWR so the resistors should be safe. 40K >should protect the diodes from any problem and under normal conditions >should dissipate 0.2 watts. > >There is an easy way to protect the amplifier without making a >modification to the amplifier it self. Buy a PL259 T adapter and a PL259 >plug. Solder one end of the 40 K series resistor to the center of the >PL259 and the other end to the shell. The resistors can be covered by >tape to prevent an accidental RF burn. Screw the PL259 /40K assembly to >one side of the T adapter. Put the other two ports of the T adapter in >series with the coax to the antenna or the coax to the 50 ohm side of a >tuner. > >The one remaining precaution is to touch both sides of the antenna lead >to ground just before hooking them up to discharge any static >electricity on the antenna. This fix will not protect the equipment from >a lightning strike but it does allow me to use my rig to check into the >ND Weather net during a blizzard. > >I hope this can save someone else from having rig trouble after a high >wind snow or dust storm. > >73 for now > >Ken W0CZ > >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:Elecraft@mailman.qth.net > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
