A proper static discharge path to ground is essential in all antennas likely to see a high E field, which in areas with thunderstorms really means all antennas.
The RF choke is probably the easiest way to ensure a low DC impedance - connect it across the centre of a dipole or from a vertical element to ground - at the lowest impedance point you can - usually the feed point. A high power high value resistor will work but not for higher fields like nearby lightning. I use an air wound coil on my higher frequency antennas 4m/6m and a high power choke using an RF rated toroid for the lower bands. As long as the impedance is 10 time higher than the antenna it should be OK. That means 500 Ohms which at 7MHz is 12uH or more. Make sure you use a large torroid able to handle the high RF currents that may occur on some bands where the antenna match is poor. If your antenna is multiband but not trapped it will have a high impedance at the second harmonic, e.g. 40m for an 80m antenna, 20m for a 40m antenna. Apart from the obvious point that this antenna is not going to work well if fed via a coax and balun, it does make things harder because you need a higher impedance. A possible alternative is to use a 1:1 transformer to couple the coax to the antenna, act as a balun and also isolate the static. As high voltages would arc remember to ground the centre tap on the the antenna side. If it is balanced, this should be a voltage minimum. Of course, if you are already feeding it against real ground, then the vertical will be already by grounded in the transformer fed configuration you will not need a centre tap. Mike -- View this message in context: http://n2.nabble.com/k2-KPA100-KPA100-schottky-diodes-tp733673p734223.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ 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
