On 1/9/2018 19:25, Bill Johnson wrote:
With a 1/2 wave a counterpoise is not used.
It needs SOME counterpoise, but not much, because the current in it is very small. If nothing else is available, the coax shield will suffice, and causes no harm. The small current at the end of the antenna has to have a return somewhere. I recall old versions of the Handbook showed an EFHW fed with open wire, with nothing at all connected to the other conductor, and never could figure out how that worked. I suppose a little common mode current in the open wire line. Later versions, I think, showed a short wire opposite the antenna, which at least made sense to me. The point is that the very small current at the end of the EFHW will find a return somewhere, and it really doesn't matter.
One way to tell with a QRP radio whether you need a counterpoise is to watch the SWR as your put your hand on the case of the radio or tuner. If the SWR doesn't change, you're good to go. I don't recommend this technique at high power levels.
All of this is true ONLY for an end fed antenna which is a multiple of a half wave.
73, Scott K9MA -- Scott K9MA [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
