If the L-net brings the system to resonance (X=0) then whatever reactance the L-net introduces must be equal to the reactance present at the antenna but opposite in sign!
For example, if the antenna shows j-500 ohms, the L-net must show j+500 ohms. So if you want to know what the antenna shows based on measuring the L-net, you must reverse the sign! Ron AC7AC -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Vic K2VCO Sent: Wednesday, March 14, 2007 5:10 PM To: Elecraft Reflector Subject: Re: [Elecraft] Re: MFJ259 Don Wilhelm wrote: > Jack, > > Yes, connecting a measureing instrument directly to an antenna can be > troublesome if there are strong broadcast stations in the area or > other sources of signals that can fool the instrument. > > Zack Lau addressed that situation in a Technical Correspondence > article in QST a while ago - his answer was to measure the antenna > indirectly with an L network - the L network provides selectivity - > adjust the L network to provide a 50 ohm match, then remove it from > the antenna, terminate what was the measurement side with 50 ohms and > measure the side previously connected to the antenna. > > Sounds like a sane way to approach it to me. I'm not sure of the reasoning, but he also said that if you do this, you need to reverse the sign of the reactance that you get when you measure the network. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
