Hi, Mick. > please can someone explain why this is important
As previously stated a halfwave end fed wire represents a very high impedance which is outside of the matching range of the T1. But thats with no counterpoise or fed against a ground stake. I have found that a halfwave long wire works as long as it is fed against a raised counterpoise, ie. a wire lying over some nearby bushes. In this case it works because the two wires are really an off center fed dipole with the radio in the middle. The end fed halfwave wire does have some interesting characteristics and people do use them, for example they are quick to erect DX antennas because they gave a very low angle of radiation. You just have to make another matching circuit to bring the imedance into the matching range of the T1. Check these web pages for details: http://www.aa5tb.com/efha.html http://www.njqrp.org/n2cxantennas/halfer/index.html http://www.angelfire.com/electronic2/qrp/efhwt.html http://hometown.aol.com/n0lx/triband_tuner.html http://www.arsqrp.com/ars/pages/back_issues/2000_text/1100_text/phased.html For excellent antenna information in general try: http://www.cebik.com/radio.html > i wish to use this tuner on the following bands 20/15/10m > so a suggested wire length would be appreciated I only have > 40ft of space to play with. Is that 40ft by 40ft or is it 40ft by 10ft :) ... Are there any trees or other antennas in that space? What kind of contacts are you interested in making? QRP? QRO? Local? DX? One antenna for all bands or separate antennas? For example if you are interested in DX, you can probably fit a full wave loop for 10m into your lot, or even a cubical quad which would give excellent performance. For local contacts you could consiter a doublet fed with twinlead or even a fan dipole fed with twinlead. If it's just a single wire length, are you planning on feeding it at the end? Or in the centre? Against a counterpoise or against ground? For a quick throw-wire I'd use 42 feet with a 14ft counterpoise. Bend the extra 2 or 3 feet at 90 degrees if you have to make it fit into your 40 feet. You could also use linear loading by using twinlead to put up a folded dipole, or many other ideas. Martin. VA3SIE. ___________________________________________________________ To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.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
