I use a traditional wide-range balanced tuner - the same circuit Cebik shows and that has been a Hamshack staple item among some of us since Marconi was around. Center link, split stator variable, and feeders tapped onto the coil.
With that tuner feedline length has never been an issue at all. It matches easily values from a few ohms up to several thousand ohms: the highest impedance one might expect with typical antenna geometries. It uses a large coil with heavy wire to avoid ohmic losses at the low impedance end and wide-spaced transmitting cap to handle the very large RF voltages present feeding high impedance loads. It's not automatic, so it's not fast, but I can change bands in about 15 seconds. And it's flexible, handling unbalanced loads like an end fed wire or coax line with equal ease. My normal feedline is high-efficiency open wire line. My open wire line is made of #14 electrical wire separated by high-quality ceramic insulators at long intervals to minimize dielectric and ohmic losses. My antenna of choice has always been the doublet, since I've not had the space for a rhombic or other traveling wave type or the room for a tower and beam. As long as the doublet is at least 1/4 wavelength long, end to end, it's virtually as effective as a half wave. So a 66 foot doublet does a very good job on 80 and a 130 foot doublet does a good job on 160. The big issue on the lower bands is usually height, especially enough height for good low angle radiation from a horizontal antenna. That requires a height of at least 3/8 wave and 1/2 wave is better. On 160 meters it needs to be close to 100 feet up: 130 feet would be ideal <G>. I count myself lucky to get the wire 50 feet up. That provides low angles for DX on 40 meters and up. On 80 or 160 it's an omni-directional NVIS or "short skip" antenna providing excellent coverage out to about 1,000 miles or so on 80; a little less, typically, on 160. Where the wire is well over 1/2 wave long, it shows significant gain as the pattern breaks up into many lobes. In spite of the antenna patterns one finds in books, a real world antenna does not have zero radiation in any direction. It's a matter of having lobes that produce a superior signal in various directions. I've never noticed any deleterious effects from the lobes and long ago quit thinking much about trying to align the antenna for specific coverage. Ron AC7AC -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Cutter Sent: Tuesday, February 20, 2007 4:14 PM To: Mike Morrow; [email protected] Subject: Re: [Elecraft] wire antennas I always advise using a non-resonant length for a multi-band doublet with tuner combination. There's a magic figure: multiples of 44ft, 88ft... that Cebik came up with which is a good compromise with impedance matching, ie not horrendously high or low X and R. I notice no-one has mentioned the G5RV and its derivatives, yet. David G3UNA _______________________________________________ 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
