Ed, I missed your initial posting but just FYI I do something similar to what you describe. I re-purpose a ZS6BKW HF doublet several ways, using vacuum relay switching, to give (1) a 160 m base loaded vertical using a rudimentary elevated counterpoise and (2) a 630 m Marconi T fed against "real" ground. At the lower frequencies the 450 ohm ladder line (which normally forms the matching section for the ZS6BKW) becomes a top-loaded radiator (being shorted to form a single conductor), with additional base loading via separate homebrew couplers for 160 m and 630 m.
In doublet mode the impedance at the bottom of the ZS6BKW matching section is 50 ohm, so I use a quality 1:1 current balun with an RG213 coax feeder to the shack. If you use a different doublet and vertical ladder line lengths you can calculate the impedance at the base of the ladder line and choose the best balun for the job. My setup is very much a compromise on a suburban block but does allow decent 630 m operation, along with HF capability. 73, Peter. -----Original Message----- From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> On Behalf Of Ed Cole Sent: Sunday, 31 October 2021 7:26 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] feeding a half-wave dipole with ladder line Bob, Either you did not read what I wrote carefully enough, or I did a poor job of explaining. First off: I an not a HF DX chaser or HF Contest junkie. HF is a very occasional activity when I want a casual chat or check in a local net. Thus a compromise antenna for the "low bands". The existing 80/40m dipole is a fan dipole with 80 and 40m wires. I plan the new setup to run 40m at right angles for less interaction between them (been there done it experience). If all I wanted to do is 80/40 I would install the existing 1:1 balun at the feed and run coax to it. But I was thinking I could use window wire (commercially made) instead of the 12-inch parallel wires I show in the diagram. Whatever its impedance (probably like 300-ohm or 450). By shorting the ladder line I could feed the antennas as a shortened vertical on either 160m or 630m where the dipole wire would add "top-hat" loading. Similar to how the horizontal wire in an inverted-L works. I already have my 630m loading coil to use at the base; adding a tap it could work at 160m. I have vacuum relays to do the shorting. And yes there will be radials that are too short on 630m (1/4 wave is 522 feet and my property is 200x 300 foot). My question regarded choosing a proper balun to use on 80 & 40m. Running 140 foot of ladder wire on diagonal to the shack defeats using it as a vertical. Ideal would be a QRO ATU at the ground-end of the vertical wires (but I'm too cheap for that). I have a QRO Drake Tuner to do the job at the shack. I'll try out my 1:1 balun. 73, Ed - KL7UW ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
