Vic Here's an idea that I haven't seen anyone else use, but it might just do the trick for you.
Lower your vertical and connect a 33 ft piece of good wire at the top. Put a good egg insulator at the free end of the wire and attach a long nylon string. When you want to work 80m, draw the wire away from the vertical until it is as horizontal as possible. When you want to work 40 or 30m, lower the wire so it is right up against the vertical. This will cancel the effect of the wire, making it as if it wasn't there. As a belt and suspenders approach, you could even put an alligator clip at the end of the wire and clip it to the bottom of the vertical when the wire is down. You will have to improve the radial system for 80m. At least get some radials that are full size for 40m. These don't have to be run straight, either. Remember the function of the radials, to collect the current radiated by the vertical and return it to the feed point. Resonant lengths collect more current because they are longer and intercept more current. A second function of the radial system is to mask the lossy ground below the radial system, thus giving the return current the lowest loss return path possible. You can do a lot to improve your setup, just by working on the radial system. You will not be adding gain, but you will be reducing losses, which will have the same effect on your signal. Hope this gives you some ideas, Vic. Good luck and 73 Bob N6WG The Little Station with Attitude -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Vic K2VCO Sent: Wednesday, December 07, 2005 1:20 PM To: Elecraft Reflector Subject: [Elecraft] Clever antenna tuning ideas wanted OK, here is what I want to do: I have a 33' (10m) vertical with the base about 10' (3.3m) above ground. It has four 8' (2.4m) radials which are connected to the feedpoint through a coil which resonates the system on 7 MHz. It works as well or better than any vertical that I've used on 40m -- low SWR and good results. It's fed through a relatively short (20', 6m) length of RG-213. I would like to use it on 80m and 30m as well. My first try was to simply use the KAT100 to tune it. It tunes fine on both bands (1:1 at the rig), but results are fair-to-poor on 30 and poor-to-worthless on 80. On 30m, the coax losses are reasonable (the SWR on the coax is about 8 to 1, but it's very short). I suspect the problem is that the radial ground system is very poor on this band (on the other hand, the long vertical radiator should provide a slight amount of gain). So I may try paralleling a set of radials tuned for 30m. They will also be short, but resonated with a coil or stub. Does this sound like a good analysis/solution? On 80m, it's more complicated. The ground system is terrible, the radiation resistance of the vertical very low, and the SWR and losses on the coax very high. No wonder it's a dummy load! I guess the way to deal with it is to add more tuned radials in parallel and a switchable base network, but I would like to avoid any more control wires that have to go through my lightning suppression panel (I can't pass DC through the coax, either). Does anyone have any suggestions? -- 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
