Craig WB0GUU wrote: I got ambitious yesterday and ran a 50' copper wire between a couple peaks on the roof, about 3' above the roof. One end is connected to the center conductor of a 25' piece of RG-58 I had laying around and the other end of the RG-58 is plugged into the K1. The new antenna tunes up fine on 30, 20, and 15 meters, but on 40 meters the power bounces randomly from 0.1W to 5.0W and I never see an SWR reading. The manual says I'm getting too much RF back into the radio. It suggests I reduce power and try again. That doesn't help.
-------------------- What's happening is that you don't have a decent RF ground at the rig. Connect a 33 foot length of wire to the case of your K1. That's 1/4 wave 'counterpoise' on 40 meters. You can just lay it on the floor or anywhere convenient. The only requirement is to keep the far end insulated because it's hot with RF. That should provide a ground reference for the rig on 40. The way a 'counterpoise' wire like that works is this. If the end of a wire is insulated from any other conductor, it must be a high impedance (high voltage) point for RF. After all, no current can flow at that point if it is insulated. Moving from the end of the wire toward the rig you will have a low impedance point 1/4 wave later (about 33 feet on 40 meters) which makes a decent RF ground. If the wire is longer, 1/2 wave from the insulated end you'll repeat another high impedance point (that's why the ends of a dipole, which is 1/2 wave end-to-end, are high impedance points and the center, 1/4 wave from each end, is a low impedance point). Moving on, you'll have another low impedance point at 3/4 wavelengths, and so on. The braid on the coax would have worked as well but obviously it's not close to 33 or 99 feet long (1/4 or 3/4 wavelengths on 40). That coax will introduce some significant losses, especially on the higher frequencies, due to the high SWR on it. Remember, your ATU will match the antenna connected to the rig to the rig itself, but it has no effect on the SWR on the coaxial line leading away from the rig. Ron AC7AC _______________________________________________ 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
