Should work just fine, Mike, since your inverted L is > 1/4 wavelength and has some series inductive reactance. You're tuning out a portion of that series inductance, leaving the remainder to work with the shunt capacitor to form an L network to transform the resistive component of the inverted L up to 50 ohms. Even at full power, I wouldn't expect enough voltage at the 50 ohm point to arc capacitors of any reasonable spacing!
Regards, Charlie, K4OTV -----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of Mike Waters Sent: Tuesday, September 17, 2013 1:24 PM To: topband Subject: Re: Topband: Hairpin Matching Coil Questions I didn't read everything in this thread, but there's a good alternative to a matching coil. On my 160m inverted-L, I just use two air variable capacitors, and they work great. One adjusts the impedance, the other tunes out the reactance. The interaction between them is fairly small. Like this: http://www.w0btu.com/files/antenna/ http://www.w0btu.com/files/antenna/Inverted-L_L-network_100_3760.JPG One cap is in series with the coax center conductor and the antenna (a 155' inverted-L). The other is in parallel between the coax shield (and two 1/4 wave 10' high elevated radials) and the point where the first cap is connected to the antenna. They don't arc or heat up at 1500 watts, and I'm sure I could have used caps with a smaller spacing. There's no ground rod. And not shown is a choke made from several turns of RG-6 feedline through 4 or 5 stacked 2.4" OD #31 ferrite cores. I use an MFJ-259B between the coax connector and the choke. Just keep your antenna analyzer up off the ground lying on a dry 2x4 (or other insulator) while you're adjusting the capacitors, or you'll get screwy readings. There's also a small spark gap in parallel with a 33K Ohmite OX resistor, connected between the antenna and radials. I've got some more photos and a schematic with capacitor values here, if anyone is interested. 73, Mike www.w0btu.com _________________ Topband Reflector _________________ Topband Reflector
