OK, I know this thread is over two weeks old, but I have to chime in. I have two of the 275 watt Johnson Matchboxes. One needs repairing right now. I think the 80 meter switching is defective.
I borrowed an idea from a review on eham.net. The Matchbox doesn't do well with low impedances. The reviewer said to use a toriodal Un-Un to step down the impedance. And it works! A toroid at the input doesn't suffer from the disadvantages that the toroid on the output as a balun does. It will always see a non-reactive load when you tune the Matchbox. The only real downside is the extra gadget hanging off of the Matchbox with coax leads. Another idea is to move the tap on the input link closer to the grounded end. I moved it down a couple of turns. My delta loop with balanced feeders, wouldn't tune on 80 without the Un-Un mentioned above. Moving the tap down a couple of turns did trick. It is too bad the link coupled tuners aren't made anymore. Yes MFJ makes the 974H. I have it and it does match well on all frequencies. But the small knobs are touching to work it on some loads. Also the review in 9/2004 QST showed to 974H not to be as efficient on the lower bands on lower impedances. The Matchbox showed real high efficiency. The Un-Un might reduce the efficiency a little, but it is way better than an output balun. Moving the input coil tap is probably the most efficient of all. I hope this info helps some of those how have a Matchbox, but are frustrated by the limited tuning range. 73, Steve N6VL K2 #2289 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Goody K3NG Sent: Thursday, November 15, 2007 11:00 AM To: Elecraft List Subject: Re: [Elecraft] KAT100 with Ladder Line Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. _______________________________________________ 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
