_
_
There are things we just never get around to, aren't there? There was an antenna tuner in the 1957 ARRL handbook that I always wanted to build but justnever got "around to it." Then, as I was perusing the homebrew pages on eBay, what do you know - there was a homemade tuner that was almost a duplicate of the one I'd always wanted to try. Nobody wanted it because modern hams had no idea of what it was. So I snapped it up for a very reasonable price. If it didn't work, or wasn't as suitable as I had always thought, at least it had good components that I could always use for something else. The tuner showed it's years of wear and tear so I had some work to do, but when I finished I was amazed that this simple tunerfrom 61 years ago still compared favorably to any manual tuner of today.
The old tuner had mis-aligned tuning capacitors which required reversing one. and adding a flexible coupler between them. Since I didn't want to cut the shaft of the rear capacitor I drilled a hole in the back and let the original shaft stick through! It didn't hurt anything and I retained the shaft length without resorting to cutting it.
The input capacitor (with the long shaft to the front) had a broken coupler which had to be replaced and that improved the alignment for that one. There was some wiring that need to be re-routed and some that needed to be replaced.
The tuner had been built in a metal "drawer" and had a little bracket on front for the card which told what was filed inside. I removed that and gave the whole thinga new coat of black paint. If you look carefully at the schematic you will see that it is made up of two individual circuits (coils within coils).. They are both link coupled to the output jacks on the back. Remember, this was in th days when hams almost universally used twin-lead (now "Window Line") or open wire feeders to their antennas which were doublets or half waves which (because they were fed with low loss open feeders) would work on several bands. We were restrictedd to 1 kilowhatt INPUT in those days (it was AM, remember?) and this tuner would easily have handled that much power. Today, with SSB, it would handle a ton of power.
I simply placed alligator clips soldered to banana plugs on the feed line from my 80 meter half wave loop. I plugged that in the the "Low Band" jacks on the rear and got nice low SWR readings on 80 and 40 meters. Then I moved the feed line over to the "High Band" jacks and got good low readings on 20, 15, and 10 meters. I regret that I only took one picture of the LP-100 on 20 meters, but at the time I never intend to add this to my "projects" web site. Here is the result on 14.070Mhz.
