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A little play on words there. ("Tuna"/Tuner?) Do you remember when QST published an article on the "Tiny Tuna?" It was a two-transistor CW transmitter built in a tuna fish can. I built one, but on a homemade PC board. It ran a half-watt, and I made a number of contacts with it. If I didn't tell the other station I was only running 500 milliwatts, I often got a RST of 599. But, I digress. When I bought this old tuner at a hamfest I had the Tiny Tuna on my mind, so when I started the restoration I decided to call it the "Giana Tuna" It seemed funny at the time, but as I look back on all that work, maybe not so much. But the name stuck, and here's the story.
This old tuner was built for war, and I'm not kidding. The components are all WW-II surplus items and, although I have no idea of when it was originally put together, I suspect that the heavy-duty parts were dirt cheap. It is for sure that you could not duplicate a tuner of this quality and "stamina" with today's components. But looking at it with admiration won't get it restored! SO...
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The first thing to do is disassemble the thing. All the parts go into Mama's dishwasher. Yes, you read that right. I've washed many a part in the dishwasher. You just have to be careful when they come out clean, to replace grease and oil where it originally was. For instance, those dials are verniers and they had to be packed with heavy grease to work smoothly. And all bearings are lightly oiled. While all that is going on, I turned my attention to that awful looking case. It was well made, and the builder had access to good metal bending equipment because everything was square. I used a rotary sander to smooth out the pits and gouges followed by progressively finer sand paper ending with 1000 grit. Then I gave it two coats of automobile "primer/filler." That was followed by several coasts of auto-finish black paint, allowing each coat to dry before applying another. The Face Plate needed special attention and it was painted with a small brush and modeler's black paint.
The rear panel had four SO-239s in it. The middle two were not used, so I reamed them out and inserted two very large (and very old!) feed-thru insulators. It is my intention to make this tuner also capable of feeding open wire, or window line feeders. Originally it was only a T-match tuner for 50 ohm feed lines, but we will make this a SPC tuner so it can be used with resonate antennas or it can feed extended Zepps, Loops, or random long wire antennas. You can search ARRL's archives for info on SPC (Series/parallel Circuit) tuners. To make it work this way requires a balun for the parallel feed lines.
On the the rear panel we have two PL-259s. The one on the right is input from the transceiver. On the left is output for a 50 ohm balanced line (coax). The two big insulators are for parallel feed lines. But we need a 4/1 balun for that, so let's make one. Following Jerry Sevrick's fine book "Baluns and Ununs" this one used an Amidon core, 25 feet of wire covered with insulating tubing. This balun will not breakdown with 10,000 volts across it! This is overkill, but it was the first big balun I had made and it was quire expensive. Now, I make baluns for Heath Tuners with far less expensive parts and they work very well. If you want more info on what I now use, send me and email and I will fill in the details. Building your own baluns is not difficult, it just requires time and patience. Commercial baluns are far too costly, when you can do the same ething at half the expense and the pride of doing it yourself. With all the wiring done I put the tuner on-line and found that it would tune my 80 meter loop ON 160 METERS! But, it had too much inductance to go up to 10 meters. If I still had it I would add about 4 turns of copper tubing on the top end of the inductor which would be enough to tune 10 meters.
I think I paid about $150 for this junker in its original condition. When I finished, the guy I bought it from was so impressed he wanted it back! I sold it to him for the $150 plus the $60 that went into the parts for the 4/1 balun. No, I didn't charge anything for the several months I spent working on it. I get great pleasure from turning gear destined for the recycling yard back into a useful and better looking piece of equipment that any ham would (or should!) be happy to display in their shack. If you have any questions about this restoration I will be glad to answer any emails sent by CLICKING HERE.