It was my very great pleasure to have a QSO with Lou, VA3AWA in St. Mary’s, Ontario, Canada, on the evening of October 17. I am still power supply limited (320 volts maximum) and was getting only about 2 watts out to the antenna. The band was somewhat noisy with storm static, but we made it!

I now have two good UX-210 tubes so I should be all set there for a while.

I decided to have a go at taking project photos myself. After buying 2000 watts of high intensity halogen lighting (cheapies from the hardware store) my old digital camera was able to do a somewhat credible job. I have created a TNT transmitter page on my web site which has all the photos.

Three weeks ago I was asked if I would bring my 1929 transmitter to the next club meeting and talk about what ham radio was like in those days. I had just over two weeks to prepare. The TNT wasn’t finished, I wasn’t sure of all my facts, and I’m in a major time crunch lately. But I said yes.

In the following days, I stayed up late into the night (after working 12 hours) preparing. The meter finally got painted successfully. Now that I have the technique down I will write it up when I have a little more time. I will take pictures of the process next time I do one. It turned out quite nice in the end. The grid resistor was restored, including 15 coats of paint applied by hand and a new paper label which is an exact replica of the original. Thanks VE3AWA! The only thing remaining to be done is to install a wire with period appropriate copper clip from the rear of the antenna coil to a binding post. A clip is on its way. It is the final item to complete the rig.

I talked about ’29 rigs for about twenty  minutes at the club meeting. Most seemed interested and there were several questions. I was very disappointed that a technical glitch prevented playing sound files of ’20s rigs but such is life.

Meanwhile I got serious about buying a “big dog” UX-210 tube. I got one at a reasonable price. Unfortunately it was DOA with an open filament! Aargh! I’ve sent it back and have already bought another. This one was more than I wanted to pay, but I will make cuts somewhere else next month. Eating is overrated anyway.

Being unable to locate enough parts to make a “pure” ’29 power supply for the TNT, I’ve settled for close enough. I have bought some filter chokes (which are ’29 appropriate) and transformers (which as far as I know are not, being of the mid-1930s period). I have some period appropriate meters which I will put on the power supply.

That brings me to the subject of pictures. I want good pictures of the TNT, which means I either need to buy a new camera ($$$ ouch!) or take it to a professional photographer ($$$ ouch!). I will do something about it soon.

Once I had all the parts for the TNT I was anxious to start building it! I decided I to skip the prototype and just build the final version. I figured the worst that could happen is the rig would not work for some reason, requiring a major rebuild or layout change. In that case I would only be out my $17 board and some hours of labor.  I was willing to take that risk.

After sliding parts to and fro on my kitchen table for a while, I settled on a layout. This wasn’t going to be a perfect reproduction of the original or any other TNT. It was to be my version. I started drilling holes and mounting components. This was fun and oh so exciting! A vintage 1929 rig was beginning to take shape!

Some components needed to be mounted on brass angles. Having been unable to find pre-fabricated brass angles that I considered suitable, I had opted to buy 1/2″ wide by 1/16″ thick brass strip stock and make my own. I was quite concerned about bending the stock nicely, as this wasn’t my first attempt at metal bending. All the others had gone very poorly. I destroyed a number of brass strips and spent nearly three days coming up with a technique that, while somewhat precarious and prone to mishaps, was capable of yielding “good enough” bends.

The method involved clamping the strip to be bent between two thick metal blocks and bending it by hand. It worked out that the thick blocks with a brass strip between was just wide enough to wedge securely in to a channel in an equipment rack I had in my shack. The bottom portion of the rack holds my homebrew 1500-watt amplifiers used for DXing. A guide along one edge of the stock was also found necessary in order to assure a proper bend. This was accomplished by screwing a board across the front of the rack and using a piece of think aluminum bar stock laying on top of the board. The pictures explain this setup better than words. Even with this bending jig, approximately one in three bends was “good enough” so I needed plenty of “extra” brass stock! I really need to invest in a metal bending brake one of these days! It takes a surprising amount of force to bend a 1/2″ x 1/16″ brass strip while getting a good crisp 90 degree angle. Prior to bending, the strip was clamped in place such that the bend would be the desired distance from the end for one side of the finished angle. The strip was left several inches longer than needed for the other side of the angle to aid in bending. It was cut to length after bending.

The next hurdle was getting holes drilled in the brass angles properly centered and at a uniform distance from the end. Several attempts to mark, center punch, and drill either by hand or using a drill press proved unsatisfactory as the results were not repeatable enough from piece to piece. I wonder how they did this in the 1920s? Builders were probably more skilled at such crafts back then! Obviously, I needed a jig to hold the brass pieces in position for drilling. After several attempts to create such a drilling jig, I found a workable approach using scrap wood, woodworking clamps, and some pieces of brass strip. Let’s not talk about how many attempts it took to get the jig clamped to the drill press table in exactly the right position to center holes in my brass angles! Again the photos explain this setup better than words. There were times during this whole brass bending and drilling adventure, I was very tempted to take my brass strips and a drawing of what I wanted to the local machine shop and have them do the work! But that wouldn’t be in the spirit of 1920s rig building, so I pressed onward until I found a method that works well enough. I won’t say I am completely happy with my brass angles, but I am convinced they are the best I can do with my current shop tools.

When the rig was complete enough to be able to test it, I plugged one of my mighty Cunningham CX-301A tubes into the socket and fired it up. I discovered the rig did not want to work in the 80 meter band but would oscillate fine several hundred kilohertz higher than I wanted. I was very surprised at this. As a test to see if the rig was OK but needed modifications to the grid coil, I temporarily wired a 110 mmfd variable condenser across the grid coil, essentially making the rig a TPTG (tuned plate, tuned grid). It worked perfectly in that configuration, so it seemed I would need to modify the grid coil.Actually I was going to have to wind an entirely new coil, since I needed more turns than the present coil had.

Meanwhile, having realize how dismally low the output was with the ’01A tube, I decided to purchase something a little more beefy. I couldn’t afford the much desired UX-210, but I did find a reasonably priced Majestic G-71-A which should be a nice intermediate output tube.When my new tube arrived, I found to my dismay it would not fit in the bayonet socket I had used! The base of the tube was slightly too large in diameter to fit the Federal tube socket. Everyone I asked about this seemed surprised, but nevertheless it did not fit. I liked the Federal socket because it was in very good condition and would also offer the ability to use short pin (UV) versions of vintage tubes. However, this tube fit problem was not a disaster. Albeit in poor condition I had one of the much loved and sought after Air Gap sockets (not of the bayonet variety). It so happens the footprint, post spacing, and mounting hole spacing on the Air Gap is identical to the Federal, so I was able to swap one for the other with no changes to my rig.

Upon plugging the G-71-A in, the filament didn’t light. I thought it must be a bad tube, but then realized the fancy-ass modern “bench” supply I was using to power the filament had gone into current limiting. Huh? It turns out the G-71-A filament requires 1/2 amp, not the more typical 1/4 amp for a ’71A tube. This required a power supply swap. My next surprise was that the filament in this tube produces a dull reddish orange glow, not the bright yellow / white I was expecting. While tuning up the rig, I had to re-adjust the grid tuning condenser, which ended up with the plates fully open. Interesting. I removed the condenser from the circuit entirely, making the rig a true TNT configuration again. It worked perfectly. At first I thought this must be due to differences in the tube, but later discovered it also works perfectly in this configuration with the CX-301A. In fact, it was not the tubes at all, but difference in the tube sockets that caused it to not work as expected with the Federal socket! Fascinating.

The ’71A was a nice upgrade. Most of my HF antennas, including 80 meters, had been wiped out in an ice storm late last winter. As a result I was not successful in making any contacts with the rig but it appeared to be capable of producing about 2 watts out with reasonable note quality.

At this point it was time to tidy up some details. Primarily the meter and grid resistance needed to be painted. Something had to go wrong eventually, and apparently this was the time. I spent two hours trying to get the Jewell 54 meter apart, when suddenly it let go and flew across the room! The scale and pointer were bent. This was a much prized part, as I’d had my heart set on a Jewell meter all along, and had finally found this one after months of searching. I managed to straighten out the bent parts but the pointer is missing some paint, making bright silver spots on it. I was devastated! Nevertheless I decided to press on and restore this meter as best could be done under the circumstances. Soon thereafter I learned that my skills at painting panel meters leave much to be desired. This shouldn’t really come as any surprise, given my often demonstrated lack of ability with painting of any kind.

It was at this point I realized I was frustrated and discouraged. I really needed a break from the project or else this condition might be permanent. Having many other things on my plate for the summer I  carefully wrapped the rig in plastic so as to keep evil dust away and set it aside for a while.

I had been collecting rare vintage parts much of the winter, and having a good measure of success with it. Now that I had almost everything in hand to build the TNT rig, it was time for the simplest item of all: a board on which to build it. I set out for the city one fine Spring day to get a board. I had two options in mind. One, I would buy a hardwood board and cut it to length. Two, I would buy a kitchen cutting board that was about the right size and thus have less finishing work to do.

I went to all the lumber yards and big box home centers that sell lumber. I looked at maple boards, oak boards, poplar boards, and a few other species which escape me now. To say these things were hideous would be to give them too much credit.  The wider boards were all made from glued up narrow strips. The strips were not all laid flat when they were glued; some stuck up as much as an eighth of an inch above the others. Most of the boards were warped, split, or both. Many had a rough, irregular surface. I would never be able to sand these things down and make them look decent, and if I did, the board would be no more than a half inch thick when I finished.

On to plan B. I visited big and little stores that sell kitchen items, in search of the “just right” cutting board. Hmph! To begin with, I found very few square or rectangular ones. Most were round, oblong, triangular, octagonal, heart shaped, etc. etc. ad nauseum. Whatever happened to just plain old rectangular cutting boards for Pete’s sake? The few of that shape I did find were ruined by having a large hole cut to form a handle or a juice groove all around the perimeter. Good grief! I did find one store that had 18″ x 24″ cutting boards that looked like I could possibly cut the size I needed out of the center, thus discarding all the edges with that hideous groove. The things were of horrible quality though. They were obviously made of scrap wood, many narrow strips glued together. A given strip wouldn’t even be the same width from end to end. Nevertheless they had been forced together and glued, bowing the strips under pressure as necessary to accomplish that task. The groove around the edge was the worst milling I’d ever seen, very rough as though the bit that did the job was extremely dull and/or the work was forced at  far too  high a rate. I decided to forget it and have a look on the internet. Surely I could do better there.

After two weeks checking every online retailer I could think of or dredge up through searches, I was still without a board. Again there were lots of fancy shapes. There were some rectangular boards but many were either very thin or very thick. I did find a very few that seemed suitable, but they were more than $100. I find that a bit pricey for a small slab of wood!

In the end I decided to go back to the one big box store that had those hideous 18″ x 24″ cutting boards. I sorted through the stack of 16 such boards, and selected the best one for my purpose. It had the least light to dark color gradient and was also the least warped of the lot. In fact, it was darn close to perfectly flat. Better yet, at $17 it was cheap!

I cut out my desired size board from the center, using a table saw. After a few hours of hand sanding it didn’t look all that bad. Since woodworking and wood finishing is not my thing I decided to forget about traditional 1920s style finishing. Instead I opted for a technique I had used successfully (after many failed attempts) for woodwork in my newly renovated kitchen. I applied two coats of stain and two coats of wipe-on satin finish polyurethane. I will leave the reader to judge the final outcome when the rig is completed and photographed. Meanwhile I offer this photo of one part of it which was cut away in the making of my project. This may serve to convey something about the original “quality” of the board (click thumbnail for full size photo).

Note: the images are thumbnails. Click on them for a high resolution version.

Most vintage parts aren’t very clean when you find them. Years of dust, dirt, and sometimes just plain grime have built up. It is highly desirable to clean the parts before using them. With some items this is easy; with others, not so much. One of the toughest items to clean is variable condensers. The goal is to clean and restore the parts to as near original condition as possible, without doing any damage in the process. Many vintage condensers contain insulating materials such as hard rubber, which could be easily damaged during cleaning. The plating on some metal parts can be quite thin and easily removed by any abrasive. Some variable condensers can be completely disassembled so that each and every plate, spacer, etc. can be cleaned. Others, like the Cardwell Type B which I’m cleaning today cannot. The stator plates of the Type B are swedged ito aluminum blocks and cannot be separated. That makes it challenging to clean them fully. So how does one clean such a thing? I had heard of various methods, but either could not find details or did not have the apparatus needed (such as an automatic dishwasher). So I set out on my own to find a method I could use. I did some research on methods for cleaning delicate metals, then experimented on non-precious (not antique) parts until I came up with a method I was comfortable with. The method to be described is probably not the best way of restoring these condensers, but it works well enough for my tastes. It is possible to damage the parts with this process if care is not taken.

The first step in the restoration process is to disassemble the variable condenser, either fully or partially depending on its design and one’s preferences. With the Cardwell Type B, I leave the rotor assembly intact. The stator assembly, as mentioned previously, cannot be taken apart. I also don’t remove the shaft bushing from the front end plate or the bearing/tension adjustment from the rear end plate. Most variable condensers have a ball bearing at the rear of the shaft. It is very important to watch for this, as it could easily get lost. It may or may not roll out on its own, as thee grease might hold it in place when the unit is disassembled. Some variable condensers may have several ball bearings in a race at the front or rear. Be sure to note how the parts were assembled.

After disassembling the condenser, it is very important to remove all grease before doing anything else. There will be grease on any ball bearings, bearing races, shaft bushings, etc. My method of removal is 99% rubbing alcohol and cotton swabs. Changing the swab frequently, I continue wiping until I see no evidence of further grease being removed. In other words until the swab remains perfectly white after repeatedly wiping the greased areas. Failure to remove all grease at this point will almost certainly result in unacceptable results later in the restoration process.

The next step is to pre-treat the parts before boiling. Using a paste made of cream of tartar and water and a soft cloth, I rub/buff all the larger metal parts; end plates, round spacers, the outermost rotor and stator plates, edges of all plates, etc. Areas with accumulated grime may require additional rubbing to get it off. After buffing each part, rinse it with water and inspect it. If it doesn’t look reasonably clean or has spots that still appear dirty, it needs further work. I do not clean the hard rubber strips this way. More on those later. I place the smaller hardware items – nuts, screws, washers, ball bearing(s) into a jar with a tight fitting lid. I put about1 tablespoon cream of tarter and one ounce of white vinegar in the jar, put the lid on, and shake moderately for a several seconds. I then let it sit a few minutes and shake again. It is not wise to shake too hard or too long, as plated parts may be damaged easily. I then remove one or two parts, rinse them, and inspect. If they don’t seem to be reasonably clean, I then add 2 tablespoons of baking soda to the jar, and enough water to get a liquid emulsion. I then shake for 30 seconds or so, no longer. The small parts should them be removed and rinsed thoroughly. I find a plastic strainer very handy for this step.

Now it is time to boil the condenser. All parts except the hard rubber strips are placed in a stainless steel sauce pan. I add enough water so that all parts are completely covered, then add about 1/4 cup of white vinegar. After this is brought to a boil, I reduce heat, cover, and simmer about 45 minutes, gently rearranging the parts once or twice. At this point the parts should look very clean and uniformly shiny. All parts should be removed from the cooking solution and thoroughly rinsed with clean water. Distilled water is preferred but any water is better than not rinsing. I rinse the smaller parts in a plastic strainer. At this point I only handle the clean parts with wood or plastic implements or while wearing vinyl gloves. I do not want any skin oils getting on the parts. It may be just paranoia, but I don’t want to risk the presence of any foreign contamination causing the parts to dull more quickly in the future.

While the metal parts are cooking is a good time to clean the hard rubber parts. I use 99% rubbing alcohol and a soft cloth to clean those. It is best to use a light colored cloth, or strong paper towel, so as to be able to see how much dirt is coming off the parts. I continue cleaning until I’m not seeing any more dirt accumulating on a clean section of the cloth. I then wipe them dry with a clean, dry cloth. That is all there is to cleaning the hard rubber parts.

After shaking off as much water as possible from the metal parts (post rinsing), I arrange the parts on a glass baking dish, then bake in an oven at 200 degrees F for about 20 minutes or until completely dry. Gently moving the parts around every few minutes will help. It is not wise to bake any longer than necessary to get the parts dry. Convection baking is better if available. Plated parts sometimes look a little off color after drying, but I have found (so far) buffing with a soft, dry cloth brings back the proper color. I’m not sure what is causing this discoloration.

Before reassembly, the shaft bearing(s), ball bearing(s) and any associated friction areas should be given a small amount of lubricant. Many people use light machine oil. I’m sure that works just fine, but it seems apparent to me the original lubricant was grease of some sort. I like to use a very small amount of moly high temperature grease, mainly becuse that’s what I have available. I apply it using a toothpick.

All that remains now is to reassemble the condenser. I like to start by laying out the parts in a convenient manner before starting this, but it’s not important as long as one remembers which items went where, and how. I wear vinyl gloves for the entire reassemblyprocess, to avoid contamination as noted previously.  Then end result should be condenser which looks close to original condition.

A few additional words on reassembly may be in order. These Cardwells are fairly user friendly to assemble, but if the plates don’t seem to mesh quite right after it is put together, the hard rubber strips may need to be adjusted slightly. Slightly loosen the screws holding the hard rubber strips to the end plates, and you should find the strips can be moved fore and aft slightly. If this doesn’t correct any misalignment, it is possible the left and right insulator strips were reversed during assembly. Swap them and check again.

Some other types of variable condensers are less friendly to adjust correctly after putting them back together. I once spent half a day fooling with a National Type DX condenser after I had cleaned it. The plates just didn’t want to maintain spacing correctly at all settings. It was a matter of adjusting the hard rubber insulating strips and the nuts that control the position of the stator plates on the stator plate mounting rods. I had completely disassembled the Type DX for cleaning… every nut, every plate, every spacer. That is a lot of small parts!

Once I decided to build a 1929 station, I knew immediately I wanted to use only 1929 authentic parts wherever possible. I would only use more modern parts if the early ones could not be found or I could not afford them. There was one catch: I didn’t know enough about vintage parts to recognize them if I saw them!

Fortunately I was invited to join AWAGroup, a Yahoo group “celebrating the history, building, and restoration of radio gear from the era 1920-1941 in a supportive way that both encourages and nurtures newcomers”. There I received a warm welcome and tremendous support, education, and assistance in my quest. A few parts from my own junk box were quickly identified as being appropriate for 1929 construction. I was off and running.

Since getting out to swap meets isn’t really an option, I would be looking for parts online. I knew eBay would be a primary source, but an expensive one. I spent most of the next several weeks searching there for parts and digging through old issues of QST magazine in the ARRL Online Periodicals Archive. I was slowly gaining some insight into parts and techniques of the era. There was just one major glitch I had failed to see coming: the more I read and looked at transmitter designs of the late 20s era, the more I fell in love with all of them. I found I had to suppress a growing desire to build more than one!

Parts hunting on eBay was fun and exciting, but hard on a limited budget. I started selling off some of my 30 year parts collection in order to support my new addiction. I had seen some discussion about certain parts being rare or hard to find, so I naturally assumed I might have to make compromises… but I wasn’t going to do that without making a reasonable effort to get the parts I really wanted. As it turned out, many of the things I expected to be scarce showed up on eBay. I made some mistakes early on by not realizing what something would be worth to others, but I quickly learned. Whenever possible I bid as much as I could afford for an item, if I though it was somewhat rare and it might be some time before another example showed up. The last few seconds of some of those auctions had my heart pounding so hard I wondered if I was healthy enough for this activity. 🙂 My own three or four daily eBay search sessions were augmented by tips from AWAGroup members. I am most grateful for the pointers.

Sure enough, I started to see parts I didn’t need f0r the TNT or receiver, but which would be excellent in some of the other ’29 transmitters. I wanted them too! Now what? Sell more of my stuff and bid on them, of course! Soon I had most of the major components for the receiver and not one, but three transmitters. The TNT remained my main focus, however. By early April I was close enough on parts for the first project – the TNT – that I could see success on the horizon. I set about ordering the hardware for the project.

It has been a few weeks now since I found any needed vintage items. There seem to be far fewer vintage parts appearing on eBay. Whether this is a temporary lull or a seasonal trend remains to be seen. There are still a few “must have” parts that have not shown up anywhere. I have begun an exhaustive search through other venues, but still coming up empty. I have been on the hunt just three months, which is not long at all. It is quite likely just a matter of time, patience, and continued diligence.

While I want to use only vintage parts and techniques known at the time, I do not propose to create an exact replica of a design as it was originally published. The 1920s was an era of experimentation and innovation. It was also a time when builders used whatever was at hand, or even built their own parts from common items! In that spirit I have some ideas I want to try when I get to the building stage. I plan to construct a somewhat “ugly” experimental version of the TNT on which to test my ideas. Once I have decided on the final version, I will rebuild it in “pretty” form. I will note successes, failures, and valuable (?) lessons here.

While most of my ham activity has centered around building and using high power gear for DXing, I have always felt an odd fascination for “antique” radio, especially ham rigs from the 1920s era.  Many times through the years I have come across pictures of these old beauties in books, magazines, or on the web.  Invariably my heart skipped a beat, my eyes glazed over (so I’m told), and I started to think how much fun it would be to build something like that.  How can you not love the wonder and simplicity of the era, the magic of it all?  A primitive tube and handful of components mounted on a board, and voila… you have a transmitter!  Not much different for the receiver.

Somehow I always managed to close the book or shut off the computer and run like heck before temptation got the better of me. Until, in early 2011, my long time friend and EME mentor Ron, N4GJV, told me people were not only still building 1920s ham gear, but using it on the air! What?! In particular Ron mentioned the Bruce Kelly event held in December each year. The object is to fire up rigs representing 1929 or earlier technology and make QSOs. Ron mentioned VE7SL’s TNT Transmitter page as a good place to see some of these extraordinary rigs. There I found not only pictures of many rigs, but Steve’s construction notes and – perhaps most intoxicating of all – links to other sites, some of which led me to videos and audio recordings of “1929” rig signals. There was no getting off the hook now! I knew I had to build one of these rigs!

I decided of all the designs I looked at, I was most interested in building what is known as a TNT transmitter, short for tuned plate, not tuned grid. Like most simple (affordable) transmitters of the era, the TNT is a self excited oscillator. These rely on a simple L/C tuned circuit to set the frequency of operation. From all that I read one has to be careful about every detail if a good sounding signal is to be had. The power supply should be well filtered and have minimal voltage sag with keying; the transmitter needs to have good components, rigidly mounted to avoid movement, and the transmitter should be isolated from any environmental vibration; and it must be tuned very carefully. Sounds like a fun challenge!

I also wanted to build a 1929-appropriate receiver to use with the transmitter. Being on a tight budget I wanted something simple but not too simple. After some thought I decided on a design using two tubes: a UX-201A regenerative detector and a UX-201A audio amplifier.