Live To Air – National NC-101X finally back together tonight newly installed coil rack, with the bronze bushings and fabricated band indicator. Slides like it’s on glass, super smooth and low effort.
Listening to the melodious tones of the old Gray Hair Net, using Amplitude Modulation, on 160 meters shortwave. Exact frequency is 1.945 MHz. Not bad for a 80 year old radio, I think the original owner W1KEK would be pleased to know that his treasured set, that he bought back in 1937, has returned to the air.
Very pleased with how this project turned out. The audio is very sweet, with some nice wide bandwidth for hifi AM audio. Just waiting for the electrolytic filter capacitors to finish the project.
National NC-101X. Testing the newly installed coil rack, with the bronze bushings and fabricated band indicator. Slides like it’s on glass, super smooth and low effort. Very pleased.
Here’s the solution to the sliding coil deteriorated bushing problem on the National NC-101X shortwave receiver. Unlike that other National products with “plug in” coils, like the HRO, the early NC-100 series use a “catacomb” coil assembly that slides inside the chassis to switch bands. A very ingenious design, and it works very well..for 80 years or so, and then the plastic bushings deteriorate from age and use.
The chances of finding new old stock bushings is slim to none, and even if they were available, they’d be just as deteriorated as the ones inside my receiver.
The solution, order a 1/2” to 9/16” bronze bushing from McMaster Carr, machine it down so the outside diameter is .512 inch, press in place using Loctite to retain, ream the ID so the shaft slides through the bushings freely.
I’d like to thank Marc KA2QFX for his very gracious and kind skills in the machine shop, machining the new bushings to fit properly into the sliding coil form.
After two long months, I can finally see the end of the NC-101 project in sight.
National NC-101X Project – Update
Fabricating a new band indicator became a necessity since spare parts for a 80 year old radio are just not something you can find at your local Radio Shack, if you can even find a Radio Shack.
So the old sheet metal, aluminum actually, band indicator, which provides a white dot in each of the band windows as the coil rack moves, was literally falling apart. Given the flimsy nature of the failed unit, I almost wondered if someone made this one.
So, one of the final steps on this project, now that the bushings are installed in the moving coil housing, was to fix or fabricate a new band indicator.
A trip to my local hardware store yielded me some nice 22ga sheet metal to start the project. Thin enough to work with on the bench with simple hand tools, yet rigid enough to last another 80 years. To get the correct form, I straightened the old one out, and used it as a template for the new replacement, scribing around it.
Carefully I trimmed it out, and then used a file for the final shape and deburring. Several coats of white Krylon did the trick.
Better than it was before, better, stronger and faster.
Tonight, Radio surgery.
1937 National NC-101X shortwave receiver.
Replacing 80 year capacitors.
Four down, seventeen to go.
Making ready for another 80 years.
Progress continues tonight on the National NC-101X project. First real desoldering and parts replacement work. Remove and replaced dry rotted old line cord and chassis feed through grommet. Installed new a three wire line cord, with grounding chassis, for electrical safety.
Tomorrow evening I start with replacement of the old wax paper capacitors, 21 total. Then onto the replacement electrolytic, reinstallation of the moving coil assembly, paint some Extend rust convertor on the bare chassis spots, and finish off with an alignment.
Had a few minutes this morning to get Scott W9WFA’s old National NC-101X out of storage and onto the new 1930s station desk. I’ll be moving the other 101X over once the restoration is finished, but it’ll be on the workbench for a bit, so time to fire up something else.
Listening to 40 meter CW on the National NC-101X receiver with the green “magic eye” tuning indicator. Bands are pretty lousy this morning, much static.
Transmitter is a MOPA (Master Oscillator Power Amplifier) built by amateur radio operator AB9ZG, modeled after one of the early Aero designs.
CW “Bug” (keying device for transmitter) is an early Vibroplex “Zephyr” model built in New York City. Believe this belonged to my Elmer Dick W2UJR. “Cans” (headphones) are vintage Brandes “Superior” model, built also in New York City in the late 1920s or early 30s.
Antenna is a traditional balanced feed line 160 meter dipole up about 50’, right on the coast.
Photos on wall are of a teenage ham radio operator from the 1930s who lived in Kennebunk, Maine. The other of some young radio hams from Syracuse, NY in a home built ham shack.
73 DE Bruce W1UJR
I removed the sliding coil assembly, often called a “catacomb coil” for cleaning and service. Needed it too, 80 some years of dirt, and old grease build up make it a mess.
Removed the coil sets, used a sharpie to id the location with small dots, and threw the aluminum housings, top and buttom, in the dishwasher. Worked like a charm, the reassembled, and carefully cleaned each coil set, and wiped down the pins with Deoxit. Lubricated the shaft that it slides on, and cleaned on the old nasty hardened grease out of the gear drive on the front. Tomorrow I have to paint the white band indicating tab, and reassembly. Or, I may go after the recap work first, the old wax paper caps aren’t too bad with the catacomb coil set out. Only a total of 21, should be an afternoon’s worth of work.