Live To Air – National NC-101X

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.

Replacing Coil Housing Bushings – National NC-101X

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.

Tonight Radio Surgery – National NC-101X

Tonight, Radio surgery.
1937 National NC-101X shortwave receiver.
Replacing 80 year capacitors.
Four down, seventeen to go.
Making ready for another 80 years.

– Bruce



Estate Planning – Some Thoughts About Radios and Plows

The following is a reply to a friend via email, about the offer of a set from my hometown of Buffalo, NY.
It’s something that has been on my mind the last few years, he just provided the opportunity to share it.
– Bruce 


Some Thoughts About Radios and Plows

Hi Bob,

A long answer to a simple inquiry, please excuse, I thinking out loud here.

As tempting a radio set from my old hometown of Buffalo would be, I’m kinda of at radio saturation right now. Still picking up the selected home brew set or rig, National and Gross Radio items, and ocassional parts, but I’m starting the long process of culling the herd.

Since I was first licensed in 1994, so many times at a hamfest I’d see that perfect project, “rescue it”, and bring it home to the radio barn for that moment in the future when I was “retried and had time to work on it”. I realized two things, one I’m not likely to retire, life is too interesting, and I love learning, two years ago started a second career in Emergency Medical Services (EMS) as an EMT. My diagnostic skills, honed over the years on car service and radio, serve well, its just a systems approach to assessment and diagnostics, and then developing a treatment plan, same thing I do every day at work. Unlike the radio or car world, I’ve only got two models to master as an EMT, and neither has changed much in a thousand years.

I’m pretty young at 53, and blessed with good health (and a wife who keeps me so), but having helped more than a few friends who have become silent keys deal with the estate, I know first hand what a burden some radio collections can be. All of one’s beloved radio gear, parts, tubes, lovingly curated over a lifetime, sadly so often becomes a burden, and ends up in the dumpster. My own Elmer’s gear, beautifully hand built transmitters, deserving of a place in a museum, suffered that fate.

I don’t want to focus on my own mortality, and I know well where I’m going after I pass on, but the fact of the matter is things happen. Working as an EMT in EMS I see that every day.

What makes me sad is so many of the young folks today, whom I imagined giving some of my radio gear on to, have zero interest in radio. It’s Facebook, the internet, instant message….I guess can’t fault them, it’s likely the same excitement that you and I had tuning in that shortwave broadcast station late at night, so many years ago.

I used to plan to donate all my gear, once friends had first dibs, to the Antique Wireless Association, but lately I’m having second thoughts about that. Not sure they want it, can use it, or if it will even be on display. My other plan to was to offer it some younger local hams, budding radio amateurs, but they seem as scare as hen’s teeth.

A few weeks back I read an article in the news about the children of some older folks rejecting the inheritance of their mother’s prized tea cup collection. The essence of it went like this, the mother had spent most of her adult life collecting special tea cups, antique tea cups, painted tea cups, imported tea cups, you name it. The mother, having amassed this collection at great effort and not inconsiderable cost, understandably thought her children would be as delighted with it as an inheritance gift. Turns out the new generation views collections of anything, tea cups, old books, and I guess even radios, as “burdens”. Who knew, guess that explains why younger folks are not as excited about my offer of vintage ham radios.

I’ll share with you an analogy that has haunted me for the past few years. I’m reminded of growing up on an old farmstead, complete with barn, farmhouse, and old farm equipment sitting outside. Growing up I vividly recall an old horse drawn plow sitting on hill near the barn. It was next to a stream, by the garden, and as children we played on that plow. As teenagers and adults we watched it dissolve, over the next two decades, into the fields it once plowed. The farmer that spent his hard earned money to buy that plow was undoubtedly quite proud of it, and I’m certain he treasured it, never thinking it would be left to weather the elements. Unfortunately time, and frankly utility of use passed it by, and it was left rust and decay by future generations. Of the millions of plows like that made, our current society only valued a few that were to be placed into museums.

I’ve got to wonder if the story of the old farmer’s plow is to be the fate of my radio collection, of the sets that I and others once prized, chased, and restored with loving care. Sets we operated, and obtained countless hours of joy and satisfaction with and from. Radios that somehow represented a time capsule of our society, a snapshot of a time gone by.

I’m currently restoring a National NC-101X, which had been purchased in 1937 lovingly cared for for 75 years by the original owner, but after his passing, the son and grandson had no interest. Nor did they have interest in the impressive collection of old radio and automotive books and parts he had collected over the years, they were placed outside on the lawn to be given or thrown away.

In the past I spent nearly a year each restoring a Gross Radio CP-25 transmitter, and another year restoring a home brew TZ40 rig. I can’t begin to count the hours I spent. The parts cost and the powder coating were minimal in comparison to the long, and late hours I spent in the barn documenting, researching, disassembling, and rebuilding those sets. They turned heads, no doubt, won a Matlack Award at the AWA Convention, but other than that, no one is interested in them, the average person on the street would think them “old radio junk”. And after I go onto my reward, I expect they’ll be…well I’m not sure.

I’m starting to think that reward, the real value in these Herculean efforts, and even in the rigs or sets themselves, is in the joy they brought me during the process, the lessons learned, and the friendships made. I’m reminded of a quote from Sir Winston Churchill, “Every day you may make progress. Every step may be fruitful. Yet there will stretch out before you an ever-lengthening, ever-ascending, ever-improving path. You know you will never get to the end of the journey. But this, so far from discouraging, only adds to the joy and glory of the climb.” In less eloquent words, “The joy is in the journey.”. And I’m thinking out loud here Bob, that may be, just may be, the best joy of all…

What do you think?


National NC-101X Project – Status Update

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. 

Collins 30K Series Transmitter Data Site

Collins 30K Series Transmitter Data Site

The purpose of this site is to act as central resource, or clearinghouse, for information, schematics, images, and tech tips on the Collins 30K series of transmitters. Many have been very generous over the last year, sharing tech information, scans of Collins docs, and service information with me, and this is my effort to give back to the 30K community. Thanks to John Dilk K2TQN efforts, the story of my 30K-1 station appeared in John’s “Vintage Radio” column in QST during late 2007. Since that time, I’ve been sent numerous images, photos, and stories from other hams about the 30K series. You can view the complete story at

W1UJR StationOne of the greatest challenges I faced with the restoration of my 30K-1, and now with the 30K-4, is the lack of information. I felt collecting all this information which has been graciously shared with me, would be helpful to other 30K owners, and hams. Unfortunately much information have been lost over the preceding 60 years since the first 30K rolled off the line at Collins Radio. This site is an effort to capture, and share, what remains.

Let me begin with a few words about the 30K series. I have been a Collins fan since I was first licensed in the 1990s, but really fell in love with the 30K when I viewed one at the home of a fellow ham who owned the commercial version of the 30K-1, known as a 30K-5. Very similar in design, the 30K-4 and 5 are commercial models offering two discreet tank circuits for rapid frequency changes but lack the band switching arrangement of the 30K-1.

The 30K series was designed by Collins engineer Warren Bruene in 1945 and was first offered for sale the following year. It was, in some way, a “Hail Mary Pass” for Collins as the war contacts were drying up, and yet amateur radio operation was still banned during wartime. Collins forecast a pent up demand from the return of GIs from the war, and with the elimination of the wartime ban on amateur operation, hoped the 30K would fill the gap. Sales were somewhat limited as the 1946 cost of the 30K-1 transmitter and 310A exciter was $1450, the equivalent to approximately $15,000 in today’s dollars. According to Jay Miller’s, KK5IM, excellent publication, “The Pocket Guide to Collins Amateur Radio Equipment 1946-1980”, less than 100 of the 30K-1 are known to have been built, and few survive today, making the 30K-1 series a rare bird indeed. Less accurate records exist on the commercial variants, suffice to say they are not at all common.

Visually, the 30K transmitter series are most impressive to behold, housed in a cabinet 5 ½ feet tall, finished in black wrinkle paint, and weighing over 350lbs, this is a big transmitter! The design of the unit is pure art deco; vertical and horizontal chrome accent strips, a large window for viewing the 4-125 final tube, and a most impressive meter panel at the top of the cabinet, also housed behind glass. Looking every inch a serious transmitter, the 30K is of robust construction along the lines of commercial broadcast gear. Emission modes are CW and Fone (AM), with the plate input power given as 500 watts on CW, and 375 watts on AM. The 30K-1 offered coverage from 80 to 10 meters using two plug-in output coils. With a tube compliment of 11 tubes in the transmitter, and 10 tubes in the 310A exciter, the 30K station as much a delight to operate, as it is to look at.

In closing, my thanks to those who have taken the time to send in photos, scans, stories, or to share their experiences over the years, please feel free to contact me or forward information which you feel may be of value or interest to other 30K owners.

73 Bruce W1UJR

Collins 30K1 – Restoration Visual Essay

Collins 30K-1 Transmitter Restoration

The Cleaning, Restoration and Service of a Collins Time Capsule


Shipping a 400 lb transmitter across the country is no easy task, but thanks to a
good packer and BAX Airfreight it arrived safe and sound in just two days!

You can’t use Styrofoam peanuts with these heavyweights, nothing less than high
density packing foam will do the trick!

RF Deck

The 30K-1 RF Deck, with a W7MGA mod, the DPDT knife switch attached to the
bandswitch. MGA was using multiple antennas and his implementation of a
switching network was both elegant and easily reversible. For my purposes, a
single antenna fed with balance line, I removed the switch. Thankfully he had
left the bandswitch connectors hanging on a loop of wire on the inside of the
cabinet, it was simple to reinstall for a single output.

The one and only casualty of the cross country move were the four porcelain
standoff insulators which attach the Output Network to the front cabinet. It
would appear that the inertia of the moving was too great. Thankfully my
junk box yielded four perfect spares!

The back of the meter panel and top of the RF Deck, prior to cleaning work.

The removed Output Network, prior to cleaning. Note plug in coil set on the left
side of the air variable cap, I have both the low and high band sets, so the TX
will cover 75 – 10 meters.

The Output Network after cleaning, a quick trip through the dishwasher did
the trick, washing away nearly half a century’s worth of dirt and dust.

The Front of the RF Output Network, note the insulation panels on the front of
of the unit. I assume these prevent arc over from the meter terminals.


The cleaning of the RF Deck. The large Johnson cap was removed and
disassembled for a through cleaning. Sure it takes time, but look at the results!

Modulator Deck

The Modulation Deck before and after cleaning photos. Love that 75th glow!
I did have a problem with the audio gain pot on the audio deck, the
unit was defective and a replacement 500K A/B pot was found and installed.

Low Voltage Deck

The Low Voltage Power Supply Deck, before and after cleaning. The unit
cleaned up very nicely, no repairs were needed, other than cleaning relay

HV Power Supply Deck

The High Voltage Deck, shown with the 866 rectifiers removed for cleaning.

The Cabinet

The 30K-1 cabinet with all deck removed and ready for cleaning.


30K-1 Tour After Cleaning

30K-1 Glow

Amateur Radio Station W1UJR

Yes Virginia, There is a Zorch God

*Circa August 13, 2005

Today in the middle of a FB QSO with K1MVP the plate blocking capacitor in my 32V crapped out.

Collins 32V Transmitter

This was evidenced by an immediate loss of RF, a loud hum and the telltale pegged plate current meter. Even my trusty old buzzard RF indictor, a large neon bulb JS lashed onto to my balanced feedline terminals, showed no glowage, a very bad sign. When something like this happens out of the blue, a thousand thoughts run through your mind. Is it the final tube, did I inadvertently hit some knob, did the modulator transformer give up the ghost? I quickly unkeyed the transmitter thinking my antenna relay had stuck, as Dowkeys sometimes do. A check of the relay showed that all was intact and the fault must lie elsewhere. Switching between bands or from Fone to CW had no effect, still a pegged plate meter. I considered that something may have happened to my antenna or feedline, but transmitting into the dummy load brought the same result.

I should mention that this was my Elmer’s, W2UJR – now a Silent Key, former transmitter, so the thought of some major failure made my heart sink. When I obtained the unit from Dick’s estate, I had brought it back to life by replacing a stubborn failed screen bypass capacitor on the 4D32 final tube. Since that time it had run flawlessly, despite the somewhat troublesome reputation of the 32V series. The unit had followed me from Buffalo when I moved to Maine and had become my backup 75 meter transmitter at the office. Rumor had it that Dick only ran it on CW as he did not care for the lack of civility on 75 meter Fone.

Ironically I had just been on the telephone earlier in the day speaking to my friend and fellow Collins enthusiast, Bill K2LNU. Bill shared that, after he had spent countless hours working on them, he was now seriously considering selling some of his Collins 32V transmitters because they were such a project to service. With that cheery thought in mind it was out of the cabinet with the 110 lb transmitter, an exercise which had become an all too common event.

I say common as for most of the proceeding week I had been working on a new acquisition to the W1UJR hamshack. A exceptionally recalcitrant Collins 32V3 which displayed a most troubling linearity fault with the Permeability Tuned Oscillator (PTO). It was only after multiple attempts to diligently adjust the linearity, as specified in the service manual, each involving a trip in and then out of the cabinet, that I discovered that the linearity simply could not be restored to the 50 year old PTO. A returned call from Collins guru Howard Mills W3HM confirmed this and I was informed that some years back Dallas Langford had discovered that the ferrite compound used by Collins in the PTO changed its molecular structure with time. So it seems that unlike wine, ferrite does not improve with age, hence the PTO would no longer track properly. As the PTO was a relatively recent invention at the time, Collins had no way of knowing of this during the initial design of the 32V series. Indeed its doubtful they anticipated their handiwork would still be in used half a century later, so no provision was included in the PTO design to compensate for the ferrite change. Anyway, back to our story.

With my failed 32V on the bench I did a quick check of the mica capacitors used in the output loading network. In the 32V series these capacitors are always suspect and have a high failure rate, especially when used with non-resonant antennas. Still, each of the mica loading capacitors checked fine with the DVM, not a fault among them. This meant that I had to dig digger, or in other words this going to take some time. The next step was to remove the plate connector from the top of 4D32 final tube and see what happened with the plate current. I suspected that the tube had perhaps experienced some catastrophic internal failure. Yet again I was stymied, the tube tested out fine, and I still found pegged plate current with the tube plate capacitor removed.

Curiosity got the better of me and I then removed the tube completely from the socket and applied plate current, same result, pegged plate meter. Since the final tube was entirely out of circuit and I still had excessive plate current, as a quick test I removed the coax connector from the rear of the transmitter, Eureka, plate current was now at zero. I now knew that a fault existed in the output network, but where? The 32V series is one of the most tightly packed and difficult transmitters which I have worked on. Despite Collins excellent manuals and documentation, service on these units requires both a great deal of patience and dexterity.

At that very moment I was on the air with Larry NE1S, yes, multitasking. Carrying out a QSO and checking for plate voltage may not be the wisest course if one wants to enjoy a long life. However, in this case it had a payoff. I described the fault to him and explained my findings. Larry confidently asserted that, given my symptoms, it could only be one thing, a failed plate blocking capacitor. With the transmitter keyed, I checked for plate voltage at the RF connector, 890 volts! Sure enough, the plate blocking capacitor was allowing full plate voltage to show up on the output of the antenna! Instead of blocking the plate DC, it was in fact conducting it! Not exactly a safe thing, in fact it was downright dangerous. If I had not had the tuner in line, full plate voltage would be applied to the antenna feedline and leads, ready to zap some unsuspecting passerby. So with that discovery, the next logical step was to unsolder one lead of the plate blocking capacitor. A resistance check showed that my plate blocking capacitor was now a resistor, reading about 23 ohms on the trusty Fluke meter.

The capacitor in question is one of the older square mica capacitors that you see in transmitter output networks, with two mounting holes and solder tabs on the end. This capacitor in particular was rated at 2500 working volts and 5000 test with a value of .001. It displayed no visual sign of failure, no burn marks, case swelling or discoloration. For all intents it looked like a good capacitor, in fact it looked new.

Collins 32V Transmitter

As I mentioned before, the 32Vs are a real challenge to service.
If you have ever had the joy of replacing the plate blocking capacitor in a 32V, heck if you have done any service at all on these 32V series rigs at all, you know what a project this was. A quick check of the spare parts bin yielded the needed capacitor, those $5 coffee cans of parts dug out from under tables at hamfests sure do pay off.

Failed Collins 32V Plate Blocking Cap

However, finding the capacitor was the simple part. It took me nearly 90 minutes to remove two screws and solder connections on the failed capacitor and install the replacement. The Collins design team had conveniently located the plate blocking capacitor about 3/8 of an inch from a large wound loading coil. Since access to the Phillips head screws which retained the plate capacitor was simply not possible with a screwdriver, I had to settle for turning each screw 1/8 of a turn at a time with a pair of needle nose pliers. So to say things are tight inside the 32V is a major understatement.

Failed Collins 32V Plate Blocking Cap

Curiosity and abundant spare time got the better of me and I decided to open the defective capacitor up for an examination. After all, things that zorch out are often pretty interesting to look at. By examining the exterior of the capacitor I could see a manufacturing molding line around the upper edge of the case.
Using a bench grinder, I carefully ground away the edges of the case, removing the bonding joint of the upper and lower sections. A small chisel was then used to split the case halves open for a visual inspection. It was quickly apparent what had failed on the capacitor. The center section of the mica had been carbonized from end to end, essentially creating a carbon composition resistor. No wonder at all that I measured 23 ohms of resistance across what was once a capacitor.

So, can those more knowledgeable than I, which is probably a good number of you out there, offer up an explanation why this occurred? Operating plate current was normal, perhaps a tad conservative before the failure as this is my Elmer�s former TX and I run her lightly.

Did the 50 years finally catch up with the capacitor, or did the Zorch Gods just decide it was time? Are there other causes for this? If so I’d like correct them so I don’t have to replace another.

Bruce W1UJR

Why Not A Wire Loop Antenna?

This was written back in the last 1990s when I lived near Buffalo, NY, in a suburb that had zero lot lines, and little space for antennas. A vacant field in back of my home became the antenna field for my station.
– Bruce W1UJR

As some of you may know, I am an advocate for wire antennas, and have been experimenting with horizontal loop antennas for HF work. I am currently running a 160-meter full wave loop that is suspended about 30-40 feet off the ground. Although the feedline for my loop is currently coax, in future installations I am considering the use of balanced, or open wire feedline for reasons of low loss, which may be the topic of a future article.

One caveat that I should mention before I start. The majority of my operating, and hence my observations, is on the lower bands, typically 160 through 40 meters. At these frequencies, the use of a yagi antenna is often impractical due to size constraints. If you do operate on 20 meters and up, you may find a yagi a better choice than the loop for its gain and directivity. That being said, what holds true for a loop at 160 meters, also holds true at 10 meters, so even those who operate on the “high bands” should find something of interest here.

Wire Loop Antena

The loop antenna has a long and distinguished history, but is often overlooked in light of the current focus on dipoles. However, loops do have some rather significant advantages over a dipole. Since the design of a loop is typically a circle or square form, the need for a long straight run of wire used by a dipole is diminished. A loop is quite forgiving, and perfect symmetry is not essential. It is necessary only to hang it in the configuration providing the greatest enclosed area. As such a loop can be strung up in unusual places and still perform well. Treetop suspension is ideal, but you’ll be surprised how well it works just lying on the roof where nobody sees it. Unlike a dipole that must be center fed, the loop can be feed at any point, allowing a most flexible feedline arrangement.

A loop is an efficient broadband radiator, even when low to the ground. The majority of the amateur bands are harmonically related, typically the 1st harmonic. This is where the loop really shines, as a loop is easily tuned to resonance on all even harmonics of its fundamental frequency. A dipole by contrast is easily tuned to resonance only on its odd harmonics. A loop starts out with 1.2 dB of gain over a dipole on its fundamental frequency, and gains are even higher if the antenna is less than a quarter wave off the ground because that is where the dipole efficiency plummets. For example, in my location my loop is quite close to the ground, only about 30-40 feet up at the highest point. Nevertheless, the antenna both tunes, and transmits just fine.

A loop’s gain over a resonant dipole increases with the increasing frequency of operation, so when used on its harmonics, a loop’s signal advantage over a dipole likewise increases. For a horizontal loop, that’s not the end of the good news, because as frequency rises, radiation angle drops lower and lower, producing increasing DX results that can rival a complex multi-element beam mounted on a 100-ft tower.

The venerable loop is easy for your tuner to match, even when fed with coax. The feedpoint impedance of a loop never gets as high or low as with an antenna that has free ends. Even a 40-meter loop can offer full 80- 10-meter coverage. My 160-meter loop allows me to both receive and transmit from the 160-meter band to 10 meters. Signal reception is also quite good with a loop for a number of reasons. As it is a terminated antenna, it is much less susceptible to atmospheric and man-made noise. As the majority of man-made noise is vertically polarized, the horizontal polarized loop can reduce electrostatic noise as much as 26db when compared to dipoles or verticals, so it is great for noisy RF areas.

The theoretical feedpoint impedance for a full wave loop antenna is approximately 100 ohms, but this does change, and is dependent upon antenna height above ground, near-by structures, and ground conductivity. When used with a 2:1 balun this presents a good match to the typical 50-ohm coax. Due to the low height above ground of my loop, I used a 4:1 balun which seems to offer a wider tuning range (lower Q). With the use of a transmatch (antenna tuner) I am now able to use my loop from 160 to 10 meters.

Loops can be either a 1/2 or full wavelength long. The formula for a full wave loop antenna is as follows: Length (feet) = 1005/fMHz. For example, a loop for the frequency of 3.800 MHz would be calculated as follows: 1005/3.8 = 264 feet. You can now divide 264 by 4 to obtain the length of each of the four legs of the loop. 264/4 = 66 feet each leg.

So next time you need a new antenna installation, consider the time-honored loop. Simple and inexpensive to homebrew, you can put the money you saved toward something really important…like a trip to this years Dayton Hamvention!

-Bruce KG2IC