The MeinEnigma Enigma Machine Kit - Assembly

In this post I'll continue the discussion of the MeinEnigma kit, this time describing my experience in building the kit.

It should be noted that this was for a beta version of the kit. Some changes to the construction method, assembly procedure, and physical parts are planned to be made before the kit goes into general release.

I was the first customer for a beta release of the kit; my unit was serial number 16. As I have a lot of experience building kits and live in the same city (Ottawa, Canada) as the developer, I was a good candidate to try out an early kit and give feedback on it.

This was the hybrid version of the kit, with all through-hole components with the exception of three SMT ICs that need to be soldered.

The kit came in a box with a nice printed label. All parts were included with the exception of batteries.

The PCBs are double-sided with plated-through holes, soldermask, and silkscreen on both sides. The design is somewhat unique in that there are pads for both SMT and through-hole parts.

All the parts come organized in small bags with identifiers on them that match the instructions in the assembly manual. This goes a long way in minimizing any errors in components or needing to identify them.

I made an inventory against the provided parts list and confirmed that all parts were there. The parts are grouped into five sub-assemblies that are built separately (corresponding in most cases to different circuit boards). I separated the parts for each assembly.

One of the reasons this was still considered a beta kit was that the assembly manual was not yet complete. It was in pretty good shape though, with detailed instructions and pictures for all the steps of the construction.

Lamp and Key Board

Construction started with the lamp and key board, the largest PCB but one without too many parts - mostly the 26 keyboard keys and 26 LEDs.

The first step was to install the HT16K33 IC, a 28-pin SMT device. I was a little anxious about this as I have only limited experience with soldering SMT devices by hand. Before installing it I refreshed my memory of SMT soldering techniques by watching some YouTube videos and doing some practice with some SMT parts on a piece of bare copper PCB.

As well as using a temperature controlled soldering iron and small diameter solder, I used some flux paste, applying it to the pads on the board. The initial alignment of the IC is critical. You solder one corner pin, get the chip correctly aligned, then solder the opposite corner. It is important not to proceed with soldering the remaining pins until it is correctly aligned. Soldering the remaining pins should then be quite easy. In the past I have done SMT soldering without paste; I believe the solder paste really helped the solder flow and avoid solder bridges between pins.

I used a digital multimeter in continuity test mode to verify that all the IC pins were making contact with the board and that there were no shorts between pins.

The assembly continued with two diodes and 13 resistors. These were through-hole parts. The SMT version should also be straightforward to solder. Often the biggest challenge with SMT is being able to identify the parts and avoid dropping and losing them.

Next there are 26 keyboard switches and 26 LEDs to install, and then some connectors. The last step is to install the four standoff feet and then assembly of this board is complete.

Encoder Boards

The four wheels, known as rotors, use rotary encoders. Each encoder is installed on a small custom PCB which is later connected to the main board using a four pin connector and a plastic bracket. Each board needs to have the encoder and connector soldered in. They are then set aside until final assembly. This step went smoothly.

Main Board

The main board has the most components. It starts with some through-hole components including fuses, a diode, and resistors. Two DIP ICs are installed using sockets. There are a number of connectors to install, and then an Arduino Nano (or equivalent clone) which is mounted on headers so it can be removed if needed. A sound board is installed, then the DC-DC boost convertor which is on a small PCB.

Other parts installed are a large filter capacitor, four keyswitches, a small speaker and piezo buzzer, the "big red switch", rotary function switch, and the four alphanumeric LED displays.

Construction wraps up with the battery holder and real-time clock module.

You can now complete the mechanical assembly of the main board by installing the standoff feet and assemble the rotors by inserting the wooden disks on the encoders, and then installing each of the four rotors to the main board using a plastic bracket.

Incidently, the four rotors are made from wood and laser cut. This is one of the features that makes the kit a more realistic replica of the original Enigma than some designs that just use buttons.

At this point the two PCBS can be connected using a ribbon cable and the system can be tested. Before doing so, I carefully inspected everything for opens, shorts, and incorrect components or orientation.

Plugboard and Cables

There is still one PCB to be assembled, the plugboard.

It has two more SMT ICs to solder. I wasn't entirely pleased with the job I did on the first IC on the lamp/key board, but I must have improved with practice because these ICs were better aligned. I did have to reflow the solder on some of the pins on the SMT ICs to ensure all were making good connections.

This board also has 26 suppressor diodes, a connector, and 26 banana jacks to install (the latter do not need to be soldered).

The plugboard also includes 10 patch cables. These are assembled by cutting the wire into 30 cm lengths and installing a banana jack on each end. The cloth-covered wire that is supplied is a nice touch and looks similar to the wiring typically used in a real 1940s era Enigma machine.

Final Assembly and Testing

The plugboard physically connects to the lamp/key board using some brackets and electrically connects with a small ribbon cable. This completes the assembly. You are now ready to install batteries and test the unit. The Arduino comes preprogrammed with the software, as well as the microSD card containing the sound files for audio output.

In general, I found that assembly process was straightforward despite the assembly manual not yet being complete.

There was one issue with the LEDs. It seems in the last batch of parts that were received, the manufacturer changed the orientation of the LEDs so that they don't follow the standard convention as indicated by the longer and shorter leads and flat side on the component.

Fortunately it didn't take long to figure this out, and it was relatively easy to unsolder and reinstall the LEDs with the correct orientation. I also had one bad LED which did not work at all.

It seems that there could be a reasonably high failure rate with these LEDs, so Peter Sjoberg will be individually testing all the LEDs shipped in the kits to avoid any problems (as well as correcting the assembly procedure).

Summary

Building this kit was a lot of fun. I took my time, and built it in three sessions of a few hours each, over a weekend.

The kit should be buildable by anyone with a moderate experience in soldering. If you aren't experienced with SMT soldering you could opt for the through-hole version of kit where the SMT parts are already installed.

In a future blog post I'll go over the operation of the MeinEnigma, its features, controls, and examples of how to encrypt and decrypt messages.

References

1. MeinEnigma website: http://meinenigma.com
2. MeinEnigma YouTube channel: https://www.youtube.com/channel/UC3s44doR_q1fKQ4ZMUeAlHQ

The MeinEnigma Enigma Machine Kit - Overview

Introduction

I recently had the opportunity to build a beta version of a new kit, the MeinEnigma, a replica of the famous Enigma cipher machine, designed and offered by Peter Sjoberg.

In this, and some future blog posts, I will describe the kit, how it works, assembly of the unit, and the hardware and software behind it.

What Was The Enigma?

The Enigma machines were a series of electro-mechanical encryption devices developed to protect commercial and military communications. Most notably, they were used by Nazi Germany during Word War II.

Due to some weaknesses in the design, as well as procedural flaws in how they were used, the Allied were eventually able to find a way to break the encryption (which had to be done every day as the encryption settings were changed daily), which is believed to have been a significant factor in winning the war. Much of this work was done in England at Bletchley Park by a team that included Alan Turing, someone well known to most computer scientists. This story has been described in many books and documentary films, including the popular 2014 film The Imitation Game.

While as many as 100,000 Enigma machines are believed to have been made, most were destroyed and only a few hundred exist today. An original machine can be worth well over $100,000 and most are in museums. I've personally seen two: one in the Canadian War Museum in Ottawa and another in the Spy Museum in Washington, DC.

That puts a real Enigma machine outside the reach of most collectors or enthusiasts. There are software simulators, but it is more fun to have a device which physically looks and works like the original Enigma machine.

Kit Features

MeinEnigma is an electronic version of an Enigma machine, with a similar size and controls to the original, but using modern electronics rather than mechanical parts to implement the encryption functions.

The design is based around the popular and low-cost Arduino microcontroller, allowing the software to be easily modified by the user. The software is open source and can emulate a number of different models of Enigma machine. As well as the controls on the board, the unit can be controlled through the Arduino's USB serial interface.

It has a similar physical size and controls as the original Enigma machine. It has a 26 alphabetic keys and 26 indicator LEDs as well as four rotatable rotors that are similar to the original Enigma.

It also has a four character alphanumeric LED display with four buttons and a function switch. There is a speaker which is used for sound output, including authentic rotor rotation sounds and speech output for the encoded characters and operating functions.

A buzzer can optionally produce Morse code output (the original encoded Enigma messages were sent by radio using Morse code).

A real-time clock chip with battery backup allows the system to be used as a clock when not in use for encryption.

Like the original Enigma, the front panel features a plugboard with 26 positions and 10 patch cables. It can be powered by 2 AA batteries or from the USB port on the Arduino.

The unit will be sold as a kit that the user assembles. The kit includes all parts and should be buildable by anyone with some basic experience with soldering and identifying components.

It is built on three printed circuit boards (PCBs) that are interconnected by cables.

The kit is planned to be sold in three versions. The SMT version will use all Surface Mount Technology components (with the exception of parts like the Arduino, sound module, and real-time clock). This will require experience with SMD soldering, which is doable by hand using a soldering iron. The TH version will use through-hole components, with three ICs that are only available as SMT parts being already soldered in for you.

A hybrid version be the same as the TH, but the user will need to solder in the three surface mount ICs. This is the version I built. All three versions use the same PCB.

The kit will include several manuals. While this could still change, my understanding is that it will include an Assembly Guide, User's Guide, Enigma History Guide, and a Modification Guide.

Summary

There are some other Enigma kits on the market, or that have been offered in the past. They range from electronic versions like the MeinEnigma, to accurate mechanical replicas of the original Enigmas which can sell for tens of thousands of dollars. I haven't personally tried any of them, but this kit offers a number of advantages and nice features, most notably a design which features a similar size and rotors, keyboard, lamps, and plugboard that resemble the original Enigma machines. The Arduino controller makes it very easy to modify the software. It also has support built in for future expansion and user modifications.

I hope as the number of users of this kit expands, a community will form around it to enhance the software, support each other, and find interesting applications for it.

In the next blog post I plan to cover my experience assembling the kit.

References

1. MeinEnigma website: http://meinenigma.com
2. Source code: https://github.com/lpaseen/meinEnigma
3. Facebook group: https://www.facebook.com/MeinEnigma
4. Wikipedia article: https://en.wikipedia.org/wiki/Enigma_machine

The Superboard ///

My latest retrocomputing project is building the Superboard /// computer kit by Briel Computers.

It is a replica of the Ohio Scientific Superboard II. The original SuperBoard II was one of the first affordable computers that featured a full keyboard, video output, BASIC in ROM.

At a price of $279 in 1979, it was an amazing bargain at the time when compared to systems like the Apple II that retailed for about $1300. For that you got an assembled board but needed to add a 5 volt power supply, monitor or TV set and RF modulator, and cassette tape for storage.

I owned one that I purchased in 1979 and it was my first computer. With it, I learned BASIC and 6502 machine language programming.

The SuperBoard /// is Vince Briel's replica of the original SuperBoard. It features a 6502 processor, but simplifies the design by replacing a lot of logic chips with a Propeller CPU. It is software compatible with the original system.

It is sold assembled or as a kit. I opted for the kit.

To date I've made three YoutYube videos on the kit, covering unboxing, assembly, and basic operation. They can be found on my YouTube channel.

I also have some files on my github account including a handy Quick reference, the OSI firmware including BASIC, and a port of my JMON monitor program. The Visual Monitor program that I entered a few months ago also works.

Below are some useful web links.

My Stuff:

• https://www.youtube.com/user/jefftranter
• https://github.com/jefftranter/6502/tree/master/asm/BeyondGames
• https://github.com/jefftranter/6502/tree/master/asm/OSI
• https://github.com/jefftranter/6502/tree/master/asm/docs
• https://github.com/jefftranter/6502/tree/master/asm/jmon

Ohio Scientific:

http://en.wikipedia.org/wiki/Ohio_Scientific
http://classiccmp.org/dunfield/osi/index.htm
http://home.cmaaccess.com/~jerrytravis/
http://oldcomputers.net/osi-600.html
http://osi.marks-lab.com/
http://osiweb.org/osiweb/software.html
http://superboard.com.sapo.pt/
http://uk101.sourceforge.net/
http://www.6502.org/
http://www.6502.org/users/sjgray/computer/osi-c4p/
http://www.binarydinosaurs.co.uk/Museum/ohio/index.php
http://www.classic-computers.org.nz/collection/challenger1.htm
http://www.compukit.org/Compukit.org
http://www.cse.dmu.ac.uk/~mward/martin/software/index.html#UK101
http://www.gifford.co.uk/~coredump/uk101.htm
http://www.historyofpersonalcomputing.com/osi-superboard-i-and-ii/
http://www.lysator.liu.se/adventure/machines/OSI.html
http://www.neoncluster.com/projects-osi/osi-cassettes.html
http://www.old-computers.com/museum/computer.asp?c=572&st=1
http://www.old-computers.com/museum/computer.asp?c=860&st=1
http://www.oldcomputermuseum.com/superboard_2.html
http://www.osiweb.org/
http://www.pagetable.com/?p=43
http://www.pagetable.com/?p=46
http://www.pc-history.org/ohio.htm
http://www.technology.niagarac.on.ca/people/mcsele/OhioScientific.html
http://dabeaz.blogspot.co.uk/2010/08/using-python-to-encode-cassette.html
http://searle.hostei.com/grant/uk101/uk101.html
http://www.slideshare.net/dabeaz/using-python3-to-build-a-cloud-computing-service-for-my-superboard-ii
https://www.youtube.com/watch?v=pB2t6xG2RzE

Superboard ///:

http://forum.6502.org/viewtopic.php?f=8&t=2487
http://www.brielcomputers.com/phpBB3/viewtopic.php?f=39&t=1627
http://www.brielcomputers.com/wordpress/?cat=39
http://www.brielcomputers.com/wordpress/?cat=41
http://www.retrothing.com/2014/06/superboard-iii-briel-recreates-another-1970s-microcomputer.html

Can Heathkit Make a Comeback? Yes, and Here's 10 Reasons Why.

Despite all the reasons I listed in my last blog post on why Heathkit could not successfully reenter the kit business today, I believe they still can. Here are some reasons why, and how, they could do it.

1. Reinvent yourself. Heathkit started as an airplane manufacturer, then got into aviation electronics. Then test equipment, amateur radio, audio, and computers. The company twice lost their president in airplane crashes and had to reinvent itself. The new Heathkit could and probably should be different from the Heathkit during the heyday of the past. There are many opportunities for products different from those that Heathkit traditionally offered. They need to think outside the box and come up with new ideas for product opportunities.

2. Leverage the Internet. The Internet means there is no longer a need for brick and mortar stores. No printed catalogues or advertising. The Internet means global markets. To be successful, Heathkit needs to adapt to the times. As just one example, the large effort to write assembly manuals could be crowdsourced by allowing users to edit and improve the manuals, much like Wikipedia. Support for building kits could be handled by on-line forums. People who are active in helping others in the forums could be rewarded with some type of badges, promotional items, or discounts on kits.

3. Buy some expertise. Buy out or recruit some successful small kit companies, like Briel Computers, for example, or license their designs. Expand them in size to offer better ordering, distribution, manuals, and packaging than a one person outfit can handle.

4. Fill a size niche. I think there is a gap between the small one-person companies and the large electronics firms that Heathkit could fill and be successful while still remaining small and lean.

5. Crowdfund startup costs. Get initial funding using sites like Kickstarter and Indiegogo. Take one good idea, maybe a new solid-state ham radio transceiver like a redesigned HW-8, that is internally a new design but has the original retro look. Fund the cost of getting it to market and get initial orders using crowdfunding. That revenue could then fund R&D for future products.

6. Steal ideas from successful competitors. The experts said you couldn't offer a kit that competed with commercial amateur radio equipment for price and features. Elecraft did it. They said the market for hobbyists is too small? AdaFruit is doing okay. Learn from the successes of competitors and adopt ideas that worked for them.

7. Partner and contract out. Sell through Amazon. Have someone else do kitting. Avoid the need for a big factory and inventory. Run the company as a virtual distributed organization with staff located world-wide.

8. Link it to education. There is a huge demand for learning materials for electronics hardware and software, as evidenced by products like the Arduino and Raspberry Pi. Leverage Heathkit's expertise in developing training materials and courses (one of the last areas where they were successful).

9. Capitalize on nostalgia. Offer some of the original kits again, even if only on the outside. Consider offering some vacuum tube designs. Make the assembly manuals look like the old ones, possibly offering a printed manual (rather than download) as an extra option when ordering a kit.

10. Build credibility and reward early adopters. Lots of people would like to see Heathkit succeed. Offer incentives to people who pre-order. Reward early purchasers and they will give you free marketing. Be open about plans for the future, and the keep promises you make. As just one example, why not make the legacy Heathkit manuals available as free downloads as a goodwill gesture and a sign that Heathkit is serious about coming back?

In summary, I believe Heathkit could re-enter the kit business if they adopt some of the ideas I've outlined here. It won't be easy, and the clock is ticking as the old Heathkit becomes a faded memory, but it can be done.

Can Heathkit Make a Comeback? No, and Here's 10 Reasons Why.

Last year Heathkit announced on their website  that they would be making a return to offering kits, placed an extensive survey on their web site, and held a Q&A session where they presented many ideas for kits that they hoped to offer in the near future. Little or nothing has been heard from them in the last few months. Here are ten reasons why I don't think Heathkit can successfully make a comeback to the electronic kit business.

1. Economics. There is a huge one time cost (often called NRE or Ron-Recurring Engineering cost) to bring a new product like a kit to market. You not only have to design a product that works, but it needs to consistently work when built by customers without sophisticated test equipment, you need to develop the assembly manuals, obtain sources for components, stock the parts, have expensive custom plastics and cabinets manufactured, and put all the right pieces in the kits without making errors. If Heathkit is going to sell a kit for, say, a digital multimeter, it will likely cost a couple of hundred dollars. Meanwhile, I can get an assembled, calibrated, and working meter at Harbor Freight for $5 or free with a coupon. In addition, unlike in the past, almost every product today relies on a software component, something that is very expensive to initially develop and needs to continue to be maintained.

2. Startup costs. Similarly, to get economics of scale to be profitable, you need to set up manufacturing, distribution, and agreements with component suppliers. I don't believe that the new owners of Heathkit have deep enough pockets. Are they going to open dozens of retail stores as in the past? When companies like Radio Shack are going bankrupt?

3. The market has changed. While there has been some resurgence, the hobbyist market (sorry, now it's called the "maker movement") is small. Ham radio users are ageing. Probably Heathkit's most popular kit of all time, the HW-101 transceiver, would not have specs that would interest modern hams other than some nostalgia buffs. No one today wants to build a stereo or TV set from a kit.

4. Changing technology. Most new electronic components are only available as surface mount technology (SMT) devices that the average user cannot solder. And forget about getting vacuum tubes in any quantity. Even if they could assemble it (or it came with SMT parts pre-assembled), the average user doesn't have the test equipment needed to test, calibrate or debug modern equipment.

5. Safety. Most kit companies shy away from anything powered by line voltage. It is too easy for the user to electrocute themselves. In the litigious North American market you can be sued if a customer hurts themselves trying to do something they were not explicitly warned not to do in the instructions, no matter how ridiculous. Many of the original Heathkits required aligning or adjusting the equipment under power. But limiting the products to battery operated or external power supplies will make it impossible to offer some of the most interesting kits. This alone could be a showstopper.

6. Too much competition. The market already saturated with established players like AdaFruit, Elecraft, qrpme.com, etc. Many of these are small, Internet-savvy operations with low overhead. Some are run by a single employee on a part-time, break-even basis.

7. The need to go global. In order to get a decent sized market today you have to expand beyond just North America. But this will introduce even more challenges in distribution. How about the famous Heathkit manuals - can they be economically translated into 30 languages?

9. Lack of goodwill. A number of years ago the Heathkit name carried some cachet, but it is now long past it's expiry date. Heathkit has been out of the kit business since the early 1990s, almost 25 years now. The in-house staff and expertise that Heathkit once had is now long gone (most are retired if they are even still alive). They can no longer rely on the Heathkit name to carry any weight with customers

9. Staffing. It is very difficult and expensive to find good engineering staff, especially those with the specialized knowledge to build kits. Technical writing is also expensive and a specialized task that can't be done by the engineers. It takes a long time to build up an engineering team. And will the best people want to relocate to Benton Harbor, Michigan?

10. Differing expectations. If you poll people it seems like everyone would like to see Heathkit come back, but all for different reasons. Some hams want to see the old kits come back, others want new state of the art kits. Some users want computers, robots, radio controlled equipment, and 3D printers. They all have different expectations, but any one of these markets is too small a niche for a viable business.

Given all that, in my next blog post, I will present ten reasons why Heathkit could re-enter the kit business and be successful.

Freq-Mite Kit Assembled

Today I received and assembled a Freq-Mite kit. It is a tiny 1.75 inch by 1.25 inch circuit board with a PIC that measures frequency and reports it in Morse code. You typically install it in a radio receiver or transceiver that lacks a digital display and use it to accurately report your frequency. You can program the IF frequency of your radio using jumpers so that it correctly adjusts for the IF offset. It also works with direct conversion receivers.

I ordered a kit, which sells for US$22 in USA and US$30 elsewhere, including shipping, and it soon arrived in my mail box. It has only about 20 components, all through hole, and I was able to assemble it in less than an hour.

The kit comes with all parts.

The assembled board, before inserting the PIC chip and wires.

Powering it up on the bench with a small speaker and RF signal generator, it accurately reported the frequency that was input to it.

Testing it on the bench.

I plan to install it inside one of my QRP rigs, probably the Heathkit HW-8 . I suspect I may have to order another one or two of these for other rigs that I own.

Heathkit GR-64 Restoration

My latest radio restoration project is a Heathkit GR-64 Shortwave Receiver. This was a low-end receiver made from 1964 to 1971 and originally selling for $39.95. It covers AM and shortwave in four bands and utilizes four tubes.

This one was acquired on eBay. Other than the usual scratches and small cracks around the plastic front panel, it looked to be in pretty good shape. It had suffered a bit in shipping with some tubes and the power transformer coming loose, but there did not seem to be any damage. It appeared to be complete, and when powered up it picked up several AM stations.

The shortwave bands didn't seem to be working well, if at all, and the S-meter was always off scale.

A check of the components showed that most resistors had drifted up in value, as is normal for the old carbon composition type. I replaced a few were 20% off or more. I figured that was the likely case of the S-meter problems, as it uses some resistors as a voltage divider to compare the AVC voltage to a reference value.

However, that did not fix the problem. I spent considerable time poking around, checking components and wiring. I tried swapping some of the tubes with known good ones from a Heathkit AR-3.

After lifting several resistors in the AVC circuit, there was still a resistance of about 60K to ground that should not be there and I could not account for.

The printed circuit board really had a lot of rosin flux residue on it. On a hunch, I scraped some of it off, and the mysterious resistance to ground went way up. After cleaning the board with alcohol to remove the flux, the resistance became too high to measure. The S-meter also started reading on scale. Lesson learned - flux residue can cause problems in high impedance circuits. Obviously this flux was there since the kit was built but whether it caused a problem from day one or only later, who knows.

The next problem was that it was dead on bands other than AM. Actually band D was working (poorly). There was no local oscillator activity at all on bands B and C. All the coils looked good. But I was seeing a low resistance between the local oscillator tuning capacitor and ground on bands B through D that should not be there, according to the schematic. The local oscillator frequency on band D was also way off.

After a bit of tracing of the circuit I found the cause: two wires that crossed were touching where there was insulation missing and were shorted. One was the antenna lead and the other was from the local oscillator. After pulling them apart, the local oscillator started running on all bands.

I did a full alignment and it all went well -- I could align each band on each end of the dial. Because of the low 455 KHz IF frequency you have to watch out that you don't align to the image frequency that is only 910 KHz away from the correct one. The manual mentions this in the procedure, but I almost did this on one band and thought at first that I could not get it to align correctly.

Restoration is now almost complete. The S-meter is still off scale for no signal, so I expect to have to tweak some of the resistors in the circuit.

The limited testing I have done indicate that the radio is reasonably sensitive and can pick up lots of shortwave broadcast signals with a decent antenna. It would not be very suitable for amateur radio, as bands like the 40 meter ham band only take up a small portion of the dial. The BFO is also hard to use as it is not very stable and interacts with other controls, so it could be used for strong CW signals but would be frustrating for SSB.

I plan to make a YouTube video on this radio as I have done for the other models I own, so watch for that in the coming weeks.

Toroidal Inductors

I was reading through my 80th anniversary reproduction of the first  Radio Amateur's Handbook, published in 1926. At the back are advertisements from electronics companies.

An ad from Cardwell Condensors lists some of the contributions the company made to radio and electronics, such as "the first commercial Neutrodyne". One of them caught my eye:

"The first Toroid (abandoned due to inherent electrical defects in this type of coil, impossible to overcome!)"

Those of us who have been around electronics probably think of toroidal inductors as a relatively new phenomenon. When I started in the 1970s and 80s most inductors were wound on cylindrical cores, and back in the 1920s and 30s the most common was air wound inductors, often featuring exotic methods of winding and ways to shield or arrange coils to minimize interference with each other. But for the last couple of decades, the doughnut-shaped toroidal inductors have been the most popular type for RF use. It is interesting that someone explored toroidal inductors back in the 1920s, and a mystery why they concluded that it was not a feasible design. Perhaps the core materials available to them at the time were a factor (modern toroids use ferrites and powdered iron cores). I'd be interested in hearing anyone's ideas or theories.

The company is still in business, so maybe I will ask them about it.

More information on toroidal inductors can be found in this Wikipedia article.

Heathkit Test Equipment Industrial Design

Over the years, Heathkit test equipment went through a series of style changes, reflecting both the popular styles of the times and decisions by Heathkit's industrial designers. Sometimes the same equipment was reintroduced under a different model number that only differed in style or cabinet colour. While it varied depending on the instrument, and there were many exceptions, I've noticed a few common style themes. Going from the oldest to newest equipment, ranging from the late 1940s to the early 1990s, I've observed the following styles generally used:

1. Battleship gray cabinet with red lettering. Often used black "chicken head" knobs. Example: TS-3 Sweep Generator.

2. Gray cabinet with white lettering. Gray plastic knobs. Example: SG-8 Signal Generator (photo from http://www.nostalgickitscentral.com).

3. Two-tone light and dark gray cabinet with white lettering. Black plastic knobs. Example: IG-102 Signal Generator.

4. Beige cabinet with gray knobs having black centers. Example: IG-57A Sweep generator.

5. Blue cabinet with white front panel. Black knobs, red for concentric knobs. Example: IO-4205 Oscilloscope.

Early equipment tended to be taller than it was wide and incorporated a handle on top. The later style used wider cabinets with handles (if any) on the sides. See, for example, the IP-20 and IP-27 power supplies below which had almost identical functions but different industrial design.

The above is based on material from my book Classic Heathkit Electronic Test Equipment, available
from lulu.com  and amazon.com .

Heathkit "Ask Me Anything" Session

A member of the board of directors of the newly forming Heath Company gave an "Ask Me Anything" session on reddit.com on December 21, 2013. I thought I would post a short summary and a few thoughts on the session.

Some people were frustrated by the reddit user interface (one of the issues, for example: you need to refresh the web page to see new results), the slow pace that questions were being answered, and the lack of many specifics in the answers. Some people left after an hour, however the questions continued to be answered for almost three hours.

Here are some of the key points that were mentioned:

1. They seem to want to do this on a big scale and cover most or all of the traditional Heathkit product lines.
2. They plan to focus on more complex kits (much as they did in the past).
3. They want to revive some original kits, possibly updating them.
4. They want to move into new areas such as 3D printing.
5. They hope to introduce a few kits in the first half of 2014.

On the plus side it is good to see some information coming out from the new Heathkit. They seemed to be excited and are exploring a lot of new opportunities while being true to the values of the original Heathkit.

On the minus side they was a distinct lack of details: nothing about specific kits and no time frames other than the first half of 2014. Nothing really new was mentioned that was not already covered
on their web site.

When asked about 3D printing, the response included the statement "We have some ongoing negotiations in this area right now." That implied to me that they may be partnering with some existing manufacturers rather than building all of their expertise in-house. This could significantly reduce their time to market. The original Heathkit did this, one example being the Thomas electronic organs they sold as kits.

In conclusion, I would say I am still cautiously optimistic about the "new" Heathkit. Some attendees were asking whether they should hold off on a planned purchase and wait for Heathkit. I would encourage people to be patient and not expect much to develop until at least this summer.

Finally, they announced a little contest. To honour founder Edward Heath there is a cache hidden in the city of his birth (Brooklyn, NY). It is within arm's reach of a photo they posted. Inside is a passphrase and a set of instructions. The first fan to send the passphrase will receive one of the first kits signed by the Heathkit team.

References:

1. http://heathkit.com/
2. http://www.reddit.com/r/tabled/comments/1tdf45/table_iama_member_of_the_heath_company_heathkit/
3. http://www.reddit.com/r/IAmA/comments/1td554/iama_member_of_the_heath_company_heathkit_board/ce6r5e8

Heathkit Test Equipment Model Number Scheme

In my last blog post you may have noticed the Heathkit model numbers for the various shortwave receivers. Three were in the AR series, four were GR models, a couple were SB, and the last two Heathkit made were designated with SW. We also had the GC-1 and GC-1A. There seems to be some pattern here but not a very consistent one.

While researching my book Classic Heathkit Electronic Test Equipment I spent some time looking into the commonly used model series for test equipment.

Over the years Heathkit used various product naming systems. Other than some early accessories, they followed a system that used one to three letters indicating a major product line, followed by a unique number. For example, the IM-18 denoted an instrument in the IM (meter) series. During the heyday they had a pretty consistent product naming scheme. The table below lists the major product series. Some units, particularly test equipment, could be bought either in kit form or assembled. Some of the product lines indicate factory assembled or "wired" versions. For products that were offered assembled only, they were sometimes branded as "Heath", particularly in the later days when they were out of the kit business and the units were part of an educational product. Often the wired and kit versions used similar model numbers, such as SM-1212 and IM-1212, but this was not always the case.

Series	Description
numbers	Adaptors and probes
AG	Audio Generators
AV	VTVMs
C	Condenser Checkers
ES	Power Supplies
ETI	Instruments from Educational Series
EU	Malmstadt-Enke Instruments
EUW	Malmstadt-Enke Instruments (wired)
G	Signal Generators
GD	Grid Dip Meters
IB	Impedance Bridges
IG	Signal Generators
IM	Meters
IN	Component Substitution Boxes
IO	Oscilloscopes
IP	Power Supplies
IR	Chart Recorders
IT	Miscellaneous Testers
O	Oscilloscopes
OM	Oscilloscopes
PK	Probes
PKW	Probes (wired)
PS	Power Supplies
S	Electronic Switches
SG	Signal Generators
SM	Factory Assembled Versions of IM Series
SO	Factory Assembled Versions of IO Series
SP	Factory Assembled Versions of IP Series
T	Signal Tracers
TC	Tube Checkers
TS	TV Sweep/Alignment Generators
TT	Tube Testers
V	VTVMs
VC	Oscilloscope Calibrators

A Summary of Heathkit Shortwave Radios

INTRODUCTION

In this blog post I'll give an overview of the different models of shortwave radio receivers that the Heathkit company offered over the years. The scope only includes the models that were intended for shortwave broadcast listening and not radios that could receive amateur radio bands only. I also consider only those were offered as kits -- Heathkit resold some fully assembled radios from companies like Panasonic and Zenith toward the end of the kit era.

ABOUT HEATHKIT

Heathkit was well known as a manufacturer of electronics in kit form. Their product line included amateur radio, test equipment, and various consumer products. By building a piece of electronics you could save money and gain the satisfaction of having assembled it yourself.

A large part of their product line was shortwave and amateur radio equipment. At any given time Heathkit typically offered several shortwave receivers in different price ranges.

The models described here cover the range of years from 1949 to 1990.

SUMMARY OF MODELS

The table below (click to enlarge) summarizes the models of radios, listing their prices, the years over which they were offered, and the key characteristics and features. I'll briefly discuss each of the radios individually.

Some entries in the table are somewhat arbitrary. For example, under BFO I list "Y" if the radio could receive CW or SSB transmissions, even though technically in some cases the design used a product detector rather than a beat frequency oscillator (BFO). In general, more features tended to be reflected with higher prices, but the features don't tell the whole story. The better and more expensive receivers also tended to have better specifications (sensitivity, selectivity, stability, etc.)

The selling prices varied over the years that the models were offered and in the country in which they were sold (Heathkit issued separate catalogues in Canada, for example, with prices in Canadian dollars). In the table I've attempted to list the retail price in US dollars in the year the model was first offered. I've also included prices converted to equivalent 2012 dollars, taking inflation into account, so that prices can be compared fairly.

The table above (click to expand) shows diagrammatically the years over which the models were offered. The longest running models were the SW-717 and GR-81, both offered for 12 years. The AR-1 and GC-1 were only offered for 3 years each, but had similar models replace them (the AR-2 and GC-1A respectively). The greatest number of models were offered from the mid-1960s to early 1970s with as many as six different models on the market during some years.

Assuming the dates are accurate (and sometimes Heathkit stores sold models not listed in their catalogue), then no SWL receivers were offered in 1983. I have a Spring/Summer 1983 catalogue which confirms this.

BREAKDOWN BY MODELS

In this section I'll briefly run through each model, mentioning some key characteristics.

AR-1

This was the first shortwave radio Heathkit offered (other than some early "all-wave" receivers before Heathkit really got seriously into the kit business). Introduced only a couple of years after Heathkit's first kit product, the O-1 Oscilloscope, it was a basic shortwave radio utilizing six tubes and covers the AM broadcast band up to 20 MHz in three bands. It had no built-in speaker, no headphone jack, no BFO, and no bandspread. It featured a phonograph input and tone control, features that no later radio would have. The metal case was optional and cost an additional $4.50.

AR-2

This radio was an improvement over the AR-1. Looking similar, it added a built-in speaker, bandspread, BFO, RF gain control, AVC, noise limiter, and headphone jack. The cabinet was now wood but was still an optional extra.

AR-3

Third in the AR series, this was similar in appearance to its predecessors. The tube count was reduced to five but with no loss of features. It covered four bands. It had better selectivity that the AR-2 and also supported an optional Q-multiplier to further improve selectivity. The wooden cabinet was still optional.

The AR series were the least expensive radios offered, selling for the equivalent of just over $200 in today's dollars. It is rather astounding that today a basic desktop computer can be bought for this price.

EK-2B

This was sold as part of a course on basic radio. The course EK-2A covered basic radio concepts and built up a two-tube regenerative receiver. Course EK-2B continued the course and expanded the radio to a 6-tube 2-band superhet receiver that could receive the AM broadcast band and shortwave from 3 to 10 MHz. It has a BFO and speaker. The case was an optional extra. Unlike the AR series, which had silver front panels, the EK-2B looked more like the traditional Heathkit blue styling.

GC-1 and GC-1A

Dubbed the “Mohican”, these can be considered the same model as there were only very minor differences between the GC-1 and GC-1A versions. This was Heathkit's first all solid-state receiver, and is believed to be the first all solid-state shortwave radio on the market. It featured five bands with a calibrated bandspread for each ham band and the 11 meter Citizen's Band. With it's 54 inch telescoping antenna, carrying handle and battery pack with 8 C-cells, it as considered a portable radio. There was an optional AC power supply that was installed in place of the battery pack. Most remaining units have the AC supply but have lost the battery pack.

GR-54

The last of the vacuum tube receivers, this was considered Heathkit's top of the line radio. It sported five bands. Features include a speaker, crystal filter, product detector, S-meter, and dial light. A somewhat strange and unique feature is a morse code key jack that can be used to practice morse code. The plastic front panel cracks easily -- almost all units I see up for sale on eBay have cracked panels to some degree.

GR-64

This was a basic receiver (less than half the price of the GR-54 made during roughly the same time period). It offered 4 bands with a BFO, bandspread, and S-meter. Sensitivity, selectivity, and stability were not as good as GR-54. Also suffers from the same front panel cracking as the GR-54.

GR-78

This was a solid state portable unit that was smaller than and considered a replacement for the GC-1A Mohican. It featured six bands and is double conversion on the highest band. It has a crystal calibrator, telescoping antenna, and carrying handle. It can run on built-in rechargeable NiCad batteries (most batteries have failed by now but can be replaced with new ones) as well as 120 VAC or 12 VDC.

GR-81

The is a three tube regenerative receiver, the only one Heathkit offered other than the EK-2 which was sold as part of a basic radio course and became a superhet receiver at the completion of the course.

A regenerative receiver is based on the idea of increasing the gain of a circuit by coupling the output of an amplifier back to it's input so that the signal passes through the stage many times, increasing the level of amplification. It originated in the early days of vacuum tubes where the gain of a single amplifier stage was not very high. If the gain is too high the circuit oscillates, so a regeneration control is provided to adjust the level of feedback. Typically feedback is performed using a small coil in the tuning circuit called a "tickler coil", with regeneration controlled by a variable capacitor or resistor.

For receiving amplitude modulated signals, the receiver is most sensitive when the regeneration level is adjusted to just below the level where it oscillates. CW (morse code) and single sideband signals can be received by increasing the regeneration until the circuit oscillates. This acts as a beat frequency oscillator that mixes with the input signal so it can be heard.

As regenerative receivers go, this is a little better than some as it has a bandspread switch, headphone jack, metal case, and a decent audio output level. Compared with higher end receivers the radio is not very sensitive or selective, suffers from hum, and is tricky to adjust. Tuning is not very accurate. However, for 20 to 30 dollars it was an affordable way for someone to get introduced to shortwave listening and the satisfaction of building a radio yourself.

GR-91

This preceded and was similar to the GR-64. It is a 4-tube general coverage receiver featuring four bands. Features are what would be expected in a radio of this price range. It could optionally accept the GD-1 Q-Multiplier to improve selectivity.

SB-310

The SB series was Heathkit's high end range of amateur radio equipment. It competed with commercial equipment from Collins, and was very successful. The SB-310 was developed by modifying the SB-300 amateur radio receiver to receive shortwave bands. Like the SB-300, it is not a general coverage receiver -- it receives nine shortwave bands. Like the SB-300, it sports many high end features and is head and shoulders above the lower cost Heathkit receivers in terms of performance and ease of use. This came at a cost though, selling for the equivalent of over $1800 in today's dollars.

SB-313

Just as the SB-310 was a shortwave version of the SB-300, the SB-313 is a shortwave receiver adapted from Heathkit's SB-303 amateur radio receiver. Features and appearance are very close to the SB-310, but unlike the SB-310, which uses tubes, it is full solid-state.

This is Heathkit's most expensive shortwave radio, slightly more expensive than the SB-310 when converted to in today's dollars.

SW-717

This radio can be considered a solid-state replacement to the GR-64. It has the basic features expected of a radio in this price range. This was the last Heathkit SWL receiver to sport the traditional slide rule dial. It was on the market for 12 years, some of that time as Heathkit's only shortwave radio offering.

SW-7800

This was the last shortwave radio Heathkit offered as a kit, being sold up until the time that they left the kit business. It is a dual conversion design and features a digital display and was in the brown colour scheme that Heathkit was using at that time.

While expensive, it was not particularly feature rich or stable, and was not a particularly popular model.

SUMMARY

Heathkit offered a wide range of shortwave radio kits over the years, spanning a wide range of features and prices. Many of these old radios are still in daily use listening to shortwave stations from all over the world. Additional information can be found in the references listed below and on many Internet web sites.

REFERENCES

1. Shortwave Receivers Past & Present, Third Edition, 1998, Fred Osterman

This comprehensive book has listings of over 770 shortwave receivers made from 1942 to 1997 including all Heathkit models.

2. Heathkit A Guide to the Amateur Radio Products, Second Edition, 1995, Chuck Penson

This book covers all of the Heathkit amateur radio equipment including shortwave receivers.

3. Classic Heathkit Electronic Test Equipment, 2013, Jeff Tranter

This is a shameless plug for my recent book, which focuses on Heathkit's test equipment products but includes a section on the EK-2B and the accompanying course.

4. http://www.youtube.com/jefftranter

I own seven of the radio models listed in this article and have made YouTube videos describing each of them, as well as some videos about test equipment and radios made by Heathkit and other manufacturers.