Bell & Howell IMD-202-2 (Heathkit IM-1212 In Disguise)

Bell & Howell IMD-202-2 in place at workbench.

When my Systron-Donner digital multimeter was damaged by lightning in June of 1992, I looked for a replacement. Somewhere along the line, I found a Bell & Howell IMD-202-2 at a hamfest. This was at least twenty years ago -- I have a email message from January 2005 asking about it.

Somewhere along the line, this meter refused to measure anything. When I moved it to Ward Mountain, it was time to fix it. 

The sticker of the multimeter says "Heathkit IMD-202-2", but it's not a Heathkit number. In twenty years, there's apparently more information available. I found that it's a Heathkit IM-1212 with a Bell & Howell label. They sold this unit in the late 1970s as part of an electronics instruction course.

While I couldn't find an assembly manual, I did find a schematic and a calibration procedure. The unit is a simple and straightforward design. Opening it up, there's a single circuit board, plus a bit of wiring around the function and range switches. 

Stepping through the calibration procedure, I couldn't find anything amiss. I had difficulty using a frequency counter to set the counter oscillator. Even with an oscilloscope, I couldn't find a clear signal to measure -- yet the unit was working. I decided to use the calibration without a frequency counter.

When performing the DC and AC voltage calibration, I backed up these measurements using a modern portable digital multimeter. In the twenty years or so since I obtained the Bell & Howell, I've purchased four of these gems. 

The calibration went smoothly, and the Bell & Howell now has an honored place on my workbench. 

Measuring 1k resistor.

Compared to modern instruments, it's not impressive. It sports 2 1/2 digits -- the first digit is just a neon lamp that signals a leading "1". A second neon lamp lights a "OVER" indicator. By comparison, my modern portable digital multimeters have 3 1/2 digits, and at least one of them is auto-ranging. Accuracy isn't great -- perhaps 2% when freshly calibrated.

Still, it's sufficient to be tied to the workbench. The problem with the modern portable digital multimeters is the "portable" part. I leave them all over, and can't find one when I need it. Plus, the nixie tubes are cool.

At least until I can fix the Systron-Donner, which is a much nicer instrument. I have full manuals for the Systron-Donner. Last I looked, it had a problem with fried comparator using a LM301AH with matched FET input amplifiers. Yes, that's a TO-8 style integrated circuit, something you haven't really seen since the early 1970s. And the matched FETs are in a common plastic case with six leads -- a rather uncommon part. I intend to remove the damaged parts and install new parts with socket pins. 

The Station Notebook

When I originally set up my station as a novice, I didn't make a lot of notes. I wrote a few things on the back-side of my logbook pages: radios I used, antennas I put up. But, for the most part, I freely made changes to my setup without a lot of documentation.

Some years later, I had a small steno-style notebook lying around, and I used it to record certain information. Like the exact color-code of the RS-232 cables I wired up for my computer. That sort of thing was handy to have written down, because it saved a lot of reverse-engineering later I went to make another cable. But that was about it.

Perhaps a dozen years ago, I read a couple of articles about James Lawson, W2PV, and how he kept copious notebooks about his station. He even solved a sticky problem during a contest, because he kept notes about his antenna installation.

After that, I started writing more things down in my little Steno notebook. Most of it was changes I made to the station -- radios or antenna modifications. Or if something big happened -- like I blew up the amplifier. I recorded a lot more details, and I put dates on everything.

But when I began to spend most of my time out in Floyd County it put my little steno notebook out of reach. I had a new station and I still wanted to keep notes. My solution was dead simple -- I created a text document using TextEdit. I called it Floyd County Station Log.

Looking at it today, it's more like a diary. Each month, I put in a new heading: March 2017. And below that I record anything interesting that I do. I record the things that work, and I also record the things that don't work! If I don't do anything that month, I'll just change the heading to the next month.

The bottom of this document has a list of projects to be worked on. Silly now, since I'm no longer at that QTH: 6m antenna, K9AY controller, 20m and 30m traps for the dipole, tribander-Moxon  times 3 (now that's an interesting project I'll need to write about some day!), remote antenna switch, etc.

This method worked so well, in May 2015, I adopted it for my main station log. Not only did I make new entries, but I also entered all the data from the steno notebook. Plus, I went back through all of my contest comment submissions and recorded all the changes I had made to the station from November 1994 to date.

Today the Gwinnett County Station Log is a reasonably complete record of all the things I've done with the station for the last 22+ years. It has six pages of project notes at the end. Lots of stuff to work on! And, yes, I also have a smaller document for the Walton County Station Log.

I guess my point is that having a station notebook is extremely valuable. It doesn't matter if you use a small steno notebook, a spiral-bound notebook, a composition book with graph paper, a loose-leaf notebook, or a computer document. The important thing is to find a style that works for you to keep notes. After a while, there's just too much to try to remember. So keep good notes.

Straight Key Night 2014

Homebrew Transmitter and Receiver, ready for another
go at Straight Key Night in 2014

Last year, Straight Key Night (SKN) was kind of a bust for me. As I wrote then, I ran into trouble trying to key my 35+ year old electronic keyer to key the 40m "Novice" rig. This year, I got to operate SKN with no problems.

Despite having an entire year to figure it out, I left fixing the keyer to the last minute. Back in the summer, I had modified the keyer to use a 2N3906 to key the gate of a BS170. However, when I hooked it up to the rig, it wouldn't key -- oscillator problems again. It went back to the project shelf to be figured out later.

At some point, I took the keyer back to Gwinnett county to try to troubleshoot it there. But as fate would have it, I didn't have time to figure it out. Right before Christmas, I brought it back to Floyd county.

A bit of work with the mini-scope proved that the oscillator wasn't firing at all. It took a while until I found the source of the problem: one of the wires to the speed potentiometer had broken off, so the RC circuit was broken. Without it, there's no phase delay, and therefore, no oscillation.

Built in 1979, Mini-MOS keyer provides yeoman service again.

Great! This means I just hook it up to the rig and go right? Wrong. It appeared to work for a few seconds, but then it would continuously key. It was erratic. Troubleshooting it a bit more, and it seemed to work -- the keying signal would get to the gate of the BS170, but not beyond. At one point I thought maybe I had a bad MOSFET, so I pulled the BS170 out. (In the process, I ended up destroying the part - oops)

Pulled a 2N7000 out of the junk box. The 2N7000 and BS170 are pretty much the same part, although the pin-outs are different. Hook it up and it seems to be working great. I can see the keying on the gate on the 'scope, and the transmitter is happy. Unplug the scope probe, put the lid on, and ... it's locking up again.

Hmm. Take the lid off, put the probe on, and it works again. On a hunch, I pulled a 100k resistor out of the junk box and put it across the gate to ground. Working -- even with the probe removed. Ah ha! That's the problem. The gate of the 2N7000 (or BS170) wasn't being pulled back down to ground, so the floating leakage from the 2N3906 was just barely enough to keep it turned on. Adding the scope probe brought in just enough resistance (a few megaohms), to overcome that leakage.

All ready to go. After dining out with a church group on New Year's Eve, I managed to work seven stations all before the ball fell. Of course, I told them that I was cheating, using a 35+ year old keyer instead of a straight key. No one seemed to mind. I did find that my 7061.1 kHz crystal stopped working. Worked one more person on New Year's Day for a total of eight.

A great way to bring in the new year. I guess I'll submit mine as a check log....

Hamfest Special - $25 Oscilloscope

B & K Precision Model 1442 Oscilliscope

To paraphrase Forrest Gump, "life is like a hamfest, you never know what you are going to get." It's true. I've been to many hamfests, and even when I have a pocket full of money, I never know what I'm going to walk away with. Sometimes, I barely spend much more than the price of admission, and other times I miss out one some good deals because I just don't have the cash.

Perhaps that's what keeps me coming back over and over -- you never know when you are going to find that great deal.

The Dalton hamfest wasn't as big as last year -- no doubt the drizzly rain had kept many away. But it wasn't really cold -- just a little damp. Not enough to dampen the spirits of a true hamfest hunter.

I've gotten to the point where I take a list to each hamfest. It's too difficult to remember all the bits of equipment and parts I need to keep an eye out for. It fits on one page, so I can fold it up and stuff it into a pocket. I'll take it out a couple of times during a hamfest and go over it, just to keep the items fresh in my mind.

Despite the preparation, there's often something that catches my eye. Like this oscilloscope. While prowling the tables, I saw another unit (a model 1420 - 15 MHz) on a table that was partly disassembled. All the pieces appeared to be there, it looked like it just needed to be re-assembled. The owner was busy at the time, so I figured I'd swing back by later and ask about it. Well, someone else got to it first, because I didn't see it again the second or third time I went by that table.

Another seller also had a small 'scope -- a model 1422 - 20 MHz. It was intact, if a little dusty, and clearly the carry handle wasn't original. One of the knobs was missing. But, it looked promising, so I asked the seller how much? $25. Hmm. I've purchased a Heathkit solid-state 5 MHz scope for $10 before, but it was a full-size unit. But this was a small portable scope. Given the heft, I bet it even had battery power. I asked if it worked, and he said it did. (Not that that means a lot at a hamfest) So, the sale was made.

Now that I had another 'scope, I needed probes. Half-way decent probes can be expensive -- more expensive than this oscilloscope. After a pretty thorough search, I found a new-looking Avex 10:1 probe for $15. One is good enough for now, I should get more at the next hamfest. ('scope probes, after all, are on the list!) I also picked up a miniature knob.

Of course, the first rule of bringing any new equipment home is to take it apart. I did plug it in and verify that it appeared to be working -- two nice traces on the screen. Taking the panels off, it was apparent that this unit was battery-powered. A nice sealed lead-acid pack in the back of the unit was perhaps half of it's weight. But, of course, the battery was stone-cold dead. I wrote the numbers down in case I wanted to order a replacement.

An hour of gentle work with a soft cloth and a bit of Windex took care of the dirt. And the replacement knob fit perfectly, if looking a bit different from the others. No matter. The rubber stick-on feet had long since departed the unit, but I had a few in the junk box in Gwinnett county. A few adjustments, and this little puppy was working perfectly, as you can see from the picture.

A sweet little addition to the micro-shack -- a perfectly sized micro oscilloscope!