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!

Samlex SEC 1223

Unit #2 - before modifications.

I guess you can say I'm pleased with the Samlex  SEC 1223 power supply. After all, I own three of them.

Back in 1988, I bought a CB-grade 12 volt linear power supply capable of 25 Amps output. It needed a little work to function correctly, but it powered my venerable TS-430S and later the K2/100 for 19 years. It finally went west one day when the power transformer opened in the primary winding.

Soon after, I was hunting for a replacement at a hamfest. I found a Samlex SEC 1223 that fellow had replaced with an Astron SS-25M. Used, the price was right, at about $50. The unit is impressively small, and it had no trouble powering the TS-430S, K2/100 or K3/100 to full output on every band.

However, this unit had numerous spurs on 160m. I found the loudest one was around 1845 kHz, about S7 on the very scotch K2 S-meter. Note that the location and strength of the spurs varies with the supply load. Using snap-on ferrite cores as an experiment, I found that putting them on the power cord and the output power leads led to a reduction in the spurs.

Unit #1 - showing seven FT50-77 ferrite
toroids on power input leads.

My first modification was to de-solder the white and black power cord jumps inside the unit and slip on seven FT50-77 toroids. That reduced the spur to about S5.

Unit #1 - Output lead modifications.

I then made a modification designed by ZL2DF and published by N0SS. My unit was different from that of ZL2DF. It did not have the screw / compression power terminals. Instead, my unit had binding posts soldered directly to spade terminals on the PC board.

I pulled out the PC board and removed the spade terminals. I replace them with 16 gauge wire fed through eight type 43 ferrite beads. The wire is a bit small, but is the largest that will fit through the beads. The output terminals are bypassed across each other and to ground with .1 50v multi-layer ceramic caps.

With this change the 1845 kHz spur was just audible. Atmospheric noise covers it up at night.

Last year, I found another one of these gems at a hamfest for $20. Took it home and sure enough, a few spurs on 160m. Made similar modifications -- toroids on power leads, ferrite beads on output, caps across output terminals. Again, the spurs don't disappear, but are much less pronounced.

Unit #3 - perhaps only needs power input filtering?

This year -- you guess it -- I found another one for $5! This unit is a little different, as it has a large ferrite bead with both power leads run through it to the compression terminals. Perhaps it will only need a big of work on the power leads. We'll see when I can get it on the bench.

These are very capable little power supplies. They are easily able to power a 100 watt transceiver, and with a little work, they are quiet enough for MF and HF use.

Six Meters

In January, I operated the ARRL VHF Sweepstakes contest. I guess they don't call it that any more, it's just the January VHF contest. I haven't operated this contest since 1992, and have done no VHF events since 1993.

Back then, I had two Microwave Modules transverters: MMT144/28 and MMT220/28. I modified the latter with a new crystal to be based at 222 MHz. I had an F9FT long-boom yagi for 2m, and nothing more than crossed dipoles for 222 MHz. With 10 watts out, it wasn't much, but I made several dozen contacts on 2m. I never did make a contact on 222 MHz.

I sold that gear when I moved from Stone Mountain, GA. Instead, I focused mainly on operating HF, which is plenty challenging.

Upon receiving the K3/100 from my XYL for Christmas, I naturally had to give 6m a try. I've never before had 6m equipment. Well, that's not true. For a while, in the early 90s, I had a JR remote-control radio system on 6m that I used to fly model airplanes. But, you couldn't talk on that radio, so it doesn't really count, does it?

I had already worked four contacts on 6m on December 31st. I figured the 100 watts would be plenty to work quite a few contacts. While I don't have a 6m antenna, I could load up what I had with the tuner and make do.

On Saturday, I was also working the NAQP Phone contest, but occasionally I would take a minute and jump up to 6m and tune around for some activity. Nothing.

Sunday afternoon, I spent about four hours in the shack, mostly listening to static. I worked a few local stations, who could just barely hear me. I was beginning to wonder if I would work anyone outside my own grid.

Then it happened -- an opening. Just before 2300z, I worked K1TR in FN42. Fifteen minutes later, the opening started in earnest. I worked seven other stations up in the northeast in the next 45 minutes, along with about three locals. By HF contesting standards, it doesn't sound like much. But the signals from the northeast were booming in, and they didn't have any trouble hearing me, unlike the locals. The conditions moved like a spotlight down the eastern seaboard, ending somewhere in Virginia.

How exciting! I'm going to have to improvise a real antenna before the next VHF contest. Something with a bit of gain. Maybe a Moxon, or perhaps a three element beam. Maybe I can hide in up on the hill behind the Micro-shack. Rotating it would be nice as well.

Awards Made Easy - LotW

I passed a milestone this week. Somewhere in my NAQP Phone log upload, I passed 20,000 QSLs in the Logbook of the World(LotW). I have nearly 57,000 QSOs upload into LotW.

I can't imagine collecting 20,000 QSLs by conventional cards. It would take an enormous amount of work. Granted, most of the confirmations I have are for pretty routine contest QSOs that would likely not have bothered with the formality of a paper cards.

In any case, all those confirmations have gone a long way toward earning awards. I've already discussed getting 6-band Worked All States. I've also gotten DXCC, Mixed, CW, Phone, 20m and 15m. I have enough confirmations to get 40m and 10m as well -- I just tend to get one certificate each year.

I was intrigued when the WPX award came on-line in LotW. I found that I have enough confirmations for dozens of awards. I decided I'd hold out for the WPX Award of Excellence.

If you are interested in these operating awards, there's no better way to get the needed confirmations than Logbook of the World. Sure, it's a hassle to get on the system, but once you do, uploading submissions is relatively easy. And then the confirmations just keep on coming.

I wonder how long it will take to get to 30,000?

USB to Serial

Re-arranged a few things in the Micro-Shack just before the RTTY Roundup.

For years, I have been using an ancient Toshiba 4000-series laptop. My wife bought this monstrosity back in the late 90's in order to work with custom embroidery software. I'd upgraded it to Windows 98 SE, and it managed to do OK running various Windows contest logging software. While I'd rather run stuff on the Mac anyway, writing some good contest software for the Mac has been one of my Great Unfinished Projects (GUP) for many years now. That's far too long a story to go into right now.

The old Toshiba 4000 wasn't much, 400 MHz Pentium, 800x600 screen. One serial, one parallel and one USB port. It didn't even have networking (much less wireless networking). Old.

When I purchased my MacBook, I set it up through BootCamp to boot in Windows 7. I had tried to run the Windows contest software using it, but I ran into a weird problem. Randomly, after a few minutes to an hour, the machine would flash the screen blue, then reboot. Certainly you could use this in a contest -- at least, not one you were serious about.

About the same time, I attended PDC 09 and came home with an Acer 1420P. Every attendee got one. Although Acer built it, Microsoft had specced this machine. The idea was pretty simple. Microsoft had been tired of evangelizing technologies such as Tablet PC, or 3G networking, Windows 7, etc. Only to have developers say "Well, I don't have a machine that does that." Instead, they seeded the 4000 or so attendees of the conference with these machines. Sweet.

I tried to use the Acer to run contest software, but ran into the same weird problem. Since I couldn't see what flashed up on the blue screen before the reboot, it was hard to tell what was going on. So, I went back to the old Toshiba, and the Acer found some utility at work. Until about a year ago, when the Acer took a tumble off a desk and cracked the screen. It still worked, but the two jagged cracks across the screen made it difficult to use.

My XYL wanted the Toshiba back to do some embroidery, so I went about fixing the Acer. I found a replacement screen for $70, which seemed a reasonable investment. The replacement didn't have the touch interface -- so no Tablet PC. Considering I have an iPad anyway, and Microsoft has moved beyond the Tablet PC with the Surface, it seemed to be a small loss.

As I was setting up for the RTTY Roundup, I ran into the same problem as before -- random BSOD and reboot. However, I'd learned more about Windows 7 in the intervening years. Turns out the automatic reboot is a "feature" you can turn off. Now I can read that blue screen.

After a couple of trials, the culprit appeared to be the driver for the Keyspan USA-19HS. You see, the one thing that the MacBook and Acer have in common (other than running Windows 7), is they have no serial ports. In order to talk with the K3/100, you need a serial port. So I used this Keyspan device that I bought several years ago. Updated drivers were no help. Same problem.

This surprise me somewhat. I really like the Keyspan. It works great on Mac OS X. I was a big fan of Keyspan products -- a decade or so ago, I even met a couple of their developers at Apple's WWDC. At least, I was a fan until Tripp-Lite bought them out. Now, I'm not so sure.

While I suffered through the RTTY Roundup with the occasional BSOD, this seemed like an easy problem to fix. Elecraft sells the KUSB device which would be sure to work, but it's a little expensive at $40. I found a Plugable 2303 USB to Serial converter on Amazon for $13. I was encouraged when I read the driver release notes for this device had the same BSOD problem on Windows 7, but it had been fixed in the latest release.

I got a chance to try it earlier this week. Getting the drivers and setting the thing up was an experience, but not atypical for Windows. Once configured, I cranked up N1MM, put the K3 in TEST mode, and set it up to repeat CQ in CW after 1 second and left it for a few hours. All the DTR access should give the serial port a work-out. Six hours and no BSOD. Seems like it works.

The Plugable 2303 appears to be a good solution. I also tried it on MacOS X. Works fine there. It appears I can retire the Keyspan USA-19HS to MacOS X-only use.

Straight Key NOT!

Since I was thinking about Straight Key Night before, you might anticipate I would have an extensive operating report of the Homebrew 40m Transmitter and Receiver. Well, not exactly....

I did go and review the rules. There are no prohibitions against using electronic keyers. Indeed, the guidelines state "This 24-hour event is not a contest; rather it is a day dedicated to celebrating our CW heritage." I certainly consider my nearly 34-year-old Mini-MOS keyer part of my CW heritage.

So, that was my plan -- to cheat on Straight Key Night and use my keyer. 

I was busy during New Year's Eve, so I went out on the morning of New Year's Day and hooked up the keyer to the 40m Transmitter. With the spotting function, it appeared to work. The keying was a little soft, but I was able to find my transmitting frequency with ease. I tried two or three crystals, and then I noticed the oscillator wasn't stopping. If I unplugged the keyer and plugged it back in, I could send one element, and then it would stick on. Then it stopped working altogether.

At this point, I was sort of in a panic. I pulled the cover off the keyer and looked inside. What I saw next set me back a moment -- there was no battery in the keyer! I had been using the keyer solely on the stored power in the electrolytic capacitor for about five minutes. Now that is a low-power station accessory!

I scrounged up a 9 volt battery and verified that I had not fried the 30+ year old CMOS chips. However, it appeared that the CMOS gates had enough leakage that it would not reliably cut off the 6CL6 oscillator. 

The original Mini-MOS design keyed through a PNP transistor in order to work with grid-block keyed rigs -- with a negative keying voltage. That worked great with my SB-401 and later with a DX-60B and the FT-101E that I borrowed. When I bought a Kenwood TS-430S in 1985, it had a positive keying voltage. I simply removed the PNP transistor and connected the keying line directly to the CMOS 74C02. Since it worked, I kept using it.

I think the original problem was there are no free gates in the seven chips that make up the keyer. In order to drive a NPN transistor or enhancement-mode FET to key the transmitter, the keying sense has to be reversed -- instead of bringing a positive voltage to ground, we need to go from ground to a positive voltage for the base / gate of the transistor. In retrospect, it would have been easier to have left the PNP transistor in place, use it to drive an NPN transistor or  FET.

A quick look in the junk box revealed some 2N7000s -- an excellent enhancement-mode FET to key the transmitter. (The K1EL keyers use this same device) I just need to dig up a PNP and some resistors. Ah, a project for another day.

Oh, and what about Straight Key Night? Well, since I had just gotten the K3 going, I decided to play with it instead of SKN. I ended up working DX spots on 12 and 17m, including working VP2MRV on RTTY using the K3's FSK D CW to RTTY mode. Cool.

SKN? Maybe next year....

K3!

K3/100 build and under the Christmas tree.

I have the best wife in the entire world.

When it came time to make our Christmas lists this year, I had mentioned that it had been ten years since I bought my last ham transceiver -- I finished the KPA100 for the K2 in the fall of 2002. And while it might be time to look at something new, modern transceivers are not cheap. In the end, I decided to ask for contributions toward the "K3" fund -- money I would use to buy an Elecraft K3 at some point in the future.

Before Christmas, my wife had hinted she had gotten me something expensive. She would tease me that she had purchased a Cessna 140 or a Harley-Davidson. She did it often enough I wasn't sure what to believe.

Inside these boxes is a bit of joy.

However, due to some shipping difficulties, my present didn't arrive until three days after Christmas.

Needless to say, I was surprised to open the box find a stock K3/100!

She had the presence of mind to get me the unassembled version, instead of the factory-built. While it's a bit more work, I really enjoyed assembling my K2/100, so I figured I'd get some enjoyment out of this.

Biggest problem, though, was where to build. The Micro-Shack is, well, micro. The entire desk surface is barely 5 by 2 1/2 feet. Most of my tools are still down at the QTH in Gwinnett county. Nevertheless, I figured I'd do what I could with what I had, rather than wait a week or so until I could get to my big workbench.

K3/100 goes together on the world's smallest workbench.

As it stands, I had enough room for the job.

It was already late in the day when I got started, so I decided to forgo the Elecraft-recommended inventory. I've built a number of their kits, and I can't say I've ever been shorted a part. Indeed, they always seemed to ship me extras. In retrospect, this wasn't such a bad idea. If you've never built a kit before, inventorying the kit is a great idea.

Since all the boards are pre-assembled, there's no need to warm up a soldering iron. However, there's plenty of mechanical assembly. I thought it was weird that Elecraft has one put the left and right side panels on, only to have you remove them a few steps later.

I had never really seen the insides of a K3 before, and the pictures don't do it justice. In some ways, it really is like an over-sized K2, with the mechanical rigidity coming from the main board. Once you get the casing on, it's really pretty rugged.

Initial power-on successful.

Assembly was pretty much a joy, except for the limited work space. I had a great sigh of relief the first time I powered the K3 on, since it was clear I hadn't messed it up somehow.

I did have one item I did mess up during assembly. It was the KREF3 board. The instructions indicate you are to cut off any leads that might be longer than certain components on the board. I found a through-hole connector lead that I thought was a bit long, and when I tried to trim it, I also managed to bust capacitor C2 off the board. Fortunately, this component isn't used for anything critical. My guess is that it is used for FM only, but there's not really any documentation as to what the TXMIXFIL signal does. I've already contacted Elecraft support as to how they suggest we fix this.

After about six hours of work, my K3/100 was all assembled and calibrated. I only ran into one issue -- I had no dummy load to perform the Transmitter Gain Calibration. I ended up doing the calibration manually using the antennas I have on hand. Not perfect perhaps, but it will do until I can get my hands on a dummy load.

K3/100 assembled and operational.

Now that it's assembled, I have to go an order the other options I need. Unfortunately, the KAT100 doesn't work with the K3. I went ahead and used some of that "K3 Fund" money and ordered the KAT3 antenna tuner as well as the KXV3A transverter adapter. That should do me for quite some time.

Now, I need to sit back and read this thick operating manual so I know how to use my new rig! See you on the bands.