Ben’s Blog

I’ve got too many electronics projects going, but I’ve already got my next one picked out. It’s KD1JV’s ATS-3B, billed as “the world’s smallest, lightest, six band HF CW rig.” Steve Weber, KD1JV, is a serial designer of QRP radios and accessories. The whole thing fits in an Altoids tin and puts out four watts on all bands. (My SW-40+ only puts out 2-2.5W.) It also has a DDS VFO and a built-in keyer. Band switching is done using removable band filter modules. The whole thing is controlled by a PIC microcontroller, which some people have reprogrammed for additional capabilities. It seems to be very well though of by those that have one.

The ATS-3B was designed by Steve to be the ideal radio for backpacking. He lives in New Hampshire and backpacks the Appalachian Trail often.  (ATS stands for Appalachian Trail Sprint.) I haven’t done much backpacking lately, but I’m looking to get back into it soon.

Most ham kits use through hole parts, which are easier for some people to handle. The ATS-3B uses lots of surface mount parts, allowing it to be very small. I’ve used surface mount parts on a couple of projects and actually prefer them. I’ve always soldered them by hand. Steve seems to prefer the solder paste/warming plate/embossing gun method. I’m not sure if I’d give that a try or stick with soldering by hand. Here’s a YouTube video of Steve doing it both ways.

Steve only offers ATS-3B kits periodically. I believe he’s offered them about three different times now. He’ll be offering them again sometime in late fall, and I’ll be ready. This will also be the last time Steve will offer this kit, as some of the parts he uses are being phased out. He’s already working on the ATS-4, which looks to be a very nice (though somewhat larger) radio.

As most of you know, I’m currently afflicted with the ham radio bug. I have a VHF radio I can use to talk locally, but nothing I can talk around the world on. For Christmas last year, Cassie got me (at my request) a Small Wonder Labs SW-40+ 40m QRP CW transceiver kit.

The 40m ham band is a good all-purpose band. It’s open to somewhere pretty much any time, day or night, even at this point in the solar cycle. QRP means it’s low-power. In this case, around 2.5 watts. Most commerical radios put out around 100W. CW means it only does Morse code, no voice, which means I’ll finally have to learn Morse code.

The SW+ series is well-regarded in the QRP community. There are models available for the 20m, 30m, 40m, and 80m bands. The kits are put together by a guy in New Hampshire. There’s a waiting list of around two months to get a SW+ kit.

The SW-40+ board with 8 of the 16 sections installed. I've added a couple of sections since this photo was taken.

A few weeks ago I finally got a chance to start putting mine together. The instructions that come with it basically say to build the whole thing, then test it. I’ve built some smaller kits before, but this is definitely my largest undertaking thus far, so I wanted some assurance things were going right as I built it. So, I’ve been using Chuck Adams’s, K7QO, guide to building the SW-40+. By following his guide, you build a section, then test it. He has it broken down into 16 sections, more or less. Some of the previous kits that I’ve built are used for testing.

You can see all the pictures from the construction process here. I’ll continue to add photos as I go along. I’ll post an update here occasionally too. So far I’ve installed the power supply, audio amplifier, keying, muting, audio preamplifier, receiver mixer/detector, IF crystal filter, receiver mixer, VFO, and transmitter mixer sections. That’s 10 of the 16 sections.

Testing the transmitter mixer section by feeding the output of the transmitter mixer into the receiver.

A few months ago I bought a VE3DNL Marker Generator kit, but had never put it together. Chuck suggested using it to test the receiver mixer/detector section. It was a quick build, and the receiver mixer/detector section passed the test.

VE3DNL Marker Generator board is on left of SW-40+ board. The VE3DNL transmits tones every 5kHz that can be picked up in the SW-40+ receiver.

After building the VFO section I wanted to have a look at the waveform. Chuck’s guide shows a nice sine wave. A friend had loaned me an oscilloscope for another project a few months ago, so I drug it out and set it up. To make a long story short, I was never able to view the VFO’s waveform on the oscilloscope. Something is wrong with either the probe or the oscilloscope itself. However, I was able to confirm that the VFO is running at around the correct frequency with the FCC-1 frequency counter I built a while back.

I have also built a K1EL K12 keyer to put in the SW-40+. As designed, the SW-40+ can only use a straight key. I wanted to be able to use iambic paddles, so I found the K12 keyer. It handles the input from the key and outputs perfectly spaced Morse Code. It sounds beautiful. It’s a pretty cool little device in its own right. I may do a post on it at some point.

The K1EL K12 keyer assembled.

More on the SW-40+ when I get a chance to work on it.