Ripples in the Ether

Clackamas Schematic

Since FDIM 2010 is in the history books, it is my pleasure to finally publicly release my entry into the FDIM 2010 QRP Challenge: The Clackamas 40 Meter Transceiver.

The rig is a VXO-tuned superhet that operates around 7.030 MHz. The heart of the design is the BF998 dual-gate MOSFET (which was popularized by W7ZOI on his website and in EMRFD). The BF998 is used as the front-end mixer and as a combination product detector/BFO. My new favorite AF amp, the TDA7052, is my choice for the single allowed IC. The VXO signal is mixed with a carrier oscillator in a JFET mixer, which is then bandpass filtered and fed to a BS170 power amplifier.

Please download my contest writeup for full details of the design. I’ll dissect the design in further detail in future posts.

LogiKlipper Prototype

I recently received a very interesting e-mail from Dave W8NF regarding a very spiffy looking labeling technique that he successfully used for his latest LogiKlipper prototype (BTW, LogiKlipper is going to kick the butt of the RF clipper manufactured by that other company in the South…). Here’s the details on how he did it:

I printed out what I proposed as the “final” lettering artwork on the transparency film.  I included four alignment marks for the corners.  I laid the panel down on newspaper and sprayed the panel with “Elmer’s Multi-Purpose Spray Adhesive” – I got it from Home Depot a year or so ago for another project.

I moved the panel to on top of a magazine that had not been sprayed, and carefully positioned the transparency film over it.  The fact that the film is transparent helped a lot…this would be difficult with an opaque film.

I was worried about bubbles or smudges in the adhesive, and they do indeed exist.  They don’t look as visible as I worried about, though.  They provide a bit of texture, even.

The film is pulling up at the edges…since this was more of an alignment test than a finished piece, I didn’t really work hard to press the film into the panel.  Also, I used a pair of scissors to trim the edges, and that pulled the film up…an X-Acto, bearing against the panel edge, would have avoided this problem.

I X-Acto’d through all the holes, bearing the blade against the metalwork to form scissors.  The only problem points were the countersunk holes.  For a homebrew project, I probably would not countersink.  Or, if I did, I’d have those screws in place before the film was attached, and just glue the film right over them.  The flathead screws, when they went in, wrinkled up the film around them.

I think I’ll try the technique for my next homebrew project.  It certainly serves for what I needed to demonstrate this time.

A very nice looking front panel, Dave! I’m going to have to give this a shot. I’m a lousy mechanical engineer, but I think even I could pull this off respectably.

Over the last week or so, I’ve been coming home from work nearly every morning thinking about ways to tweak the Clackamas (FDIM 2010 QRP Challenge) rig. I’m sure that Jennifer is wondering if I have OCD at this point. This morning I was able to stamp out the last few bugs in project and get the parts count to 72. There was a nasty PA oscillation that I had to tame and I was having trouble pulling my carrier oscillator low enough to get the transmitted signal on the right sideband. Somewhat satisfied that the thing might actually work, I went to sleep with the hope that I could try a QSO this evening when 40 meters would give me a better chance of making a QSO.

After dinner I managed to slip into the shack after Jennifer laid down to rest and I bribed Baxter to leave me alone with a Kong full of treats. I thought about trying to self-spot in order to scare up a QSO, but that didn’t seem right. I wanted the first QSO to stand on the rig’s own merits, not because I asked someone to listen for me. So I parked somewhere near 7030 kHz and started banging out a straight key CQ with 1 watt output. After about 5 rounds of CQ, I started getting the sneaking suspicion that I had screwed something up, but I trusted that my pre-QSO checks on the rig were correct. So I kept at it.

After a few more CQs, I finally got my reward. A huge signal about blasted the phones off of my ears! And it was saying my callsign! I got a reply from W7MDK in Peck, ID. I was so excited that the QSO didn’t go so great, but we got all of the pertinent information across. He was going a bit faster than I normally copy, and I think my speed was impaired even further because of my extreme excitement. Dick gave my 1 watt a 579, while he was easily 40 dB over S9 here. I cut the QSO short to stop me from embarrassing myself further, but I got the first one in the log!

It’s said that there isn’t much better for the homebrewer than to turn on that newly created receiver and hearing signals off the air for the first time. It’s hard to argue with that, but I think that making a complete first QSO with a rig you designed and built yourself has to top even that experience. Sorry to toot my own horn so shamelessly, but I’m just thrilled with the love of radio right now.

The next steps are to get going on the documentation for the judges, get the prototype into an enclosure, and start working on a second copy of the rig to make sure I can duplicate it from the schematic. I can’t wait to share the design details with everyone, but that’s going to have to wait for another month or so. In order to get the rig within the required parts count, I had to trim the receiver down to 34 parts. The transmitter ended up being 30 parts and the VXO came in at 8 parts. However, I was able to make the Clackamas a true transceiver, not just a trans-receiver.

Stay tuned for additional details as I can release them!

Update: Just worked JF2QNM in the JIDX contest. 1 watt spans the Pacific! Of course, all of the credit goes to the op on the other end, but it’s still really gratifying to have your HB 1 watt signal make a nice hop like that.

KC2UHB with EFHW Tuner

Our favorite fashion hacker/ham, Diana Eng, KC2UHB, has posted a new article on the Make Magazine blog with instructions on how to build an End-Fed Half Wave antenna tuner and deploy it with an antenna. (BTW, did you see that she was recently named to the ARRL Public Relations Committee? An excellent choice the League.)

Her BOM calls out an air variable cap from MFJ and a T94-2 ‘roid, so I suspect that her tuner could handle a bit more than QRP power. In typical ham fashion, it appears that she was too eager to get it on the air to worry about little things like putting it in an enclosure. FB with that Diana, I think most of us can relate.

It sounds like she had great success using this setup with her FT-817 for some SSB QRP fun:

Setting up my antenna for 20m the first time took about half an hour, and I was able to get very close to 1:1 SWR using the 9:1 input with a vertical wire supported by a tree. Over the next hour or so, operating from a park bench in Brooklyn, using 5 watts on sideband, I made contact with stations in the US, Europe, South America, the Caribbean, and Hawaii. The furthest station was about 5000 miles away, which means I was getting 1000 miles per watt out of this setup. I’m sure it was a big contest station and not another QRP operator sitting on a park bench with a wire antenna, but it was still fun.

I’ll take this opportunity to shamelessly promote my own EFHW tuner, which I’ve managed to get back up on my new website. Don’t forget to compare to AA5TB’s design, which features probably the best page on this subject matter which I’ve seen.

Audio Amplifier Guts

As I mentioned in a previous post a few days ago, I found a nice 2 watt mono audio amplifier board that’s a perfect addition to give speaker capability to a receiver with headphone output. I purchased four of these bad boys since they were so inexpensive (and I was paying for shipping from Hong Kong, so might as well order in bulk). I figured a good test would be to build up a bench amplifier so I could have the convenience of listening to any of my homebrewed phones-only receivers/transceivers (most of them) on speaker.

To the right, you can see the pleasing results of this little project. I had a nice Ten-Tec TPC-17 that turned out to be a perfect enclosure. The 1/8″ input connector is on the left, a power LED in the middle, and a mute switch on the right (the amplifier board has an active low mute line which works extremely well). I created a speaker grille drill template in Inkscape for the 3″ speaker bolted to the top lid of the enclosure (if there’s any demand for this file, I can post it here). The actual 1″ x 1″ audio amp board is on the left and a small 7805 voltage regulator board on the right.

AF Amp on the Bench

Here’s the enclosure all buttoned up for use. You can see that the speaker grille is a bit ugly, but it works well enough. There is no power switch, since the quiescent current is so low that there’s no problem in leaving it powered up. Tonight I hooked it up to my VRX-1 (with a rock on 7030) and listened to the wide-open band with the DX contest in full swing. The audio quality was quite nice; better than I remember it when testing it out in the open on the workbench. I’m guessing this is because the speaker was properly mounted instead of having the magnet rattling against the bench. Even though it’s a simple project, it’s a great addition to the shack that makes me wonder why I didn’t do this earlier. Yeah, I could have purchased a set of amplified PC speakers, but that just didn’t seem appropriate. Besides, the amp in the Ten-Tec enclosure looks spiffy next to all of the other similar looking equipment in my shack.

Update

I got a bit bored tonight, so I took a video to demonstrate the amplifier working with the VRX-1. Yes, I know there’s nothing to really look at, but the audio is a bit interesting.

Sure Electronics EUA2005 Audio Amplifer Lash-Up

Lately, I’ve found that eBay has been one of the best ways to beef up my junk box with inexpensive electronics components (eBay Stores are my preference, the auctions often aren’t that great). I purchased a nice SMD resistor/cap assortment from a company called Sure Electronics and found that they have some other goodies that might be of interest to the homebrewer. One of those is a tiny little (about 1″ x 1″) 2 watt mono audio amplifier based on the EUA2005 IC. The spec sheet states that the IC output power is 1.5 watts, so the manufacturer might be fibbing a bit on their specs. Regardless, it’s enough power to drive a 3″ speaker to a decent volume for shack listening. The IC has a maximum V_CC of 6 V, so I had to create voltage regulator to step my 12 V bench supply down to 5 V using a 7805. The audio quality is definitely what I would call “communications” grade, but the price is great: $2.22 for a 2-pack. One word of warning: your order is shipped from Hong Kong, so expect about 2-3 weeks for your order to arrive.

For those working on W8DIZ’s frequency counter project in QQ, they also have a Atmel STK500 in-circuit programmer clone for a very inexpensive price. I haven’t had a chance to try mine out yet, but if it works as advertised it’s well worth the price (I have no reason to believe that it won’t work, but if doesn’t, I will update this post).

The usual disclaimer applies: I’m not associated with the company in any way, just a satisfied customer.

Software Defined Radio is a technology which has always intrigued me, but something I just haven’t been able to devote a lot of time to yet. I’ve built an early model SoftRock and studied the basics of the theory. Not too long ago, I built up my own little version of a 40 meter SDR based on a different topology from the SoftRock (VXO feeding a quadrature hybrid, driving passive MOSFET mixers). It worked so-so, and it ended up in my pile of experimental boards.

Subharmonic SDR Schematic

Today in my feed reader, I caught wind of a really neat topology for a minimal parts count SDR, courtesy of Joachim, DL1GSJ. His receiver uses a simple phase shift network to create the I/Q LO signals to drive a pair of Polyakov (subharmonic) mixers. It looks dead simple to breadboard and could be an easy way to try SDR without having to order a SoftRock kit. Get over to Joachim’s blog to get the full details of this fascinating design.

A little while ago, I got a hankering to work on a SSB transceiver. It’s something that I’ve never homebrewed before, and it seemed it like it might be fun to tackle. The BITX20 seemed like an obvious choice, and W7ZOI recently published an improved bidirectional amp which would be nice to try in the rig. But I’m one who likes to try stuff that’s a bit off the beaten path, so I decided to try my hand at something a bit different.

VU2PEP has a lesser-known SSB design on his website, that’s a dual-band transceiver. Besides having 20 and 40 meter capability, it also has a different topology than the BITX series. Instead of reversing the flow of the signal to generate a SSB signal, this design sends the RX and TX signal in the same direction through the IF. Take a look at the schematics to get an idea of what I’m talking about.

I decided to make a “remix” of this design. The basic topology is the same, but most of the circuits are revised. The IF was moved to 4.9152 MHz, and the VFO is heterodyne-style to provide a ~19.12 MHz LO signal. My version is only for 20 meters. The front end has a preamp added and uses a cascode JFET mixer instead of a single JFET. So far, the RX strip and VFO is complete (although I might change the VFO because of some birdie problems), but the transmit amplifiers haven’t been built yet. I got a good chance to work out the RX during Sweepstakes. Check out my YouTube video below to hear me describe the circuit so far and listen to the receiver on SS.

New England Code Talker by AA1TJ

Although there are many days when I can barely stand the level of rudeness on QRP-L (and increasingly on qrp-l.org), I am sometimes reminded why I maintain my membership. Some recent events there have helped to boost up the numerator in the signal/noise ratio, and correspondingly, my interest.

In case you haven’t followed much of what has happened on the list in the last few years or haven’t listened to SolderSmoke, there’s a fellow by the name of Michael Rainey AA1TJ, who could be considered the mad genius of the QRP world. He has created what has to be considered some of the most unique and inventive minimalist QRP circuits that our hobby has ever seen. Take a look at his website to get an idea of what I’m talking about. I’ve also attached a YouTube video below showing you how AA1TJ has to operate this very unique transmitter.

AA1TJ trying for transatlantic QSO

His latest flight of fancy is his New England Code Talker voice powered CW transmitter. Yes, you heard correctly; the transmitter is powered 100% by voice sound pressure energy (about 15 mW RF output). AA1TJ has already made numerous successful QSOs with the transmitter, proving that the concept actually works. Recently he, AA1MY and W1PID met at the beach front cottage of W1REX to attempt the world’s first voice powered transatlantic QSO, as well as what was claimed to be the world’s first transatlantic QRP QSO on 160 meters (I think I misunderstood that. It’s supposed to be AA1MY’s first 160 meter transatlantic QRP QSO), both very amazing feats. I won’t spoil the story, so get yourself over to W1PID’s website to read the details of how this expedition turned out. I must salute all of you gentlemen for pushing the boundaries of our wonderful hobby and trying something never done before. Well done!

Update: Here’s the “Rexpedition2009” report about the event from W1REX (PDF format).

Update 2: A great video from W1REX showing the transatlantic 160 meter QRP QSO:

While I occasionally get a bit worried about ham radio having to be dragged kicking and screaming into the 21st century, there are encouraging signs that some hams get it. The two areas in ham radio where this seems most pronounced is in Radiosport and DXing/DXpeditions. Outside of the United States, these aspects of the hobby seem to be doing a decent job of attracting folks under 50 to our nerdy little world (no offense to you crusty old guys; without you our hobby would be non-existent). I’m not quite sure why, but inside of the US, these pursuits haven’t quite had the same pull on the younger crowd. Speaking for myself, I’ve never felt I could seriously tackle either activity without having the ability to deploy a half-decent antenna, something I’ve only recently been able to do because I just purchased my first single-family house. Perhaps other younger folks have had a similar problem.

Anyway, let me show you the efforts of a few people who have helped in blowing a little dust off of our vintage hobby. First up is the website and video blog of XR0Y, the Rapa Nui (Easter Island) DXpedition. These guys have a very visually appealing website with tons of information about the operation, a blog to keep you updated on the latest news, a Twitter feed, and perhaps best of all, a really cool video blog. The production values are top-notch (they are promising HD video of the actual operation) and it’s interesting to get a behind-the-scenes look at a DXpedition from start to finish. Here are the first three videos in the series; it looks like many more are on the way:

Next, a topic a little bit nearer to my heart, courtesy of W2LJ. Larry was contacted by VK1AA regarding a new QRP transmitter kit from GenesisRadio called the Q5. It looks like this kit is geared towards the new kitbuilder/homebrewer, perhaps as something to build on a club “kit night”. The design uses CMOS logic for the LO and driver amp, which feeds into a class-A PA (about 1 watt output). I don’t see any low-pass filtering on the output and there’s no specification on the spurious products, so an outboard filter might be in order.

GenesisRadio got an excellent video spokesman for their kit; young VK2FJDX. Check out the FB job he does in promoting the new kit: