CC-Series, Design, Meta, OpenBeacon

Catching Up With Etherkit

The year is not starting out as well as I had hoped. Back during the beta test of the CC-20 I had set a goal to complete my revisions and be ready to sell production kits by 1 January 2012. Obviously that date has come and gone and I’m still not on the market. A few circumstances have contributed to this situation. First, the days available for me to work exclusively on Etherkit has been cut from 4 per week to less than 2 due to family member’s work schedules being changed. Second, it took me longer than expected to tackle the bugs in the CC-20 beta; the worst being the high number of spurs in the receiver.

So where does thing sit right now? The next CC-20 board revision is just about ready to be implemented. I’ve had to move to a DDS with a higher master clock frequency and change out the product detector from a dual-gate MOSFET to a diode-ring mixer. One advantage of the new DDS is that I can greatly simplify the transmitter circuitry, but this will require the trade-off of a fairly significant revision of the PCB.

I have been getting my PCBs manufactured in China, and right now many of the manufacturing firms (my board house included) are shutting down for two weeks to observe the Spring Festival (Chinese New Year). So even if I do send my Gerber files to the board house, they probably won’t be back for at least a month. In the meantime, I’ve decided to work on a side project that’s been rattling around in my head for a while: a QRSS/CW/Feld Hell/Etc. beacon. Also, in response to a lot of positive response that I have received from my simple Twin-T code practice oscillator, I also spent a few days revising the circuit to make the output a bit more robust and then created a PCB for the circuit in Kicad so I could transition my EDA to an actively developed software package (I was using TinyCAD/FreePCB previously, which seems to be pretty much a dead end).

OpenBeacon Prototype
OpenBeacon Prototype

So allow me to tell you a bit more about the beacon project. For now, I’ve decided to dub it OpenBeacon (I know, so very original). But there is a decent reason for the name. Much like the CC-Series, I intend for this project to fill a niche in the market that is very empty right now. The list of notable open source/open hardware kits out in the market is very small. The only one I think of off the top of my head is OpenQRP. As far as QRSS kits, I’m only aware of the one from the talented Hans Summers. My goal for this project is to provide a kit that is open, extensible, relatively inexpensive and simple, and ripe for user modification. Let me tell you a bit more about the project specs and how they fit into this goal.

Let’s start with the bare hardware. The transmitter is a standard, vanilla Colpitts oscillator followed by an emitter follower buffer, which feeds a class A PA with fully adjustable output power (provided by a very cheap and cheerful part, the BD139). At full-bore with 13.8 VCC, the transmitter can put out about 300 mW into 50 Ω. The brains of the operation is an Atmel ATtiny85 microcontroller. The way that it interacts with the transmitter is via its PWM output, which can generate a voltage from 0 V to 5 V after proper filtering. This control voltage is fed to a reversed-biased LED which acts as a varactor to tune the oscillator in very tiny amounts (< 10 Hz). The PWM output is essentially an 8-bit DAC, so not only can the varactor be flipped between 0 V and 5 V, but it can be set to many intermediate values, which allows for things like Feld Hell and just about any kind of graphic or glyph you can think of to be transmitted. The transmitter PA is also keyed with a PNP transistor which is controlled by the ATtiny85, which allows the OpenBeacon to operate in standard CW beacon mode.

The main way in which this project will meet the goals I stated above is in its user interface. There is a handy open source project called V-USB which gives USB interface capability to AVR microcontrollers that do not have USB built-in. This allows me to wire a USB port to the ATtiny85 and have the V-USB firmware take care of all the ugly business behind the scenes so that I can focus on interfacing the OpenBeacon to a PC. With a simple command line program, the user will have the ability to switch between the many operating modes available, set his own callsign and beacon message without having to have the microcontroller programmed for him, upload custom glyphs to be transmitter, and monitor the status of the beacon. No need to mess with jumpers or in-circuit programmers (although the ISP port will be available for those who want to hack their OpenBeacon). The client program is written in C and should be able to be compiled for Linux, Windows, and OS X machines.

KI6FEN Grabber Capture
KI6FEN Grabber Capture

Right now, the prototype is pretty much complete save a few minor tweaks. Yesterday, I got the code for the CW modes completed and put the beacon on the air in DFCW 6 second dit mode just above 10.140010 MHz. Conditions weren’t great, but I did manage to get a few weak captures on the KL7UK grabber and one from KI6FEN via Twitter. The signal was way too wide and extremely drifty, but I’ve solved those problems by changing the coupling capacitor between the LED varactor and the oscillator and by creating a rudimentary thermal chamber for the beacon out of pink antistatic foam. I’ll be leaving the beacon on for the next few days when I’m not working on the project (which will be most of the day). Any reception reports would be greatly appreciated!

So the plan is to get the CC-Series PCB revisions hopefully done by next weekend so that they can be sent off to the board house before their vacation is over. In my little bits of downtime, I’ll continue work on the code for the OpenBeacon. The plan for this project is to get the PCBs cranked out very quickly. Now that I’m familiar with Kicad, I think it won’t be too difficult or take too long to design the boards. I’m also going to be trying out a new PCB vendor which promises much cheaper prices and faster turnaround times on smaller boards such as this. With any luck, I can fast-track OpenBeacon testing and production and have it out while the CC-Series is in it’s final beta test. Stay tuned, this is make-or-break time!

CC-Series, Operating, QRP

Two Watts Across the Pacific

I don’t know exactly why, but I’ve had a bit of an obsession with the T32C DXpedition to Kiritimati since they got started a few weeks ago. Maybe because I found them easier to work than many of the DXpeditions that I’ve tried before. The fact that they are a very well-run operation has something to do with it, I’m sure. Whatever the reason, once I got a few contacts under my belt, I became driven to try to work them on all band slots practical for CW and SSB. I have a ZS6BKW antenna, so I can load it up from 10 to 80 meters. I figured 10 — 80 was a reasonable goal, but I knew the lower bands were going to be tougher since my antenna is only up at about 30 feet.

With the bands being as hot as they have been in the last month or so, it hasn’t been a great challenge to fill up the band slot chart for the most part. Almost all of the QSOs made over the last few days have been snagged within one or two calls (I also thank W9KNI’s book The Complete DXer for teaching me very valuable basic DXing skills). I will admit that I’ve been running 100 W output for these QSOs — with one important exception.

20 meters CW was one of the slots that I had not yet filled as of this morning (oddly enough, since that’s THE DX band). Over the last few weekends, I’ve been hacking away on the firmware to the CC-Series, trying to get the last major features up and working bug-free. Thanks to a request from AA7EE, I just implemented XIT on top of the RIT that was already in the firmware (speaking of Dave, go check out his even more impressive T32C QRP story). The nice thing about XIT is that it allows you to relatively easily work split stations like DX, even though there is no “official” dual-VFO capability in the rig. Since the XIT capability seemed to be mostly working correctly, I wanted to put the CC-20 on the air to try it out and be certain. The first station that I worked today with the CC-20 was K6JSS/KL7, operated by well-known Alaskan QRPer AL7FS. It was a simplex QSO, but it was nice to bust the mini-pileup with my first call. While continuing to work on CC-20 development, I monitored the DX cluster to see when T32C would show up on 20 meters. Sure enough, I ended up seeing him pop up on the cluster at about 0200 UTC. Time to put the CC-20 to the test.

I don’t have a valiant battle to describe. It took me about 10 calls to finally get him, although there weren’t a lot of people calling him. I suspect that the majority of my trouble in getting him was in zero-beating him with the unpackaged encoder knob. While in RIT or XIT mode, pressing in the tune knob toggles between the TX and RX VFOs. Trying to do that quickly when it’s not mounted on a chassis is tricky! Regardless, it didn’t take long until I heard the sweet sound of my callsign coming back to me across the vast Pacific Ocean. Two watts spanning 3600 miles to a tropical island in the middle of a huge ocean is pretty neat. This doesn’t rank in the annals of great QRP achievements, but it will always be a memorable QSO for me.

CC-Series, QRP

The First Wild Beta

AA7EE CC-20 Beta 1
AA7EE CC-20 Beta 1 Interior
AA7EE CC-20 Beta 1
AA7EE CC-20 Beta 1

Here it is, the first CC-Series beta unit completed by someone other than me! As is obvious by glancing at the photos, Dave AA7EE has done a magnificent job of assembling the CC-20, as well as creating a custom enclosure for the radio out of red copper clad using the WA4MNT technique. There’s really not much more for me to add, except to tell you to get yourself over to Dave’s blog to check out his story about the build and to see more shiny photos.

CC-Series, Random Musings, VRX-1

Junkbox

No earth-shattering news to report on the blog, but a few little things to mention (hence the “junkbox” title).

The CC-20 Beta 1 test is proceeding pretty much as planned. As of tonight, AA7EE has his receiver up and running now and a couple of the others are close behind. I’m eagerly awaiting the results of at least a couple of the builds so that I can get moving on the revisions for the Beta 2 circuit (which will hopefully also be the production PCB). I’m anxious to get the business up and running!

I got a very nice mention from Bill Meara on the latest episode of SolderSmoke. He talks up Etherkit and my blog, then mentions that he’s going to try to use the single-ended passive MOSFET mixer from the VRX-1 in his homebrew WSPR transceiver. I hope that the experiment works out well for him.

As we approach the halfway point of the gestation of our new little one, I got to thinking about mortality a bit. I hope to be around for a very, very long time to come and have been taking steps to improve my health to make that more probable. But in the awful case that something were to happen to me in an untimely fashion, it seemed that I’d like my family to have a little bit of my own thoughts with which to remember me. At first, I thought that maybe I should do a private journal, but then it occurred to me that wasn’t necessary. Barring a complete collapse of civilization, all of my descendants will be able to access an archive of all of my Internet activity. Every blog post, tweet, Google+ post, website comment…and perhaps even my email. If you Google my last name, I’m the first result. I’m active enough online that it’s not entirely inconceivable that a reasonable avatar of myself could be created sometime in the distant future (given that Moore’s Law holds up in some fashion for the next 50 years or so). Perhaps this is all pie-in-the-sky speculation and will look as foolish as the “flying car future” does to us now, but I’m pretty sure that I’ll live on in human information space in some fashion long after I’m gone.

CC-Series

The CC-20 Lives

I’ll admit there were times when I thought I might never get this thing working, but dogged persistence in the face of frustration will sometimes get the job done. Failure to accept the mushy and hum-ridden audio finally led me to crack the tough nut.

11 - 1
Today, I finally slew the new CC-20 beta dragon. Without getting into a long, drawn-out rant about what went wrong, I’ll just say that transcription errors and schematic capture screw-ups did me in. I believe that at least 5 separate problems with this PCB turn were discovered in the end. All of the errors kind of “stacked up” on each other. Solving one would lead to a marginal, but not final improvement. The big problem is that a couple of those were very subtle errors to troubleshoot.

The big one that finally restored the receiver to the glory that it deserves was a missing decoupling resistor in the IF amplifier. That one little change took the audio from minimally functional, low sensitivity, and full of DDS spurs to the clean, sensitive, and spur-free receiver that I knew the prototype to be. Even after I identified the problem, I almost missed the fix because of some kind of strange routing that I did with the VCC line. But enough banging my head against the bench, and I managed to beat some sense into my brain and fix the problems once and for all.

A bit more tweaking finally got the radio ready to go on the air for its first QSO today. Repeatedly calling CQ on 14.060 MHz resulted in no answers, forcing me to wonder if I screwed something else up, like the carrier oscillator alignment. But I heard a strong station a few kHz down and thought I would try to give them a call instead. It turned out to be KD0V in Minnesota, who was blasting in at a strong 599. He gave me a 559 in return and commented that the transmitted note sounded good to him. Due to my frazzled nerves, I kept the QSO fairly short and called it a day after the exchange of the usual information.

So it looks like the beta kit is finally in a state where I can package it and send it out. Many people will be happy with this news; first and foremost being my wife and the long-suffering beta testers. Let’s hope for the best during the beta test and maybe I can get out of this without a permanent nervous condition.