Elecraft T1 QRP Autotuner Kit

img_0841In the months since I completed my mcHF SDR transceiver kit, I have thought about building a QRP antenna tuner to go along with it. After some investigating I came across the Elecraft T1 which is available assembled or as a kit and can handle 10W of continuous power. While I have never owned any Elecraft gear, they have a very good reputation and several people in my ham radio club swear by their equipment. The kit looked like a fun project and a perfect match for my QRP gear so I decided to order one.

img_0842The kit took about a 4.5 hours to complete. The included instructions are very detailed and do a good job of emphasizing critical parts of the build. The biggest issues arise in regard to several components that need to be mounted in a very specific way in order for the case to fit properly. The circuit boards are fairly tightly packed, but anyone with good soldering experience should have no problem assembling this kit.

img_0844img_0843The finished product is very compact and incredibly simple to operate. I really appreciate that the instructions are printed on the front label in case you forget. So far I have used it to tune a couple different antennas of various designs and it performs very well. It finds matches quickly and the relays aren’t annoyingly loud like some autotuners. I look forward to getting a lot of use out of this and my mcHF.

Manual Antenna Tuner

Manual Tuner (10)Manual Tuner (9) Automatic antenna tuners are incredibly convenient devices. They also require power, interface cables, and many have a limited impedance matching range. Manual tuners, on the other hand, feature a simple design and can have a very wide matching range.

Manual Tuner (6)Manual Tuner (4)After deciding that I wanted to build a T-match type of tuner, I needed to find some high voltage air variable capacitors. I looked around at what was available and found this great pre-made assembly that features two 22-360pF variable capacitors (rated for 1kV) and a 12 position rotary switch (rated for 5A). This should be able to handle 100W when properly matched. After deciding on this component I selected an 8″ x 6″ x 3.5″ aluminum enclosure for the tuner.

Manual Tuner (2)The next part of the tuner is the inductor. In order to make use of the 12 position rotary switch I needed to make a coil with taps. I also had to keep the coil relatively small so that it would fit in the enclosure I was using. After doing some research I found that an inductance of 30-40uH is typical for a T match antenna tuner and should be able to match a good range of impedances from 160M – 10M. K7MEM has a great single layer air core inductor calculator that uses common PVC pipe as a coil form. For the coil I decided to use 18AWG teflon insulated wire since it should be large enough to handle 100W and the teflon insulation is both easy to work with and very heat resistant. Using the calculator I found that 46 turns of wire on a 1.25 inch PVC pipe resulted in a 35uH inductor that would fit nicely in the enclosure.

Manual Tuner (5)To wind the coil I used a ring terminal to secure the starting end and started winding. At every tap point I separated the insulation and soldered a jumper to the exposed wire. Then I continued winding until the next tap point and so on until I finished the coil with another ring terminal. I tapped the coil at turns 2, 4, 6, 8, 12, 16, 20, 24, 30, 36, and 42. The finished coil was then bolted on top of nylon spacers to the enclosure.

Manual Tuner (3)Manual Tuner (1)To finish the tuner I wired the taps in the order they were wound to the rotary switch. The start of the coil should be wired to the point where the variable capacitor rotors are connected together. The end of the coil should be grounded to the enclosure along with the common point on the rotary switch. Each variable capacitor stator is wired directly to the center of a SO-239 connector, one to the input and one to the output of the tuner. Finally, I added a ground stud to the enclosure.

Manual Tuner (8)Manual Tuner (7)When using a tuner of this design it is good to keep in mind that the most efficient match occurs when the capacitance is at a maximum and the inductance is at a minimum. Therefore when adjusting the tuner I always start with the capacitors at close to their maximum setting (fully meshed) and the inductor on the first tap. I then click through the inductor taps until I see a dip on the SWR meter and adjust the capacitors to achieve the lowest SWR I can.

I have used this tuner with a couple different antenna designs and it performs fairly well. When used with various dipoles and other wire antennas I have been able to achieve matches the majority of the time. However, I may need to adjust the design of the coil since it seems that I never make use of the later taps and may not require such a large coil.

mcHF SDR Transceiver Kit

A huge part of the history of ham radio involves people building their own equipment. In fact that is how things started since at the beginnings of radio no commercial hardware was available. Over the years various companies and organizations have sold transceiver kits, but in recent years most of these have consisted of basic morse code only or single frequency single side band devices intended for digital communications. With the increased development of software defined radio (SDR), however, this is changing. Earlier this year I came across the mcHF SDR transceiver project and decided to purchase one of the kits. Unlike other basic transceiver kits the mcHF is a full featured radio with 80M-10M coverage, multi-mode support, variable bandwidth filtering, DSP (noise reduction, notch filtering, etc.), sound card interface, rig control, and band scope / waterfall capability. Not bad for a $388 kit.

mcHF (1)mcHF (2)The project was originated by Chris, M0NKA in the UK about 2 years ago and the design has gone through a number of revisions resulting in the current v0.5, which is what I purchased. One of the major reasons I was willing to undertake this project was that the kit offered by Chris includes the circuit boards already populated with about 95% of the surface-mount parts, including all of the tricky to solder chips and super tiny resistors and capacitors. The only remaining parts to install are larger, and therefore easier to solder, surface-mount parts and standard through-hole components. The builder also has to hand wind several toroid inductors and transformers. You also have to provide your own final power amplifier MOSFETs, shielding plate between the boards, and case for the radio. These requirements go along with the way this kit is sold, which is to say bare bones. The kit includes zero instructions. The builder is responsible for sorting through the mcHF downloads page, the mcHF Yahoo group, and the Github Wiki to find the details regarding how to wind the toroids and transformers as well as details on any recommended mods and instructions for how to use the radio.

Since this project is open source, both the hardware and firmware have undergone considerable development. In fact, from the time I started building the board to when when I completed the project a large firmware update was released which revised the main screen and menu layout as well as added a number of fixes and features, including the ability to control the transceiver via the USB port and detect the transceiver as a sound card device with a PC.

mcHF (3)The mcHF consists of two circuit boards called the UI board and the RF board. I built the UI board first, and then built the power supply section of the RF board so that I could power up and test the UI board. Chris has a very helpful document on the mcHF webpage that steps through the process of installing the bootloader and uploading firmware to the CPU on the UI board. So after only about 4 hours of work I had a functional UI board.

mcHF (7)Next I completed the remainder of the RF board, which was fairly time consuming since winding toroids and transformers is a tedious operation. Documentation exists for how to wind the transformers, however, the only information regarding the toroids is on the RF board schematic which details how many windings each core requires. Extra attention should be paid to stripping the enamel wire used for the toroids and transformers. Even though I diligently sanded off the outer coating and thought that I had solid solder connections to the board, I did not do a good enough job on two of the toroids which prevented the radio’s operation on the 80M band. After desoldering and re-sanding the wires I achieved a good electrical connection and consequently 80M functionality.

mcHF (10)mcHF (11)This portion of kit construction is somewhat confusing because there are a ton of possible mods for the various transformers that can improve performance of the final power amplifier. I decided to build mine in the default configuration which results in a solid 5W output on 80M-12M and about 4W on 10M. When modified, users report 10 or more watts of power output. The only modification I made was with regard to the SWR bridge where RG-178 coax is used in place of a single winding of enamel wire. Construction details for many of these mods are available in a document on the Yahoo group produced by Clint, KA7OEI who has done considerable work on both the hardware and software of the mcHF.

Although not technically a mod, I did add a resistor that is regarded as “optional” on the UI board schematic. This resistor provides power for when an electret microphone is used. Since I would be modifying an Icom HM-36 I had lying around to work with the mcHF, I needed to install this resistor in order for the microphone to function. For this I used a standard 1/4W resistor since I had on of the correct value in my junk box and just soldered it to the surface mount pads. In order to avoid shorting with nearby components I carefully shaped the resistor’s leads and used electrical tape to insulate between the parts.

mcHF (5)mcHF (6)After completing construction of the boards, I turned my attention to completing the radio as a whole. The first step of this was to construct the shield plate between the boards. For this I used a thin mcHF (12)sheet of aluminum that I hand cut, drilled and nibbled according to a pattern available on the mcHF website. I then test fit and assembled the board and shield sandwich to check for proper clearance. When I was satisfied I completed the assembly using 5mm standoffs.

mcHF (19)mcHF (17)If you look around the web you will see a lot of people who have built the mcHF using the same case. This case is sold by Artur, SP3OSJ from Poland for about $63. If you email him at asnieg@epf.pl he will give you the details for how to order. The case comes with all of the knobs and buttons as well as a small piece of acrylic to protect the LCD display. The front panel is pre-machined, however, the endplates are left to the builder to complete. I also had to file some of the button holes to allow smooth operation and I had to sand the acrylic to fit the opening in the case.

mcHF (8)mcHF (9)Since the case serves as the heatsink for the power supply circuitry as well as the final amplifier transistors, a good mechanical connection between the components and the case is necessary. To mcHF (13)mcHF (14)accomplish this I soldered brass #4-40 nuts to the heatsink fin on power supply and amplifier components. I then drilled holes in the case to match where these nuts line up when the case is mcHF (15)assembled. When bolts are inserted and tightened, the electrical components are pulled tight to the wall of the case. In order to achieve a properly aligned connection, I had to grind away a small amount of material where the final amp transistors contact the case (note the hole I drilled in the wrong location due to my inability to follow the old rule of measure twice drill once). The last step in construction was labeling the buttons and ports, which I did using vinyl self-adhesive labels and my laser printer.

The final adjustment before testing the transmitter involves setting the proper bias for the final amplifier and then setting the transmitter gain for each band of operation. Documentation for these adjustments is on the Github Wiki. Basically you set the bias in one of the mcHF’s menu settings while keying the transmitter with no audio present as you watch the current draw of the radio. The transmitter gain is also a menu setting. These adjustments can be accomplished with an ammeter and a RF power meter.

mcHF (16)Finally, after about 20 hours of work I put my mcHF on the air. After adjusting my microphone gain I made a contact on 40M SSB. I then plugged the transceiver into my PC and fired up WJST-X. Following the guide on the Github Wiki I was able to get rig control working and made a half dozen contacts using JT65 on the 30M band using nothing but the mcHF and my laptop. The next day I checked into my local 10M SSB net and received good signal and audio reports from the other regulars who are familiar with my voice.

Overall I have to say that I am incredibly happy with the mcHF kit. It has been a great learning experience and the radio itself is an incredibly capable and configurable device that offers a lot of bang for your buck. I plan to use the mcHF quite a bit in the future and look forward to any future firmware updates. I also hope that this kit leads to other similar kits in the future that can help get more hams back to building equipment.

I highly recommend this kit for anyone with some electronics experience. While the documentation has not been collected into one easily digestible package, the kit itself is actually very straightforward to put together and I was able to get it on the air with only a cheap multi-meter and an RF power meter. It is also an incredible bargain for such full featured radio; I spent under $500 total for the kit, case and other ancillary parts (not including the microphone) which is not bad at all when you compare this to what is available commercially.

 

 

 

Solar Chargeable Portable Battery Pack

There are a lot of rechargeable lithium battery packs available. Some have a lot of capacity and others can be used with solar panels, however, I could never find one that fits my requirements. The solar models that I’ve seen generally don’t have much capacity and use such small solar panels that they don’t charge very fast. Then I came across Adafruit’s USB/Solar Lithium Ion Charger board and it solves all of my problems. This board has a lot of cool features: it can charge a battery via a solar panel or any other 5V input and it can deliver power to the MintyBoost from both the input and the battery simultaneously. In this way you could charge a device on a not so sunny day by drawing some power from the solar panel and the rest from the battery.

My main goal for this project is to have a versatile power pack for use when I go camping/backpacking. I have a fair amount of devices that I typically bring with me that can be charged via USB: camera, headlamp, UV water purifier, cell phone, mp3 player, etc. The 6600mAh battery can charge any of these devices multiple times, providing many days of capacity before needing to be recharged. On sunny days the 3.4W solar panel can recharge the battery if I am away from power for a long period of time. At full power the solar panel will take about 12 hours to fully charge the battery. While this is a long time, for my use case this should be fine as I will most likely be topping off the battery with the solar panel not charging it from zero. I like this solar panel for its combination of size and capacity. A larger panel could charge the battery faster, but would be a lot less portable.

Parts List

Adafruit has a detailed tutorial that explains how the charger board works and shows how to wire it to the other components. Basically the charger board is connected to both the battery and the MintyBoost and uses either a USB or solar panel input to provide input power when you want to charge the battery. The charger also has the option to output the charging status (charging, charging complete) to external LEDs.

For this project I used a red LED to indicate that the unit was charging and a green LED to indicate that the battery was fully charged. I also isolated the battery from the remainder of the system using a power switch. This prevents the small self drain inherent to the MintyBoost from discharging the battery when I am not using the unit. You just have to remember to turn it on when you want to charge the battery. In addition I used a coaxial power jack for the power input and modified both the solar panel and a USB cable with matching coaxial power plugs of the same size. The final piece was using a scavenged panel mount usb port for the MintyBoost’s output.

I have to say that I really like this setup. I can charge all of my devices and when placed in the sun, the solar panel started charging the battery with no problem.

Arduino Intervalometer – Update

Intervalometer_2+2Since I first made my arduino intervalometer two years ago, I have used it several times and come to the conclusion that I could make a few improvements to it. The first change I wanted to make had to do with powering the unit. The original design allowed for an external power source and while this allowed for maximum flexibility, it also made the device somewhat unwieldy. Whenever I wanted to setup for a timelapse shot I had to not only bring the intervalometer but also a mintyboost or other power source as well as a power cable. The other major change I wanted to make was to reprogram the timing ranges to something more useful.

Intervalometer_2+3Intervalometer_2+1In order to power the unit I could have simply placed a mintyboost inside the intervalometer and changed the wiring accordingly, however, I did not want to have to open the device to change batteries. To get around this and still be able to provide the 5V power I needed I decided to use a lithium polymer rechargable battery. This requires both a charging circuit and a voltage booster to convert the battery’s 3.7V to 5V. Luckily Sparkfun Electronics makes just a device that charges the battery via a micro-USB port and is also very compact. Since the intervalometer draws only 28mA while running I chose a 1000mAh battery which not only fits inside the case it should also power the device for over 30 hours, more than enough for a typical timelapse session. Now I have a completely self contained, rechargable intervalometer.

For timing ranges I changed the low range to 1-60 seconds in 1 second steps and the high range to 5-300 seconds in 5 second steps. I think this should end up being much more useful since most of the timing intervals I have used are under a minute in duration and having the capability to more finely tune that interval will be very handy.

Arduino Word Clock

I first saw a clock with this type of design on the Make Blog over a year ago. It is an incredibly clever idea, but the $1000 price tag is a bit much for my taste. I had seen a few attempts at a DIY version but most of them were still too complex or expensive to build. Needless to say when I saw this Instuctable I got really excited. It is based off of another Instructable, however, it simplifies the design and construction to the point where I felt confident that I could build it.

I followed the Instructable pretty closely, with the following exceptions:

LEDS:  I got my LEDs from Evil Mad Science, which sells packs of superbright 5mm LEDs in various colors. This project requires a pack of 100 white LEDs. For current limiting resistors I used 470 Ohm instead of 1K Ohm. This allowed me more flexibility since I can dim the LEDs as much as I want, but I can never make them brighter. The LEDs I used are very efficient and only draw 4.8mA with a 470 Ohm resistor, so the maximum power draw for the clock will be about 150mA. Consequently power usage is not an issue since I used a repurposed cell phone charger as the power supply and it can provide 700mA at 5V.

Letter Mask:  I had to use 4 transparencies stacked in order to get the mask dark enough. I also used a wider border for the letter mask to cover up some imperfections around the edges of my transparencies. For LED diffusion I used some translucent plastic folders that I found at an office supply store. I got a multicolor pack so that I could try different configurations and decided that a combination of one gray and one white folder cut to fit in the frame was the best looking and most functional choice.

LED Holder:  Instead of a cardboard LED holder I used foam poster board. This is a much stiffer material and makes the holder much sturdier, however, it is also thicker so I had to make the light baffles 1″ high rather than 1-1/8″.

Circuit Board:  Since the wiring on this project is fairly complex I decided early on that I wanted to keep the circuit board as simple as possible. In order to accomplish this I used two Radioshack breadboard matching printed circuit boards. These are great boards since they have power buses running down the sides of each board and they have plenty of room for the 7 chips necessary for this project. This made it very straightforward to scratchbuild an Arduino on one of the boards and then wire it to the other chips. Note: when building an Arduino in this way you need an FTDI cable which plugs into the 6-Pin header on the board in order to program the Arduino.

I mounted the boards side-by-side on a piece of acrylic to make it easier to work with. I also wired the board such that I could add a photoresistor in the future to allow for dynamic LED dimming (its wiring is bundled separately for later use as shown in the photos). Instead of wiring headers I just wired directly from the circuit board to the LEDs using multicolor wire to differentiate which word group I was wiring to (you can see each ULN2003A’s bundle grouped together in the photos).

The size of these boards prevented me from trying to mount them inside the picture frame, however, mounting the boards on the back wasn’t a problem. As shown in the photos I had use some stacked foam board as spacers between the back of the picture frame and the wall to keep the board from rubbing agains the wall. I also changed the power socket mounting from the back of the frame to the bottom by cutting a notch in the wood and gluing it in place.

Conclusion:  The biggest problem I had with this project was dealing with a slightly imprecise LED layout. This resulted in some of light baffles partially blocking the wrong letters. After removing the problem baffles, however, I found that my diffusion layers worked well at making up for any discrepancies due to LED placement as well as reducing cross-letter light bleed to an acceptable level. As far as the code goes the only changes I made were done to make use of external pull-down resistors instead of internal and to clean up the code a little bit since some of the comments no longer made sense. I really like this project. It is not only cool looking, but it is useful as well.

Arduino – Parallax RFID Reader

A few months ago I saw some Parallax RFID readers at Radio Shack on clearance and decided to pick them up since they were such a good deal. I have wanted to make an RFID related project for some time after seeing this episode of SYSTM.

Here are some pictures of my test setup. As you can see the reader’s LED changes from red to green when it is reading a tag.

Peggy 2 LED Matrix

The Peggy 2 is a 25×25 LED matrix kit from Evil Mad Scientist Labs. Ever since I first saw the Peggy kit I thought it was one of the cooler kits available. I finally got around to getting one of these awesome kits and it is a sight to behold. By far the largest kit I have ever built, it is also the best quality kit I have come across. The Peggy 2’s circuit board is probably twice the thickness of a normal printed circuit board, a welcome feature for such a large board since the added thickness makes the board very rigid. You can purchase the Peggy 2 in a variety of kit configurations; I got the so called awesomeness bundle which includes a power supply, extra pushbuttons, and 640 diffused 10mm LEDs in the color of your choosing (white in my case).

The build itself took around 2 hours to assemble the control circuitry and another 4.5 hours to solder all of the LEDs. It’s a bit of an undertaking, but when you’re done it’s a great feeling when all 625 LEDs light up. To program the Peggy you use the Arduino IDE and download the Peggy Library. I haven’t experimented too much with it yet, but I did try out some of the demo programs from the library and you can see what the Peggy can do in the video below. I look forward to playing with this project a lot in the future.

Remote Camera Shutter & Focus Controls

In the process of building two intervalometers (analog, Arduino powered), I learned how easy it is to construct a remote trigger for a DSLR’s focus and shutter controls. Both of those units featured manual controls for focusing and taking photos, but I wanted to build another separate project that would only feature that ability. This would allow the device to be much smaller and lighter.

For this build I used a 3″x2″x1″ RadioShack project box, a 3.5mm stereo socket, and two momentary pushbuttons. In accordance with how my Canon Rebel XSi works, I wired the shutter trigger (red pushbutton) to the tip of the socket and the focus trigger (black pushbutton) to the middle contact. Then I wired the other side of both switches to the shield of the socket. I am a big fan of using a socket for a project such as this since I can now use a cable of any length or configuration as long as it has a 3.5mm plug on the end that plugs into the box. This is an incredibly simple build that works great and should come in very handy for all my remote triggering needs.

Vacuum Tube Audio Amplifier – Update

 

Tube_Amp_Enclosure1Ever since I first completed this project I have wanted to build an enclosure for it. I wanted something that would decrease the risk of electric shock while also showing off the cool aspect of the vacuum tubes, ie. their characteristic glow.

In order to keep it simple I bought a sheet of aluminum that had a pattern of pre-punched holes in it at the hardware store. This allows the tubes to be ventilated while still being visible. I then made a template out of cardboard to determine what shape needed to be cut from the sheet of aluminum that could then be bent into a proper enclosure. I made sure to leave tabs on the sides so that I could secure adjacent sides of the box to one another with sheet metal screws. I then relocated the power switch to the top of the case and attached the enclosure to the wood base with screws. Overall I am fairly satisfied with this enclosure. It’s not the perfect case for a project like this since you have to remove the box to change burnt out tubes, but it is good enough for my purposes.

Tube_Amp_Enc23 Tube_Amp_Enc21About two months ago I made an enclosure for my vacuum tube amplifier. While a decent first effort, I became more frustrated with it as time went on. The poor nature of my design prevented me from accessing the tubes themselves as well as the speaker wire connection points on the main board. Also, esthetically, it blocked the view of the vacuum tubes too much.

Tube_Amp_Enc22Instead of starting over from scratch, I decided to try to reuse the existing enclosure. In order to solve my complaints with the previous design I came to the conclusion that what the amplifier really needed was a circuit board cover, not a full enclosure. To accomplish this, I shortened the enclosure by cutting off the back couple of inches of aluminum. This allowed access to the speaker wire terminals. Next I removed a couple more inches from the bottom, shortening the overall height of the enclosure. Then I cut out a rectangle in the middle of the top to allow the tubes to stick through. Finally I re-attached the case to the base board using six screws instead of four, the two additional screws in the front greatly stiffened the whole unit.

I am much more pleased with my second attempt at enclosing my vacuum tube amplifier. It is much more functional, as well as better looking.