Ham Radio EMCOMM Go Kit – Radio Cases v4

I’ve been building and rebuilding my go kit for a couple of years now and every time I do it I learn something. What I learned since I built my last version is that I really value versatility. When building a go kit you should think about what you need the kit to do and how you will be using it. The two previous versions of my kit (see here and here) both used rack cases to contain the radios and other equipment in one complete package. This works great for multiple reasons: it provides a lot of protection, with the covers on the cases are dust proof and water resistant, the cases are stack-able and the operator has easy access to all the radio’s ports. There are two big negatives that go along with rack cases as well: they are bulky and they add a lot of weight.

For my new go kit build I wanted to cut the bulk and weight of my kit substantially (I did some math and found that for my previous VHF case the rack case itself weighed more than the radios inside it). I also wanted to divide the kit into more versatile modules so that I only have to carry what I need in a given scenario. This is a similar idea to what I did when I rebuilt my battery box; going smaller and simpler instead of all out.

To achieve this goal I decided to use Tac-Comm tactical radio carriers. These carriers are made of aluminum, are lightweight, they stack on top of one another, tilt bales & handles are included and they offer a lot of flexibility for how you can mount equipment. On their website they emphasize the use of nylon webbing straps to secure radios, power supplies, etc. That’s fine, but I prefer to bolt things solidly in place. These carriers are not weather tight, so in the event that I need to expose them to inclement weather I will keep them inside a plastic bin to prevent equipment damage. In the end I used three carriers: two standard size (for power supply & VHF/UHF) and one large (for HF).

The power supply module uses the same Powerwerx power supply I have used on all the previous builds. It works great, is compact and doesn’t put out RFI. I mounted it in the standard carrier using the same brackets as previously and added two Anderson powerpole ports to the back of the case. It’s a very straightforward build. I thought about putting a top on the carrier, but leaving it off gives me an easy way to store the power cord and radio power jumper wires. I removed the standard tilt bale to allow for stacking on top of the larger carrier. Including cables the power supply module weighs 5.6 lbs.

The VHF/UHF module uses the same Kenwood TM-V71a and SignaLink USB combo I’ve used in the past. The radio is mounted in the carrier using the standard mobile mount. I added an ABS plastic plate in the back of the carrier to allow a place to mount a USB pass-through port and a powerpole. This provides a convenient place to hookup when in the field and gives every internal cable a place to land so nothing is loose and flopping around. The layout I chose leaves space on the side to mount the microphone inside the carrier for easy transport. Tac-Comm also sells covers to protect the front and rear of the carrier and I used a front cover with an ABS plastic extension to protect the radio’s display & knobs as well as keep the microphone cable inside the carrier. To top it off I used Tac-Comm’s steel top cover which is magnetic and allows for the use of a small mag-mount antenna for instant field deployment. The VHF/UHF module weighs 7.9 lbs.

The HF module uses the same Yaesu FT-450D transceiver I have used before, but this time I changed my digital interface. Instead of a SignaLink USB I decided to use an inexpensive USB soundcard wired directly to the radio’s data port and I key the radio via it’s serial port using rig control. I chose this soundcard because I know from previous experience that it has a low noise floor and works well for digital communications. This new arrangement saves a lot of space and allows me to reduce the carrier to its minimum height without sacrificing any functionality. The transceiver is mounted to the carrier using the same angle brackets as previous builds, only the hole placement is different. Similar to the VHF/UHF module I used another ABS plastic plate for USB & powerpole connectivity and another optional front plate for protection. I also was able to mount the microphone internally for transport. The HF module weighs 15 lbs.

The end result of all this is that I now have a very versatile and vastly lighter go kit. Since each radio and power source are separated from one another, I no longer have to carry anything I don’t need when going to the field; if I’m going to run on battery, I can leave the power supply module and vice versa. Even as a complete kit I reduced the volume of equipment by at least 50%. All together this new kit weighs 28.5 lbs, compared to 40.5 lbs for v2 and 52.25 lbs for v3, a reduction of 30% and 45% respectively. Needless to say I am very happy with the end result. Any protection I have sacrificed is more than made up for by the additional versatility and reduced weight.

Elecraft KX3 Station Accessories

Earlier this summer I purchased an Elecraft KX3 to use as a portable radio as well as my main station radio when paired with my Hardrock 50 amplifier. To facilitate both of these scenarios I had to make a couple of accessories to adapt my existing gear to the KX3.

The KX3 has several 3.5mm and 2.5mm jacks on its left side for the microphone, headphones, accessory connections, RX I/Q data, etc. Since the mic jack is the only way to get audio into the radio and I operate both voice and digital interchangeably quite often, I didn’t want to have to unplug the mic connection every time I changed modes. To solve this problem I built a microphone connection switch box. The box allows for the connection of a common 8-pin round microphone plug (in this case wired to the Kenwood/Elecraft wiring convention) as well as a 3.5mm jack for the output of the sound card I use for digital modes. The two are switched via a DPDT toggle switch and connect to the KX3 with a TRRS 3.5mm right angle plug. Both connections also feature 0.1uF DC blocking capacitors and the sound card side includes a 10:1 voltage divider which results in a 20dB reduction of the sound card output. This allows for much easier control of the audio going into the radio and helps prevent over-driving of the mic input. The blocking capacitors were intended to prevent any mic bias voltage from affecting my dynamic desk microphone, however, I found that some still got through. To solve this issue I made some macros for the KX3 to switch between desktop voice, digital, and portable voice configurations. This allows me to turn the microphone bias on or off and adjust the mic gain and compression depending on whether I am using the desk mic and foot switch in my station or a handheld microphone while portable.

The other accessory I made is for portable digital operation. I wanted to keep my setup as compact and light as possible, so I wanted to avoid having to take my SignaLink USB with me in the field. I found a good compact USB sound card, but I wanted to add some isolation from the radio as well as some signal reduction from the sound card output to the radio similar to what I did in my microphone switch box. For isolation I used ground loop isolators to reduce the possibility of interference between the radio and the sound card. To reduce the sound card’s output I used another 10:1 voltage divider to reduce the output by 20dB. In this case I only did it to the left channel since this is the default used by most digital programs and it is the same position on the 3.5mm mic jack as the microphone input on the KX3. Fortunately I was able to install the voltage divider inside of the isolator case itself by carefully prying apart the two halves. The voltage divider resistors were then soldered directly to the isolator circuit board and fit inside the case with plenty of room. The isolator case snapped back together when I was done modifying it without any glue necessary.

So far my KX3 accessories have been performing well and they make an already great little radio that much easier to use.

Ham Radio EMCOMM Go Kit – Power Box v2

I only built the previous version of this box a few months ago, but I learned a lot from building that case. The main thing I learned is that rack cases aren’t necessarily the best option for a power case. Rack cases are great for radios because they provide ready access to the front and rear of radios and other gear. For a power box the extra lids, bulk, and weight of a rack case don’t provide enough benefit to overcome the drawbacks. I also quickly realized that I really don’t need an inverter. I found a very compact and high performing 12V adapter for my laptop that makes the inverter unnecessary. This all combined with the awkward power wiring and inadequate power monitoring of my previous case pushed me to rethink my power box.


I wanted a case that would make the most of the small size of my 40 Ah lithium-iron-phosphate battery. The one I ended up using is only $15 at Lowes. The battery sits in the case and is kept from shifting by stacks of cardboard cut and glued to fit the taper of the case. This works well to keep the battery stable while allowing for easy removal when needed. The power circuit is wired with 10 AWG wire and the battery is fused using 40 Amp ATC fuses.

Power System

From the battery the power flows through a West Mountain Radio PWRcheck. This device is an inline power monitor that measures voltage, amperage, power, and amp hours. It can also log power usage and provide a battery gauge when the battery’s amp hour rating is input via the unit’s control software and USB connection. The PWRcheck can also be setup to alarm at low and high voltage along with other features. The PWRcheck then feeds a WMR Epic PWRgate. I used this device in the previous build and it works well as a battery charger in addition to channeling power from solar, battery, or power supply inputs to the output. Both the PWRcheck and PWRgate are mounted using heavy duty velcro, the PWRcheck to the top of the battery and the PWRgate to the side of the case. This allows for easy removal, while also securely holding them in place. The PWRgate’s solar and power supply inputs and its power output are wired to powerpoles mounted to the outside of the box. All wiring was done using 10 AWG wire except the solar which is 12 AWG since it doesn’t carry as much current. I also used blue & gray powerpoles for the solar connections to differentiate them from the others for easy identification. The final piece of the power system is a WMR RIGrunner 4005 mounted to the outside of the case using heavy duty velcro. This allows flexibility to either provide power distribution from the case itself or move the RIGrunner to another location and provide power from there via an extension cable from the power box. All of the power system devices are rated for 40 Amps of continuous current which is more than enough for my purposes.


I really wanted to keep this build super simple and flexible while maintaining a lot of functionality and I feel good about how it turned out. The case itself is just the battery, power monitoring and a charging/distribution system. Everything is modular, light and there aren’t any unnecessary devices or wiring. This new version of the power box weighs in at only 16.5 lbs, a little over half the weight of the previous build. My previous go kit total weight was about 70 lbs (radios + power) and the new arrangement totals about 69 lbs. This doesn’t seem like much of an improvement, however, since I rarely need both radio cases I end up saving quite a bit of weight for real world applications. For example, a Field Day or QSO party deployment (HF + power) with my new cases totals about 46 lbs, over 20 lbs lighter than my previous iteration and over 50 lbs lighter than if I used my lead acid battery. I especially like how much less bulky this version of the power box is and the ease of portability that this provides.

Update (June 2018)

After using my new power box for a little while it became apparent that it would be a good idea to have a more convenient way to turn off the power, and therefore minimize any discharge from the battery, than simply unplugging the main powerpole connection. To this end I decided to remove the fuses and in their place put a 40 A circuit breaker. This breaker is bolted to the outside of the case, making it very convenient to access compared to the fuses. This change also necessitated rerouting some of the wiring, but I think it ended up better arranged than before. I used the power box in this configuration for Field Day with my solar panel and everything worked perfectly.

Ham Radio EMCOMM Go Kit – Radio Cases v3

This third version of my go kit is more of a revision than a compete rebuild. After using my previous build for about a year I realized that while it is nice to have everything in one box, it is also a lot of extra weight and bulk that I don’t necessarily need. For the most part, when I operate a portable radio station I don’t use both HF and VHF/UHF, so carrying both is excessive. The solution for this is something I considered while planning my previous build, splitting the kit into a HF unit and a VHF/UHF unit.

HF Case

In order to keep this revision simple I tried to keep the shelf layouts as similar to the previous build as possible. The HF case reuses the lower shelf of my previous kit with only small modifications. The shelf was mounted in a 3 unit shallow rack case. The removal of the upper shelf from above the HF radio necessitated moving its SignaLink to the top of the power supply where it was attached using heavy duty velcro. This arrangement led me to remove the HF radio’s external speaker since there is now unobstructed space above the radio which allows for decent sound projection. The power wiring is also very simple. I kept the power supply output powerpoles as they were and added another powerpole connection for the HF transceiver. This allows for easy access to either connection. I also changed the power supply’s power cord to be removable; the previous build had it wire tied in place which turned out to be an awkward arrangement. Finally I added a new rack panel with a USB pass-through for the SignaLink. The HF case ended up weighing 29.5 lbs (including lids, microphone, and cables).


The VHF/UHF case reuses the top shelf from my previous build and includes several modifications. The shelf was mounted in a 2 unit shallow rack case. The biggest change was the addition of a dedicated power supply (Astron SS-12). In order to hang the power supply from the shelf I removed the top cover of the device and mounted it to the shelf using #8 hardware and fender washers. Then the power supply was reassembled. The bolt locations were chosen to avoid the internal electronics of the power supply while still distributing the weight of the device.  The SignaLink and microphone connection had to be re-positioned to make room for the power supply. The separation of the radios also necessitated eliminating the powered USB hub. As in the other case the power supply output and radio power input were pulled out to the back of the case for easy interconnection. Finally I reused the rack panel from my previous build to provide access to the dual-band transceiver’s antenna and the SignaLink’s USB connection. The VHF/UHF case weighed in at 22.75 lbs (including lids, microphone, and cables).


Each case can be used by itself or as a pair. When used independently a jumper can be used to power the radio from its associated power supply, or an external power source can be used. When stacked I can use the HF case power supply or other sources (like my Power Box) to feed a RIGrunner which distributes power to both radios.

Either single case configuration results in me saving at least 10 lbs compared to my previous kit. If I do need both, the total weight is more (52.25 lbs vs 40.5 lbs), but since it is split between two cases it actually makes it easier to move. This also has the benefit of not physically tying both stations together. I can deploy somewhere and one person can operate the V/U station and another the HF and they don’t have to be sitting on top of one another. In the end I think this is a much more versatile and useful setup than my previous go kit.

uBITX QRP Transceiver

Last year I assembled a BITX40 QRP transceiver from a kit and it turned out well. For under $60 it is a surprisingly good 40 meter radio. Now it has a big brother that adds more bands, more power, better performance, more features, and is still incredibly affordable. It’s also easier to build.

The uBITX is much more than just a multi-band BITX40 (the uBITX covers 80-10 meters); the receiver is much more refined and the difference between the two is not subtle at all. The uBITX has much cleaner audio and sounds more like a commercially available radio than the BITX40. It also tunes like one with a proper encoder for tuning instead of a potentiometer. To access the various modes and features of the radio there is a clever menu system that makes use of the encoder’s built-in pushbutton for navigation. Like the BITX40 before it, more advanced firmware (firmware upgrade instructions) has been developed for the radio’s microcontroller and a ton of features have already been added (Rig Control, IF Shift, CW keyer, memories, band limits, WSPR, and many more).

The amount of improvements implemented in the uBITX are especially evident in the assembly process. Where the BITX40 had many individual connections between components and the pre-assembled boards, the uBITX needs only four:  power, antenna, audio, and digital. This makes wiring the uBITX a much simpler process than its predecessor. The one added complexity was aligning the screen with the cases front faceplate since the screen’s header now plugs directly into the main board instead of using a cable.

My uBITX build is similar to that of my BITX40. I used the same style case made of shielded ABS plastic with aluminum end plates (Hammond 1598RDBK) and a top mounted speaker. Due to the additional band capabilities and other upgrades the main board is about a half inch bigger in each dimension. This small change required me to use a different case model from my previous build.

The case’s removable end plates and the socketed board connections make it very easy to assemble & disassemble the radio. I kept the wiring as short and tightly bundled as possible in addition to using small coax for the antenna connection to try to reduce interference. Beyond the standard controls and connections I added a power switch, used a USB panel mount extension to provide easy access for firmware updates & rig control, installed a pushbutton in place of a CW key jack to use as a tune button, and upgraded the volume pot & audio jacks to higher quality versions than those supplied. This also allowed me to use the volume and tuning knobs that I liked. The headphone jack is wired such that it cuts off the speaker when headphones are plugged in.

If you want to build a simple, but still perfectly usable radio the uBITX is absolutely the way to go. It offers many more features and vastly improved performance over the BITX40 for less than twice the price at $109.

Update – Two Simple Mods (January 2019)

Sources for tons of uBITX mods and upgrades

  • Audio Pop Fix – Solves the issue of getting a blast of audio static from the speaker when switching from receive to transmit. This fix has been incorporated into the new v4 circuit boards (v4 schematic), but since mine is an older v3 board (v3 schematic) I did the mod myself. I followed the guides here, and here and mounted the parts directly to the board similar to the latter example. What I like about this method is that everything fits on the main board so final result is fairly clean. This mod involved drilling a hole in the board and scraping off some of the insulating film on the bottom, as well as exposing a few traces on the top side of the board. The mod works perfectly and looks more tricky than it is if you take your time. Be careful to get the orientation of the transistor correct since different parts have different pin-outs.
  • Increase Mic Gain – The default microphone gain is inadequate for the three different mics that I have tried. I could never drive the transmitter properly with a normal speaking voice. This super simple mod definitely improves the microphone response and is highly recommended if you have poor microphone response, even on the new v4 boards which do not incorporate this mod. There are more complex microphone mods around but this one works well and only involves replacing two resistors.

HobbyPCB Hardrock 50 Amplifier & Auto Tuner Kits

Now that I have a couple of QRP radios, especially the very capable mcHF, I became more interested in amplifier options to boost my power output when the need arises. I also wanted to build the amp myself to add to my collection of kit built equipment. After looking around, I decided to go with the HobbyPCB HARDROCK-50 Amplifier and ATU.

At $300 for the amplifier and another $180 for the tuner this is not the most economical kit, however, this is a very full featured amplifier and the antenna tuner adds a lot of additional functionality. The amplifier can be driven by a PTT signal or a carrier and also features rig interfacing with some QRP radios for automatic band switching. Both the amplifier and tuner can be inline or bypassed. This is a great feature since the tuner can be used with your radio at QRP levels when you don’t need to use the amp. It is also a very wide range tuner, covering roughly a 10:1 SWR range. The tuner board also adds 60 meter band and standalone Watt/SWR meter functionality.

The kits themselves are very well put together with well made boards (pre-populated with surface mount components) and good quality components. The case is super rugged and all of the machining and fit and finish were very well done. I really like that the amp is completely air cooled and should only require a fan under extreme circumstances. The instructions (HR-50, ATU) are also very well put together with lots of pictures and a ton of detail to step you through the assembly, calibration, and operation of the amplifier.

The amplifier section took about 7 hours to build and calibrate. Most of this involves soldering all the components (including all 15 relays) as well as winding and mounting the 14 inductors. The auto-tuner board took another 3 hours to assemble. This board is almost entirely relays (17) and inductors (9). Integrating the two boards together is very straightforward. It’s a testament to the design of these kits that you can build the amplifier as a standalone kit and then add the auto-tuner later and only have to modify one coax connection.

These kits have been around for a few years and various corrections and bugs have been ironed out, so my kits didn’t require any hardware mods and came pre-loaded with the current firmware revisions. The amp’s screen displays the hardware, amp firmware, and ATU firmware versions on boot-up.

Once everything is running the screen displays the current keying mode, the band selected, heatsink temperature, and power supply voltage. When the amp is keyed the LED turns red and the display shows a bargraph of power output as well as the SWR and output power in PEP. To initiate the auto-tuner you press the Key Mode button after keying the amplifier.

In order to integrate the amp with my mcHF I adjusted the full power setting of the radio from 10 watts output to 2-4 watts output depending on the band. This was done to provide the appropriate drive level for 50 watts out of the amplifier. Using this setup I tuned around the bands and found a Belgian station calling CQ on 80 meters and received a good signal report when I responded to him. Not a bad first contact. I look forward to using this amp and tuner more in the future especially with my mcHF since I am no longer limited to QRP operating.

Ham Radio EMCOMM Go Kit – Power Box

In the months since completing my revised go kit earlier this year, I have been considering building an improved version of my battery box. I wanted to use the same style of rack case that I used for my go kit and at the same time add a lot of versatility and functionality compared to what my basic battery box offered.


  • Reduced Weight
  • 12V Power Output
  • 12V Charging, Switching and Distribution in the Box
  • 120V Power Output
  • Battery Voltage & Current Monitoring
  • Solar Compatible


Reducing weight meant moving away from the lead acid battery that I used previously. These work fine and are not overly expensive, but they have a lot of limitations. My battery box used a deep cycle battery that weighs about 55 pounds. This new build uses a Bioenno 40Ah lithium-iron-phosphate battery that weighs about 10 pounds. It is also significantly smaller and can supply power for a longer period than my old battery. These batteries are not inexpensive ($360), however, they should last through significantly more charge-discharge cycles than a lead acid battery and when combined with the weight and space savings these benefits justify the price.


To handle the battery charging, power switching, and solar power requirements I used the West Mountain Radio Epic PWRgate. This device is a major step in evolution compared to other power gate products in the past. Older units could automatically switch power between a battery and power supply in addition to trickle charging the battery when the power supply was on, but they were only compatible with lead acid batteries. The Epic PWRgate supports multiple battery chemistries and charge rates, making it much more versatile (you select the battery chemistry and charge rate by removing the cover and setting two jumpers to the appropriate values). It is also much more efficient with a reduced voltage drop and no large heatsink. It can take inputs from a power supply, battery, and solar panels while it simultaneously outputs power. Depending on the state of each it can charge the battery from the solar panel or power supply, or direct battery power to the output if the power supply is unavailable. To complete the DC output power distribution system I used the 5 port West Mountain Radio Rigrunner from my old battery box.


While not always required, I wanted to have the option to power or charge devices that use 120V. To accomplish this I added a Samlex 300W Pure Sine Wave Inverter to the system. While this is a fairly low wattage for an inverter, the intent of this is to power devices such as laptops, monitors, HT battery chargers, etc. that don’t require a lot of current. I went with a pure sine wave model since they produce much cleaner power, which should help reduce RF noise as well as work better with whatever electronics I am using.

Power Monitoring

For battery voltage and current monitoring I used a standard 1.125″ digital DC Voltage Meter and a Blue Sea Systems Shunt Current Meter. This current meter can measure current in both directions which allows me to monitor both the current draw under load as well as the charge current depending on how I am using the system at that moment. I wired the power inputs for both meters through a switch so that when I don’t need to monitor the state of things I can turn off the meters. This is very handy at night when you may not want bright LEDs shining in your face.


The DC power wiring consists of an inline Maxi Fuse Holder connected to the battery’s positive terminal. I used a 50A fuse for the main feed and 8AWG wire. This is routed through the current meter shunt and into a 4 circuit Blue Sea Systems ATC Fuse Block. I used 2 of the circuits:  a 30A, 10AWG feed goes to the PWRgate and a 2A, 16AWG feed is used for the meters. The battery’s negative terminal was connected directly to a Blue Sea Systems Busbar. The inverter was wired directly to the current meter shunt and the common busbar. I also ran a ground wire from the inverter ground terminal and through the hole in the back panel. This wire was terminated with a green powerpole for easy connection to a ground rod and serves as a safety ground for the AC circuit.


The case itself is very similar to that used in my go kit, except this box is a 3 unit shallow case instead of a 4 unit. The shelf is the same model used in my go kit. All of the components were mounted to the shelf using 8-32 & 10-32 machine screws. I had to get a little creative to figure out how to secure the battery to the shelf. In the end I used 3 heavy duty jumbo wire ties to cinch the battery to the shelf and 2 nylon spacers secured with 10-32 machine screws to prevent the battery from sliding laterally under the wire ties. So far this arrangement seems very secure.

The front and back panels were made using 11/64″ thick sheets of ABS plastic. The front panel required notching in the bottom corners to allow for the shelf mounting screws as well as ventilation holes for the inverter fan. The back panel features a large cutout for the inverter outlet & switch and serves as the mount for the PWRgate & Rigrunner. I also added section of 1″ aluminum angle to the back panel which adds a lot of rigidity and prevents flexing when power cables are plugged and unplugged. One unforeseen modification involved the rear case lid. Since the PWRgate is mounted in the center of the case, it’s powerpole connections protrude just enough to make contact with the center brace of the lid. I debated moving things around, but in the end I notched the lid brace using my Dremel and a small cutting wheel. Due to the tight packaging, the jumper wire from the PWRgate to the Rigrunner has to be removed when putting on the lid.

Go Kit Integration

Since the PWRgate is now separate from my go kit I had to modify my go kit’s power wiring to accommodate this new arrangement. This involved adding a powerpole distribution block and permanently mounting the power supply output to the case. For full charging and battery backup capability jumper wires have to be run between the power supply in my go kit to the PWRgate and from the Rigrunner to the new distribution block in my go kit. I tried to organize my jumper cables the best I could to keep things as neat as possible and I used very flexible 10AWG wire with silicone insulation to minimize any cable stress and tangling. When stacked, the two units integrate together very well.


All together the power box weighs just under 31.5 lbs which is pretty good in my opinion. I’ve added both capacity and a huge amount of capability compared to my old battery box and it still only weighs about half as much.

BITX40 QRP Transceiver

The BITX40 is an interesting project. It is an inexpensive ($59) QRP 40 meter band SSB (LSB only) transceiver that comes as a semi-preassembled kit. The main boards are built and tested by the manufacturer in India and the end user only has to mount the boards in a case and wire the power, controls, and antenna connections. The radio itself is controlled by an Arduino microcontroller using a version of the Raduino firmware and a digital synthesizer chip provides frequency stability. Due to its simple design it is easily modified and there are dozens of mods on the internet that can be performed to add features. My ham radio club did a group build project of this radio and we had over 20 members put together their own BITX40.

One of the most convenient features of this kit is that the main boards make use of connectors to simplify construction. This also makes the radio very easy to disassemble since nearly all of the wiring can be unplugged. The kit comes with all the parts you need (other than a case, speaker, and knobs), however, I made a few changes. I had a couple of 6mm shaft knobs that I wanted to use that did not fit the potentiometers that were supplied. I also wanted to implement a couple of the simplest and most useful mods. I ordered the following parts from Mouser:

The pushbuttons are useful due to the features added in the modified Raduino firmware. With the new firmware installed, the white pushbutton serves as a Menu button that provides access to the additional features included in the firmware (Multiple VFOs, RIT, Split, USB, CW, frequency calibration, scanning features, and many others). One of the interesting things about the firmware is that if you have it installed and do not add any buttons or other mods, it still behaves like the default firmware. Only when you perform the appropriate mods does the additional functionality become accessible.

Another mod I performed allows the red pushbutton to serve as a Tune button. When pressed the radio automatically switches to CW mode, keys the transmitter, and generates a tone to allow tuneup of an antenna tuner. This functionality actually requires 3 separate mods (PTT Sense, CW Carrier, and TX-RX) which are detailed in the updated firmware’s documentation. They involve soldering a couple of resistors to specific locations on the board as well as a transistor across the PTT line and wiring from these components to the Arduino’s IO points. In order to maintain my ability to easily disassemble the radio by removing the case’s front and rear panels, I used a 2 pin header to create my own connectors for plugging and unplugging some of the additional wires that were added for these mods. The final modification involved soldering a 100pF capacitor in parallel with the inductor L7. This helps suppress the 2nd harmonic to levels that are acceptable to the FCC.

For the speaker I drilled some holes in the top of the case to let the sound out and mounted the speaker.  I left the wires long so that it is easy to remove the top of the case and lay it to the side without having to unplug the speaker cable from the main board. Using a speaker is highly recommended for this radio instead of using headphones. This is due to the fact that the BITX40 has no AGC (although there are mods to add one) and consequently the audio from strong stations is drastically louder than weaker ones. This difference in volume could easily hurt your ears if you were wearing headphones.

An electret microphone element is provided with the kit and I wired it up with a pushbutton in a small enclosure to work as a hand mic. I secured the mic element and the shielded cable using hot glue. This arrangement required me to wire the mic and PTT lines to the same 1/8″ stereo jack on the front panel, even though they have separate connections to the main board. As basic as this setup is it functions well and I have had good audio reports on the contacts I have made using it.

The best word to describe using the BITX40 is funky. After years of using modern complex transceivers, the BITX is almost shocking for how simple it is. You tune around and adjust the volume, that’s about it. Nevertheless it works, as long as you abide by QRP operating procedure:  find the strongest station on the band and weight for them to call CQ or QRZ. It’s pretty impressive how simple this radio is and how little you really need to make contacts.

I put a fair amount of effort to construct this radio carefully, however, some of my ham club’s members who built their own ended up with a spaghetti of wires and their radios still functioned fine. Because all of the complex circuitry is pre-assembled and tested, the hardest part of this project is already done. That is a key part to this being a great project because it allows people of all skill levels to build something and be virtually guaranteed that at the end they will have a working radio. In my club we had people who had never soldered before build this radio (with plenty of guidance) and they were all smiles when we powered up their creation the first time. The combination of affordability and functionality make the BITX40 an amazing piece of technology and a fantastic addition to ham radio.

QRP Link Dipole Antenna

Dipole antennas are some of the simplest antennas to build in addition to being very efficient and solid performers. I wanted to make a simple dipole antenna for QRP portable operation that could be used on multiple bands. I also wanted it to be light enough to be supported by my light-duty 31 ft Jackite mast in an inverted V configuration.

Link dipoles are a great way to make a lightweight multi-band antenna because you only have one run of wire (vs a fan dipole), there are no traps or coils, and you don’t need a complicated and heavy balun (vs an off-center-fed dipole). Band selection is achieved by connecting or disconnecting the appropriate links to make the antenna as long or short as needed to work on the band you want. To keep the antenna as light as possible I used 26 AWG insulated stranded copper-weld wire from The Wireman (#534). This wire is small, but because it has a steel core it is stronger than pure copper wire would be. It also has very tough insulation that protects the wire very well and is exceedingly lightweight (1000 ft weighs under 1 lb, and I am only using about 66 ft).

For the physical links in the dipole I used Nite Ize MicroLock S-Biners. These are small polycarbonate double-carabiners that are more than strong enough and very light. I made a loop at each end of every antenna section and secured it using adhesive lined heatshrink tubing. While not the strongest connection this should be adequate for this application since the antenna is so light that there isn’t much strain on any one point. The electrical links in the dipole were made using Anderson Powerpoles. The antenna itself was cut for the 20, 30, and 40 meter bands. I am considering adding an 80 meter section in the future, but that may add too much weight.

The center feed-point was made using a small piece of 1/8″ acrylic. This was drilled for antenna wire strain relief as well as #8 bolts for the connection between the antenna and the coaxial feedline. I decided to forego using a 1:1 balun at the feed-point to save weight. The feed assembly is secured to the mast using wire ties. Since every mast section is tapered the assembly can only slide so far down from the top before it fits tightly to the mast. I adjusted the wire ties to place the peak a couple of feet down from the top where the mast is somewhat more substantial and can more easily support the weight of the antenna. For coax I have been using RG-58, again to keep the weight down. I may end up moving to RG-8X in the future if the mast can support it since it is much lower loss.

A handy feature of this antenna is how easy it is to put up. The mast is a good match for my car’s flag pole hitch mount (using a 2″ PVC spacer) and is strong enough to be freestanding. To erect the antenna I just have to secure the upper three sections of mast (the sections friction lock together), place the mast in the mount on my car, unroll the antenna, slide the feed-point onto the mast, connect the coax, push the rest of the mast up, and spread out & secure the antenna ends. I can be on the air in about 5 minutes.

All of my efforts to keep the antenna as light as possible definitely paid off. Together the antenna and winder weigh only 15 oz (not including feedline). This makes it a perfect match for the lightweight mast and a small QRP radio. I look forward to getting a lot of use out of this setup.

Ham Radio EMCOMM Go Kit – Solar Charging System

Field operations using batteries are very common and my battery box is a very convenient source of power. For longer term operations, however, keeping the battery charged is just as important. In order to supplement my battery system I put together a small solar charging system.


  • 50 Watt, 12V Solar Panel – Renogy
  • 10 Amp PWM Solar Charge Controller – Renogy
  • 1″ Aluminum Angle

The goal here was to have a simple solar system that would be large enough to charge my battery box at a decent rate, while still being small enough to transport easily. I also wanted to keep the costs fairly low.

I went with a 50 watt solar panel since it is fairly compact (around 2 ft square), inexpensive (about $80), and puts out almost 3 amps at peak sun. The charge controller (under $30) prevents the panel from overcharging the battery when the sun is out and blocks the panel from discharging the battery when the sun goes down. The aluminum angle frame holds the parts permanently together (which simplifies field wiring) in addition to holding the panel at a 30 degree angle. A 30 degree panel angle is a good compromise for my latitude and helps maximize the panel’s sun exposure throughout a full day. All together the panel, controller, and frame weigh about 12 lbs.


I used this setup with my battery box and go kit for Field Day this year and it performed very well. I generally do digital only on Field Day and made over 160 contacts using PSK31 and RTTY with the radio set for 50 watts output. With the sun out, the panel kept up with my power usage and by sunset the battery was essentially fully charged despite me operating for several hours. I continued to operate after sunset and quit around 1AM. I resumed operating mid-morning and the few preceding hours of morning sun had recharged the battery back to near full charge.

As with any battery testing, the current draw is the deciding factor for how long your charge will last. Since Field Day is in many ways a contest I was transmitting quite a bit which increased my current draw compared to more casual operations. Overall I operated around 16 hours and never drained the battery below 12V. If I turned the power down, I could probably operate the entire 24 hours and dropping from 50 to 25 watts would have minimal impact on my ability to make contacts.

Update (June 2018)

Along with upgrading my power box, I also wanted to upgrade my solar charging capability. Since I already had a 50W panel, I decided to buy another of the same size from Renogy and make my own folding 100W panel system. I used basic zinc plated hinges and keep the panels folded using a simple bolt and aluminum plate system. The bolts also provide points to allow the attachment of aluminum legs to keep the panel tilted at a 30 degree angle to pick up maximum sun. I also mounted a comfortable handle to make the panel system easier to carry. The two panels are connected in parallel and then connected to the power box via anderson powerpoles. This allows the panels to charge my 40 Ah lithium iron phosphate battery via the Epic PWRGate inside the power box.

I used this setup during Field Day this year and it worked very well. We had a mix of clouds, sun, and some rain but the panels were capable of keeping up with my HF digital station (running at 50 watts). In full sun these panels will charge the battery with about 6 amps, more than enough to keep up with the radio’s average power usage which is about 3 amps (mostly receiving, transmitting  about 25% of the time). This keeps the battery more or less topped off during the day. I didn’t operate all night, but I did put in several hours after the solar panels had stopped producing power. In the morning the panels came to life again and charged the battery back up some even while I was operating. By the time I packed up I still had about 28 Ah left in the battery according to my PWRCheck. Overall I am very happy with my new power box and larger solar panel system.