Boafeng UV5R USB Soundcard Interface

I recently purchased a Baofeng UV5R5 to throw in my Go Kit as a backup handheld and I decided to build an interface to be able to send and receive digital signals. The interface was intended to be as simple and inexpensive as possible, much like the radio itself.

VHF/UHF digital EMCOMM transmissions in my area typically use the MT63 mode which is very robust and can work quite well using only acoustical coupling. While this technique works surprisingly well, it has limitations. If the area you are operating in is too noisy, your audio is too weak, etc. the data transmission can have issues getting through correctly. It also doesn’t work very well for modes other than MT63.

USB soundcard interfaces are very common, I have multiple SignaLink USBs myself, but they are definitely overkill for this application. After some experimentation, I built this simple interface for under $20.



The main idea for this project was to replace the external speaker microphone functionality with that of the USB soundcard. In order to do this I used the speaker mic cable and wired it to two 3.5mm stereo audio cables such that the speaker output from the radio connects to the microphone input of the soundcard and vice versa. Each splice was soldered and insulated with heat-shrink tubing. The entire joint between the three cables was then secured with more heat-shrink tubing. Each 3.5mm plug was marked with colored electrical tape to make it easy identify which cable plugs into which port of the soundcard (red for microphone, green for speaker).


To operate, I plug simply plug in the cables and connect the USB soundcard to my computer (a big advantage of this model of soundcard is that it does not require special drivers for Windows 10 or Linux, it is truly a plug-and-play device). When I am ready to send data I simply key the radio using the PTT switch on the side and click the transmit button in the digital software. When the transmission is finished I unkey the radio. I had originally played around with an external VOX circuit as well as the UV5R’s internal VOX feature, however, neither of them would reliably key the radio and stay keyed throughout an entire data transmission and I decided they were unnecessary. Using manual keying is actually somewhat of an advantage since it simplifies the interface, reduces complexity, and doesn’t require changing the radio’s configuration.


I used FLDIGI to test the interface over simplex to another radio. After some experimentation I found that with the radio’s speaker volume set at a comfortable level (about 1/4 turn) a setting of 50% for the soundcard’s microphone gain was a good audio level for receiving data. For transmitting, I found that a setting of 1% from the soundcard’s speaker produced the cleanest output.

If I was going to build more of these I think I would add a 10K ohm resistor at the connection between the soundcard’s speaker output and the radio’s microphone input. This would attenuate the signal somewhat and allow for finer control over the transmit audio level. Even so, as it stands now the audio is clean and data transmission worked flawlessly. I have used this interface on my local digital net and it performs very well. This has definitely found a place in my Go Kit.

Ham Radio EMCOMM Go Kit – Version 2

Last year I put together both VHF/UHF and HF go kits. While functional, neither of these was as capable or robust as I ultimately wanted my go kit to be. My new goal was to build an all-in-one station in a box that was not overly bulky or heavy.


If you look around the internet you will see a lot of people building go kits in rack cases. I always liked the sturdiness and modularity of this type of case, but not the bulk. Most builders us a full size 6 unit case, which is not compact (roughly 24″ square and 13″ tall) nor lightweight (over 18lbs). After evaluating the equipment I planned to use in the kit I realized that I did not need a full depth case. Using a shallow case saves me 8″ of depth and cuts the weight as well. I laid out several possible equipment arrangements in CAD and found that if I kept the kit fairly barebones (no SWR meters or external antenna tuners, only one external speaker) I could also move from a 6 unit case to a 4 unit and still fit everything I needed. The 4 unit shallow case I used is 22.4″ x 16.2″ x 9.1″ and weighs 12.8lbs.

The general design philosophy for this project was to have all of the equipment mounted to two shelves (one on the bottom and one at the top). After my experiments in CAD I found that a good organizational layout was achieved with the power supply, power distribution, and HF transceiver mounted on the bottom. As part of the power distribution system I wanted to incorporate an automatic backup power switch. This allows the power system to seamlessly change from AC wall/generator power to battery power. While not necessary, this is a nice feature to have because it prevents your radio from turning off while operating if there is an interruption of power (which can easily happen in emergency and field operations).

This left the VHF/UHF transceiver, speaker, and two SignaLinks for the top shelf. The SignaLinks are separated by the speaker to easily differentiate which unit is connected to which radio. I went with multiple digital interfaces because while I will most likely never be transmitting on both V/U and HF simultaneously, it can be very handy to be able to monitor both at the same time or to monitor one while transmitting on the other. Having two units also allows me to never worry about changing radio and SignaLink wiring to operate on the band I need to.

In order to simplify the cabling between the SignaLinks and my laptop I decided to us a powered USB hub and to make the USB hub accessible on the back of the case. This makes it very convenient when in the field since I don’t have to reach into the case to plug in the interface cables. The addition of a rear mounting plate gave me a place to pull out the V/U transceiver’s antenna connection for easier access as well.

I decided one external speaker would be adequate based on the layout I settled on. In this layout there is a fair amount of space below the V/U radio’s speaker to allow for sufficient sound output. The HF radio, however, has much less space above its top mounted speaker. Another consideration I made was that FM audio on V/U is generally very clean, especially compared to SSB audio on HF. Based on this I chose to use the speaker with the HF radio.



The Powerwerx power supply is perfect for go kits. It is very compact (6″ x 5″ x 2″), has convenient Anderson powerpole connections on the front (in addition to terminals on the back), and can be secured with mounting brackets.

The Yaesu 450D offers a lot of bang-for-your-buck and is relatively compact and lightweight as well (9lbs). The built-in automatic antenna tuner does not have the widest range (3:1), but I don’t plan to use it with non-resonant antennas so it should be more than adequate. Making use of the internal tuner also allowed me to eliminate an external tuner from the design, which was one of the key reasons I was able to fit everything inside a 4 unit case. The 450D was mounted using 2.5″ steel brackets along with M4 machine screws and 1/8″ nylon spacers to prevent the brackets from rubbing against the radio’s enclosure. I had originally intended to use Yaesu’s mobile mount for the 450D, however, it took up too much space and would have affected my layout. This arrangement lifts the radio about 1/2″ off of the shelf which should provide plenty of ventilation.

In the preliminary layouts I had planned to use a West Mountain Radio PWRgate and Rigrunner for backup power switching and power distribution. This plan proved impractical due to space restrictions, however, I found the perfect substitution in the Low Loss PWRgate. It is about half the size of the other backup power switch and it provides 3 output powerpoles which eliminates the need for a Rigrunner or other distribution block. While the LLPG is rated for 25 amps vs the 40 amps of the other unit, this should still be adequate for my purposes. The LLPG is very lightweight and was mounted using heavy duty double stick tape.

The Kenwood V71A was mounted using it’s mobile mounting bracket. The voltage converter for the USB hub was screwed to the shelf using its mounting tabs. The other equipment on the upper shelf was mounted using either heavy duty velcro (SignaLinks, USB hub) or double stick tape (speaker). I also added some rubber strips to the bottom of the speaker because I found in test fittings that the clearance between the speaker and the HF radio was only about 1/8″ and I didn’t want any inadvertent contact between them when the case is moved.

Cable Management

Part of eliminating the Rigrunner from my build meant that I had to provide some protection for the power wiring and radios. This was done using inline fuse holders with ATC style fuses. I also had a fair amount of radio interface and USB cables to manage. The shelves I chose are vented which makes them perfect for using wire ties to secure everything in place. I also wanted to make the go kit as straightforward as possible to assemble and disassemble. Part of this goal was limiting the wire tying of cables to individual shelves. This means that if I want to remove a shelf, I only need to disconnect the handful of cables that are connected between the two shelves (two power, one speaker audio, one SignaLink), then unscrew the shelf and pull it out. No cutting of wire ties is necessary.

I really wanted to be able to stow the radio microphones inside the go kit and I found that I could velcro the V/U radio’s mic to one of the HF radio’s mounting brackets and the microphone’s cable would then fit nicely between the power supply and HF radio. This is especially convenient since the microphone jack is in a position that makes disconnecting it a bit of a pain.

The HF radio’s mic is stowed using velcro and a strap to the inside of the front case lid. The lid has enough depth that the mic can fit without contacting the front of the power supply. The power supply AC power cord is stowed using a similar strap method as the HF mic, except it is in the rear case lid.


Part of the goal of using a smaller rack case was to cut down on weight as well as bulk. I had estimated that I could build the go kit and keep the weight around 35lbs. In the end the kit weighs 40.5lbs. I think the lesson I took from this is that wire and mounting hardware add up to more weight than you might realize.


The kit is very straightforward to setup. Once the lids are off I simply unstrap the microphones and power cord. Then I can either plug in AC power or a battery, hook up my antennas, connect USB to my laptop, and I’m on the air. I am very happy with how little bulk this kit has; with the lids removed the case is only 12″ deep and easily fits on a small table. The kit is small enough to integrate perfectly into my home station, which makes it very convenient to make sure everything is fully functional for field operations. I am very pleased with how this kit turned out and I learned a lot of along the way, especially about case layout and parts fitment.

Update – Microphone Connector (February 2017)

After using my Go Kit for a few weeks I realized that the Kenwood V71’s microphone connector was not in the best location. It is on the side of the radio and when the mic is being used it twists and otherwise stresses the microphone’s connector. To improve this situation I decided to extend the radio’s mic connection to the front of the Go Kit. I accomplished this using a 1 foot ethernet patch cable and a RJ45 Inline Coupler. The coupler was mounted on the top of the power supply with heavy duty double stick tape. This new arrangement makes the microphone connection much more accessible and greatly reduces the stress on the connectors.

Ham Radio EMCOMM Go Kit – Antennas

Having a bunch of hardware and the power to run it is all fine and good, but if your antennas aren’t capable of getting the signal out all of those radios are useless.

Mast System

My first priority was to have a good VHF/UHF antenna system. A magmount on the roof of your car is OK, but for local line-of-sight communications the gain and height of your antenna are very important. I also wanted something that I could easily transport and erect by myself.

Antenna Mast (2)After some investigations I decided to aim for a simple lightweight mast system that I could mount to the trailer hitch on my car. The base for this setup is a hitch mount flagpole mount. For the mast I chose the MFJ 1904H. This mast solves a lot of potential problems for a portable mast system:  it is 5 feet long when collapsed making it easily transportable in my car, it is non conductive and will not interfere with any antennas mounted on it, and despite being made of fiberglass it is fairly sturdy (each tube wall is 1/8″ thick). I don’t intend to heavily load this mast so this should serve my needs well. In order to achieve a tight fit between the flagpole mount and the mast I used a section of 2″ PVC pipe as a spacer. When fully extended the top of the mast is about 21 feet high.

I also purchased a 33 foot version of this mast design from Max-Gain Systems. While this version requires some guying, the additional antenna height can greatly increase performance.


Antenna Mast (3)Antenna Mast (1)For the VHF/UHF antenna I chose the Two Way Electronix Dual Band Slim Jim. As someone who uses a J-Pole antenna as my base VHF antenna, I am very familiar with how well these antennas perform. The Slim Jim is a J-Pole made from 450 Ohm ladder line so that it can be rolled up for easy storage and transport. I mount the antenna to the mast using a nylon bolt and wingnut the passes through the insulation at the top of the antenna and a hole drilled in the top fiberglass section. This setup is very light weight and has virtually no wind loading which makes guying the mast unnecessary (under average wind conditions).


For HF I did considerable research regarding what type of antenna is appropriate for emergency communications. A lot of ham radio is focused on making contacts at great distances (DX). This necessitates a low angle of radiation from the antennas being used. For a dipole this means that the antenna should be at least a half wavelength above ground. The most common HF bands used for EMCOMM are 40 & 80 meters (one half wavelength on 40 meters is about 66 feet, 132 feet for 80 meters). For EMCOMM purposes, however, we generally only need to communicate within a couple hundred mile radius of our location. This requires a Near Vertical Incident Skywave (NVIS) propagation path. It turns out that this makes our lives a lot easier since a dipole can be used for NVIS when it is mounted much lower than it would typically be. Instead of trying to get a dipole very high, mounting it at 15 to 20 feet is ideal for this application. Another benefit of this approach is that at this height the dipole loses almost all of its directionality and is essentially omnidirectional.

HF Antenna #1 – Loaded Dipole

My 80/40 Loaded Dipole was built specifically to be center supported by my 21 foot fiberglass mast. It is lightweight, only 78 feet long (60% of a typical 80 meter dipole), and resonant on both bands.

HF Antenna #2 – End Fed Half-Wave

Similar to the Loaded Dipole, my 80/40 End Fed Half-Wave antenna is resonant on the two most common EMCOMM bands. It is also only 76 feet long (58% of a typical 80 meter dipole) and is quick and easy to deploy in the field as a sloper when a single strong support (tree, pole, etc.) is available.

HF Antenna #3 – Folded Skeleton Sleeve Dipole

Field Setup (1)Field Setup (2)When space and strong antenna supports are available my 75/40 meter Folded Skeleton Sleeve Dipole makes for an excellent EMCOMM antenna. It is resonant on both bands and is only 107 feet long (81% of a typical 80 meter dipole) making it somewhat more space efficient without reducing performance through the use of loading coils like my Loaded Link Dipole and End Fed Half-Wave.

HF Antenna #4 – Hamstick Dipoles

Antenna Mast (4)In an effort to maximize portability and reduce both setup time and the footprint of my antenna system I bought 80 and 40 meter versions of MFJ’s hamstick dipoles (MFJ-2240, MFJ-2275). These are heavily loaded antennas that use a base section consisting of a coil wound on a fiberglass rod with a stainless steel whip on the top. While a small loaded antenna will not have the efficiency or the bandwidth of a full size antenna, it is considerably smaller (15 foot span). The dipoles are lightweight and my fiberglass mast seemed plenty strong enough to support them.

Performance (updated February 2017)

I have done 24 hour WSPR tests of both the Loaded Dipole and End Fed Half-Wave antennas and they perform similarly, which is to say they are quite effective antennas. I used the End Fed Half-Wave during Winter Field Day and was able to easily make contacts on both 40 and 80 meters using both SSB and PSK31.

To test the Folded Skeleton Sleeve Dipole my Ham Radio club used it during Field Day 2016 and made over 350 contacts. They even loaded it up on bands other than 80 and 40 meters and it performed well. I would say this is definitely the best antenna of the four, however, it is also the largest and heaviest.

I have yet to do much with the Hamstick Dipoles, but I plan to do some testing in the future.

Ham Radio EMCOMM Go Kit – HF

HF Kit (1)After some thought I decided that I wanted to treat this as more of a HF Field Kit than a true Go Kit. I had heard good things about the Yaesu FT-450D and after seeing sale prices and mail-in rebates drop the price to $600 I decided to buy one. The Yaesu (9”W x 3.3”H x 8.5”D, 8.8 lbs) is not as compact as some HF rigs, but it is nowhere near as unwieldy as my Kenwood TS-590SG  (10.6″W × 3.8″H × 11.5″D, 16.3 lbs) which serves as my main HF transceiver in my station. For such a compact radio it contains many comparable features to my larger and considerably more expensive Kenwood.


The Yaesu 450D is an entry level transceiver, however, it includes a lot of features that give you considerable bang for your buck.

  • HF/6M Coverage
  • 100W Transmitter
  • IF DSP Filtering (Width, Shift, Contour, Notch, Noise Reduction, etc.)
  • Backlit Buttons (perfect for field use at night)
  • Voice Keyer (perfect for contesting and Field Day)
  • Built-in Antenna Tuner

Field Case

HF Kit (2)To house the Yaesu I used a Monoprice 22″ x 14″ x 8″ Weatherproof Hard Case. This should keep the radio, SignaLink, and microphone secure. Less damage prone items like the power cable can be transported in my backpack. For additional capability I decided to add a second case to the kit.

Accessory Case

This case is the same model used to house the Yaesu 450D. In this case it contains my Manual Antenna Tuner, a MFJ 4125P 22A switching power supply, and a MFJ 822 cross-needle SWR Meter. This case greatly expands the capabilities of my HF kit. The manual tuner has a much wider tuning range than the autotuner inside the 450D, the switching power supply allows me to power the radio from line or generator power if available, and the small SWR meter is perfect for station monitoring in the field.

When line or generator power is not available I will rely on my Go Kit Battery Box. I think that this setup will prove to be versatile and the Yaesu 450D provides many modern conveniences as well as 100W output in a compact package.

Ham Radio EMCOMM Go Kit – Laptop & Software

Asus (2)Asus (1)I had a few key priorities for an EMCOMM laptop: adequate performance, decent screen size, full size keyboard, lightweight, good battery life, low price. After looking around at the laptops available I decided to get the Asus VivoBook E403A-US21.


  • CPU – Intel Pentium N3700 (Quad-Core, 1.6 GHz)
  • RAM – 4GB
  • SSD – 128GB
  • Display – 14″ (1920 x 1080)
  • Wireless – Wifi (AC), Bluetooth (v4.0)
  • Ports – USB 3.1 Type C, USB 3.0, USB 2.0, HDMI, Audio
  • SD Card Reader, Webcam, Microphone
  • Battery – 57 Wh
  • Weight – 3.3 lbs
  • Price – $400

Asus (4)Performance

The Asus VivoBook easily runs Windows 10 and all of the ham radio applications that I need (N3FJP log, FLDIGI, FLWRAP, FLMSG, FLAMP, WJST-X, etc), which allows me to use it as my main station computer. Consequently, if I need to grab my equipment and hit the road I can just disconnect a couple of cables and take my laptop with me, armed with the knowledge that it is up to date, functional, and that the battery is fully charged. By using one laptop for everything it allows me to not worry about maintaining a secondary machine just for my Go Kit.

Asus (5)Power Usage

The VivoBook is fairly miserly when it comes to power usage compared to higher powered laptops and is well suited to field use.

  • Idle Maximum Brightness – 8W
  • Idle Minimum Brightness – 6W
  • FLDIGI, FLMSG, FLAMP, File Browser Open, Maximum Brightness – 11W
  • FLDIGI, FLMSG, FLAMP, File Browser Open, Minimum Brightness – 9W
  • Charging Battery – 33W

While this extremely low power usage provides the benefit of great battery life it also means that the VivoBook can run for hours and hours on an external battery pack like the Energizer XP18000 or the Intocircuit 32000mAh battery pack. Starting with a fully charged laptop and battery pack this laptop could easily run for over 24 hours without needing to plug into 120V. Being low power also means that the system doesn’t get hot, there’s not even a fan for the processor.


Asus (3)The VivoBook is thin and light and the keyboard and touchpad are excellent. It has a good selection of ports and the build quality is very solid for such an inexpensive machine. The high display resolution is also nice to have especially for a laptop in this price range. The display’s contrast and viewing angles are not very good as was expected for this price range. I was, however, able to improve the color reproduction using my Datacolor Spyder screen calibration tool. Overall this is a fantastic laptop for the money and it is a good addition to my Go Kit setup.

Ham Radio EMCOMM Go Kit – Battery Box

Battery Box (1)Battery Box (2)A portable battery system is a very handy item to have for ham radio in general (think field day, special event stations, etc.) and is essential for an EMCOMM kit. I based my battery box around a deep cycle lead acid battery and I ended up choosing a group 27 battery with a reserve capacity of 160 (66.7 Ah). Reserve capacity refers to the number of minutes a fully charged battery is discharged at 25 amps before the voltage drops below 10.5 volts. This figure can be converted to amp-hours by multiplying the reserve capacity by 0.4167. According the Battery School within a BCI group size, the battery with higher ampere-hours (or RC) will tend to have longer lives and weigh more because of thicker plates and more lead. While lead acid batteries are heavy, they are also versatile and can be continuously trickle charged to keep them at full charge until they are needed. A deep cycle battery is appropriate for this application since their power level can be drained very low without damaging the battery, unlike a typical car battery.

Battery Box (3)For ease of transport and to keep the wiring organized and neat I store my battery in a plastic battery box and hardwired it to a Rigrunner 4005 power distribution block mounted on the box. I went with a small Rigrunner since this system will only be used with a few items at a time (1 or 2 radios, inverter for laptop power, low voltage lighting, etc.). I keep the battery charged using a NOCO Genius G3500 charger which is smart enough to not overcharge the battery and powerful enough to recharge the battery at a decent rate. After years of thinking about it I finally got around to standardizing all of my power connections with Anderson Powerpoles which make 12V power connections very modular and interchangeable.

This is a very useful and simple project that performs well for my purposes. I could easily parallel another battery with this one for increased capacity if the need arises in the future. You could buy a premade battery box with a Rigrunner, but doing it yourself is a lot cheaper.

Ham Radio EMCOMM Go Kit – VHF/UHF

VHF Go Kit (7)Recently myself and others in my ham radio club have been getting more involved in emergency communications (EMCOMM) training and activities. As part of this effort to be better prepared for emergencies I decided to build a go kit or “station in a box” that could be used as a portable communications system.

VHF Go Kit (2)VHF Go Kit (1)Since VHF and UHF are the most used bands for EMCOMM I started with that. I already had a Kenwood TM-V71a dual band (2 Meter and 70cm) transceiver which is an ideal radio for this application. At full power it can output 50 watts and unlike many transceivers of this kind it features a data port on the back for easy connection to an external sound card (I use the SignaLink USB) for digital communications. It also has a detachable faceplate which allows for a lot of flexibility regarding where and how the transceiver body is mounted.

To house the electronics I chose the Monoprice 14″ x 16″ x 8″ weatherproof hard case which is similar to Pelican cases at a fraction of the price.

VHF Go Kit (4)VHF Go Kit (3)For power, I chose to include a 10 amp switching power supply in the go kit. I used the Astron SS-12 since its dimensions were such that it fit perfectly in the case when mounted next to the transceiver. In case 120V is not available, I can simply unplug the transceiver’s powerpole connection from the power supply and plug it into my battery box.

In order to mount all of the equipment in the case I built a base of 1/2″ plywood. The base consists of a single sheet cut to fit in the case glued on top of a four 1/2″ spacer blocks which raise the sheet above the bottom of the case. This serves two purposes:  first it negates the need to round the bottom edges of the sheet to match the curve of the case and second it doubles the thickness of wood that the mounting screws have to grip when screwed in through the bottom of the case. An added bonus of raising the sheet is that it provides space to store excess cable from the faceplate separation kit in an out of the way location.

VHF Go Kit (6)VHF Go Kit (9)Mounting the transceiver to the plywood is done using the mobile mounting bracket for the radio. The power supply is mounted by removing the rubber feet from the bottom of the power supply and replacing them with spacers and screws for a strong connection to the plywood. The microphone mount is also simply screwed to the plywood. The faceplate is mounted to the lid of the case using the separation kit mount which uses very strong double stick tape. The SignaLink is mounted to the top of the power supply using industrial strength velcro which allows for easy removal of the unit if I want to use it in a different configuration while holding it very secure when I want to leave it in the case.

VHF Go Kit (5)Before I mounted anything to the plywood I applied a coat of clear polyurethane. This not only makes the oak veneer look a lot better, it also seals the wood and provides some protection. The equipment was then mounted to the board and it was mounted in the case using 4 wood screws driven through the bottom of the case. In order to help restore the weatherproofing of the case I used silicone caulking to seal around the screw heads.

Overall I am very pleased with how this go kit turned out. To get on the air all I have to do is open the case, hook up power (either 120V or 12V), hook up the coax to the antenna and plug in the USB cable to my laptop if I need to run digital. In all it’s a very capable VHF/UHF station that weighs about 17 lbs and isn’t much bigger than a shoe box.