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.

Goals

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

Battery

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.

PWRgate

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.

Inverter

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.

Wiring

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.

Construction

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.

Weight

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.

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.

Parts

  • 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.

Operation

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.

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.

Parts

Construction

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).

Operation

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.

Calibration

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.

Update (March 2017)

I recently discovered that FLDIGI has a built in TX Audio Attenuator feature. Using this I can achieve much finer control over my transmit audio level, even with the soundcard’s speaker output set to 1% volume. This makes adding a resistor in the transmit audio wiring unnecessary.

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.

PSK31 Sound Card Interface

psk_interfaceIf your sound card has Line In and Line Out jacks, and your radio has an accessory port, this is the easiest way to interface between the two. Using your radio’s accessory port eliminates the need for more circuitry to control the audio level going to and from your radio. This interface has worked perfectly during regular use and several Field Days. All the parts are available from RadioShack, and it can be constructed in under an hour.