Powering Field Day

An interesting idea floated at Field Day 2017 was the start of the power solution for St. Louis Metro Amateur Radio Emergency Service (ARES). What if we used a volunteer’s car to power our radios? The suggestion from Norm Guittar, Master Tinkerer and husband to Dolores Guittar, KD0CIV, was a novel idea. Norm, who jokingly goes by N0CALL, was already using his 2013 Chevrolet Volt to power their adventures in their camper, why not test it as a power source for the ARES Field Day setup?

Field Day is the open house for amateur radio. Across North America more than 40,000 radio operators, or hams, relocate to public places to demonstrate the science, skill and service to the community that amateur radio offers. The event is part community outreach, part emergency services demonstration and part contest that combines into a full 24-hours of fun for enthusiasts and visitors alike. Since 1933 Field Day has been the most popular event in ham radio.

Groups are encouraged to use power sources other than commercial electric power. In the past St. Louis Metro ARES has experimented with solar power and battery sources to run radios for the event. This year the logistics would change to include the car as a primary power source.

Attached to the 12-volt battery under the trunk, Guittar has permanently wired in 300-amp Anderson Powerpoles® that power a 2,000-watt continuous, 4,000-watt peak power inverter. The inverter supplies 120-volt power that’s usually used to power cooking equipment when camping. For Field Day that power was put to work to run a microwave and griddle to make breakfast.

To generate power for the radios, Guittar attached additional alligator clips to the battery to route power to a distribution hub that included a watt meter to monitor output from the car. The plan was to leave the car turned on, allowing the electronics to draw from the 12-volt battery system. When power levels fall too low, the car automatically recharges the 12-volt 

system from the main battery pack that runs the car. When the main pack runs low, the car starts the back-up generator, better known as the car’s engine. But a safety feature of the car required the addition of the watt meter to ensure radio operations wouldn’t be knocked off the air. 

“One problem with this plan is that the electronics decides after an extended period of no movement that we accidentally left the car on, so it helpfully turns the car off for us, which is a bad thing (as) now it will allow the 12V battery to run down,” Norm explained.  “That is one reason I have provided the Power Meter on the “power distribution panel” to give a read out of the twelve volt (system) which should be monitored, alerting to the fact the car has turned itself off, allowing the battery to start running down.”

The solution to this engineering problem was to simply turn the car back on when the meter fell below 12 volts. With 24-hour radio operation, the system was thoroughly tested. By day this arrangement was easy to maintain. By night, however, power levels dipped, signaling the car had turned itself off. However, the engine couldn’t be turned back on until the Guittars were woken up to locate the key fob.

Technical Challenges

Another technical problem with the arrangement was an issue with “power vampires.” These are unexpected drains on the battery system beyond the requirements of radios and other equipment. At one point the air conditioner was left on in the car. 

Other drains included the dome light, the headlights and the car’s dashboard displays. These power parasites tipped the energy usage upwards until each was discovered and eliminated as much as possible.

A total of 44 people attended the event including three youth and one served agency visit. Social media posts covered three platforms with a total of 14 posts and one video. Including all traffic on Facebook and Twitter, the posts received more than 6,300 views. Two press releases were put out. Proclamations were granted by the St. Louis Mayor, the St. Louis County Executive, and the Missouri Governor.

Operating the radios with the varying power available from the 12 volt system did affect radio performance. At full power, the radios exhibited some fluctuations and stability issues in output performance. Dropping the radios to about 80 watts stabilized their performance when operating with less than 13 volts applied.

Total available power at the start of the event was 4.4 kilowatt hours. A solar panel provided about 250 watts to supplement the 12 volt system. The car was restarted three times from when set up began around 9:00 am on Saturday through tear down at 11:00 Sunday. The system maintained three radios operating on stand by or actively transmitting throughout the event as well as the appliances needed for cooking. Before cooking, Guittar put the car in mountain mode, to give a strong charge to the battery and to limit the need for the car to run. Outside of the drain of the 120 volt needs, it would have been possible to leave the car off throughout the event and more closely monitor the power levels. This would have limited the drains from the power vampires.

Field Day Results

St. Louis Metro ARES operated under the callsign NØARS, powered by the Chevrolet Volt. Field Day contacts totaled 516, with 130 on Morse code, or CW, and 386 on voice. Contacts were made in the US, Puerto Rico, Canada, Balearic Islands and Hungary. The longest contact was 5,128 miles away via CW, and the closest contact was 1.1 miles away on voice on simple wire dipoles. Every state in FEMA Region VII was contacted, and we were able to reach every state except Alaska, Delaware and Nevada.   

Future Modifications

Planning has already started for Field Day 2019, and the lessons learned this year will likely result in a few changes. The St. Louis Metro ARES group is considering moving the power needs for the logging laptops onto the car’s 12 volt system as well. The computers could certainly be recharged using their traditional 120 volt charging cords and connect them to the inverter. However, to eliminate any possible power losses, Guittar suggested using Powerpole® adapters and powering them directly from the power distribution panel. 

Another improvement will be to more closely monitor power vampires by keeping the car off for the majority of the event. This will require operators to keep an eye on power levels throughout the event. However, without the car turned on, the car’s systems will not be putting a load on the electrical system. With that change comes the need to cap the transmit power on the radios. They appear to be fully functional at 80 watts power, and the lowered power levels will draw more consistent performance when the battery levels start to drop off. 

The group is also considering a second solo tent reserved for low power operations. This would allow greater separation of QRP radio operations and limit the amount of bleed over on nearby antennas. If enough volunteers can be found, the group may also split operations and have a location inside Saint Louis city limits. This would better showcase the group to served agencies inside the city.