Hams occasionally like to take their toys to remote locations and play radio from the top of a mountain or at a pleasant picnic in a park. This gives us a chance to set up equipment in odd places, erect antennas and generally practice for emergency communications contingencies. To encourage this practice, the ARRL (American Radio Relay League) has an annual Field Day the last weekend in June, where ham radio operators across the country set up their stations outside and chat with one another on the radio. In preparation for such events, I spent some time building a portable operating desk.
As usual, I made use of materials I had on hand which included a large panel of 3/4″ cabinet plywood. Although a bit on the heavy side, the plywood made a stout box. I made the top hinged to open upward so that it was easy to arrange the contents and make electrical connections. Folded down, the top becomes the work surface for the desk upon which a laptop computer can sit.
I made the desk with a pair of hinged legs that fold up underneath the unit if you want to place it on a table or when transporting in the trunk of a car. When standing on the ground, the legs are splayed out with tension chains to hold them ridged against the weight of the equipment.
I made the box just tall enough for the battery, which is also just tall enough to fit a small antenna tuner on top of the radio, when and if I get one. The system is powered by a 40 AH 12.8V LiFePO4 battery that provides more than ten hours of typical operation. For charging I use a regulated lab supply that can supply up to 10A of current. On the back of the desk there is a plug for 110 VAC when it is available, and a set of binding posts that connect to the battery for either another charging source such as a solar panel, or for an auxiliary load. I found a nice battery monitoring meter that displays the battery voltage and charge or discharge current. The meter also keeps track of the battery charge state so you can know approximately how much capacity remains as you run it down.
The first outing with the new radio desk was up on top of Prairie Mountain on the Lane / Benton county line for the 7QP QSO party. The desk worked fine — my computer software and the antennas I brought along could have been better — but we did have fun.