Completed VHF/UHF GoKit for Field Day and EMCOMM

We’ve been thinking about building a portable GoKit for VHF/UHF EMCOMM and Field Day Applications for a while now. The following is a list of our requirements for a GoKit –

• 2m and 70cm operation with FM simplex and repeaters
• APRS capability and tactical display for portable coordination
• Digital messaging capability
• Weather band monitoring capability
• AC Power with flexible battery backup options

A plan to build our GoKit came together during our Dayton Hamvention trip this year, and we used it during Field Day.

Kenwood TM-D710GA At Dayton

The heart of any GoKit is the Transceiver. We’ve been using Kenwood equipment for our APRS iGate for some time now, and we have had good results with it. Kenwood’s latest 50W transceiver with APRS is the TM-D710GA. This unit provides full support for APRS tactical applications and now includes a built-in GPS receiver making it ideal for our GoKit application.

AvMap GeoSat 6 APRS Tactical Display

We have been using the Kenwood TM-D710 and an AvMap GeoSat APRS display in our APRS iGate setup, and the combination works very well. The AvMap display lets one see the location of portable and mobile APRS stations on a map display. This arrangement is perfect for coordinating activities in an EMCOMM situation. The AvMap GeoSat 6 APRS display is no longer in production, but I was able to locate a nearly new unit on eBay.

We had a chance to look at the iPortable enclosure at Dayton and decided that their Pro 2 4U deep unit would be a good choice for our GoKit application. The iPortable enclosures are based on a portable rack mount case and include a DC power system, speaker and headphone hookups, a light, and provisions for a cooling fan.

Radio Shelf

With all the components in hand, we began the construction of our GoKit. Reliability is important in any portable system like this, so we put some time into securely mounting all the equipment and neatly arranging the cabling. First came the shelf containing the Kenwood transceiver and a SignaLink USB sound card. A combination of drilling the shelf to secure gear with large cable ties and #8 stainless hardware was used here.

Coax Connector Cables

Our iPortable case was equipped with SO-239 and N-connectors on the front panel to allow antennas and feed lines that use either connector type. To make the changeover between the connector types easy, we installed separate PL-259 jumper cables for each connector. One simply connects the appropriate jumper to the radio.

Display and Power Shelf

The power and AvMap display shelves were next. The AvMap display mount was dissembled and modified to accept a custom mounting bracket.

PWRgate Battery Interface and Charger

The iPortable enclosure was drilled to mount a West Mountain Radio PWRgate to handle backup battery charging and management. The PWRgate supports instantaneous switching between an AC power supply and a backup battery and can accommodate various battery types and sizes.

Backup Battery

The PWRgate was configured to properly charge our 18AH AGM backup battery. Note using a fuse in series with the battery for safety reasons. We used a Powerwerx SPS-30DM adjustable power supply set to 14.5Vdc to operate our GoKit and to provide proper charging voltage for our AGM battery.

Diamond X-30 Antenna and Mast for Field Day and EMCOMM

The last piece of the setup was the antenna. We wanted something that was portable, easy to set up for Field Day, and would provide good performance. We choose a Diamond X-30A 2m/70cm ground plane antenna and mounted it on a 12′ fiberglass push-up mast. The feed line is made from 25′ of LMR-400UF coax. Several bungee cords are used to attach the mast to a fence post or other vertical structure.

The picture above shows the completed GoKit in operation. We typically set one side of the Kenwood TM-D710GA as an APRS transceiver and Digipeater and the other to operate on a local repeater or simplex FM. The SignaLink sound card is used with a laptop computer running Fldigi and NBEMS for messaging applications. The iPortable case has a 13.8V lighter socket which connects to a power brick to power our laptop PC.

GoKit Packaged for Transport

The GoKit is quite portable when closed. All of the equipment and cable connections are enclosed and protected by the case’s removable end caps. We’ve tested our GoKit during our club’s weekly repeater net, and it worked great. The first real use of our new GoKit will be at Field Day this year. It will be located in our public information tent and will be used as a “talk-in” system.

Fred, AB1OC