RFUANZ report: building a skid-mounted DMR Tier III radio site

The Radio Frequency Users Association of New Zealand (RFUANZ) invites guest columnist Lloyd Wensley from Mount Campbell Communications to recount his company’s recent efforts to create a skid-mounted DMR Tier III radio site…

Having been invited to provide radio communications to multiple locations in the remote wilderness of the northern South Island for an international event, we decided to leverage off our existing DMR III network and our high-site Engine Alternator (EA) Set design. Three transportable skids with lifting arrangement were designed and built within a very tight time frame. The system was deployed over the two-month event with the three skids ‘leap frogging’ along the event course and various event locations. Some sites required half-hour helicopter-slung loads to an altitude of just over 2000 m AMSL, while other sites were set up on standard 6′ x 4′ road trailers, and one was even on a barge moored off the coastline looking into the coastal race way.

Each skid comprises a steel channel frame on which the EA Set and radio cabinet are mounted; a triangulated frame for a 4 m antenna mast with rugged Kathrein dipole. Certification of the lifting arrangement was required for slinging under a helicopter.

All the Mount Campbell team were involved one way or the other and with this teamwork the company achieved and exceeded the client’s expectations despite the very short time frame.

The delivered results were very satisfactory, giving the client direct communication from operations staff to remote field crews as well as location services, PSTN calls and man down alerts. Each skid was fitted with two RF channels giving three traffic time slots, which provided uncongested traffic between the client’s management operations and safety teams.

The skids can easily accommodate four RF channels providing seven time slots or a mix of DMRII or conventional in either the UHF or VHF bands. The skids are easily relocated and run autonomously at each location for more than two weeks. We recently ran one for 20 days without intervention for a temporary job.

The design has several novel features, including capacitor start (200F) instead of starter batteries and a purpose-built 80 L fuel tank with desiccant air breather and convenient fuel drain. The engine is an air-cooled rugged electronic engine with CAN bus to facilitate telemetry. The tank allows for approximately 100 hours run time. Each skid is TCP/IP linked to the network node via the Starlink commercial satellite service, which allows deployment anywhere!

Having got through the event, we are now reworking the electrical design for other applications to provide 14 VDC, 50 VDC and 230 VAC single-phase as well as a local engine control unit. The skids have recently been deployed for service while permanent sites are being engineered and for other applications.

Lloyd Wensley, Owner, Mount Campbell Communications.