Power supplies for field operation

Most amateur radio gear runs on a supply voltage of under 14V but there are many LiPo battery packs that produce more than that and need to be regulated down. Frequent SOTA operator David, VK3KR, has been building supply adapters for this purpose.

At Gresswell Hill, of the power supply running the mcHF transceiver. Primary power source is an 18.5V LiPo which has sufficient power for many hours of activating

David was lucky enough to obtain a commercial grade DC-DC Converter, recovered from obsolete equipment. It’s a Cincon CHB75W-48S15 – nominal spec is 15V at 5A output (75W). Note that the converter has a voltage adjust function allowing a variation of +-10% – with the voltage set at the lowest level it’s around 13.5V, just right for most transceivers used by amateur operators.

An earlier project from VK3KR has batteries mounted internally.

Inspired by David’s good work, Peter, VK3TPM, who has a number of Ozito battery packs (which produce about 20V when fully charged), took a spare single pack charger and connected wires to output the voltage from the cells. The charging circuitry doesn’t seem to mind this simple addition.

Modification to an Ozito single pack charger.

The regulator used is a variable buck down converter found on AliExpress. It makes for quite a neat arrangement.

This particular variable regulator creates noticeable bands of noise so the output DC cable was threaded nine times through a toroid which did reduce the noise considerably. While switching regulators are very efficient, noise can be an issue.

Richard, VK3LRJ, built a version with a linear regulator for low noise. It’s clamped to a thick aluminium plate and does not get warm powering his KX3 on SSB transmit.