We all know that Hans Summer’s QMX is an outstanding QRP transceiver. However, portable operation naturally requires a fair amount of additional equipment. My goal is to house everything in the smallest possible enclosure, enabling operation with an end-fed half-wave (EFHW) wire—ranging from roughly 7m for the 15m band to 26m for the 60m band.
- 1500mAh LiPo battery with battery management system (protection against under- and overcharging)
- 1W audio amplifier with speaker
- Touch-key paddle integrated into the housing
- Manual antenna tuner for EFHW
- Additional auto-switching 50-ohm antenna port
The use of a 3.5mm audio jack as an additional 50-ohm port is unusual. However, since the RF current remains below 0.25A at a maximum output of 3W, and the connection point in the antenna line is located directly at the power amplifier (PA), it works well. For the skeptics: An older 100W Yaesu transceiver used an internal RCA connector to link the PA to the antenna socket.
The resonant circuit, serving as a variable matching network for the EFHW, also allows for the use of antenna wires of non-ideal lengths or wires laid over bushes or directly on the ground (e.g., a „bush antenna“).
