FDIM 2026 Transmitter Challenge

 Among the many virtues which are embodied in the QRP radio hobby is that of economy. While the specific definition of QRP is operation at 5 watts or less, there is an unstated aesthetic which prefers the QRP radio do so with a certain minimalism in design, using as few components in its construction as possible, to be as economical as possible, and to operate with the highest efficiency possible.

While we have in past Design Challenges explored designs which have maximized power out from a few inexpensive amplifier devices, for 2026, we turn our attention to operating efficiency. We announce the 2026 FDIM QRP Transmitter Efficiency Challenge!

 1. The transmitter is to be operated from a fixed 12.0v power supply, and must demonstrate delivery of between 4.0 and 6.0 watts RF in the 40M band into a 50 ohm load.

2. The transmitter is to employ a 40M crystal as the frequency source.

3. A regulated 12.0 volt supply, 40M low-pass filter, dummy load, and power meter will be provided at the event.

 4. All circuit power is to be obtained from the 12.0v supply. No other power sources or energy storage may be used. Any cooling fans or other auxiliary circuits are to operate from this same 12v source, and their power consumption factored into overall efficiency.

 5. Output power from the 12.0v power supply will be calculated, and power into the dummy load measured. DC-to-RF efficiency will be calculated as the ratio of these two power numbers. The duration of the operational test will only be long enough to record power readings.

 6. There are no restrictions on the type of circuits, quantity or type of components, or class of amplifier that may be used, as long as the 40M crystal is the frequency source.

 7. Entries are to be checked in at the FDIM contest table by 8:30 PM on Friday May 15th during Club Night during the Four Days in May event.

 8. The circuit with the highest calculated DC-to-RF power efficiency will be declared the winner! Winners will be recognized at the FDIM Awards Dinner on May 16th.

 9. A schematic of the design is to be made available for review, and possible publication in QRP Quarterly magazine.

Good luck, happy designing, and see you in May!

73/72 Dave Cripe NM0S