DK7IH Publishes a Detailed Build Log for an Experimental High-Frequency SSB Transceiver

Radio amateur Peter "DK7IH" Rachow has reached the end of an excellently-documented project to build an experimental high-frequency six-band single-sideband (SSB) modulated transceiver.

"It is some sort of 'remake' of my last multi-band QRP SSB transceiver that has been entitled the 'Gimme Five'-Transceiver and that was finished in 2015," DK7IH wrote of the project when it was first outlined earlier this year. "'5' in that case stands for the 5 major (i. e. 'classical') RF bands: 80m, 40, 20m, 15m and 10m the radio covered. This new project (called the 'Midi6', because it is not a 'Micro' or a 'Mini' transceiver) covers one band more, the range has been extended to 160m."

Rachow's design is based around two DDS frequency generators, a 320x240 color LCD interface, a Microchip ATmega128 microcontroller, a single-conversion superhet receiver, a five-stage transmitter with microcontroller-driven regulated gain stage, integrated two-tone oscillator, and a backlight for its front-panel controls.

None of these, however, explain its "experimental" moniker: "'Experimental radio' means that there is enough space inside the cabinet to change boards and test new ideas in the same space," DK7IH explains. "Also certain components like the SSB-filter have been made as 'plug-in' components to enable quick change of the part. Also the connector between the various transmitter and receiver stages have been done by 'jumpers' and header strips so that resistors and capacitors can be changed quickly to experiment with other values."

In the weeks since beginning the series, DK7IH has presented the core outline then documented each stage of the system in turn: The oscillators;the microcontroller;the band-switching logic circuits;how to measure data from the transceiver;the receiver;the transmitter; and the transmit/receive switching unit.

Now, DK7IH's documentation series has reached the stage of being assembled into a housing. "My transceivers usually don’t use any ready-made cabinets. To save space and have full and easy access to all parts of the radio during construction, adjusting, assessment and repair I prefer an open 2-layer sandwich method," he explains. "There usually is one centred frame that is fixed using M3 or M4 bolts to the front panel carrier and the rear wall or carrier (if the rear wall consists of a more complex structure)."

The full series is available on DK7IH's website now, with a linked table of contents available in the very first post.