MDRF is pleased to offer the next batch of this kit version of N6QW’s P3ST SSB transceiver for 15, 17, or 20 meters (it can be built or modified or any one of these). Its modular construction allows for easy assembly, testing, and modification. Most of Pete’s recent designs are intended as experimenter’s platforms. Any of the modules that make up the P3ST’s superhet SSB architecture can be swapped out for different designs or modifications. By the way, any of the modules can be used in other homebrew rigs as well.

Modules plug into headers on the motherboard which carry relay-switched power. Where possible, components are spaced apart as far as possible for ease of assembly by those who suffer from FFS (fat-finger syndrome). With a standard module size–2.5 x 1 inch (5 x 6.4 cm)–and connector spacing, it will be easy to swap them out or to modify them. For P3STs that will be taken into the field, a simple clamping arrangement will firmly hold the modules in place. The pin and header arrangement shown here is already pretty secure for stationary use. The motherboard is 6 x 7.5" (15.2 x 19.5cm)

A key feature of the P3ST is the reuse of circuit modules for both transmit and receive. The mixers, the IF module, the band-pass filter, and the RF amp are switched by relay from RX to TX with a signal from the push-to-talk line.

The kit does not include an enclosure, but it does include a 16x2 LCD display, a rotary tuning encoder, and potentiometers for the mic and audio levels. The digital VFO/BFO module makes the I2C and SPI bus ports available for various displays (LCD, TFT, OLED) and for rotary-encoder input. The digital VFO/BFO comes pre-programmed with code for the included LCD/encoder combo. Buyers who wish to use other types of display or control devices are of course free to reprogram the VFO/BFO accordingly or to modify existing code. The Seeed Studios Xiao MCU is programmable either in Arduino C/C++ or in MicroPython. MDRF is able to provide only limited help in doing so. For those not fond of winding toroid inductors and transformers, an optional set of all seven toroids is available pre-wound.

For those who are interested in building the P3ST, here is a caution: This is not a project for beginners. If you’ve have some experience in building radio (or other electronics) at the discrete-component level, you should do just fine actually building the P3ST. Additionally, some level of understanding of the various module-level functions (filters, amplifiers, and mixers) is also essential. Of course one benefit of the modular approach the P3ST kit takes is to reduce its electronic workings to their essential functions–its “architecture”–as shown on the block diagram. Thus identified and highlighted, building the P3ST can also be a learning experience, even if you do need to know some things already. As Pete Juliano, N6QW, the designer of the P3ST likes to say, “When you know stuff you can do stuff.” The corollary of that is if you don’t know stuff you can’t do stuff.

Fortunately, we now have at our fingertips access to vast knowledge through the internet. There is also an online forum available on the MDRF website for questions and answers. There is also an ongoing forum available at https://groups.io/g/pssst-20/topics where you can search for previously-answered ones (new membership for this forum is closed). Both forums should be the go-to source for your inquiries. MDRF will not be able to provide anywhere near the level of support you can get from fellow builders on the forums. Pete N6QW will not be able to provide support at all except as he wishes to participate in the forum. Todd K7TFC will, of course, be a regular participant.

Please note: This is a pay-as-you-go venture for MDRF. The purchase of kit materials and components will take place in batches of at least ten kits after their sale. Shipment of kits to buyers will take place within 30 days after each batch is full. The current batch is for 20 kits. Buyers will be alerted by email of any delays.