P3ST Modular Transceiver Kit

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After several months of development, MDRF is pleased to offer 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). It’s 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, and they will be available for sale separately.

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.

Here’s some more photos of the transceiver and its modules (click on a photo to enlarge):

The P3ST is available as a full kit of PCBs and components -or- as a kit of PCBs only. The full kit does not include an enclosure or front-panel controls. 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 documentation that will accompany the kit includes suggestions (including suppliers and catalog links) for suitable enclosures and front-panel devices. As seen below, an optional add-on kit is offered that includes a serial 16×2 LCD and a rotary-encoder module. The digital VFO/BFO comes pre-programmed with code for that 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 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 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 ongoing forum available at groups.io/g/pssst-20 where you can ask questions or to search for previously-answered ones. This 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 groups.io forum. 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 five kits after their sale. Shipment of kits to buyers will take place 14 days after each batch is full. Buyers will be alerted by email of any delays.

P3ST Schematic Diagrams

The current batch of kit orders will close on January 1st, 2024. The shipment of the kits in this batch will be on or about January 15th. Buyers will be emailed regarding any delays. Kits ordered after January 1 will be added to the next batch, which will be closed once it’s reached five orders. Shipment of those orders will be on or about fifteen days after that. Many thanks for your patience.
P3ST Transceiver Kit (PCBs and components) $109.95 Buy on Tindie
P3ST Transceiver Kit (PCBs only) $34.95 Buy on Tindie
LCD display and rotary-encoder kit $14.95 Buy on Tindie
A set of all seven pre-wound toroid coils and transformer $34.95 Buy on Tindie


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