QRPGuys MMM+ 40m Transmitter – $20
The original “Michigan Mighty Mite” transmitter has evolved in many forms over the years. We believe the original design started with Ed Knoll, (W3FQJ) and Tom Jergens, (KY8I) and later modified by Chuck Carpenter, (W5USJ), and others. We have seen them in Altoid tins, built on wooden slats, and inductors wound on everything from pill bottles to pvc tubing. A quick search on Google will reveal many versions and modifications, and we have found they have been configured for 160, 80, 40, and 30 meters, all crystal controlled.
The QRPGuys version, called the “MMM+” is for 40m. It uses a through hole, double sided PCB including all the needed components. Our design is also crystal controlled, has one toroid for the oscillator and two for the lowpass filter, with a built-in simple stainless steel transmitting key. We use the metal cased 2N2219A transistor with 300-400mW output depending on supply voltage, also a manual T/R switch which is fed to a 50 ohm dummy load on receive, to protect the transistor in case of accidental keying during receive. We have included a two position switch for the crystals, (7.030MHz & 7.122MHz included), 3.5mm jack on the front edge for an external key, 5.5mm x 2.1mm DC socket for the 12VDC input, and pcb mounted BNC connectors for connection to the receiver and antenna. All this is contained on a 2.60” sq. PCB, 1.8 oz., (51 grams). At 12V the current draw is about 100mA. Spurious outputs -50dB or better. It’s an excellent club or beginners project that uses most the basic kit building skills required for larger projects. On a difficulty scale of 1 to 5, 5 being the most difficult, this is rated at 2 or 3 depending on your experience.