Michigan Mighty Might: Another Version

Scratch-built by W5USJ

Mighty Might Assembly

Completed assembly ready for initial testing and check out

Development and Assembly

Mighty Might Pre-Assembly

The Polyvaricon mounting adapter plate is from Rex, W1REX at QRPme.com. The MeSquares are also from QRPme.com
There is an extra MeSquare because I wasn't sure which side I wanted to bring the power into the circuits
The mounting tab for the key jack is made from a strip of PCB
SIP pins are used as sockets for the crystal and Q1. Pin "leads" are formed to provide better contact surface for soldering
Use a transistor as a holder for the pins while soldering in place. Similarly, a crystal for the crystal socket

Michigan Mighty Mite Schematic: W5USJ Version

Mighty Might Schematic

Topper Low Pass Filter Elsie Plot

Topper 40m Low Pass Filter Plot

♣ To view O'scope plots of waveforms, click here —MMM Wave Forms

♣ Additional O'scope plots using various transistors for Q1 in the works

Notes: Initial Test Results

• Testing and measuring using 7047.5 kHz nominal crystal (from QRPme.com)
• Frequency measured with MFJ-886 frequency counter.
• Power source is regulated and adjustable -- For testing set the supply voltage to 12.5 Vdc
• Power Measured with the 4SQRP QRPometer with internal 50 Ohm dummy load, 2% Stated Accuracy

So, with my particular batch of parts, tools and their associated tolerances...

Actual Measured Frequency: 7049.93 kHz (some experimenting with loading needed)

Power output peaked by adjusting the polyvaricon. Measured 420 mW with Topper LPF and 360 mW with Lil'Squall LPF**

**Note: The Lil' Squall LPF band module uses chokes for the inductors (lower efficiency), the Topper uses T50-2 wound toroids.

I'll try 30 meters next and see if the toroid winding will work. May not...

Fun stuff...

2015 Foreward, Chuck Carpenter, W5USJ — Rev: 1 Jan 2015