Completed assembly ready for initial testing and check out
Development and 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
Topper Low Pass Filter Elsie 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
© 2015 Foreward, Chuck Carpenter, W5USJ — Rev: 1 Jan 2015
• 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...