- Latest Schematic 04/07/01Lesson 023 , 20M Band Module
This lesson covers the MP20 20meter band module.
- Latest Schematic 04/07/01
FINALLY, the last module for the MP20!!!
Build the blank band module as shown in pix 0,1 and 2. Make sure that your ISA card has all the needed fingers per the schematic. The copper board is 2.8 x 6.9 inches.
Place short jumpers from the board to the fingers per the schematic. Be careful not to get solder down the end of the card fingers; we need to be able to plug this thing into the xcvr socket.
Solder 2 one inch long bare wires to fingers 1 and 2 on the ISA card. Make them stand straight up for 1/2 inch, then bend them 90 degrees toward the card. Twist the free ends together. Wind 8 turns on L112; strip, tin and mount. Solder one end of L112 to the wires from fingers 1 and 2 and the other end to ground. Solder C138 (220pF) from the wire to ground. Wind 2 T37-6 yellow toroids with 14 turns. Plac2 L110 and L111 as shown.
Solder one end of L111 to the finger wires. Solder together L110 and L111. Solder TWO 220pF caps C136,C137 from the junction of L110/L111 to ground. Solder C135 220pF from the free end of L110 to ground.
Wind 6 turns of BARE wire on a FT37-43 toroid. On the center turn, place a small screwdriver between the outside of the core and the winding and pry the wire from the toroid to open a small space between the toroid and the winding. Insert a one inch wire thru and around the winding and solder the wire. This is the centertap connection for L109. Mount L109 as shown in the picture Mount the FINAL PA transistor Q104, the 2SC1969 as shown in the picture. Q104 requires a heat sink.
There are many approaches to take for a heat sink. I found a small heat sink in my junk box. First I aligned the heat sink to the edge of the board. Then I drilled a hole thru the heat sink and also thru the copper board. I then used some heat conduction compound between the copper board and the heat sink. Then I installed a mica insulator and mounted Q104 on top of the insulator. I also used heat sink compound on both sides of the mica insulator. Then insert a screw from the back of the board thru the heat sink and transistor. Place a nut on the screw and tighten down.
Make sure that the TAB of Q104 is not shorted to the copper board. Solder Q104's emitter to ground; Its the right lead from Q104 in the pix. Clip the thin portion of the BASE lead; its on the left in the pix. Connect the center tap wire from L109 to the center lead of Q104. Connect a 10 ohm resistor R112 from the BASE to ground. Connect the free end of C131 to L109. Use the picture for reference. Wind L106. Strip and trim and mount as shown in the pix.
The 2 turn winding points toward Q104. Solder one end of the 2 turn winding to the base of Q104 and the other end to ground. Connect C124 from ground to the lower end of the 14 turn winding on L106.
Wind L105 and mount below L106. Connect one end of L105 to the junction of C124/L106. COnnect C125 100nF to the lower end off L105. Run a wire from the low end of L105 to the low end of L108.
A NOTE ABOUT THE TRIP CAPS: To properly mount the trimmers, you must first bend both leads of the cap. On the flat side of the trimmer, carefully bend the lead up a little more than 90 degrees. On the round side of the trimmer, the ground side, it is easy to snap the lead if you bend it exactly at the point where the lead bends inward. You do not want to bend the lead at this point, as it will stress/break.
Bend the lead just below this point with a pair of small needle nose pliers to 90 degrees. Connect C118, the trim-cap and C119 150pF to the top end of L106 and ground. Connect the collector of Q103, the 2N3866 to the junction of C118/C119/L106.
Connect C120 100nF and R111 15 ohms from the emitter of Q103 to ground. Connect R106 1k from the base to ground.
Connect the banded side of PIN diode D107 1N5767 to the junction of C131/C135/L110. Position the diode as shown in the picture, under the power lead for Q103 and Q104.
Wire up R115,R114,R113,C133,C128,C134 and C132 as shown in the picture. Use the schematic as a reference.
This completes lesson 23.