Step 6


This step gives instructions for winding the two coils for the kit, the input coil and the VFO coil.

Both coils use a T80-6 (or T68-6) toroid supplied with the kit. Wire size is not critical. Larger sizes (#22 - #24) are easier to handle. Sizes #20 to #28 will work.

The input coil has two windings. The primary is wound first (Part A). Then the secondary is wound over the primary (Part B).

The VFO coil has one winding with a tap. Instructions are in Part C.

A. Input Toroid - Primary Winding

Band Cap Across C2 Turns Tap From Ground Wire Length
80 300 pf 40 4 40"
40 40 4 40"
30 30 4 32"
20 20 4 22"
17 40 pf 12 3 14"
15 12 3 14"
12 10 2 12"
10 10 2 12"

Cap Across C2 - Place across C2 on copper side of board. Install when placing the toroid on the board.

Mark the primary wires with a piece of tape so they will not be confused with the secondary winding.

B. Input Toroid - Secondary Winding

Wind 10 bifilar turns over the primary winding - same for all the bands.

1. Take two wires, 12 inches long

2. Twist the two wires together leaving 1" leads at each end.

3. Wind twisted pair over the primary - 10 turns

4. Trim extra lead length. Scrape the enamel from the ends (about one inch) with fine sandpaper, knife or razor blade.

5. Connect A to B', this is your secondary tap.
Then B and A' are your secondary ends.

C. Wind VFO Toroid

Tap for 40 Turns, 10 Turns
Tap for 20 Turns, 5 Turns
The tap is counted from the ground end. Find the toroid information in the first chart, value for C35 in the second chart.

Toroid Turns
Band Crystal VFO Freq Toroid Wire Align with
Mtrs (MHz) MHz MHz Turns Length Tuning Cap
80 (3.5) 10 6.5 20 21" Open
40 (7.0) 10 3 40 40" Open
30 (10.15) 4 6.15 20 21" Closed
20 (14.0) 10 4 40 40" Closed
17 (18.06) 10 8.06 20 21" Closed
15 (21.0) 16 5 40 40" Closed
12 (24.89) 16 8.89 20 21" Closed
10 (28.0) 20 8 20 21" Closed

C35
Band C35 C32 Range C32 Set Tuning Cap Range*
Mtrs (MHz) Cap MHz MHz Wide (kHz) Var Cap
80 (3.5) 220 pf 6.1-6.9 6.5 500 50
40 (7.0) 300 pf 2.9-3.2 3 175 20
40 (7.0) 330 pf 2.8-3.1 3 175 20
30 (10.15) 220 pf 6.1-6.9 6.15 500 30
20 (14.0) 120 pf 3.5-4.2 4 576 15
17 (18.06) 100 pf 7.6-9.4 8.06 1290 100
15 (21.0) 100 pf 4.3-5.2 5 135
15 (21.0) 47 pf 4.2-5.4 5 918
12 (24.89) 100 pf 7.6-9.9 8.89 200
12 (24.89) 47 pf 7.7-9.7 8.89 1808
10 (28.0) 100 pf 7.6-9.4 8 1290 100

*Use a 35 pf or smaller capacitor in series with the tuning cap to adjust the range to smaller values than shown in the chart.

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Last Update: 7/14/08
Web Author: David White, WN5Y