QRP PROJECT ZM-4, Manual

3

Example:

This core counts 6 Turns

The ZM4 main Torroit needs 1 main winding (the resonate winding) 

with 2. taps plus two different coupling windigs for the low and high impedance 

outputs. To make it easier to difference them we use coloured wires. Start wit the 

red wire. Put it from the backside of the core through the core, tis is the first turn. A 

short end (abt 2-3cm of the wire remains at the beack side, the longer end is in front 

of you. Feed the long end around the core to the 

back and again from back to front through the coer 

which gives the second turn (remember, count 

inside the core). The long end of wire must be 

RIGHT side of the first turn now. Pull the long wire 

tight to the core body. Now wind the remaining 6 

turns of the first winding (complete part 1 is 8 turns 

INSIDE)

Later on the 8 Windings will be soldered to the 

PCB. They are the first part of the main winding 

which has a total of 34. The PCB is marked with 

1/34 which means 1 of 34 at the beginning and 

GND/34 which means Ground of 34. Lay the 

Torroid on the PCB and cut the wire at both ends. 

Leave the ends long enough to fit them through 

the holes named 1/34 and GND/34. Remove the 

insolation but do not solder yet.

The next part of the 34 turn winding of course 

must start where the first part ends. So that is the 

reason to have two holes in the PCB here. Use 

the brown wire and wind the next 8 turns following 

the same way: From back to front, new turn 

allways right side of old turn.

Count 8 turns and cut and remove insulation so 

the ends fit into hole GND/34 and 16/34 (16 of 34)

Now the remaining part of the main winding. This 

are 18 turns. They start at the second hole of 

16/34 and end at 34/34.

Use green wire, count inside, shorten the wires 

and remove the insilation at both ends to make 

them fit into the PCB holes. Do not solder yet, you must wind the couplings first.

Let´s start with the shorter coupling 

winding. It contains of 4 turns. The 

coupling must be as symmetrical around 

the ground point of the main winding as 

possible. Remember, grounding point is 

named GND, actually it is the connection 

between the red and the brown wire. 

Symmetrically means, the ground point 

must be exactly in the middle of the 

four coupling turns, two before and two 

behind. 

Use the yello wire and wind two turns 

between the last 2 of the red and the first 

two of the brown wire.

Pay attention to the fact the the holes 

for the coupling at the PCB are a little 

bit away from the torroid, 

so do not shorten the wire 

ends too short.

So, we are not far away 

from our goal, it is only the 

longer coupling winding 

missing. 

Use the blue wire to make 

it. This one also must be 

symmetrical around the 

ground point so we need 

8 turns before and 8 turns 

after the ground point. Start 

left of the red number one 

and wind again from back 

to front. every blue turn 

is laying between two red 

turns. Turn number 7 and 

8 just before you come 

to ground point must lay 

between the red and the 

yellow wire. Yes, there is 

not to much space left, 

but you will see they fit 

all together. Behind the 

ground point wind the 

remaining 8 turns.