3.5 Wind and install Low Pass Filter inductors L4 and L7
Measure and cut two 30cm lengths of the 0.6mm wire for winding inductors L4 and L7. These two
inductors are wound on T50-6 toroids (yellow). The number of turns and inductance of L4 and L7
are given in the table below:
Band
Turns
Inductance
80m
24
2.42uH
40m
17
1.38uH
30m
15
1.09uH
20m
13
0.773uH
Wind and prepare the inductors as in the previous section.
Install L4 and L7 as shown below.
Now use a DVM in resistance or continuity-beeper mode (if available) to check for DC continuity.
Resistance should read zero if the DVM is in resistance mode. Poke the red and black probes in
the pads of C14 for this measurement. If you do NOT see DC continuity then it means that one or
more of the inductor wire ends is not properly stripped of enamel and trimmed; this is a common
error.
3.6 Wind and install bifilar transformer T2
Measure the remaining length of 0.6mm wire and cut it into five equal lengths. For example, if the
remaining length is 230cm then cut it carefully into five equal lengths of 46cm each.
Two of these wires now need to be prepared as bifilar windings. To do this, hold two ends and
twist the wire repeatedly along its entire length. Try to avoid the situation where one wire remains
straight, and the other wire just wraps around it. Try to keep the twists even. It is difficult to do this
and end up with a beautiful result. Don’t worry! Regardless of how imperfect or messy it looks, it is
going to work just fine.
50W QCX PA kit assembly
1.00q
14
