But scheme in Fig. 10 has advantages. At first, it is much easier to use
only one grounded high-quality capacitor instead of two ones but
insulated from metal cabinet. Secondly, it is wise to substitute
expensive inductor with slide control to two cheapie spools with
The MU made
by me at home conditions worked well on all amateur ranges from
1,8 up to 30 MHz and did
matching to 50-Ohms
transmitter to antenna with resistance from 15 up to 500-Ohms.
The inductors were made as Fig. 11
shows. Form of inductors is made of PC- board with slots for turns.
On the plate switch for taps is installed. The plate is disposed
not in center of the inductor but little sideways as Fig.
Pi - MU is
used in radio amateur practice for a long time. It is possible
to find Pi - MU and disputes on this subject at radio amateur
journals issued on 20s of the 20 century till our time in the
Internet. Fig. 13 shows
Pi- MU. As usual Pi- MU is used at inner MU at tube and transistor
PA or straight at antenna clips.
Pi- MU seldom is used at separate ATU. For matching in a wide frequency
ranges loads with resistance 10- 1000- Ohms it need to change
C and L at Pi- MU too greatly. So, it is impossible to do universal
It is desirable to use slider inductor because. In case if an inductor
with fixed taps is used you can carefully to select the tap for