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ANTENTOP- 01- 2004, # 005

Something about ATU




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 taps.


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. 12 shows.





Pi- Matching Unit


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 Pi- MU.


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 real antenna.

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