US4LEB ATU for HF- Bands

Parts:

 Variable capacitors C1 and C2:

If the ATU would be used at power up to 100- 150 W it may be used usual variable capacitors 2 x 12- 500- pF from old tube receiver. If the RF power would be large it should be used variable capacitors with proper gap between plates.

 Inductor L3:

 It is home-made inductor contains 4 turns of the copper wire in diameter of 2.5- mm (10- AWG). Diameter of the turn is 50- mm. The inductance of the coil should be adjusted by stretching at the ATU when it is tuned at 10- meter band.

Relays K1- K4:

 It may be used any high power RF relays.

Symmetrical transformer T1:

It may be used any symmetrical transformer, commercial or home- made, that will be stand the RF power at the ATU.

 Switch S1:

 It was used RF rotary switch. However it is possible use any RF switch that can stand the power going to the ATU. It is possible use to instead of the RF switch a pair of RF relays- it will be simplified the design of the ATU.

Switches S2- S5:

 It may be used any DPDT, SPDT, SPST switches that available for amateur.

Main transformer T2:

 Any transformer that provides voltage and power for switching of the RF relays.

Operating with the ATU:

 Operating with the ATU is very simple. By combining the Switches S2 and S3 then rotating the C1 and C2 find minimum SWR at the ATU.

 References:

 S. Bunin, L. Yaylenko: Radio-amateur Handbook.- Kiev, P.H.: Technica, 1984

Z. Benkovsky, E. Lipinsky: Amateur's HF and VHF Antennas.- Moscow, P.H.: Radio and Svyaz, 1983

I. Grigorov, ATU // Radioamateur HF and VHF,- 1997, # 10, P.: 32

73! de US4LEB

Picture 1 Ball Variometer from R140

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