ANTENTOP- 01- 2014 # 018

Simple HF ATU on Lengths

of Coaxial Cable

Note: Pay attention that "ground" of the socket J2 is not connected to the ATU case. The socket is placed on a dielectric plate (it was used a piece of PCB without foil).

The design was very simple. A big metal box from unknown surplus device was used for the ATU. Lengths of the coaxial cable was coiled and then dressed on to a plastic tube. It was used plastic water pipe (something like 1- 2-inch OD).

The ATU is very simple to use. Just connect the ATU between transmitter and antenna system. Then rotate S1 on to minimum SWR. Figure 3 shows connection of the ATU. It is possible to use the transceiver's internal SWR meter or an external one. Do not rotate the S1 when transceiver is in transmission mode. S1 breaks the transmission line so it may cause high SWR. Go to receiving mode, switch the length of the coaxial cable, go to transmission mode and check SWR.

Figure 2 Design of the Simple HF ATU on lengths of Coaxial Cable

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