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Symmetrical ATU

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ANTENTOP- 01- 2015 # 019

Symmetrical ATU

 

 

Taps are from 8, 12, 13 and 14- turns from ends of the inductors (see Figure 2). The five taps were enough to tune antenna at all amateur’s bands (including WARC). Taps of the inductor L1 placed at the other side of the dielectric plate.

 

It was used a three – plate rotary switch at the ATU. It allowed used the ATU at high power – up to 500- Wtts. Take a look to the Figure 2. Taps for upper bands for L2- 1 and L2- 2 are connected to one plate (near the inductor) of the rotary switch. Taps for lower bands for L2- 1 and L2- are connected to separate plates (one plate for one inductor) of the rotary switch.

Capacitor C1 is 500- pF air capacitor from old tube receiver. Capacitor C2 should be high quality high voltage capacitor with maxima 150- pF. For 150- Wtts going to the Symmetrical ATU it would be enough to install air capacitor with 2… 3 mm gap between plates. However when I used the Symmetrical ATU with such capacitor connected to my amplifier FL-2100 it is happened sparking between plates of the C2. Vacuum variable capacitor (as seen on Figure 2) installed in the ATU resolved the problem.

 

References

 

(1) Gierlach, W.: Das DARC Antennenbuch. DARC-Verlag, 1994

 

 

 

 

Figure 2 Design of the Symmetrical ATU

 

 

 

 

 

 

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Last Updated:

May 1, 2016 22:16

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