Antenna was tuned with help of a tuner shown in Figure 4. The tuner could match all of three helical antennas
with transceiver. Tuner matches with the transceiver with help
of a triple variable capacitor 11- 75- pF It is a usual variable
capacitor from an old tube receiver. However each second plate
at the capacitor is deleted. Second capacitor C2 is air- dielectric
capacitor with gap between plates 2-mm. Such ATU could afford
RF-Power going through in 100- watts.
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For L1 inductor it was used an old variometer with roller from ex-Soviet military transmitter.
The ATU could be tuned by internal SWR- Meter of the transceiver
or by a neon bulb. You just need to install proper capacitor to
view glowing of the bulb. It is possible to tune the antenna system
by FSM installed at the transmitting site.
All of the three antennas was tested at QRP Power
and showed good result.
73! DE RX3MS
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