Antenna tuner. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / HF antennas
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The tuner and its tuning method from the W1FB article are described below. The above scheme provides matching Rin=50 ohms with a load R=25-1000 ohms, providing suppression of the 2nd harmonic by 14 dB more than Ultimate in the ranges of 1,8-30 MHz.
Details - variable capacitors have a capacitance of 200 pF, for a power of 2 kW at the peak, the gap between the plates should be about 2 mm. L1 - coil with slider, maximum inductance 25 mH. L2 - 3 turns of bare wire 3,3 mm on a mandrel 25 mm, winding length 38 mm.
Setting method:
- for tube transmitters, turn the switch to position D (dummy load), set the transmitter to maximum power
- reduce the power to a few watts, turn the switch to the T (tuner) position
- put both capacitors in the middle position and adjust L1 to achieve a minimum SWR, then adjust the capacitors again achieving a minimum SWR - adjust L1, then C1, C2, each time achieving a minimum SWR until the best results are achieved
- apply full power from the transmitter and once again adjust all the elements within a small range. For small powers of the order of 100 W, a 3-section variable capacitor from the old GSS G4-18A is well suited, there is an isolated section. It will be very convenient to use an automatic SWR meter.
Below are the possible configurations of antenna tuners, who want to read the article in more detail, where their advantages and disadvantages are discussed, they can read the QST Aug 81 magazine. If there are a lot of them, I can send it, but of course in the original language.
Author: I.A. Dobrokhotov (UN7GM); Publication: cxem.net
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