Coaxial INVERTED L antenna. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / HF antennas
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W4TWW has been operating on 160 meters since 1951 and has built quite a few antennas since then. As a result of numerous experiments, he settled on the coaxial INVERTED L (see figure), which gives vertical polarization and allows you to work without additional tuning in the entire range of 160 m. At 1,8 MHz SWR = 1,3; at 1840kHz-1,1; at 1998 kHz-1,5. It should be noted here that the indicated SWR values to some extent depend on the loss resistance in the grounding system, i.e. on the number and length of counterweights. Three quarter-wave counterweights are used.
The sufficiency of the grounding system can be determined by the deviation of the SWR of the antenna after rain - if the grounding system is effective, this change will be insignificant.
The design of the antenna is clear from the figure. Due to the broadband, with exact observance of dimensions, no additional adjustment is required. If it is necessary to change the resonant frequency of the antenna, this can be done by changing the length of the horizontal two-wire line. You can build an antenna entirely from a coaxial cable - use coax instead of two wire lines 300 ... 450 Ohm. In this case, the braid and the central core of the cable must be bridged both at the end of the antenna and at point A.
Literature
- CQ, 8/1984
- Radio amateur KB and VHF 11/97, p.27
Publication: N. Bolshakov, rf.atnn.ru
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