Antenna for 21, 24, 27, 28, 30 MHz bands. Scheme, description

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Antenna for 21, 24, 27, 28, 30 MHz bands. Encyclopedia of radio electronics and electrical engineering

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The antenna is a 10-element Log-yagi (Figure 1) calculated by UA3THQ and modified by me.

Fig.1 (click to enlarge)

Specifications:

L_boom = 7000 mm
G₂₈=9db F/b=30db
G₂₄=6db F/b=20db
G_2l=8,ldb F/b=24db

Material: tubes D16T with a diameter of 24 mm. Vibrators W1 - W7 are isolated from the boom, the distance between the halves of the elements is 80 mm (Fig. 2).

Antenna for 21, 24, 27, 28, 30 MHz bands

Ris.2

The setting consists in selecting the length of the loop to achieve the minimum SWR on the 21 MHz band. It should not exceed 1,3 over the entire frequency range. At power points X-X, the resistance is 200 ohms. To match with a 50 Ohm coaxial cable, a matching-balancing ShPTL with a transformation ratio of 1: 4 on a 200NN K100x80x10 ring is used. Windings 2x10 turns MGTF1, one twist per centimeter. =

The collection line is made of PK-75-74-15 cable, only the outer braid is used. The loop is made of copper wire with a diameter of 1,5 mm, the total length of the loop is 1,5 m.

Author: S. Ershov (UW3TU), Nizhny Novgorod; Publication: N. Bolshakov, rf.atnn.ru

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