Multi band antenna 3,5-28 MHz. Scheme, description

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Multi band antenna 3,5-28 MHz. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / HF antennas

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The prototype of this antenna was the antenna proposed by UW4HW ("Radio", No. 12/1968), and a variant of this antenna UA6HKH ("Radio" No. 9/1981). My version of this antenna operates from 3,5 to 28 MHz.

Multi band antenna 3,5-28 MHz

While in Essentuki (UY5AP / UA6H), I met Georgy - UA6HVX, who had an antenna similar to UW4HW, 20 m high. The antenna worked perfectly at 3,5 MHz and not bad at 1,8 MHz! Then I converted my 7 MHz GP into such an antenna, but with a height of 10,2 m fig.1. The antenna has been in operation since 1986. Hundreds of DX QSOs have been made on various bands. On 3,5 MHz JA gives 569 at 120 W output power. On all other bands almost every DX I hear responds. With an output power of 0,5 watts, there is a QSO with NM7G on 14 MHz, which rated my signals at 449. SWR on the bands: 3,5 MHz - 1,2; 7 MHz - 1,2; 10 MHz - 1,2; 14 MHz - 1,1; 21 MHz - 1,3; 28MHz-1,2.

Multi band antenna 3,5-28 MHz

The antenna is stretched with two tiers of guys. Horizontal spacers are made of metal tubes with an inner diameter of 10 mm, which are mounted on bolts with a diameter of 10 mm, welded with their heads to the brackets (position B). At the other ends of the tubes, roller insulators are fixed, to which wires are attached. An insert equal to the inner diameter of the mast with a central hole under the MCH is fixed in the upper part of the mast. A washer made of double-sided fiberglass with a thickness of 1,5 - 2 mm is screwed here (position A). Both foil sides of the washer must be soldered. The ends of the wires are inserted into the seven holes of the washer and soldered to it. The washer is screwed with an M4 screw.

Multi band antenna 3,5-28 MHz

Thus, at the top of the mast, both mechanical and electrical contact of the antenna wires is obtained. The seventh wire is needed to eliminate bad contacts in the mast joint and runs along the mast, connects to the counterweights and cable sheath. In the lower part of the antenna, 6 wires are threaded through the holes of the L-shaped insulators (position B) and are interconnected in the form of a ring. These insulators are attached to the mast with electrical tape. The core of the cable is soldered to this ring. Cable sheath - to counterweights, which are connected in pairs to four bolts on the metal antenna thrust pad, located on a flat roof.

Multi band antenna 3,5-28 MHz

Thus, all connections of the working part of the antenna are soldered and not subject to climatic influences, which is very important! If you also connect four counterweights with a length of 20,4 m, then the antenna will work better at 3,5 MHz.

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