Yagi antennas for 144 MHz (Hairpin) and 435 MHz

September

2024

Yagi antennas for 144 MHz (Hairpin) and 435 MHz

антенны, УКВ

20 September 2024 17:01

The following antennas can be used to searching of "fox" (transmitter) or for satellites V/U, U/V on the bands 144 and 435 MHz.

Introduction

Over the past week, I listened to the ISS (international space station) with the release of the relay at 437.800 MHz: the quality of the reception (rating) by ear from 44 to 57 unsatisfactory, up to 2 points by S-meter. One of the amateur radio amateurs said that he worked through the AO-51 satellite, but not through the ISS for whom "serious equipment is needed". Having watched the video- to take the descending UHF channel on 437.800 +- 10 kHz at least a 7-element antenna, and a transfer is needed for the transfer of 145.xxx "уда-яги" from 3 elements. It is easiest for her to use an antenna with a split vibrator than with loop, to make it easier to make it at home.

Material and cost of the antenna

In the construction store "Maxidom" I bought materials: - a traverse 15x15mm (263 rubles), a brass pipe for a brass vibrator (727 rubles), an aluminum bar 3 pcs. 126 rubles, goals, screws, nuts (87 rubles each) - the total amount came out 2800 rubles. It concluded that it is unprofitable to make the antenna from the store materials and profiles.

In one of the video hosting, I saw a design -"antenna from measuring tape". It was a 3-element "Uda-Yagi". In terms of size found on another site, I restored its model and studied it. The antenna consists of 3 elements - a reflector, a vibrator and director, but a power unit with the approval of the type "hairpin" (from the word "заколка"). Hairpin is an additional inductance at the power point, which increases the input resistance of the active element by introducing it into resonance and removes negative reactivity.

The frame of the antenna type "from measuring tape" radio amateurs are performed from PVC (polyvinyl chloride) segments of tubes and crosses, which can be bought, for example, in a store "Leroy Merlin"(In 2022, he changed the name in "Lemana Pro"). Ceres of a metal roulette with one screw and two screeds are attached to the plastic crosses. The cable is connected with a wave resistance of 50 Ohms using terminal tips, to the roulette tape, to the bolts, washers and nuts cleaned from paint. Hairpin jumper usually has a small height: from 30 to 50 mm.

In the future, I plan to make the same antenna. While now I posted modified antenna models "from measuring tape" for 2m and 70cm. Instead of roulette, you can use any suitable material - tubes, hard bimetallic wire, etc. .. For this, I calculated the antenna 144 and 434 for various diameters.

A feature of the given modified antenna of 144 MHz is 4 elements instead of 3, which significantly expands the working range of frequencies, improves matching with cable and therefore increases repeatability. Around the central frequency of 437 MHz, a range of good matching and amplification is wide - about 20 MHz (overlaps 430-446 MHz), with low SWR up to 1.1.

Focus diagram of 144 MHz - with a wide main petal and strong suppression of the reception from the reverse direction reaching 60 dB.