10-element antenna "UDA-YAGI" for the band 70cm

June

2024

10-element antenna "UDA-YAGI" for the band 70cm

антенны, УКВ

21 June 2024 18:34

I used to count the antenna "UDA-YAGI" for one range of 70 cm. It was accidentally possible to choose the parameters better in a wide frequency band, for two ranges: 430-440 MHz and PMR-446.0-446.2 MHz.

Introduction

This antenna is relatively short - only 10 elements. However, the gain relative to the dipole is 12 dBd, which is equivalent to increasing the power in a certain direction by 15.8 times. Since the power of portable radio stations does not exceed 7-10 W, and the sensitivity of the receiver is limited to 0.2 μV, the use of such an antenna will allow transmitting from a stationary station (80 W - effective radiated power (EIRP)) without disturbing others, and also hear signals that are not received on the whip antenna.

The dimensions of the 10-element antenna are optimal for a 2-meter traverse. The aluminum profile of the square section, pipes or pine rails that are sold in construction stores, most often 2 meters long.

The spectrum of amateur band "70 centimeters" (430-440 MHz) on the site 433.075-434.750 MHz is subject to interference from automobile signaling, radio stations of builders and guards. Therefore, the optimization of the antenna is made according to the criterion for suppressing side and rear petals of the orientation diagram (F/B). Also, the antenna captures the PMR 446.0-446.2 MHz range with a low level of SWR.

The design dimensions of the antenna elements provide good matching of the antenna to a 50 Ohm cable, and the Standing Wave Ratio (SWR) is low over a wide frequency range of 430-446 MHz.

Correction of the length of the elements in comparison with the calculating with a wooden or plastic basis is not needed.
When using a metal traverse, you need to use plastic insulators and lengthen the antenna elements to the same size - a few mm ("бум-коррекция").
I did not conduct research and calculations. About the boom correction in the range of 432 MHz is described in article DG7YBN, in messages on the forums qrz.ru, vhfdx.ru and cqham.ru.

Orientation diagram, SWR, f/b and amplification