The Multiband Directional Antenna

The Multiband Directional Antenna: Compact, Cost-Effective, and Switchable

06/11/2023 Off By radioarenadmin

The quest for a space-efficient and cost-effective multiband antenna is a common concern for radio amateurs. The innovative multiband directional antenna with a switchable directional pattern is a testament to inventive amateur spirit, offering a practical solution that satisfies these requirements without the hefty price tag.

Space-Saving Design for Multiband Operation

HF Multiband Directional Antenna

HF Multiband Directional Antenna

At the heart of this antenna is the sloper system, emanating from a 15-metre mast at angles between 30 to 40 degrees to the ground. A minimum of five rays, each roughly 20 metres in length after adjustments for relays and insulators, ensures a compact footprint. This design, working across 3.5, 7, 14, 21, and 28 MHz bands, incorporates the principle of RA6AA and UA4PA antenna structures, tailored for the space-conscious amateur.

Enhanced Directional Control

The directional pattern is readily adjustable from the operator’s station, connecting the desired ray to the cable’s central conductor through a relay system. This switchable feature significantly improves signal focus, providing an average side-lobe suppression of 2 to 3 points, outperforming rear suppression.

Construction and Setup

A telescopic mast from P-140 serves as the backbone, grounded without extra measures. The rays, made from robust field telephone cable P-275, ensure a long-lasting build. The 75 Ohm coaxial cable can be replaced with any impedance suitable for the user, and even open two-wire lines with 300 to 600 Ohm resistance. Using TKE52 relays for switching, powered by a dedicated four-wire cable, allows for seamless direction changes.

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Minimal Adjustment Required

Setting up this antenna is straightforward. Adhering to specified dimensions ensures resonance within amateur bands, and a matching device is advisable due to the antenna’s 30 to 400 Ohm input impedance range.

Antenna and Feeding Line Dimensions

The dimensions of the antenna and feeding line are adaptable using the formula L2=(84.8-L1)*K, where L1 is the length of one arm, L2 is the feeding line length, and K is the velocity factor (0.66 for coax, 0.98 for open-wire line).

Input Impedance Table

The following table outlines the input impedance across various frequencies, highlighting the antenna’s versatility.

Frequency (kHz)Input Impedance (Ω)
175020
3510270
3600150
7020360
7100400
1011050
14100260
14250200
14350180
1800050
1812050
21150190
21300180
21450160
2494059
2515050
28050160
28200200
28500130
2900065
2960030
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Conclusion

The multiband antenna with a switchable directional pattern stands as an optimal choice for amateur radio operators seeking a blend of space-efficiency, affordability, and performance. With minimal tuning required and flexible installation options, this antenna brings advanced capabilities to the space-restricted amateur, proving that you don’t need a large field to reach the world.

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TZT Windcamp

This is Horizontal Dipole Shortwave Ham Radio Antenna for the 5 – 50 MHz range. The operating frequency is continuously adjustable, giving you a full-size portable horizontal dipole antenna. The antenna is designed for portable use. Windcamp wants to maximize your portable operating experience.

TZT Windcamp

Featured is the TZT Windcamp 5-50MHz Ham Radio Dipole Antenna, a high-performance HF horizontal dipole shortwave antenna available for purchase. This full-size half-wavelength antenna is versatile with a tunable resonant frequency ranging from 5-50 MHz and includes nine-band preset resonance points for various frequencies like 5, 7, 10, 14, 18, 21, 24, 28/29, and 50MHz. It boasts a waterproof balun, constructed from a combination of carbon fibre tube and aluminium alloy for durability. Key technical specifications include continuous frequency adjustment within 5-50MHZ, an SWR of ≤1.5, a 50Ω input impedance, and a 100W PEP power capacity. The antenna uses 18AWG tinned copper wire and an SL-16 socket type, with a 1:1 forced balance voltage type Balun.