The UR0GT Broadband Avia Antenna is one of the most respected wideband VHF designs used by amateur radio operators, aviation band listeners, and monitoring enthusiasts across the world. This modified version by RW4HVN further enhances the antenna’s bandwidth and performance, making it a practical and efficient solution for the 110–150 MHz range. With an SWR below 1.75:1 across this wide span and a perfect 1:1 SWR at 145 MHz, it is especially suitable for the 2-meter amateur band.
In this article, we will break down the antenna’s construction, electrical behavior, and real-world advantages, with precise measurements taken directly from the improved diagram.
Overview of Broadband Avia Antenna
At its core, this Broadband Avia antenna is a broadband vertical radiator designed to achieve stable impedance and low SWR across a wide frequency range. The RW4HVN modification includes refinements in element lengths, spacing, and feed-point optimization.
The design is simple but extremely effective:
- Two vertical elements
- A central feed point
- Ferrite-choked coax
- Broadband length ratio for wide frequency coverage
This antenna is well-known for excellent performance on 145 MHz (2 m band) and solid behavior across aviation bands, commercial VHF, and public service signals.
Dimensions and Mechanical Layout
The antenna uses 6 mm diameter rods or tubes as radiating elements, separated by 8.7 cm. Each side consists of two segments:
Element Lengths
- Total height: 98.2 cm
- Upper section: 57.8 cm
- Lower section: 40.4 cm
These lengths are not symmetrical decorative choices—they are precisely calculated to support wideband resonance and maintain a more linear SWR curve across the 110–150 MHz band.
The spacing between the two elements (8.7 cm) creates a unique broadband impedance characteristic similar to that of a folded dipole, but in a simplified form suitable for HF/VHF construction.
Feed-Point Structure and Ferrite Ring Choke
At the junction between the upper and lower segments lies the feed point, where a standard 50-ohm coaxial cable is attached. The inner conductor and shield are connected directly to the two vertical elements.
To prevent common-mode currents—often responsible for distorted radiation patterns and SWR instability—a stack of ferrite rings is installed on the coax near the feed point. This acts as an effective RF choke, ensuring:
- Cleaner radiation
- Better SWR stability
- Reduced coax radiation
- Improved reception sensitivity
This is an essential part of the broadband behavior of the antenna.
Performance Across 110–150 MHz
The modified UR0GT Broadband Avia antenna is well-known for its exceptionally flat SWR curve.
Measured SWR Characteristics
- SWR< 1.75 from 110 MHz to 150 MHz
- SWR 1.0 at 145 MHz
The UR0GT Broadband Avia Antenna (Modified by RW4HVN) is a powerful, easy-to-build broadband antenna that offers reliable performance across a wide VHF range. Whether you are a ham radio operator, aviation listener, or VHF monitoring enthusiast, this antenna provides exceptional SWR, durability, and simplicity.
RW4HVN is a Russian amateur radio callsign belonging to operator and antenna designer Roman, known for his modification of the UR0GT Broadband Avia Antenna for wideband VHF coverage. His well‑known “UR0GT Broadband Avia Antenna Modified by RW4HFN/RW4HVN” design enhances the original UR0GT concept to provide efficient broadband performance roughly over the 110–150 MHz aviation band, with practical construction details published in Antentop and various online guides.
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