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The ATAS-120A is an active tuning antenna system designed for mobile operation, specifically for use with Yaesu transceivers equipped with the ATAS system, such as the FT-897, FT-847, FT-857, and FT-100/-100D. Its primary function is to provide automatic tuning across various amateur bands, eliminating the need for multiple, expensive, or inconvenient monoband resonating whip assemblies. This is achieved through a motorized tuning system that actively resonates the radiating element to achieve the lowest possible Standing Wave Ratio (SWR).
The core functionality of the ATAS-120A revolves around its ability to automatically adjust its radiating element. When connected to a compatible Yaesu transceiver, the antenna's internal motor system fine-tunes the antenna's length and electrical characteristics to match the operating frequency. This automatic tuning process ensures optimal performance and efficient power transfer from the transceiver to the antenna across the supported frequency ranges, which include HF, 50 MHz, 144 MHz, and 430 MHz amateur bands. The system is designed to simplify antenna operation for mobile users, allowing them to change bands without manually adjusting the antenna.
For operation on the 144 MHz and 430 MHz bands, users may consider purchasing a Duplexer (for FT-857, FT-897, and FT-100/-100D) or a Triplexer (for FT-847). These devices connect to the transceiver's appropriate antenna jacks and automatically route RF power from the active band while isolating the other two antenna jacks. Without a Duplexer or Triplexer, the coaxial cable from the ATAS-120A must be manually moved to the correct antenna jack when switching between VHF/UHF and other bands.
The ATAS-120A is designed for straightforward installation and operation. The installation process involves several steps:
For mounting, it is strongly advised to use a mount that provides secure and strong mechanical contact to the vehicle's frame. This is important not only to support the antenna's cross-sectional area while driving but also for proper grounding. Suitable mounts include models like the Diamond TE5M and K400. Simple magnetic mounts are not recommended due to the ATAS-120A's cross-sectional area, as they may not provide sufficient holding power.
When operating, users should always employ the minimum transmitter power necessary for communications and restrict transmission when pedestrians are within one meter (3.3 feet) of the radiating element. It is critical to avoid touching the radiating element during transmission due to the high RF voltage present, which can cause burns. The ATAS-120A should not be installed where the radiating element could contact electrical wiring, which could cause lethal shock, or a grounded metal surface, as this could disrupt communications and cause arcing.
Furthermore, users should avoid touching the Antenna Coil Assembly to prevent undue stress or damage to its mechanical components. The tuning process should never be attempted while driving a vehicle. When washing the vehicle, the ATAS-120A should be disconnected to prevent water ingress due to high water pressure or damage from brushes.
The ATAS-120A is exclusively designed for automatic operation with Yaesu transceivers equipped with the "ATAS" system and is not compatible with other transceiver models for automatic tuning. For base station operation, if a good counterpoise system (like a townhouse balcony) is not available, VHF/UHF performance can be enhanced by installing the optional ATBK-100 Antenna Base Kit.
The ATAS-120A is designed with no user-serviceable parts inside. This means that users should not attempt to disassemble or repair the antenna themselves. Reckless turning of the top of the antenna coil can lead to breakage of the antenna coil wire or other internal damage, which would likely void any warranty and require professional service. The emphasis is on proper installation and careful handling to ensure the longevity and reliable performance of the device. Regular checks of the mounting integrity and coaxial cable connections are advisable to maintain optimal performance and safety.
General| Impedance | 50 ohms |
|---|---|
| VSWR | Less than 2:1 |
| Tuning Speed | Approx. 5 seconds |
| Length | 1.2 m (extended) |
| Operating Temperature | -10°C to +60°C |
