Navigating the world of mobile scanner antennas can be complex, especially when aiming for optimal reception for trunking systems and VHF frequencies in your vehicle. Many enthusiasts, like yourself, seek to maximize their scanner performance without compromising their car’s aesthetics or functionality. Let’s address your questions about setting up your Car Trunking Scanner Antenna and VHF antenna to ensure you’re on the right path before you start drilling.
Utilizing an 800MHz Antenna for Trunking Scanners
It’s perfectly reasonable to consider repurposing an existing 800MHz antenna, even if it wasn’t explicitly marketed as a “scanner antenna.” Often, antennas designed for Motorola radios or similar professional communication equipment can function effectively as receiving antennas for 800MHz trunked systems. The key factors are the antenna’s frequency range and impedance matching.
If your antenna is indeed designed for the 800MHz band, connecting it with RG6 coaxial cable should generally yield satisfactory results for receiving signals. RG6 is a common and cost-effective coaxial cable known for its low signal loss, particularly at higher frequencies like 800MHz. Ensure you use quality connectors and proper termination techniques to minimize signal degradation.
However, keep in mind that antennas are often optimized for specific applications. An antenna designed for transmitting might have different characteristics than one specifically engineered for wideband scanning reception. While it will likely work, a dedicated scanner antenna might offer broader bandwidth and potentially better performance across the 800MHz band, depending on the specific systems you intend to monitor. For initial setup and testing, your existing 800MHz antenna is a great starting point to assess its performance in your scanning application.
Mounting an 800MHz Antenna on a Plastic Sport Wing
Your Mazda hatchback’s plastic “sport wing” presents an interesting mounting challenge for your 800MHz antenna. You are correct in understanding the importance of a ground plane for most antennas, including your 800MHz antenna. A ground plane is a conductive surface that acts as a counterpoise, influencing the antenna’s radiation pattern and impedance.
Since plastic is not conductive, mounting your 800MHz antenna directly onto the plastic wing, five inches from the metal roof, will indeed require creating an artificial ground plane. Your idea of cutting a piece of sheet metal and fitting it inside the wing to provide a metallic base is an excellent approach.
Here’s how to implement this effectively:
- Sheet Metal Selection: Choose a sheet of aluminum or steel. Aluminum is lighter and corrosion-resistant, while steel is more readily available and cost-effective. The size of the sheet metal isn’t overly critical, but aim for a square or circular piece with dimensions roughly comparable to the wavelength of 800MHz signals. A size of approximately 12 inches by 12 inches would be a good starting point.
- Secure Mounting: Ensure the sheet metal is securely attached to the underside of the plastic wing. You can use screws, bolts, or strong adhesive, ensuring it’s firmly in place and won’t vibrate loose.
- Antenna Ground Connection: When mounting your 800MHz antenna to the sheet metal, ensure a good electrical connection between the antenna’s ground and the sheet metal. This connection is crucial for the sheet metal to function as an effective ground plane.
By implementing this ground plane solution, you provide the necessary conductive surface for your 800MHz antenna to operate more efficiently, even when mounted on a non-metallic surface like your car’s plastic wing. This approach allows for a less conventional mounting location while still striving for optimal antenna performance.
VHF Antenna Mounting on a Hatchback
Moving on to your VHF antenna, the challenge of mounting a longer VHF antenna on a vertical hatchback is a common consideration. You’re right to anticipate potential ground plane issues when mounting an antenna on a vertical surface, particularly at the bottom of the hatch.
Hatchback NMO mounts are designed to attach to the edge of the hatchback, which is often vertical. When a VHF antenna is mounted vertically on a vertical surface, the ground plane effect is indeed compromised compared to a roof-mounted antenna with a large, horizontal ground plane (the car roof itself).
However, “no ground plane” is not entirely accurate. In this scenario, the car’s body panels, especially the hatchback door itself, will still act as a partial ground plane. The effectiveness of this ground plane will be less than ideal, potentially affecting the antenna’s radiation pattern and impedance. This can lead to:
- Directional Reception: The antenna might exhibit a more directional pattern, potentially favoring signals from certain directions more than others.
- Reduced Efficiency: The overall efficiency of the antenna might be slightly reduced compared to an ideal ground plane setup.
Given your приемлемость for “good enough” reception, as you mentioned your Radio Shack all-band mobile scanner antenna performs adequately, a hatchback NMO mount for your VHF antenna might still be a practical solution for your needs. Many scanner enthusiasts successfully use hatchback mounts for VHF antennas and achieve satisfactory reception.
Mitigation Strategies for Hatchback VHF Mounting:
- Maximize Hatchback Surface: Mount the NMO mount as close to the center of the hatchback door as feasible to utilize as much of the metal surface as possible for the ground plane.
- Consider Antenna Type: Some VHF antennas are designed to be less ground plane dependent than others. Researching “ground plane independent” or “low ground plane” VHF antennas might yield options that are more forgiving in hatchback mounting scenarios.
- Experimentation is Key: Since you’re not seeking crystal-clear reception, install your chosen VHF antenna with a hatchback mount and assess its performance in your typical scanning locations. You might find the reception is perfectly acceptable for your needs.
Before drilling any holes, remember to thoroughly plan your cable routing and ensure you are comfortable with the chosen mounting locations. Starting with your existing 800MHz antenna and proceeding step-by-step with your VHF antenna installation will allow you to optimize your car scanner setup effectively while minimizing potential issues.
