When should you use a No Ground Plane (NGP) antenna?
If you try to use standard (mass required) 27MHz antennas with a vehicle that requires a no ground plane antenna, you will experience both high SWR levels and extremely poor performance.
Vehicles and vessels requiring NGP antennas:
- Vehicles with a fiberglass body or a coating that covers most of the entire vehicle
- Trucks and cars with little to no metal chassis on which to ground the antenna.
- Vehicles that need to use NGP antennas
- Campers and caravans with large plastic surfaces
- Camper housing where the antenna is mounted directly on the plastic fiberglass body instead of on the vehicle itself.
- On boats
- On engines with little to no ground surface
In these circumstances and with these vehicles, NGP equipment must be used. Please note that NGP installations require a special NGP coaxial cable and antenna. Using a ground based coaxial cable or a ground based antenna will cause problems. Although NGP antennas and coaxial cables can be purchased separately, they are usually sold as part of a complete NGP kit.
Do you want to place a 27MHz antenna on a boat?
Is the boat made of metal or fiberglass? Then you have to use a whip antenna of a certain length if the boat is made of fiberglass.
Additional information:
A ground plane for a 27MHz antenna is the metal surface required under the antenna. In mobile applications, the vehicle body/frame acts as the ground plane (reflection unit). The metal surface allows the signal generated when transmitting to reflect off the surface and travel into the atmosphere.
An antenna ground plane should not be confused with an electrical ground. A typical mobile CB antenna does not transmit horizontally, but rather radiates in a downward pattern. A metal surface (the larger and flatter the better) is required under the CB antenna to launch the signal into the atmosphere. Without an adequate ground plane, the signal will not travel into the atmosphere, resulting in a limited transmission range. Damage to your CB radio can also occur if you don't have a proper ground plane, as this will typically cause a high SWR and the signal can flow back to the transceiver, causing internal damage to your radio.
It is worth noting that a poor ground plane or radiating surface may not affect radio reception. You can still receive transmissions from other radios with or without a ground plane. In short, you can receive transmissions on a clothes hanger!
It is essential to understand that you need to check and tune your antenna (tuning your antenna) to ensure that it is functioning properly.
If you have a fiberglass vehicle or boat, you need a No Ground Plane Antenna. In No Ground Plane systems, the coax shield is used as a counterpart (replacement for the ground connection).
No Ground Plane 27MHz antenna
A no ground plane CB antenna is a CB antenna that does not require a ground plane (large metal surface underneath) to function. Ground plane antennas are specifically designed to work on fiber optic vehicles and boats. A No Ground Plane antenna installed on a metal vehicle or boat will not function properly. A no ground plane antenna is designed to use the ground or water to transmit horizontally. A No Ground Plane antenna won't perform as well as a traditional CB antenna of the same length, but in situations where you don't have an adequate ground plane, such as on a boat, RV or motorcycle, they do the job. Make sure you read the instructions thoroughly before installing the antenna.
Ground boosters
There are some devices available that can improve your ground plane. This is usually accomplished by adding a 3-point radial to the bottom of the antenna. Ground plane boosters are not designed to be the only ground plane for an antenna, they just help achieve a better ground plane.
