Why a Cel-Fi System Needs Two Antennas
A Cel-Fi GO or GO2 system requires a minimum of two antennas to operate: one external (donor) antenna to capture signal from outside, and one internal (server) antenna to rebroadcast the boosted signal inside the building or vehicle. Multiple donor antennas are possible on more complex setups, but that's a bespoke configuration best confirmed with a qualified installer rather than guessed at.
A Cel-Fi PRO system is a bit different. It doesn't always need an external antenna. If you've already got a reasonable signal, at least 2 bars, the existing internal antenna is often sufficient. Genuinely poor signal is what pushes you toward needing an external antenna as well.
Getting this pairing right is the single biggest factor in whether a Cel-Fi installation actually performs the way it's supposed to.
Choosing an Internal (Server) Antenna
Internal, or donor-side, antennas distribute the boosted signal from the Cel-Fi unit throughout the building or space. Most wideband internal antennas cover all current NZ mobile bands (4G and 5G), so band compatibility usually isn't the deciding factor, coverage pattern is.
- Wall panel antenna: directional, spreading signal across roughly a 90° beamwidth in the direction it faces. Easy to install and unobtrusive, well suited to long, narrow spaces like sheds, demountables or single-storey homes.
- Ceiling dome antenna: spreads signal in a full 360° pattern, making it the better choice for offices or open-plan spaces where ceiling mounting is practical.
- Adhesive mount antenna: compact, roughly 10cm, with an adhesive back. Common in marine, caravan and vehicle applications where other internal antennas are too powerful to maintain the required separation from the external antenna.
Choosing an External (Donor) Antenna
External antennas split into two families, and the difference matters more than any spec sheet number.
Directional Antennas
Directional antennas need to be aligned toward the signal source and are built for pulling signal over long distances where a clear line of sight exists, useful in remote areas or where you know exactly where the nearest tower is.
| Type | Beamwidth | Best For |
|---|---|---|
| Yagi | Narrow (5-10°) | Maximum gain over long distances, requires precise alignment |
| LPDA (wideband) | Moderate (32-55°) | The general go-to option for rural, regional and urban sites |
A Yagi offers the highest gain but the narrowest, most demanding alignment. An LPDA is more forgiving to install and, when it's a genuinely wideband model, covers current 4G and 5G bands rather than being locked to older specs.
Omni-Directional Antennas
Omni antennas pull signal from all 360° and don't need aiming at a specific tower. They're the right call when a clear line of sight to the nearest tower can't be established, or where ease of installation matters more than maximum range, common in suburban or built-up areas.
Vehicle-Mounted Antennas
Vehicle installations need an antenna built for constant vibration and changing orientation as the vehicle moves, which usually rules out narrow-beamwidth directional antennas as a practical choice. Compact omni-directional antennas, roof, gutter or bullbar-mounted, are the standard setup for utes, trucks and 4WDs, since they maintain a connection regardless of which way the vehicle is facing.
Mounting position matters here too. A lower-profile mount clears underground car parks and low-clearance areas, while a bullbar mount often gives a cleaner line of sight than one tucked under the roofline.
If you're deciding on the booster device itself rather than just the antenna, our guide to choosing a vehicle cell phone booster covers that side of the decision.
Getting the Right Antenna for Your Situation
Mobile Systems Limited is 100% New Zealand owned and based in Mount Maunganui, with over 25 years supplying and installing cellular signal solutions. We have access to nationwide cellular frequency information and offer a free consultation to help you choose the right antenna setup, rather than guessing and hoping.
