How to Choose Between an AIS Transponder with a Built-In Splitter or a Dedicated VHF/AIS splitter
Feb
When you’re installing an AIS transponder on your vessel, one of the first questions is: how should it share the VHF antenna? AIS and VHF radios both want access to the same antenna, and this requires careful planning. There are two common approaches:
Using an AIS transponder with a built-in splitter or using a dedicated standalone VHF/AIS splitter.
Both methods work, each has its pros and cons. The right choice depends on your priorities. Here we will have a look at what this means and help you decide on what is the best solution for you.
Understanding how AIS and VHF share an antenna
The AIS transponder and your VHF marine radio both transmit and receive on the VHF antenna. Without separation, the powerful VHF radio transmission can overwhelm the AIS receiver circuitry. A splitter ensures that both devices can safely share the same antenna without interfering with each other.
AIS transponder with a built-in splitter
AIS transponders that include an internal splitter or integrated VHF interface allow them to directly share the antenna with a VHF radio.
Benefits:
- Simpler installation: Fewer external components mean fewer connectors, less cabling, and a cleaner setup.
- Compact system: Good for smaller vessels where space and wiring simplicity matter.
- Lower visible cost at point of purchase: You don’t have to buy a separate splitter device.
Considerations:
- Performance depends on internal hardware: Built-in splitters can work well, but they often compromise performance compared to purpose-built external splitters, especially in noisy environments.
- Less flexibility: Built-in splitters are fixed to the AIS transponder and don’t allow advanced configurations or upgrades.
- Cooling and space: Combining splitter and AIS in one housing can affect thermal performance if the engineering is not optimised.
This solution is often preferred for cruisers and leisure boats where simplicity and tidy installations are important.
Dedicated (external) VHF/AIS splitter
A dedicated splitter is a standalone device placed between the antenna and your VHF/AIS devices to share the antenna properly.
Benefits:
- Best performance: Purpose-built splitters are engineered specifically for isolation and filtering, which can reduce interference and protect sensitive receivers.
- Greater flexibility: You can change radios or AIS units without affecting the splitter setup.
- Easier troubleshooting: Separate components make it easier to identify and fix issues.
Considerations:
- More cabling and connectors: Installation complexity is higher – you will need to plan antenna runs, splitter location, and cable routing.
- More upfront parts: Buying a separate splitter adds cost and requires extra space.
This option is generally preferred for commercial vessels, high-traffic waters, or performance-focused installations where signal purity and reliability are critical.
So which should you choose?
| Need / Priority | Built-In Splitter | Dedicated Splitter |
| Simplicity | ⭐⭐⭐⭐⭐ | ⭐⭐ |
| Space & Cabling | ⭐⭐⭐⭐⭐ | ⭐⭐ |
| Performance in Noisy Environments | ⭐⭐ | ⭐⭐⭐⭐⭐ |
| Flexibility & Upgradeability | ⭐⭐ | ⭐⭐⭐⭐⭐ |
| Best for Cruisers & Small Boats | ✅ | ⚪ |
| Best for Commercial / High-Performance | ⚪ | ✅ |
In simple terms:
- If you want a quick, neat installation and you’re not pushing your system to its limits, an AIS with built-in splitter works well.
- If you want optimum performance, flexibility, and future-proofing, a dedicated VHF/AIS splitter is the more professional choice.
A real-world example
Imagine you’re sailing in a busy harbour with strong VHF traffic. A high-quality external splitter can help:
- Reduce false AIS targets caused by radio pulsing,
- Protect the sensitive AIS receiver from overload,
- Give cleaner AIS reception – especially in congested conditions.
In contrast, a built-in splitter might work fine during coastal cruising but show limitations in such busy RF environments.
Tips before you install
- Check cable lengths and losses: Poor cable quality or long runs can degrade performance more than the choice of splitter.
- Use quality connectors: VHF and AIS are sensitive to SWR and reflections – poor fittings hurt performance.
- Plan access & ventilation: Especially if using external splitters – they should be accessible and not heat-trapped.
- Always properly terminate unused ports and connectors to prevent RF leakage.
Our view at Quark-elec
At Quark-elec, we believe in practical performance and reliability. Whether AIS is built-in with a splitter or used with a dedicated external splitter, the key is having a good system design. We’re committed to engineering products that work reliably in real marine environments.
As we continue to innovate in AIS receivers and integrated marine electronics, we always test splitter performance under real-world conditions. Our philosophy is simple: clarity, reliability, and ease of use matter, especially on the water.
Our engineering team are currently in development of our next generation of AIS devices which will feature built-in splitters, with these scheduled to be available in Q2 2026
