Short Answer
A duplexer is a tuned filter system that separates the transmit and receive signals of a repeater. This enables a repeater system to operate with a common antenna while simultaneously receiving and transmitting. Key factors include frequency separation, tuning, insertion loss, decoupling, power, mounting quality, and regular inspection.
Duplexers are inconspicuous but central components of many repeater systems. Incorrect tuning can significantly degrade range and reception.
Purpose of a Duplexer
| Task | Benefit |
|---|---|
| Separation | Transmit signal does not interfere with receiver. |
| Common Antenna | One antenna can be used for both transmitting and receiving. |
| Filtering | Undesired signal components are reduced. |
| System Protection | Repeater operates more stably and with less interference. |
Important Planning Factors
- Frequency pair and duplex spacing.
- Transmit power and permissible load.
- Insertion loss and decoupling.
- Antenna system, cables, and grounding.
- Tuning, measurement, and documentation.
Typical Errors
Duplexers are considered standard accessories, even though they must match the frequency and system. Transport, temperature, aging, or modifications can necessitate follow-up checks.
FAQ
Does every repeater need a duplexer?
If a repeater is to send and receive simultaneously via a common antenna, typically yes.
Can a duplexer be adjusted by oneself?
For professional systems, measuring tools and experience are required. Incorrect tuning can cause significant disruptions.
Does a duplexer cause loss?
Yes, insertion loss usually occurs. This must be accounted for in the planning.
What is the difference to a combiner?
A duplexer separates sending and receiving. A combiner combines multiple transmitters onto a single antenna system.
Sources and Currency
This page was created on 06.07.2026. Technical and regulatory information must be verified against current manufacturer data, standards, frequency specifications, and site conditions for specific projects.