Also known as: splitter, combiner, power divider, power splitter
A splitter divides one RF signal into two or more output ports; a combiner is the same device run in reverse, merging several signals onto one port.1 Splitting power N ways means each output is inherently weaker — a two-way even split loses about 3 dB to each port before any real-world loss — so the design’s job is to divide cleanly while keeping the ports matched and, ideally, isolated from one another.
Overview
The core specifications of a divider are its split ratio (usually equal), insertion loss above the theoretical split, isolation between output ports, and return loss at each port. The unavoidable ~3 dB per port of a two-way split is not a defect but the arithmetic of sharing power; a good divider adds only a small fraction of a dB of real loss on top and keeps every port well matched.
How it works
There are three common approaches, trading simplicity for performance:
- Resistive — a small network of resistors. Broadband and dead simple, but lossy (each output of a resistive two-way is ~6 dB down, not 3) and the ports are not isolated.
- Reactive (transformer/transmission-line) — uses transformers or quarter-wave lines to divide with near-ideal ~3 dB loss, but with limited isolation between outputs.
- Wilkinson divider — the workhorse. Two quarter-wave lines plus an isolation resistor between the outputs. The resistor dissipates no power when the load is balanced, yet provides good isolation and matches all ports. This is why it dominates RF splitter design.
Run any of these backwards and it becomes a combiner. Combining is subtler than splitting: the sources must be in phase for their power to add efficiently, and the isolation resistor in a Wilkinson absorbs the difference when they are not, protecting the sources from each other.
Relevance to SDR
Splitters are everywhere in multi-receiver setups: feeding one antenna to several SDRs, tapping a signal for a spectrum monitor, or distributing a common reference. A closely related device, the directional coupler, is essentially an unequal, direction-selective divider used for sampling rather than even division. In receiving arrays, splitters and combiners route signals for antenna diversity and phased feeds. Remember the 3 dB-per-port cost: splitting one antenna to several receivers lowers the signal at each, which a low-noise preamplifier ahead of the splitter can offset.
GopherTrunk is receive-only software and includes no splitter or combiner. The device is purely part of the RF plumbing ahead of the SDR — relevant to GT users who want to share one antenna among multiple receivers or SDR instances, where the split loss and port isolation directly affect the quality of each receiver’s I/Q stream.
Sources
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Power dividers and directional couplers — Wikipedia, on resistive, reactive, and Wilkinson power dividers, insertion loss, and isolation. ↩