The Wilkinson Divider Is a Superior Choice for Splitting RX Antennas
Or: Antenna system design meets RF hygiene.
In receive-only antenna systems—especially with broadband active antennas or phased arrays—the way you split and distribute signals across multiple receivers matters. Many reach for a diplexer or cheap resistive splitter, but in most cases, the Wilkinson power divider is the vastly superior option. Here’s why.
Diplexers: Selective but Limited
A diplexer is a frequency-selective device. It uses low-pass and high-pass filters to separate or combine different frequency bands into one port. They’re simple, passive, and reciprocal, but:
- They only work when the bands don’t overlap.
- Impedance match is only maintained within the intended band.
- They offer little or no port isolation unless specially engineered.
They’re fine for splitting 144 MHz from 430 MHz—but not when both receivers need the same 1–30 MHz broadband signal.
Wilkinson Divider: Broadband, Matched, and Isolated
The Wilkinson divider is a broadband, resistively isolated power splitter. When designed correctly, it delivers:
- Perfect impedance match at all ports
- Excellent port-to-port isolation via the isolation resistor
- Flat amplitude response and linear phase over wide bandwidths
This isolation is vital in receive chains where multiple SDRs, ADCs, or front-ends could leak local oscillator or digital noise back into the antenna. The Wilkinson stops that crosstalk cold.
When Noise Matters: Choose Isolation
Receive systems live or die on noise performance. Imagine a shared broadband active antenna feeding:
- Receiver A for a waterfall/skimmer
- Receiver B for main listening or diversity
A diplexer or resistive splitter lets noise from one receiver leak into the other, and possibly back into the antenna’s active stage—hurting SNR. A Wilkinson decouples them, giving the active stage a clean load and both receivers clean signals.
Bonus: Wilkinson Scalability
Wilkinsons can be scaled for 4-way, 8-way, or more using cascaded stages. They work in 50 Ω, 75 Ω, or even 600 Ω systems, and can be built with stripline, microstrip, or lumped elements—ideal from HF to UHF.
Bottom Line
- Works over broad frequencies
- Provides superior isolation
- Maintains matched loads for both antenna and receivers
- Prevents inter-device interference
For serious RX systems—especially those using active antennas or SDRs—the Wilkinson isn’t just better. It’s essential.
When you split, don’t just divide—isolate.
Mini-FAQ
- Can I use a resistive splitter instead? — Yes, but you’ll lose isolation and introduce more insertion loss.
- Will a Wilkinson work for transmit? — Not without redesign for higher power; the isolation resistor will dissipate significant heat.
- Does it need to be PCB? — No, lumped-element versions work fine for HF.
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