Example Data Table
| Input |
Z₀ |
Outputs |
Arm Resistor |
Insertion Loss |
Power Each Output |
Network Heat |
| 1 W |
50 Ω |
2 |
16.67 Ω |
6.02 dB |
250 mW |
500 mW |
| 1 W |
50 Ω |
3 |
25 Ω |
9.54 dB |
111.11 mW |
666.67 mW |
| 1 W |
50 Ω |
4 |
30 Ω |
12.04 dB |
62.5 mW |
750 mW |
Formula Used
For N equal outputs and system impedance Z₀, this tool uses a matched symmetric star network.
Arm resistor R = Z₀ × (N - 1) / (N + 1)
Ideal split loss = 10 × log10(N)
Resistive excess loss = 10 × log10(N)
Total splitter insertion loss = 20 × log10(N)
Power at each output = Input power / N²
Total load power = Input power / N
Network heat = Input power × (N - 1) / N
Input arm heat = Input power × (N - 1) / (N + 1)
How to Use This Calculator
- Enter the input power and select its unit.
- Enter the system impedance, such as 50 Ω or 75 Ω.
- Select the number of equal output ports.
- Enter the actual load impedance for mismatch checks.
- Add cable and connector loss for each output path.
- Enter resistor wattage and a safety margin.
- Press Calculate to view resistor values and power levels.
- Use CSV or PDF download for records.
Resistive Power Splitter Guide
What This Calculator Does
A resistive power splitter divides one matched signal into equal outputs. It uses only resistors, so it is simple, wideband, and easy to build. The tradeoff is loss. A matched resistive splitter wastes part of the input power as heat. This calculator estimates that loss, the output power, and the stress on each resistor.
Why Matching Matters
Radio, audio test, and measurement systems often use a reference impedance. Fifty ohms is common in radio work. Seventy five ohms is common in video and cable systems. When every port is matched, reflections stay low. The source sees a predictable load. Each output receives the same share. If a load impedance is wrong, the result becomes less exact. The mismatch section helps you judge that risk.
Key Design Idea
The calculator models a symmetric star splitter. The input and all outputs connect to a common node through equal resistor arms. For N outputs, the total number of ports is N plus one. The arm value is chosen so every port sees the selected system impedance when all other ports are terminated. This gives a practical matched divider for lab signals and low power distribution.
Power Loss And Heat
An ideal lossless splitter divides power by N. A resistive splitter has extra loss because resistors absorb energy. For equal outputs, each output receives input power divided by N squared. The total power reaching all loads is input power divided by N. The rest becomes heat in the resistor network. The input arm usually dissipates the largest share. Always compare calculated dissipation with the real resistor rating. Add a safety margin for heat, enclosure temperature, and continuous use.
Practical Use Tips
Use accurate, non inductive resistors when frequency is high. Keep leads short. Place the splitter close to the measurement point. Use matched cables and loads. Increase resistor wattage when input power rises. Do not use this network for high power transmitters unless each resistor is properly rated and cooled. Label every port clearly. Recheck wiring before connecting sensitive instruments to any active source first. For minimum loss, use a reactive or transformer splitter instead. Use this tool when broadband simplicity is more important than efficiency.
FAQs
What is a resistive power splitter?
It is a passive network that divides one signal into multiple outputs with resistors. It is simple and broadband, but it loses power as heat.
Why is the output lower than an ideal splitter?
An ideal splitter only divides power. A resistive splitter also dissipates power in its resistor arms. This creates extra insertion loss.
Does every output need a matched load?
Yes, for best accuracy. The formulas assume every unused port has a matched termination. Open or mismatched ports change the split and reflections.
Can this calculator handle 50 Ω and 75 Ω systems?
Yes. Enter any positive reference impedance. The arm resistor value and power results update from that impedance.
Can I use this for high power transmitters?
Use caution. Resistive splitters waste power as heat. High power use needs correctly rated resistors, cooling, shielding, and safe RF construction.
What resistor type is best?
Use low inductance resistors for RF work. Metal film or dedicated RF resistors are common choices. Avoid long leads at high frequencies.
What does safety margin mean?
It reduces the usable resistor rating for safer design. A 50 percent margin means the calculated heat should stay well below the nameplate rating.
Can this split unequal power levels?
This version models equal outputs. Unequal resistive pads need different equations and often need separate matching checks for each port.