Advanced Transmitter Power Form
Formula Used
Total loss: L = cable loss + connector loss + filter loss + mismatch loss + other loss + margin.
Loss factor: LF = 10-L/10.
Feed power: Pfeed = Ptx × LF × active transmitters.
Peak total emitted power: Pemitted = Pfeed × antenna efficiency.
Average emitted power: Pavg = Pemitted × duty cycle.
EIRP with directivity gain: EIRP = Pemitted × 10G/10.
EIRP with realized gain: EIRP = Pfeed × 10G/10.
Power density: S = average EIRP ÷ 4πr².
Electric field: E = √(30 × average EIRP) ÷ r.
How to Use This Calculator
- Enter transmitter output power in watts or dBm.
- Add cable, connector, filter, mismatch, and extra losses.
- Enter antenna gain and choose the correct gain basis.
- Add antenna efficiency, duty cycle, active channels, distance, and bandwidth.
- Press calculate to see emitted power, EIRP, field strength, and density.
- Use CSV or PDF export for records and project files.
Example Data Table
| TX Power | Total Loss | Efficiency | Duty Cycle | Gain | Peak Emitted Power | Average Emitted Power | Peak EIRP |
|---|---|---|---|---|---|---|---|
| 50 W | 2.5 dB | 80% | 50% | 6 dBi | 22.50 W | 11.25 W | 89.50 W |
| 5 W | 1 dB | 90% | 100% | 2.15 dBi | 3.57 W | 3.57 W | 5.86 W |
| 100 W | 4 dB | 70% | 25% | 9 dBi | 27.87 W | 6.97 W | 221.30 W |
Transmitter Power Planning
A transmitter does not send every watt into free space. Some power is lost in cable, connectors, filters, and matching networks. Some power is also limited by antenna efficiency and operating duty cycle. This calculator joins those pieces into one practical estimate.
What Total Emitted Power Means
Total emitted power is the power that actually leaves the antenna system. It is often close to total radiated power. It is different from transmitter output power, because output power is measured at the radio port. It is also different from EIRP, because EIRP includes antenna gain in the strongest direction.
Why Losses Matter
Small decibel losses can remove a large part of useful power. A three dB loss cuts power nearly in half. Long feed lines, worn connectors, splitters, and filters should be counted carefully. The planning margin field lets you test worst case conditions before equipment is installed.
Antenna Gain and Efficiency
Antenna gain helps concentrate radiation in a direction. Efficiency shows how much feed power becomes radiation instead of heat. When the gain value is realized gain, efficiency is already included in that gain rating. In that case, set efficiency carefully for total emitted power, and read EIRP as the realized directional value.
Peak and Average Results
Peak power is useful for component rating and maximum field estimates. Average power is usually better for duty cycled transmitters. Pulsed, packet, radar, and time shared systems can have high peak output but lower average radiation. The duty cycle input converts peak values into average values.
Planning With Distance
Distance is used for power density and field strength estimates. The tool assumes clear space and main beam exposure. Buildings, ground reflections, polarization, and near field effects can change real readings. Use the result as an early design check, then confirm important installations with calibrated instruments and approved procedures.
Good Engineering Practice
Use measured values whenever possible. Replace catalog assumptions with cable sweep data, actual connector counts, and verified antenna figures. Enter each channel separately when transmitters operate at the same time. Review local radio rules before transmitting. The calculator is an engineering aid, not a certification tool. Keep records for audits, maintenance, troubleshooting, and future upgrades over long service life.
FAQs
What is total emitted power?
It is the power that leaves the antenna system after feed losses and antenna efficiency are considered. It is usually lower than radio output power.
Is emitted power the same as EIRP?
No. Emitted power is total radiated power. EIRP includes antenna gain and represents directional equivalent power in the strongest beam direction.
Should I use watts or dBm?
You can use either. If both are entered, the dBm value is used because it often comes directly from RF test equipment.
Why does duty cycle change average power?
Duty cycle shows how often the transmitter is active. A 50 percent duty cycle makes average emitted power half of peak emitted power.
What does planning margin do?
Planning margin acts like extra loss. It helps test aging cables, installation variation, uncertain data, or conservative design conditions.
When should realized gain be selected?
Select realized gain when the antenna gain rating already includes mismatch and efficiency effects. Many measured antenna reports provide realized gain.
Can this replace compliance testing?
No. It is a planning calculator. Certified measurements, approved procedures, and local radio regulations should control final transmitter operation.
Why is distance included?
Distance is used to estimate average power density and electric field strength. These estimates assume simple far field conditions.