CartRF Detector - SMA - RF-DETECTOR
Released: August 2013 - rev2
Want to know how efficient your antennas is? This RF detector can be used as part of a system to measure the effiency of an antenna by measuring the forward and reflected power. It is designed to work with a -10 dB coupler and an accurate 50 Ohm terminator.
Can be used on any transmitter up to 5.8GHz. Works best with 100mW (20dBm) to 500mW (27dBm) transmitters. Input power over 500mW should be lowered using 3db/6dB/10dB attentuator(s) between the transmitter and the coupler to get it within the mentioned range, otherwise the rectifier diode will burn out.
The diode is a Avago Technologies HSMS-2860-TR1G single RF detector. SMA male plug.
Based on Mictronics and IBCrazy's design.
Specifications
- Product ID: RFD-01
- Revision: Rev2 Aug 2013
- Frequency range: 100MHz to 6GHz
- Minimum input power: 20dBm (100mW)
- Connector: SMA male jack - center pin
How to calculate VSWR
The principle is to connect the RF Detector to the coupler's Vreflected port and measure the voltage using a multimeter, then measure the Vforward port, and calculating the SWR to get a ballpark figure of how efficient your antenna is performing (input power).
Example: to calculate the VSWR, let's assume the Vref is 0.25V and Vfwd is 1.35V - the complete formula would then be VSWR = (1+(0.25V/1.35V))/(1-(0.25V/1.35V)) = 1.45, which is 1.45:1 or about a 97% efficient antenna - very good in other words.
Percentage losses:
| SWR Reading | Power loss | Output to antenna |
| 1.0:1 | 0.0% | 100.0% |
| 1.1:1 | 0.3% | 99.7% |
| 1.2:1 | 0.8% | 99.2% |
| 1.3:1 | 1.7% | 98.3% |
| 1.4:1 | 2.7% | 97.3% |
| 1.5:1 | 3.0% | 97.0% |
| 1.6:1 | 5.0% | 95.0% |
| 1.7:1 | 6.0% | 94.0% |
| 1.8:1 | 8.0% | 92.0% |
| 2.0:1 | 11.0% | 89.0% |
| 2.2:1 | 14.0% | 86.0% |
| 2.4:1 | 17.0% | 83.0% |
| 2.6:1 | 20.0% | 80.0% |
| 3.0:1 | 25.0% | 75.0% |
| 4.0:1 | 38.0% | 62.0% |
| 5.0:1 | 48.0% | 52.0% |
| 6.0:1 | 55.0% | 45.0% |
| 10.0:1 | 70.0% | 30.0% |