Safe measurement of the output of transmitters
- Calculating with dB is not too difficult.
- Every factor of 10 increase of the power of a signal raises the dB level with +10 dB.
- Every factor of 10 decrease of the power of a signal reduces the dB level with -10 dB.
- Typical output power of a transmitter.
- 100W equals +50 dBm
- 10W equals +40 dBm
- 1W equals +30 dBm
For best measurement of harmonics in the output of transmitters the input level of the tinySA should aim between -20dBm and -10dBm.
Required attenuation between transmitter and tinySA.
- For 100W : between 60 and 70 dB For 10W : between 50 and 60 dB For 1W : between 40 and 50 dB
The best approach is to use ALWAYS a 30 dB attenuator directly connected to the tinySA and to use power attenuators to reduce the output of the transmitter to the target input level of this 30 dB attenuator, that is +10 dBm.
So you will need these power attenuators.
- For 100W output: 30-40 dB
- For 10W output: 20-30 dB
- For 1W output: 10-20 dB
Another option is to use a dummy load and an inline 50 dB attenuating sampler. A nice example of how to build one yourself can be found here (PDF).