ERP Calculation

[Se7en]

50w with 6.5dBi give you: ERP 136.18402 watts, Does this sound about right?
Effective Isotropic Radiated Power (EIRP) would be: 223.34179 watts.

 

[W5LZ]

To stay 'real', I wouldn't use 'dBi' gain figures for ERP calculations. As you can see, it can make quite a bit of difference. The problem with those isotropic figures is that they only hold true for 'ideal' or 'free space' calculations, not for 'real world' stuff. You would be closer to 'true' if you deducted 2.1 from that 'dBi' gain figure. Still not 'real world', but closer.
- 'Doc

 

[bob85]

yes thats right, there was a thread on here where freecell gave us a challenge, it has gone along with other good threads in the changover,

Pure ERP And EIRP Calculator

50w with 6.5dBi give you: ERP 136.18402 watts, Does this sound about right?
Effective Isotropic Radiated Power (EIRP) would be: 223.34179 watts.

 

[KC9Q]

Erp or EiRP: It's all math and something you can't really measure in the field. However, to get true ERP or EiRP you need to factor in all the devices between the transmitter and the antenna too. This can be as simple as the main transmission line plus connectors, to additional items like Jumper Cables, Lightning Arrestor, Duplexer, Isolator, and other miscellaneous protective devices. You can further skew the facts by using dBw rather than dBm for the transmitter.

By the way, dBi is used by the microwave community to calculate EiRP for Point-To-Point systems, or for persons that like to make their Two-Way systems look way too good.

 

[Captain Kilowatt]

I never use dBi and prefer to use dBd when computing ERP as the dipole is a real antenna that many use and can readily relate too rather than an isotropic antenna. Like KC9Q said, you need to take all gains and losses into account when calculating ERP. When in broadcasting we always used dBw, or dB over one watt, and even included connector losses and in some cases path losses when calculating expected signal strength at the receiver.

 

[Se7en]

I never use dBi and prefer to use dBd when computing ERP as the dipole is a real antenna that many use and can readily relate too rather than an isotropic antenna. Like KC9Q said, you need to take all gains and losses into account when calculating ERP. When in broadcasting we always used dBw, or dB over one watt, and even included connector losses and in some cases path losses when calculating expected signal strength at the receiver.

Of course. That calculation is a ruff compute, because I cannot compare it too a dipole in a perfect environment via chamber.