Loads and Terminations are specified in several manners, such as:
- Power Dissipation - usually in Watts
- Impedance - usually either 50 or 75 Ohms
- Accuracy or Tolerance - for example 2% or 5% etc +/- of stated value
- Flatness - how much the impedance varies in the frequency range
- VSWR - varies by frequency
For example concerning the accuracy, lets assume you have a 50 Ohm load with a +/- 5% accuracy or tolerance for the Ohm value. This means your load will be expected to function in the Ohm range of 47.5 Ohms to 52.50 Ohms. Obviously the lower percentage yields results closer to the stated value. You will find Google will be able to produce many specifications based on brand and model number.