Bird Plug-In Elements have a flat frequency response over their specified operating range. A sample set of curves is shown below. Notice that for the low power element, the roll-off outside its frequency band is more pronounced than for the high power elements.

**Representative Frequency Response**

These curves are typical for all element types (H, A, B, C, D, ...) at their respective frequencies. Since a C type element has a frequency range of 100 - 250 MHz, response curves for other element types can be approximated by replacing the 100 and 250 MHz points on the chart with the extremes of the element’s frequency range, and recalculating the other frequency points accordingly.

**Example** - For a B element (range 50 - 125 MHz) simply divide all frequencies by two. For an E element (range 400 - 1000 MHz) multiply all frequencies by four.

Harmonics or sub-harmonics that lie outside of the frequency range of the element may exist in the circuit under test. A rough approximation of the element’s response to harmonics can be made with these curves.

Using an element for measurements outside of its frequency range is not recommended. The response curves presented are only typical, and not guaranteed.