Selecting Protection - Coaxial



Coaxial line surge protection must:

1.    Provide adequate protection for all equipment. 
2.    Achieve a long working life. 
3.    Allow the signal to pass under normal operation and not 
have an adverse affect on insertion loss and return loss. 
4.    Optimise the cost and size of the surge protection devices (SPDs).

Options for Surge Protection Devices

Novaris manufacturers two types of RF coaxial SPDs.

  • Those containing a gas discharge tube (GDT) are suitable for a wide frequency range but must be chosen carefully taking into account the power on the line if used for a transmitting application.
  • Quarter wave stub protectors offer exceptionally low let through voltages but are frequency sensitive. Their power handling capability is only limited by the rating of the coaxial connectors employed.

Selection of Surge Protection Devices

1. Identify the connector type - Novaris manufactures a range of coaxial SPDs to suit most common connectors and gender variations.

2. Select the clamping voltage - The clamping voltage of the SPD must be greater than the peak voltage on the line. This is particularly important when used for transmitting applications. 
The following is a guide.





3. Identify the maximum operating frequency - For standard models using N-type connectors the maximum frequency is 2GHz. 3G models feature replaceable GDTs and will operate to 3GHz. For other variations the upper frequency is dependent upon the connector type.

4. Tuned stub protectors - For narrow bandwidth applications where no DC voltage is injected, tuned stub protectors provide exceptionally low let through voltages and very low inter-modulation products. The centre operating frequency must be specified when ordering.