Cross Country Wireless have announced two new versions of a receiver front end protection unit to protect sensitive VLF/HF or VHF receivers from high levels of RF from other stations on the same site or large antenna arrays.

It is particularly suitable for multi-station contest groups where receiver damage may occur from high power stations operating in the same frequency band. It is especially suitable for SDRplay RSP owners wanting to run receivers 24/7 unattended as the protection unit will divert electrostatic charges and near lightning surges to ground.

How does it work?

The protection unit has three levels of protection against over-power damage, electrostatic charge on the antenna and nearby lightning surges.

A gas discharge tube rated to take nearby lightning surges of 10 kA is connected across the input socket. An isolation transformer connects between the two sockets. This isolates the output socket from any electrostatic charges on the input socket. If the unit is used as the sole protection device for a receiver we recommend that the M6 terminal and wing nut is connected to a good earth or ground connection so that excess energy can safely flow to ground.

The isolation transformer is designed to saturate with very high RF power levels so that a cascaded diode limiter can limit the output power to a safe level.

The multiple levels of protection are such that if the output of a 150W transmitter is inadvertently applied to the protection unit input it will still protect the receiver.

The latest version (June 2021) now limits the maximum output signal to a level lower than the 10 dBm limit allowed by SDRplay receivers.

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