[Elecraft] Protecting the RX ant input K3/K4

[Al Lorona]

Viggo, I was worried about this same thing. I built a PIN diode switch that disconnected the RX antenna during transmit and that worked well, but it is quite a complex system because it requires a special power supply to switch the bias voltage from receive to transmit.

When I set up a new station I did something much simpler: I now have a limiter connected in line with the receive antenna input of the K3. I used this part from Minicircuits: RLM-33-2W+. https://www.minicircuits.com/WebStore/dashboard.html?model=RLM-33-2W%2B 

This part is quite costly, but it is the simplest way to limit power. It is able to absorb up to 2 W and limit the power level to +13 dBm (20 mW) at the receive input, which is safe for the K3/K4. I built it into a small box with coaxial input and output connectors.

I hope you can try one of these interesting devices.

Regards,

Al  W6LX