Hardware Issues that have been corrected by Elecraft

From Zerobeat

RX ANT input signal handling during TX

- N6KR reported on Feb 3:

"The KXV3's ANT IN jack includes a carrier-operated relay circuit (COR). If the COR kicks in too soon, they relay will switch off/on during keying. So its threshold is set high. It will still serve its primary function, which is to protect the transceiver when unsafe signal levels are present, such as when the RX antenna is in the near field of a KW transmit signal, or when a transmitter is accidentally connected to this port.

This leaves a gray zone where the COR doesn't kick in, but the transmit signal may still be very high. High-power contest stations sometimes use additional external T/R switching if they can't avoid the use of closely-coupled receive and transmit antennas.

We recently to a close look at this gray zone, and found that we could make an "RX ANT jack on steroids" by adding two more diode isolation sections. The resulting parts count is considerably higher, but we feel that the added protection during transmit would be worthwhile. So this change will be included in production units (once we use up our present supply of assembled KXV3 modules).

Meanwhile, if your antenna configuration and power level warrant this higher degree of isolation, and you already have a KXV3, you can modify it. We're designing a small add-on board to make this easier. It will be supplied free of charge, on request.

This unit has not yet been assigned an Elecraft part number, and isn't available yet, so PLEASE don't request it until we announce the details."

- N1EU reported that an ICE 196 RF Limiter in the rx ant feedline alleviated ARC FAULT errors in an Acom 2000A caused by the above problem.

- W4ZV reported: "There's definitely a problem with RX ANT isolation on the KXV3. I immediately experienced it when I first used my K3 on 160 in early December. I temporarily solved it with an RF choke on the Beverage input but the real cure is a KXV3 mod from Elecraft (now installed). Contact Elecraft for the mod. I had used exactly the same RX ANT setup with a TS-930S, FT-1000MP and Orion with no problems so this was definitely a problem unique to the K3 (now solved)."