[Elecraft] Muting the K2

[John Magliacane]

 Ray,

For what it's worth, I've been running a homebrew solid-state QSK CW transmitter for the past 4 years. My T/R relay is an AXICOM V23105A5303A201. It is a dual SPDT relay where each SPDT section is tied in parallel for greater power handling capability. The receiver is connected to the antenna through the relay on receive, and is allowed to "float" as an open-circuit on transmit.

The relay is controlled through timing and logic circuitry so that it becomes energized before any RF is produced, and de-energized after the RF envelope has decayed to zero. While I own a K2/100, I have been using this transmitter with either a Drake 2C or R4C receiver until I homebrew my own.

I just ran an experiment where I terminated the RCVE port with a 50 ohm load and measured the RF voltage across the load with a scope. On 40 meters where my transmitter produces 64 watts, I measured about 0.8v p-p across the terminated RCVE port, or about 1.6 mW (2 dBm) of RF. That equates to 46 dB of isolation at 7 MHz. This seems consistent with the isolation specs on the relay that can be found here: https://www.farnell.com/datasheets/1918250.pdf.

The Drake receivers handle this signal level with ease, but I haven't tried the K2.

Incidentally, Jim, W6PQL has additional information on using inexpensive relays in RF circuits at his website: https://www.w6pql.com/using_inexpensive_relays.htm


73 de John, KD2BD