Three Receiver Operating Technique
An effective technique for lowband contesting is to utilize three independent receivers when operating SO2R, otherwise referred to as SO2R-3RX. The implementation I have successfully used is specific to the Elecraft K3 and Microham MK2R/MK2R+, other equipment has not been tested but may work equally as well. When the K3 is in diversity mode, in this case only the “run” radio, the main and sub receivers in the radio are phase locked, tracking not only frequency, including RIT, but also filter bandwidth/shift. This permits the use of receive antennas aimed in different directions while running, increasing the effective azimuthal coverage.
Using the MK2R/MK2R+, “RADIO1-A” and “RADIO2-A” audio streams are routed to the “LEFT EAR” channel, while “RADIO1-B” and “RADIO2-B” audio to the “RIGHT EAR” channel. With the “run” radio (ie. RADIO1) in diversity mode, the main and sub receiver’s audio within that radio are streamed only to the left and right earpieces respectively, typically with no cross-over between earpieces (in rare cases certain phase relationships can cause the audio to “center” momentarily) . The second (ie. S&P) radio’s main receiver audio, another K3 with sub-RX OFF, is routed to both earpieces, resulting in audio that is spatially centered in the headphones with the K3’s AFX setting turned ON and in BIN (binaural) mode. However, the use of the K3’s AFX also depends on the headphones used. I have a favorite pair of old Lafayette headphones that require AFX be turned off using the above audio routing. Some Heil headsets have a phase selection switch, which can be toggled to produce the desired effect regardless of the AFX setting, which may lend themselves to use with other radios in the S&P position.