[Elecraft] Using dual watch with RX SHFT=8kHz

[Matt VK2RQ]

A long long time ago on another mail list there was a discussion about why it was not possible to use dual watch together with the RX SHFT set to an 8kHz shift. If this would be implemented in a straightforward way, such a shift would result in an asymmetry in range of frequencies your second VFO could cover above and below the first VFO (eg. ADC covers LO+/-15kHz, VFO_A is LO+8kHz, so VFO_B can range from VFO_A-23kHz to VFO_A+7kHz.

However, if you tried to set VFO_B to greater than VFO_A+7kHz, one possibility would be for the KX3 to change the shift from LO+8KHz to LO-8kHz. This would then permit coverage from VFO_A-7khz to VFO_A+23kHz. Everything would seem to be on the opposite sideband, so the demodulation code would need to compensate.

By combining these two modes of operation, the dual watch could be extended so VFO_B has a ranges of VFO_A +/-23kHz. If you used a greater IF shift than 8kHz, say 11kHz for example, then this could extend the range even further, say +/-26kHz.

Regardless whether such such extended coverage is implemented for dual watch, the PX3 would need to behave sensibly when using of dual watch with IF shift.

73,
Matt VK2RQ