Two-Radio Switching Capability

All the major logging programs like TRLog, CT etc. offers the users the ability to switch between 2 radios during the process of logging during a contest, DXpedition or when casual contacts are being made.

In most if not all cases the user is required to wire up some sort of switching array using a few relays to switch the audio and key lines to the radios. Units are available commercially that will do the switching but mostly it is just another box on or below the table that clutters up the operating environment with extra cables thus increasing the chances of getting RFI or earth loops induced into the system.

The Combo Keyer offers the ability to connect one cable from the LPT port of the PC to the keyer. The pin that controls the Rig1/Rig2 switch control is fed into the Combo keyer and the combo keyer will switch the AF, CW-key & Amp-key lines over to whatever Radio is selected by the logging program. The user can also override the PC selection by means of a 3-way toggle switch on the front panel. If the toggle switch is in the centre position it will follow the control from the PC. Two DB9 connectors at the back of the box provides the interface to the radio and amplifier from the keyer.

Pin 1 and 6 of the DB9 is the audio outputs from a 600 ohm isolating transformer with Pin 1 having a 10 mF non-polarised decoupling capacitor in line. An article on two-radio contesting can be found at:

Last updated 15 January 2001 by [email protected]

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