Originally Posted by Snowflake
With some diodes to ensure the two GPS' don't try to send to each other, you could possibly wire it up without the switch.
Sorry, but that wouldn't work. Each Aera is constantly transmitting NMEA and VHF data including frequencies and frequency identifiers for hundreds of nearby airports and the airports in the flight plan.
This allows you to press and rotate the knobs on the GTR 200 and always have an airport frequency list for the nearest airports without having to look it up.
The infrequent command to send a single selected standby frequency to the GTR 200 is a negligible amount of the total communication which is occurring.
Tying two Aera transmitters together with diodes would create mayhem with both of them constantly stepping on each other. It is likely that nothing would work if you did this.