[Icom] problem with 2710

[William Lambing]

This type of problem is what led avionics installers (and most OEM Equipment
Manufacturers) to recommend the installation of what is called an Avionics
Master.  Power is removed from all radios when an engine is started, due to
spikes.  Another problem is voltage sag.

What most people do not realize is that most equipment made today does not
use a "hard" ON/OFF switch.  They are now days a "soft" switch, which means
that power is always applied to the radio and all you do is provide a logic
ground (or +12V) to the radio to turn it on.  These spikes can and do, cause
problems intermittently.  It is these intermittents that cause avionics
people to have grey hair.

What I do with my 706IIg in the car, is use an external relay and switch.
Battery power is provided to the relay and switch.  The switch goes to
ground, closing the relay contact applying +12V to the radio.  In normal
"unuse" state, the relay is off and no power to the radio.  Thus, when
starting the car, no spikes are evident.

Personally, I would recommend anyone who is installing a mobile radio, to
use a relay for power switching.  It is an added benefit and cheap insurance
policy.

73

Bill, W0LPQ
Collins Avionics Field Service, Retired