GA cockpit and radio recorder

I have a couple of instrument students that are having
some trouble with the radio communicaitons during
their instrument training. It occurred to me that
recording ATC & their transmissions for post-flight
debriefing and review would be a value learning tool.

An easy way to do this is to plug a recorder into
an unsed headset jack. In my case, this would be one
of the back seat intercom jacks. Then operate the intercom
in the "ALL" mode so the passenger posistionshear all
radio and intercom traffic. A voice activated recorder
would be ideal, if it turns on fast enough to catch the first
word of each audio burst.

I'm thinking a 1/4" plug, cord with an attenuator /
impedance network and a connector to match to the
line in or mic input of a recorder is all that is needed.

Has anyone tried this? If so, how did it work out?

Comments?

Ronnie