would like to have the hand held radio on listing out on another frequency (121.5!)
I don't get it.
The fact that you only seem to have one panel mounted radio and no audio select box seems to suggest you're flying a fairly low-capability aircraft. Not one that's designed to fly the "high seas" such as the Atlantic or worse. At the very least, such a setup would not fulfill IFR requirements.
All of mainland Europe, and a fair amount of places beyond that, have 100% ATC coverage on 121.5, and those ATC units will be able to handle an aircraft in distress much better than you can from your aircraft. (Assuming the aircraft in distress isn't being handled on the FIS/ATC/whatever frequency it's already on in the first place.)
Furthermore, if ATC does need your help in dealing with an emergency of somebody else, and they know you're there (either from a position report or from a mode-C return) they will contact you anyway. Usually on the top-three of most likely frequencies you could be on. Which makes an excellent case for monitoring the FIS frequency, or the ATC frequency of nearby airspace (and squawking the appropriate "monitoring" squawk if appropriate).
So why would you want the distraction of listening in continuously on 121.5? Particularly if it means messing about with lots of cabling, converters, battery chargers/power cables and whatnot.
Don't get me wrong. I think there are several good reasons to have the capability to listen to multiple frequencies at once:
- ATIS
- When in a club flyout/formation flight/photo shoot/whatever, to chat with the other aircraft in your party
- When "over the high seas" to monitor 121.5 because there might not be a ground station able to monitor that frequency with adequate coverage.
But in an aircraft that's only equipped with one COM box I really wouldn't bother listening to 121.5.