At 21:01 12 August 2013, wrote:
Hi. I have a Becker AR4201 in my powered aircraft (sorry, I know this
group is for glider pilots but I can see that there are some Becker radio
experts on here) When the intercom is switched on there is a 'hiss' in the
headphones,engine running or not, but louder with the engine running. I am
using Bose are and Pelltor headsets. When I shield the mic (by putting it
in my mouth)the hiss' disapears. Is this something to do with the mic
setting - SF16 ? Or something else?

If you have not installed a switch to select when the intercom is activated
then you have probably wired it so the intercom is hot all the time. In
which case you will have hot mics all the time. So rewire the radio so you
can select intercom or no intercom.

There can also be an issue with mismatched headsets. Like using a David
Clark with an old Sigtronics. Of memory serves me correctly
it doesn’t cause a hiss, but I think I remember it causing only one
headset to either be able to transmit or an inability to hear each other on
the intercom. But you did not ay anything about either of those problems.

Marty