Operation and Installation Manual
KRT2 VHF-Communication Transceiver
Doc.-No: KRT2.A-MAN.en
Rev. 0101
Page
48
6.11 Microphone general
The correct setting of the MIC and VOX values is of great importance for the Intercom system (see
“4.4.3 VOX – Intercom Voice Trigger Level Setting” and “4.4.11 MIC – Setup”).
The VOX intercom voice trigger level must be set to such a value that the intercom system is activat-
ed when speaking at a normal voice level into the microphone. It should be set so that it is not trig-
gered by normal cockpit noise.
In addition, VOX should be set to level 01 and the intercom switch permanently enabled.
The manual intercom operation is possible with one or two separate, optional parallel connected in-
tercom switches. These switches are not the
PTT switches. The intercom switches connect pin12 (intercom) with GND (pin1).
The intercom-deactivation will be indicated with “e” if pin12 is not on GND.
The intercom requires the connection pin 12 to GND either permanently or through the intercom
switches.
Cockpit noise suppression is only possible with differential microphones used in modern headsets.
Normal electrical microphones are not suitable.
6.12 Post-Installation Check
A certified maintenance shop must verify the proper operation of the VHF
transceiver or as required by national regulations.
A complete check of all airplane systems is required to certify that the new wiring is not causing any
malfunction.
The standing wave ratio (SWR) must be less than 3:1.
A test flight is recommended to verify proper transceiver operation. The following items should be
checked:
•
Check transceiver operation with a radio station at least 50 km away when at 2000ft or above.
•
Check if there is unusual electrical interference or noise.
•
If possible check the transceiver operation on low and high frequencies of the VHF frequency
band.
