OldBoldPilot
New Member
OK, gang, it’s time for the dreaded noob-with-questions, so thanks in advance for any help you can offer. Before I start cementing configurations and buying components, I want to have a solid understanding of the overall architecture. I’ve learned a lot by reading existing threads, but I haven’t found any discussion addressing this particular wrinkle.
I’m planning a lot of HOTAS controls, some of which mimic the military aircraft I’ve flown. In an airplane with 2 radios, we used a single rocker switch on the throttle grip for PTT—rock one way to transmit on radio A, rock the other way to transmit on radio B. Looking at the schematic in the intercom install manual, it appears I can accomplish this dual function with a DPDT rocker.
MIXING
My intended installation is a SV-COM X25 as primary comm and a Garmin GTN650xi for nav and secondary comm. I haven’t been planning to use an audio panel or mixer because the SV intercom has dedicated inputs for everything: both COMMs, nav audio (pin 17), Skyview audio (pins 6 & 19), and I’m used to monitoring multiple radios so I don’t see a need. (If a radio gets annoying I can usually switch it to guard or a quiet freq, or just turn down the individual volume.) If the nav audio can’t be muted within the GTN650, I could add a simple SPST switch to (de)select it. What benefit(s) would a mixer provide?
INTERLOCK
I haven’t gotten access to the Garmin install manual yet, but my understanding is that the GTN650 doesn’t have an electrical transmit interlock connection, it uses software to mute itself when it magically senses another radio transmitting. All well and good when the SV-COM is transmitting, but what about the SV-COM when the GTN650 is transmitting? I’m planning to put one COM antenna on the turtledeck and the other on the belly, but I don’t know if that will be enough to rule out coupling. Anyone have experience with this?
I’m planning a lot of HOTAS controls, some of which mimic the military aircraft I’ve flown. In an airplane with 2 radios, we used a single rocker switch on the throttle grip for PTT—rock one way to transmit on radio A, rock the other way to transmit on radio B. Looking at the schematic in the intercom install manual, it appears I can accomplish this dual function with a DPDT rocker.
- One set of poles is the selector: pin 12 connects to the switch’s common terminal, and the other terminals connect to the PTT IN pin on each radio.
- The other set of poles is the PTT, connecting pins 2 and 10 indirectly via the mic jack. These terminals would be jumpered so this circuit would close in either rocker position.
MIXING
My intended installation is a SV-COM X25 as primary comm and a Garmin GTN650xi for nav and secondary comm. I haven’t been planning to use an audio panel or mixer because the SV intercom has dedicated inputs for everything: both COMMs, nav audio (pin 17), Skyview audio (pins 6 & 19), and I’m used to monitoring multiple radios so I don’t see a need. (If a radio gets annoying I can usually switch it to guard or a quiet freq, or just turn down the individual volume.) If the nav audio can’t be muted within the GTN650, I could add a simple SPST switch to (de)select it. What benefit(s) would a mixer provide?
INTERLOCK
I haven’t gotten access to the Garmin install manual yet, but my understanding is that the GTN650 doesn’t have an electrical transmit interlock connection, it uses software to mute itself when it magically senses another radio transmitting. All well and good when the SV-COM is transmitting, but what about the SV-COM when the GTN650 is transmitting? I’m planning to put one COM antenna on the turtledeck and the other on the belly, but I don’t know if that will be enough to rule out coupling. Anyone have experience with this?