Menu Sign In Contact FAQ
Banner
Welcome to our forums

Anybody have installed dual transponders on their plane ?

What I was thinking of is that with an active TAS installation you have a tap (a “transponder coupler”) on the transponder antenna cable which feeds back to the TAS box, and if you have two transponders, you would need a tap on each of the two antenna cables, and somehow the outputs of the two taps would need to be merged to the same single TAS box.

But, looking at the TAS6xx IM, there does seem to be a way to combine the output of the two taps if you have two transponders:

So that’s the question answered.

Presumably, still, only one of the two transponders would be powered up.

Administrator
Shoreham EGKA, United Kingdom

Presumably, still, only one of the two transponders would be powered up.

In our case, both power up, but only one is active.

EGKB Biggin Hill

Hmmm; I wonder how that is arranged. Which one decides to be active, and how does it notify the pilot?

Administrator
Shoreham EGKA, United Kingdom

Many transponders have an external standby discrete which when connected to ground forces it into standby mode. So a simple SPDT toggle switch will suffice for XPDR1/2 and the inactive one will annunciator STBY on the display.
When dual remote transponders are connected to a Garmin GTN, the standby function is controlled through the GTN by RS232.

Avionics geek.
Fairoaks. EGTF

Just upgraded our GTX330 to ES / ADS-B out, and put a used GTX327 in the no. 2 slot as a mode C backup, replacing an old King unit which was u/s. We did this to avoid being grounded in awkward places (e.g. Egypt) in case of a txpdr failure. It also provided a use for our GTX327, which had been replaced by a GTX330 in another aircraft. The installer told me he has racks full of used 327’s !

NeilC
EGPT, LMML

Would you not still be grounded in many places with a 327? Or, at least, not given access to controlled airspace?

EGKB Biggin Hill

True, but Cairo FIR requirement is carriage of mode A/C. Plus, in other parts of Africa where they have SSR, why take the risk

NeilC
EGPT, LMML

Peter wrote:

Hmmm; I wonder how that is arranged. Which one decides to be active, and how does it notify the pilot?

In larger aircraft there is a switch to select TXP1 or TXP2

Darley Moor, Gamston (UK)

See picture above; toggle switch on the right marked xponder

NeilC
EGPT, LMML

OK, so both TXPs are always on, but the toggle switch enables only one of them to be active. And you have two TXP couplers, etc.

Administrator
Shoreham EGKA, United Kingdom
30 Posts
Sign in to add your message

Back to Top