TDR-90 replacement?
 

looking for sensible replacement option for existing TDR-90 transponder to enable us to satisfy Elementary Helicopter Mode S regulations.
Current use is for destinations inside designated airspace but generally operating outside CAS with occasional overseas trips to Europe.
Current fit is 2xTDR-90 controlled by CTL-92.
Would like to keep with TDR range but price looks silly for replacement - especially when so many other systems around but - as ever - panel space is priority - hence wish to keep current control head.
Would appreciate suggestions.
AS365N1

TDR90 replacement
 

No cheap solution if you want to keep a CTL-style controller. You'd have TDR94 with CTL92E, but also a big bill!

Try a Becker BXP6401 transponder fitted in place of the CTL92 - that's all you need. Wire to existing antenna and altitude encoder. The transponder has a dongle (programming module) that plugs into an additional connector to store the Mode S address, so you don't have to re-programme if swapping a faulty unit. You should allow for squat switch input - JAA TGL13 for ELS is shortly going to be replaced with an new EASA AMC which will make this a mandatory requirement - either a squat switch or an airspeed switch for automatic GND mode operation.

We've done this Becker mod a A109's where CTL was mounted in the glareshield panel. It works very well.

Regards

Mode S option
 

Wigglyamp
Thanks for that.
After some more background reading - your solution sounds ideal as we should have enough room in console to slot one in.
Avionic guys are looking at it......
Would like to keep dual transponder capability although I appreciate units have better reliability these days.
currently measuring console for space!

Dual transponder
 

I gave some thought to a dual transponder system using the Becker. How about this:

"BXP 6402-Remote (Class II): Mode-S-Transponder 2 1/4 '' mount:
Remotely controlled by Control-Unit CU6401-1-(01). Extremely small and compact; directly exchangeable with ATC4401 (same dimensions and connectors), Software to DO178 B Level C Class II Level 2 es, for VFR/IFR operation up to 15.000 feet. Standard input for Blind-Encoder, parallel and serial RS 232/422. Address Module AM6400-1-(01) required."

The BXP6402 can be found in Becker's Primeline range, rather than the Compact range which has the BXP6401.
Use two remote units and a single controller with appropriate external switching for the RS422 control lines - in effect the same as using dual TDR90/94's with a single CTL92/E.

Regards

Wigglyamp