Altitude Encoder with Mode S Transponder

[2001ft]

Looking at upgrading some avionics and trying to price it up...

Throwing out a Bendix King Transponder and replacing with a shiny Garmin GTX328 S Mode.

Do you need an altitude encoder with the 328? I have an Ameri King which states Mode C on it, can I use it for the 328 as well or is there a different encoder required (at additional cost?)

thanks all

[rick1128]

Not sure about the Garmin 328, but for the other Mode S transponders out there, you must have an encoder. All the Mode S does different from the Mode C is put an aircraft ID on ATC radar and talk with other Mode S transponders. They still need encoders. Since there are a great many different encoders out there, I believe that Garmin will at least interface with the major types. And AmeriKing is a major type. However, you should check with your avionics shop or Garmin to confirm this.

[VeeAny]

Installation manual for the 328 says its needs an external encoded altitude source that supplies either gray code or RS232.

The AK-350 (the most common Ameri King one) encoder seems to be compatible with most transponders, but a phone call to one of the big avionics sellers will probably confirm that.

If it is a 350 the installation manual is here it might help http://www.ameri-king.com/pdf/9.1.23.pdf

[perfrej]

Or rather, Sandia SAE5-35, is cheap and works well with Garmin's transponders... Buy either from Garmin or from Sandia.

/p