Sandia Stx 165 Panel Mount Mode C Transponder For Certified Aircraft

Part# 11-09251
MFR Model# 705832-00


The STX 165 Sports a professional 1/2 3ATI Bezel that compliments any aircraft panel. Its bright OLED display is readable in virtually all lighting conditions and automatically dims for night time operations. Check out just a few of the STX 165 features.
  • Built-in Encoder
    Simplifies installations and lowers cost.
  • Three Timer Functions
    Elapsed Flight Time, Up Timer, Down Timer
  • Pressure Altitude Display
    See what altitude your transponder is reporting to Center
  • Optional OAT Probe Input
    Displays Outside Air Temp.,Density Altitude, Icing Alert
  • Small and Light Weight
    7.4" behind the panel depth, 1.3 lbs.


  • Electrical Input Voltage: 11-33 Vdc
  • Current Requirements: 500mA@28Vdc
  • Power Output: 200 Watts Nominal
  • Transmitter Freq: 1090 MHz
  • Receiver Freq: 1030 MHz
  • Receiver Sensitivity: -74dBm Nominal at 90% reply rate
  • Dimensions: 1.78"H x 3.5"W x 7.34"L
  • Weight: 1.30Lbs
  • Alt. Encoder: Built-in 35K' Encoder; External RS-232
  • OAT Probe: Sandia STP 78 (Optional)
  • Temperature: -20 degrees to +55 degrees C
  • Altitude: -1000 to 35,000 Ft.
  • Certification: DO160F; DO178B Level C; TSO C74d; TSO C88a
  • Accessories
  • Frequently Purchased With
  • Customers Also Viewed


Reasonably easy installation with good installation and user manuals. Good tech support for questions or concerns. It works well thus far.

Allan M
June 4, 2020

Installed in my 172, and it has worked flawlessly so far. Installation is very simple, integral encoder negates need for additional unit and associated wiring.

Red S
September 18, 2019

Holy! Im impressed... perfect for a homebuilt (Flybaby), using a tinfoil pizza plate for a ground plane in the belly, 12AH gel battery which should last me all day. Small size and light weight are ideal for an airplane where there is really no margin for extras, and the built in encoder makes installation so easy... FSS reporting same as I was seeing on the altimeter,

Ian C
January 30, 2017

Wow! The perfect solution for the experimental. Inexpensive, you can get it at air shows for about $200 less, and small. Easy install. Cheap antennae and if you have the seller make cord it is the easiest install youll ever do. Easy to use and the company support is excellent.

February 5, 2016

Easiest mode C transponder to install because the integral blind encoder excludes the need for wiring to a blind encoder. Very compact, uses little panel space. Only downside is it is easy to get rusty on inputting a squawk code. If you fly 1200 most the time, make sure your remember how before popping in to that b or c airspace.

Stan S
October 17, 2022


Please note, Aircraft Spruce Canada's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce Canada assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Does the Sandia STX 165 transponder need an external antenna?

Yes, an external transponder antenna is need. One is not included in the box so you can search for “transponder antennas” on our website to select one for your aircraft.

Q: I have just purchased the Sandia STX 165 transponder. Is the adapter plate needed to mount the transponder or is there a mounting tray? I want to place the transponder under my instrument panel rather than in the panel.

The STX 165 does not come with mounting tray as it is small enough not to require a mounting tray for support. The adapter plate 11-10805 is to adapt the transponder into a 3-1/8" hole. It is intended to be mounted in the panel with or without the adapter otherwise you will have to make your own bracket for it.

Q: Does the STX 165 work on 12 volt systems and what is the amp draw at 12 volts?

Per the manual, the STX 165 and STX 165R operate on 11-32Vdc. Power should be protected by a 1 amp fuse or circuit breaker.

Q: Does the STX 165 without harness at least come with the required connectors and pins for installation?

Yes, the STX 165 does come with connector and pins for you or the avionics shop to wire.

Q: For the Sandia STX165 Panel Mount Transponder, can the Outside Air Temperature sensor be added-on at a later time after delivery of the transponder?

Per the Manufacturer: Yes, you can. Directions for this are in the installation manual.

Q: Does the SANDIA 165 have an Extended Squitter? Does it need an encoder? Which antennas can I use for it?

The Sandia 165 is a mode C transponder and does not have an Extended Squitter. It has a built in encoder. For an appropriate antenna you can search “transponder antennas” on our website to select one for your aircraft.

Q: Can I use the STX 165 in a certified aircraft?

Yes, this unit is FAA TSO Approved for use in certified aircraft.

Q: I have an existing OAT probe for my EIS, can I split off of those leads to this STX165 Transponder? In other words, if they are connected to each other will that cause a problem?

Per Sandia - The STX165 Transponder and the SAC 7-35 Airdata computer can only be interfaced with the Sandia STP 78 OAT probe, We have a different circuit value for Sandia units to measure.

Q: With this Sandia STX 165 transponder, is there any addition equipment required to meet the FAA 2020 ADSB mandate?

No, this transponder cannot be used for the FAA 2020 ADSB mandate.

Q: What does SANDIA STX 165 ADAPTER PLATE OPTION 3-1/8 INCH HOLE 11-10805 do exactly?

The adapter plate option allows you to install the Sandia STX165 in a standard instrument 3-1/8 hole in the panel.

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