Last month I got my SuperMouse back with a new GTX327 transponder, used (but new new for me) GMA340 audio panel/intercom, and a factory refurbished GNC 300XL TSO GPS/COM. This review is for the GTX327 Transponder. Going into my upgrade I had a King KT78A that failed the transponder check miserably. At the time based I would install a yellow tagged replacement analog with a cavity tube for $800 or so or based on 2005 prices I could get a new GTX320 for ~$1400 and a new GTX 327 for $1650 (list 2006 prices the delta is more like $400 and the GTX 327 is selling for more like $2k but a few places seem to still have some units at 2005 prices sub $1700). Both units are all digital without a tube and should serve the 5-10 years needed (until ADS-B forces us to upgrade to next gen Mode S equipment). The GTX 327 is a little more than “just” a transponder, enough that it is worth the extra cost to me. First, it’s hard to convey how much it helps being able to just enter squawk code directly. Takes 4 seconds instead of 30 and no accidently tripping the “magic” codes on entry. The big feature (to me) is the auto-alt and auto-standby modes. Basically the unit comes up in Standby by default and automatically goes to ALT once flying (it can use an external squat switch, RS-232C ground speed input or pressure alt input to decide) and back to Standby on landing. Speaking of timers – this unit has three. A flight timer (automatic by default), a count down and a count up timer. All three timers are independent and can run at the same time. Thanks to a full set of 0-9 keys entry of times is easy. Having to do a timed approach is much easier than it used to be. The flight timer can be user configured to per-flight or cumulative mode (thus being a useful substitute for a Hobbs timer). Lastly the unit will display the pressure altitude being reported. As someone who’s had to deal with Mode C troubleshooting multiple times this is invaluable. Finally – readability. The display is fully readable in all conditions from direct sunlight to pitch blackness. Like all of the Garmin DSTN display devices it has a photo-cell that “auto-dims” the display. Below a certain level (configurable, but the defaults work great) the display will invert from Black on Green to Green on Black so it’s not flooding the cockpit with too much light. Integration point – the GTX 327 accepts both “grey code” and RS-232 inputs so it should work with your existing encoder. It also has a separate RS-232 _output_. So you can use the unit to feed a 2nd input like a GPS without having to invest and integrate a newer (and more expensive) dual RS-232 output encoder. This alone is worth $200-$300 or so if doing an IFR GPS or fuel-air computer install (what a new dual output encoder or a Grey Code to RS-232 converter will set you back). You can also tie the “Ident” and “Standby” switches to an external input.
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