PIREP Request: Using GRT Mini-X to Control Trig TT22

Reaching out to the brain trust here as I contemplate some changes to my instrument panel setup.

Am currently using the Trig TC20 control head to control the remote-mounted TT22 transponder. This is working fine, other than what i perceive to be a challenge of legibility of the TC20's display. A future upgrade may well expand into the panel space currently occupied by the TC20.

At the moment the Mini-X is my stand-by EFIS, always left in PFD mode. It backs up a 6.5" HX which I use in PFD and split PFD/HSI/MAP modes. I don't have the GRT RS232/RS485 adapter to allow the HX to control the TT22 and I don't think I want to go that route as the HX is already very busy when I'm flying.

Bob Turner kindly informed me the most recent HX software includes a right-knob-hold feature to quickly access transponder controls so that might make using the HX to control the transponder.

I'll shortly be installing a third GRT EFIS, a Sport EX, over on the right side of the panel. It, too has the requisite RS485 interface to directly control the TT22 transponder, thus opening up the possibility to use the Sport EX as my transponder controller, but it will be located in front of the copilot.

I would like to hear from folks who use the GRT Mini-X to control the Trig TT22. Particularly I'd like to hear your impressions of the GRT transponder user interface.

Thanks for sharing your experiences!

Just to be clear, with the Hx, the menu shortcut is to push and hold the right-most button, not the knob.

Me again.
1. As I mentioned, pushing and holding the right button is a shortcut on the HX to go directly to the squawk code entering menu. I do not know if the mini has a similar short cut.
2. Once on that page, I believe the operation is identical to your TT22 control head, e.g., turn the knob, you change the first digit; push the knob, cursor moves right; rotate knob, second digit changes; push the knob, etc. Push save when done. Both HX and mini work the same. HXr is different, with the larger screen and more buttons. Details in ?TT22 with HXr Supplement? (or something like that) on the GRT web site. The Hx and Mini are in the appendix at the back of that manual. GRT really should re-name it.
3. If you go directly from mini to TT22, then that?s your control. If you have a free RS232 port on your mini (and HX), then you can buy GRT?s dual 232 to 485(?I think) adaptor, and control the TT22 from either efis.

Finally, to answer your question, this works fine for me, controlling a TT22 from two HX units. I actually like having a knob to hold on to in turbulence (with a ?push the number button? like a 327, I sometimes hit the wrong one). I like the menu shortcut button; and I like having my IDENT function remoted to a stick button (local tower asks for ident 50% of the time, even for vfr traffic).

Thanks for the excellent follow-up, Bob.

At the moment I don't have a spare RS232 port on the Mini-X although I have given some thought to purchasing port expansion. With its built-in RS485 I would be tempted to use that interface on the Mini-X.

What I was really hoping to hear was how easy or difficult the user interface is to use. How easy is it to determine transponder mode of operation and whether the transponder is being interrogated.

Your comments on the buttonology for setting squawk code are appreciated.

Canadian_JOY said:

What I was really hoping to hear was how easy or difficult the user interface is to use. How easy is it to determine transponder mode of operation and whether the transponder is being interrogated.

Click to expand...

As I said, I think the menu shortcut button, and a remote stick ident button, are worth consideration. With these, setting squawk code is no more difficult than on any other transponder, and an ident is easier. A small data box appears in the lower left side of the PFD. It shows a reply ?light?, like a standard xponder; it blinks ?ident? for some seconds following an ident; it shows the adsb status (ground or airborne); it shows squawk code.

Hi Mark,
I've been using the Mini to control a TT22 for a few years now. It seems to work fine. Bear in mind I'm VFR and rarely have to change squawk codes, so in my case it is literally a "power up and forget about it" since the TT22 takes care of switching modes for you.

Setting squawk codes is not difficult, but I can't compare against using a dedicated control head. My guess is a slight bit more work since you have to access the menu on the Mini versus having it immediately available on the control head, but I can't imagine it adding so much additional overhead as to cause you to regret the decision.

Given your current setup, you could leave the control head installed and just move the wiring to the Mini so you can do some testing before making the decision.

-Dj

Thanks for your comments, Dj. Don't know why my little pea of a brain had forgotten that you control your TT22 via the Mini. Big DOH on my part!

You've hit the nail on the head in terms of my thinking - just fab a harness to plug into the existing TC20 control head harness in order to pick up the TMAP-A and TMAP-B RS485 signals, thus minimizing disruption in the cockpit.

I do like Bob's suggestion to use a discrete IDENT switch as one frequently needs to IDENT in the airspace here. OK, let me rephrase that... There are days when one needs to ident frequently, and there are days when one can fly several hundred miles with only an initial IDENT. Some days it just feels like you're going to wear that button out!

Check out page 14: http://grtavionics.com/media/TrigTransponderA2.pdf

Looks like the sequence is:
Press any soft key.
Press the XPDR soft key.

Then to IDENT
Press IDENT soft key.

or for squawks:

Press CODE soft key.
Use the knob to enter the code (turn to choose digit, press to select, then it goes to the next field. Repeat until done).

-Dj