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Experiences with Garmin GTR 225

The display on my Narco com radio is getting flaky (again) and with the 8.33 mandate coming up soon, I’m not even going to attempt to repair it.

It looks like the Garmin GTR 225 would be a really nice option – it has some nice features for those of us with only one radio – but has anyone used one?

Specifically, what’s the viewing angle like on the display? I have no panel space for a radio so the radio is in an overhead tray, so I’ll be looking at the display from below. Many modern LCDs have excellent viewing angles and this wouldn’t be a problem, but before I drop 2 grand on this thing I want to make sure I’m going to be able to read the display :-)

Andreas IOM

alioth wrote:

GTR 225 would be a really nice option

I have the GTR 225 in my Flight Design CT. The LED display can be viewed from any angle and there is a photocell that dims the display automatically for night flying.

alioth wrote:

but has anyone used one?

I have a GNC255 as #2 radio. So far it works pretty well. Viewing angles are not limited by the display. The two minor nitpicks I have with the radio is:

  • Garmin radios generally (applies to the GTN650 as well) seem to have worse squelch circuitry than Bendix King
  • The GNC255 drives an old KNI520 indicator. The glideslope flag of this indicator wasn’t used before, so got a bit sticky. In the beginning, the GNC255 not always managed to get the glideslope flag out of sight, while on the bench with a lab power supply and appropriate series resistance it worked. This has by now fixed itself, but it seems like the GNC255 flag output is a bit low.
LSZK, Switzerland

tomjnx wrote:

GNC255 as #2 radio

He asked about the GTR225, not the navcom radio.

USFlyer wrote:

He asked about the GTR225, not the navcom radio.

I know, thanks, I can read. But since these radios are very similar (the GTR225 is the GNC255 without the nav part).

LSZK, Switzerland

Thanks for the replies :-)

Talking of squelch, a friend had one of the new touch screen Garmin panel mount GPS with COM (GNS 530W? I’m not entirely sure of the model) and it was a bit of a struggle to get the squelch working at the correct level. I think the unit ended up being exchanged under warranty and they’ve not had any problems since.

Andreas IOM

I had the same problem – my GTN650 used to break COM squelch all the time like a Labrador fed on beer and chick peas. I fixed it by going into setup mode and adjusting the squelch level. Then one of the recent software updates addressed the same problem, so I reduced the squelch a bit. It’s good now, so if anyone is interested I’ll check what level I ended up with.

Glenswinton, SW Scotland, United Kingdom

There have been some software issues to deal with the squelch levels on Garmin units so check you have the latest software installed

EGSG / EGHH

Simon wrote:

so check you have the latest software installed

I certainly haven’t, and it’s on my todo list to upgrade. I ended up turning up the squelch level in the setup menu, but that seems to come at a loss in sensitivity…

LSZK, Switzerland

The carrier noise squelch level is ideally at about 1.5uV soft 30% @ 1Khz modulation level

Not sure if the unit has a carrier level squelch setting / adjustment but if so should be around 6uV soft @ 85% 8Khz modulation level

With climax / offset carrier transmissions from ATC if the carrier level squelch is incorrectly set it will result in a loss of reception of ATC calls, although other aircraft will still be heard, this can be very confusing!
I see a lot of comm’s that have been incorrectly set I always check them as a matter of course, I imagine that 8.33 Khz channel spacing may further effect reception on 25 Khz units

There is no test for this on a radio annual, indeed the ramp gear cannot generate the required signal!

Narco COM-810 /811 and the ICOM A200 units have a design defect that can cause the ATC issue, both companies were told Narco authorized a mod to cure the problem Icom showed no interest

EGSG / EGHH
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