GTR225A issues

Hi all

I have read a lot of posts how to tackle down comm. noise problems but I couldn't resolve my issues so far.
First issue I have on my GTR225A is that I have a constant static noise, however I try to squelch it out. I tried out everything I can imagine, but with no success so far. Transmitting works fine. The radio interfaces Van's RV-12 contro boxl. I guess it is just a tiny thing to solve that but I have run out of options to check anything further.
The 2nd issue I have is that the GTR225A does not interface with the SV-1000T. I can not see the radio on any serial ports. I also tried Garmin SL30/SL40 but without success. I have updated SV firmware to version 15. On the input device list the GTR225A is listed.
I would really appreciate if somebody can point me in the right direction.
Thanks a lot!!

Simple thing possibly - check the NAV monitor. Ask me how I know........

As for interfacing, you need to configure one of the serial ports to GNC255 - it's listed as one of the standard interfaces. Then you connect the tx/rx wires (and, IIRC, the RS232) to the appropriate SV1000 inputs. Note - make sure you connect rx to tx and tx to rx NOT tx to tx and rx to rx - again, ask me how I know...... The connection diagrams are in the install manual.

You also have to configure the top bar to show the frequencies. I don't think you can get the full functionality outside the US as the SV-1000 doesn't have the necessary frequency database.

First issue solved

Thanks a lot for your input Paul.
I could resolve the first issue with the permanent static RX noise of the radio. In order to preserve battery while fiddling around with SV, I hooked up a switched power supply 13.8V/10A. The switching caused a lot of noise and was picked up by the com antenna. Re-positioning the power supply was all I had to do. (sometimes things can be that easy )

However, I still have the problem that SV does not see the GTR225A. I doubled checked RX/TX lines from SV connector via Van's control box up to the radio. TX goes to RX and vice versa. The connections are fine and correct according to Van's schematic. On SV I see TX counts incrementing on the serial port but never once a RX count. But I get some Group errors occasionally. I went through all devices on the SV to see if I get a single reception from the radio, but no joy. The display is configured to show radio FRQ on top. But as SV does not see any radio, that spot is crossed out of course.
Now, I assume it's really the radio who does not like to talk at all.

Hmmm.... sort of reached the limit of my knowledge!

The only thing I could suggest now is a bad crimp/connection/pin on the rx line. Or, double check that you have the correct wire to the SV - some of the colours look similar.

One more thing - Install Manual p4-30 - have you configured the 255 serial port correctly?

Problem solved

Hi Paul
Now I feel like an idi...
I didn't know that there is a config. mode which is entered by holding the ENT key during boot. I only had the pilot's manual of the radio before and not the installation manual.
The default value of IO-Mode is set to none. No wonder the radio didn't talk.
Now the radio is happily talking to SV and frequencies are shown in the top bar.

I just find it a pitty that Garmin seems to provide the install manual to dealers only. I was able to find a copy in the internet, but if my radio came with one, I would have saved a lot of time checking wirings, signal levels and so on.
A BIG thank you for giving me the hint.

magiccarpet said:

I just find it a pitty that Garmin seems to provide the install manual to dealers only. I was able to find a copy in the internet, but if my radio came with one, I would have saved a lot of time checking wirings, signal levels and so on.
A BIG thank you for giving me the hint.

Click to expand...

I think you can get to all of the install manuals on the internet these days. And that's pretty much true of all the avionics and EFIS manufacturers these days - almost no one print s out a 400 page manual - you get it electronically. I always download them onto my iPad and use that in the shop. Easier than a laptop, which isn't my next choice.