Brantel

Brantel

Well Known Member
UPDATE: See post #7, Garmin has created a MOD to bring this feature to the GTN series....

This only applies to dual COM installations.....

One thing to understand about the GTN650 is that it does not have a COM interlock feature like the GNS series had.

I used that feature back when I had a 430W installed. The purpose of it is to interlock with the other COM radio and when either radio xmt, the opposite radio's receiver is disabled or it runs at a reduced sensitivity.

This feature prevented feedback from one radio to the other when the antennas were located close together like they are when people mount em both on the belly.

I was unable to do this with my new panel since I went to a GTN650 and I get crosstalk on the two radios. Good news for me is that the GMA240 has a feature that can be enabled to mute the opposite radio when xmting. This prevents the feedback squeal in your ears....

My antennas are on the belly...

Not sure why Garmin's certified engineers removed this interlock but they did....
 
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Timely

Thanks for your post Brantel,

I am looking at removing my 495 and AirGizmo to install both the GTN650 and 240 that you mention above. I intend to still use my SL30 as a second radio so good to know the 240 will work here with the GTN shortfall. Any other gotchas worth mentioning. I have to install a second VHF antennae so will keep this in mind.

Cheers,
 
Just make sure to install the jumper in the GMA240's harness that enables the feature to mute the non xmitting radio's audio.

Page 2-5 in the install manual:
MUTE ON COM TX: This input configures the audio panel to mute all selected radios (COM, NAV, AUX) except the mic selected COM (COM selected for transmission) when a PTT key is activated for COM transmit.

More details in the manual on where and how to wire it...

The GTN650 is an amazing device. You will love it!
 
Thanks

Thanks Brian for sharing your insight about the problem!

Just wondering:

1) Did you hear cross-talks over the radios all the time? Or did they occur only in a particular configuration (e.g. listening on both radios)?

2) While you were able to solve it via GMA 240, what are the options for folks who dont have that audio panel? Any thoughts on that? I suspect many RV-8s (and 6,7,9 too) have belly mounted antennas so they'll suffer from the same problem.

Thank you again for the details on this problem.

Ashish
 
Airzen said:
Thanks Brian for sharing your insight about the problem!

Just wondering:

1) Did you hear cross-talks over the radios all the time? Or did they occur only in a particular configuration (e.g. listening on both radios)?

2) While you were able to solve it via GMA 240, what are the options for folks who dont have that audio panel? Any thoughts on that? I suspect many RV-8s (and 6,7,9 too) have belly mounted antennas so they'll suffer from the same problem.

Thank you again for the details on this problem.

Ashish
Click to expand...

When I originally installed my 430W prior to the current panel, I did not hook up the interlocks and had issues when one radio would bleed over on the other anytime the channels were close enough together. I solved the issue back then by installing the interlock wires.

On question #1, I never heard anything with the current new panel because I anticipated the issue and used the GMA240's feature from the beginning. I can tell you however that the RX lights up on the non Xmitting radio when the channels are close enough together so I know there is some crosstalk going on strong enough to open the squelch.

On question #2, Keep the non xmitting radio deselected on the audio panel will do it if you have an audio panel, if you don't, turn down the volume on the non xmitting radio. Switches are also an option for no audio panel...One could have a switch that selected COM1 AUDIO/BOTH/COM2 AUDIO or something like that. The other thing you can do is put one antenna on bottom and one on top or put em out on the wings to get em far enough apart.
 
Great info.

Great info. Thanks for the reply.

In fact I did experience similar thing in C172 euqipped with 430W (i.e. feedback/cross talk when frequencies were close together).

Ashish
 
Good Afternoon everyone,
My name is Trek Lawler and I'm the Supervisor of the Aviation Field Service Engineering team for Garmin International based out of Olathe, Kansas. As you know we have a couple of our G3Xperts that comment on the forum and I do some lurking however try and leave the Sport Aviation side to these experts. However this thread caught my attention as this is part of my support team and I wanted to get with everyone to explain this and the features of the GTN series of radios.
Yes, at the initial release of the GTN series of radios there was in fact no process for providing a transmit interlock, early on in the release of the product line we discovered this in fact will be a necessity and quickly started working on this. As of March 2013 we have in fact incorporated this feature in all production GTN series units. The uniqueness of this new interlock feature is the radio will now detect another radio transmitting and via software will reduce the GTN comm. radio receiver sense so that the noise or crosstalk is disabled. This does require a hardware change in the GTN series radios however can be added to any fielded units that may be installed already. This will be identified as mod 2 on the unit. Should you desire to have this mod installed on a unit please get with your local Garmin dealer and have them contact us to coordinate getting this scheduled.
As I indicated I do lurk from time to time on the forum however if there is any questions please feel free to drop me a note and I will be glad to assist you.

Best Regards,
 
Trek,

Thanks for the very open and honest reply to this thread. It is another example of how Garmin is experiencing a paradigm shift within its organization! Sounds like the unique solution used to bring this feature to the GTN series will be a real winner since no wiring mods are required. Most of all thanks for listening to and informing the customers!

I have one technical question for you....Is there any risk for damage to a GTN unit that does not have this MOD implemented when it is used in an installation/environment that is conducive to crosstalk similar to the types of interference that this MOD is intended to prevent?
 
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Brantel said:
I have one technical question for you....Is there any risk for damage to a GTN unit that does not have this MOD implemented when it is used in an installation/environment that is conducive to crosstalk similar to the types of interference that this MOD is intended to prevent?
Click to expand...

Hello Brantel,
Thank you everyone for the warm greeting, one of our senior RF engineers was able to supply me with some very good data regarding this.

"There is no risk of damage to any circuits in the radios front end only the annoying squelch popping.

As both versions of the GTN stand today, with and without MOD 2, non mod 2 receivers can take up to 1 watt of on channel RF applied directly to the receiver front end while those with the TX interlock mod have been tested with more than 5 watts directly applied on frequency and neither models were damaged."

Obviously depending on your comm units on board and the proximity of the antennas will dictate how much RF energy is being absorbed however the GTN units are a very robust design and I've yet to see a problem with them in the two years they've been on the market.

Hope this helps, let me know if there is any other questions,
 
Trek,

What is the cost of implementing Mod 2? Is it covered under warranty?

Out of curiosity, what are features the other mods available enable or fix.

thanks,

bob
 
rleffler said:
Trek,

What is the cost of implementing Mod 2? Is it covered under warranty?

Out of curiosity, what are features the other mods available enable or fix.

thanks,

bob
Click to expand...

Hello Bob,
Mod 2 is the latest and greatest mod for the GTN units for fixed wing airframes. There is a mod 3 however this is only a requirement for the new HTAWS or rotorcraft for vibration requirements.

Mod 2 is covered under warranty here at the factory, however if there is any need for a dealer to remove and re-install it, this labor is not covered.

Best Regards,
 
GTN Mod2 update

Can we go to any local Garmin dealer and get this done? Will it be possible to just take the unit to them and get it done (or does it need to be installed in the plane)?

Ashish
 
Airzen said:
Can we go to any local Garmin dealer and get this done? Will it be possible to just take the unit to them and get it done (or does it need to be installed in the plane)?

Ashish
Click to expand...

The unit will need to come back to the factory for this mod to be installed. It usually take about 3 to 4 days depending on schedules.

Best Regards,
 
Info

Trek - Sorry to bug you again. I am still not clear how does it work:

1) Do I go to a local Garmin dealer and he ships the unit to you?
2) Or do I myself ship the unit to you?

Where can I find more information?

Unfortunaltely, I am highly nervous about shipping high dollar avionics. Isnt there any way where such updates could be done by the users themselves (or at least by a local shop)?

Ashish
 
Airzen said:
Trek - Sorry to bug you again. I am still not clear how does it work:

1) Do I go to a local Garmin dealer and he ships the unit to you?
2) Or do I myself ship the unit to you?

Where can I find more information?

Unfortunaltely, I am highly nervous about shipping high dollar avionics. Isnt there any way where such updates could be done by the users themselves (or at least by a local shop)?

Ashish
Click to expand...

Hello Ashish,
We rely greatly on our dealers as the interface between Garmin and the end customer and our system is setup as such to provide warranty work to make sure that the units are installed and configured correctly. With that being said the best process is to get with your local dealer so that they can contact us for the RMA, get the unit packed up correctly and shipped to us. This process works very well with a out a 3 to 4 day turn around time.
As for being able to perform this mod in the field. regrettably this mod requires the comm. board to be replaced and without a great deal of very expensive test equipment the dealers cannot properly perform the necessary alignment and return to service.

Let me know if there is any questions,
 
What about the other comm radio that precipitated Mod 2? In my case it's a SL-40. Does it have the capability of transmit interlock? If so, I suspect it uses hard wire instead of software. That means Mod 2 addresses victimization only without provision to interact. Any answers out there?

John Siebold
 
Typically the hard wired interlock inputs just connects to the PTT line. Not a problem.

However, I don't think the SL40 has an interlock input.

The A210 does as well as the GNS series.
 
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rleffler said:
Trek,

So we now know about Mods 2 & 3. What's Mod 1?

thanks,

bob
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Hello Bob,
Mod 1 was a NAV board reliability problem that was identified early on and had a serial number effectivety to it. This was found in March 2012 so if you have a unit that was purchased after this there should be no problems however if you purchased this unit prior you should have received a notice if the unit was registered with us. There is a process where the dealer has to open the unit to verify the part number of the NAV board, mark it if it complies and then return it to airworthiness status. If the unit had a possible defective board it requires being returned to us for replacement and re-certification.

Let me know if there is any other questions,
 
TrekLawler said:
Hello Bob,
Mod 2 is the latest and greatest mod for the GTN units for fixed wing airframes. There is a mod 3 however this is only a requirement for the new HTAWS or rotorcraft for vibration requirements.

Mod 2 is covered under warranty here at the factory, however if there is any need for a dealer to remove and re-install it, this labor is not covered.

Best Regards,
Click to expand...

I was just told by my local dealer that Mod 2 can only be performed if there is a demonstrated failure and that there isn't any automatic upgrade.
 
rleffler said:
I was just told by my local dealer that Mod 2 can only be performed if there is a demonstrated failure and that there isn't any automatic upgrade.
Click to expand...

Hello Bob,
That would be correct, if the unit is not exhibiting any problems like comm or NAV interference then there is no need to have this mod installed as it is not a mandatory modification. I actually addressed this call when it came through to my team.

Best Regards,
 
TrekLawler said:
Hello Bob,
That would be correct, if the unit is not exhibiting any problems like comm or NAV interference then there is no need to have this mod installed as it is not a mandatory modification. I actually addressed this call when it came through to my team.

Best Regards,
Click to expand...

I have been fighting an interference problem between nav and com, every time I transmit with either com (GTN650 or SL30) after 6 second both VOR indication fail (from GTN650 and SL30), that is happening on ground and I don't know in fly because I have not flown with my new full garmin panel yet. Today I found that if I disconnect com circuit breaker from GTN650 and I transmit from SL30, I don't have interfere on VOR.

So should I have problems with GTN650???

I bought it on December 2012 and I leave in Chile, we have a Garmin dealer at my airport, but who is going to pay for shipping and taxes (imports taxes in Chile are 30%):mad:
 
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AirbusPilot said:
I have been fighting an interference problem between nav and com, every time I transmit with either com (GTN650 or SL30) after 6 second both VOR indication fail (from GTN650 and SL30), that is happening on ground and I don't know in fly because I have not flown with my new full garmin panel yet. Today I found that if I disconnect com circuit breaker from GTN650 and I transmit from SL30, I don't have interfere on VOR.

So should I have problems with GTN650???

I bought it on December 2012 and I leave in Chile, we have a Garmin dealer at my airport, but who is going to pay for shipping and taxes (imports taxes in Chile are 30%):mad:
Click to expand...

Hello,
It does sound possibly like this unit may be a candidate for mod 2. If the GTN has been removed and verified to not have mod 2 (since I'm assuming it hasn't based off of the sale date). The unit will have to be handled through your local Garmin dealer, this is a requirement for TSO certified equipment. Since this is an optional service bulletin the shipping charges are the responsibility of the dealer/owner. Garmin will pay for ground shipping back to an international location.

Let me know if there is any other questions.

Best regards,
 
I'm experiencing this issue

Mine was bought new in August 2014. Is there s possibility my unit did not get modded? Her is a cut/paste from my post. "My newly installed (by a gamin dealer avionics shop) is receiving something from somewhere causing the RX to show intermittently, and it's very annoying. It's almost like it's squelching but it is set to auto squelch. The antennas are whip style and share comm with my klx155. My klx never had nor has this problem. My audio pnl is kma-24. When I talk, it also sounds like I'm in a box. Very hollow sounding." Pretty hoaky for the small price of 10k. :-(
 
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Garmin is usually pretty good about labeling the mod level. There should be a sticker on on the unit with the mod numbers identified.

I had to set squelch to about 75 to get the rx triggers to go away after I got my unit back from garmin.
 
rleffler said:
Garmin is usually pretty good about labeling the mod level. There should be a sticker on on the unit with the mod numbers identified.

I had to set squelch to about 75 to get the rx triggers to go away after I got my unit back from garmin.
Click to expand...
Will ck that today. Thx
 
Ship battery time

Approx how long would one want to have on ships battery (with all other breakers out) to mess around with the 650, as in creating some flt plans, and customizing? Not to long to get off top cowl, but rather not. ��
 
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drmax said:
Mine was bought new in August 2014. Is there s possibility my unit did not get modded? Her is a cut/paste from my post. "My newly installed (by a gamin dealer avionics shop) is receiving something from somewhere causing the RX to show intermittently, and it's very annoying. It's almost like it's squelching but it is set to auto squelch. The antennas are whip style and share comm with my klx155. My klx never had nor has this problem. My audio pnl is kma-24. When I talk, it also sounds like I'm in a box. Very hollow sounding." Pretty hoaky for the small price of 10k. :-(
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Hello,
if the unit is that new then the mod will have been incorporated in production as it was released in March 2013. you're unit will contain the correct NAV board with the internal isolation.
what we found that caused mod 2 to be incorporated was a comm antenna to NAV antenna being a perfect quarter wavelength from one another. we added internal isolation.
the only way you will be able to determine if this is in fact a similar issue on your airframe will be to relocate and move the antenna further away from one another if possible.
 
Not under warranty anymore...

I contacted Garmin to get a Mod 2 update. Its not covered under warranty anymore :(. Hope many of you got this done when this was covered.

"mod two for the GTN requires modification to unit and is not longer covered under warranty. if the unit requires mod 2 it can be completed at our factory for the flat rate repair charge."
 
Airzen,
how old is your unit in this case or do you have a serial number so I can look into it further? it's really odd that the unit has not been modified as the problem for mod 2 really would stand out when you keyed the comm it would blow out the NAV's if the problem existed this long.

Let me know,
 
Airzen said:
I contacted Garmin to get a Mod 2 update. Its not covered under warranty anymore :(. Hope many of you got this done when this was covered.

"mod two for the GTN requires modification to unit and is not longer covered under warranty. if the unit requires mod 2 it can be completed at our factory for the flat rate repair charge."
Click to expand...

I read the Service Bulletins religiously for this reason and usually have quartely conversation with my avionics dealer too. That $975 service call is expensive to us homebuilders.
 
GTN 650

Well I got it when building my panel in Jan 2013. I had mentioned this problem in the following thread: http://www.vansairforce.com/community/showthread.php?t=99606

At that time it was required that the problem be demonstrated before Mod 2 upgrade under warranty would be done. Of course, I couldn't demonstrate it as the airplane was a pile of parts. Now I am close to demonstrating it but find that the upgrade is not under warranty. So don't know how could I have handled it better.

This is brand new unit (from the use perspective) as it was sitting in while the airplane was being built. That s why perhaps the fuse has never been blown. (maybe I should stop experimenting trying to fix antennas distances etc. now).
 
Airzen,
I'll do my best to explain what mod 2 addresses and how it was found.

basically in short we had an airframe come to us that when it had the GTN's installed when they were tuned to a NAV frequency when they keyed the comm's the NAV needles on the EFIS system parked. So basically the comm's were blowing out the NAV signals and rendering them invalid. through a great amount of testing with the plane what we found was on this airframe (it was a PC 12 byt the way) the NAV antenna and comm. antenna's were exactly a quarter wave length apart. this basically caused one of the harmonics to have an affect on the NAV system. we basically incorporated isolation internally in the GTN to prevent this from happening. so far to date the only reported issues of this happening have been on the PC 12 platform.

but if you can get with your dealer and provide them the details of this e-mail and have them contact me directly since you did comment on this prior to the end of 2014. I'll be happy to look into this for you under warranty.
 
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