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GTR200B not breaking squelch

RV74ME

Well Known Member
Noticed lately missing radio calls from ATC because they weren’t breaking squelch. If I turned squelch OFF (press power knob), I could hear their calls loud and clear. Turn it back on, and nothing. Doesn’t happen all the time, but enough to where I can’t trust it. And it’s usually an ARTCC frequency. Today in was ATL and JAX center at 10,500’.

For those not familiar with this radio, there is an RF squelch setting in configuration mode. Settings are 0-10. The default is 0, and is most sensitive (should let even the weakest transmissions thru) and where mine is set. In normal mode, the only squelch control is either ON or OFF. No in between.

Anyone else having similar issues or have suggestions on what to try?

Thanks
 
Steve,

One quick check is to make sure that pin 5, TX Interlock In is not grounded.

TX Interlock In is an active low input that desenses (protects) the COM receiver when a 2nd COM radio in the same aircraft is transmitting.

Having this input permanently grounded would significantly impact your receiver range.

Steve
 
Thanks Steve, i will check. Looking at my wiring diagram, I don’t have a wire going to pin 5. I’m single radio, so that makes sense. But I will pull the radio to verify
 
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RF squelch is set in the configuration mode which is very easy to use. Get a GTR200 install manual for details.

If you don’t have access to the manual, contact me via email and I’ll send a copy.

Deeneogden(at)Gmail(dot)com
 
RF squelch is set in the configuration mode which is very easy to use. Get a GTR200 install manual for details.

If you don’t have access to the manual, contact me via email and I’ll send a copy.

Deeneogden(at)Gmail(dot)com

I have the manual, and RF sq is set to zero
 
Just took to avionics shop to do a vswr check. Reading was about 1.6 (good/normal) throughout normal freq range, so that tells me we can eliminate the coax and antenna. Stumped
 
Systems and Dynamics Questions:
What type of antenna (mfg, make, model) are you using? Where is it installed? Type of cable/terminations?
On which frequency are you missing calls? Have you tracked it down to a particular sector/transmitter/RCO location?
Propeller Type? RPM when issue occurs? Flight attitude - climb, descent, etc.?
Aircraft Lighting? Other RF sources active?

I ran into similar issues with my GTR200; at a certain distance and altitude from the tower, with a certain prop RPM I could not receive and my transmissions were not received. Changing aircraft attitude, RPM, altitude, combination of all three would resolve the issue.

I rationalized/explained it to myself as some kind of blanking effect by the propeller disc and the line of sight + signal polarization (antenna is a bent whip) issue .
 
Systems and Dynamics Questions:
What type of antenna (mfg, make, model) are you using? Where is it installed? Type of cable/terminations?
On which frequency are you missing calls? Have you tracked it down to a particular sector/transmitter/RCO location?
Propeller Type? RPM when issue occurs? Flight attitude - climb, descent, etc.?
Aircraft Lighting? Other RF sources active?

I ran into similar issues with my GTR200; at a certain distance and altitude from the tower, with a certain prop RPM I could not receive and my transmissions were not received. Changing aircraft attitude, RPM, altitude, combination of all three would resolve the issue.

I rationalized/explained it to myself as some kind of blanking effect by the propeller disc and the line of sight + signal polarization (antenna is a bent whip) issue .

Delta Pop comm antenna, mounted bottom of fuselage underneath pilot seat. BNC connecters. All looks good.

It's weird. There's no rhyme or reason. Yesterday it happened while at 10,500' talking to ATL center, then again with JAX center. Only reason I knew they were calling me was a relay from another aircraft. As soon as I turned the squelch "OFF", by pushing the power button, I could hear them 5x5. Loud and clear. And I've never had a transmit issue. I'm always told my transmissions are loud and clear.

I should also mention that Garmin just sent me another brand new GTR200B to try, and it happens with this one too. That tells me it's not the radio, unless it's software issue (squelch sensitivity). But not sure, because I haven't heard yet of anyone else with similar issue.
 
Same issue withy recently installed GTR200. I have a bent whip antenna mounted on the bell aft of the baggage compartment. Check connections and everything appears in order. I'll need to get in and have a more detailed inspection soon. I would greatly appreciate any info if someone comes to a conclusion on what the issue is.
 
Double check that the radio is fully seated in the rack (the faceplate should contact the sides of the rack). I've seen a number of issues caused by the radio not being fully seated, usually hitting the panel opening before it fully seats.
 
I have the manual, and RF sq is set to zero

Steve,

The zero RF Sq setting is a factory calibration setting. It might be somewhere in between 1 and 10, so start with 1 and work your way up until the squelch turns off.

Also, with it happening with yours and the one from the factory, it could still be the RF Sq setting of zero. Next, if that does not work, I would try and just run a new antenna coax, use RG-400. No need to permanently route it, just let it be loose until you try it. If it works good then, reroute the new cable. Last resort is the antenna, as they rarely fail, but they do.

Good luck.

Brian
 
To answer a few others...yes, the radio is fully seated into the rack. Took to avionics shop and did a second VSWR check, and readings were 1.6 across freq range (good). So I would assume that means the coax and antenna are good.

RF is set to zero, and I would think any number higher would make it worse but will try 1-10.

Got some advice to try disabling a USB charger that’s in my panel. Was told that sometimes the cheap ones (like mine) can cause some electronic noise that would affect radio reception. So I did that and recently flew a 200nm IFR cross country without any issues. But I will need many more data points before I’m ready to label that as the cause.
 
RFI

RFI (radio frequency interference) is a mysterious thing. Looking at the history of a couple of products in recent times, I see LED replacement bulbs for nav and position lights were often suspect. Cheap designs without proper engineering were ending up on expensive airframes and causing trouble.
USB converters are another example. Some companies (Mid Continent and Guardian Avionics) for example have stepped up and engineered nice quiet, reliable devices. Of course the price tag reflects that development cost. I am often surprised that Aircraft Spruce will offer both the really low end and the better offerings. I recently researched the nav light replacements (again) and still find the low cost, unreliable options for sale.
Garmin has also had a history of squelch issues on coms in the last five years or so. It has commonly resulted in squelch opening too easily and not what you are experiencing.
Please report back when this is resolved. That knowledge can become a great data point for others down the road. BTW, all radios will function at a greater range with squelch manually opened. Your technique can serve as a tip for newer pilots who never flew with a Narco or King that had a rotating squelch knob. Particularly when listening to ATIS miles from arrival.
 
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RFI (radio frequency interference) is a mysterious thing. Looking at the history of a couple of products in recent times, I see LED replacement bulbs for nav and position lights were often suspect. Cheap designs without proper engineering were ending up on expensive airframes and causing trouble.
USB converters are another example. Some companies (Mid Continent and Guardian Avionics) for example have stepped up and engineered nice quiet, reliable devices. Of course the price tag reflects that development cost. I am often surprised that Aircraft Spruce will offer both the really low end and the better offerings. I recently researched the nav light replacements (again) and still find the low cost, unreliable options for sale.
Garmin has also had a history of squelch issues on coms in the last five years or so. It has commonly resulted in squelch opening too easily and not what you are experiencing.
Please report back when this is resolved. That knowledge can become a great data point for others down the road. BTW, all radios will function at a greater range with squelch manually opened. Your technique can serve as a tip for newer pilots who never flew with a Narco or King that had a rotating squelch knob. Particularly when listening to ATIS miles from arrival.

Yes, I’ve been talking with Garmin tech every week for last month or so. They are out of ideas.

My plan is to do a little more testing with the usb. Gonna wire in a switch so i can easily turn it on/off in flight while doing radio checks to see if anything changes. Also will try different RF squelch settings, and another antenna coax. But i want to be careful to only change one thing at a time. The problem seems to be extremely random and may be difficult to pinpoint, so its probably gonna take a while.
 
Update. Disabled the Usb ports. Still have the random missed radio calls. Gonna try another antenna and see what happens.
 
Just curious if you ever found a solution. We are going through the exact same problem currently. Radio works great most of the time but we have had 1/2 dozen occurrences of losing ATC, but when you turn the auto squelch off, ATC comes in loud and clear. Trouble shooting so far as involved swapping radios but that did not seem to make a difference. We also are running 1 radio (G3X system).
 
Just curious if you ever found a solution. We are going through the exact same problem currently. Radio works great most of the time but we have had 1/2 dozen occurrences of losing ATC, but when you turn the auto squelch off, ATC comes in loud and clear. Trouble shooting so far as involved swapping radios but that did not seem to make a difference. We also are running 1 radio (G3X system).

Check your PM’s
 
Same issue

I think I am having the same issue. When flying around Chicago Bravo I monitor ATC. I can hear ATC but not most of the aircrafts they are talking too. In the past I never noticed this problem with my old ICOM A200. I still have the ICOM as a back-up so I plan to compare the two next time I'm up. I also would like to know what you have found out so far.
 
I think I am having the same issue. When flying around Chicago Bravo I monitor ATC. I can hear ATC but not most of the aircrafts they are talking too. In the past I never noticed this problem with my old ICOM A200. I still have the ICOM as a back-up so I plan to compare the two next time I'm up. I also would like to know what you have found out so far.

Frank,

I am on my third antenna, this time a comant. Flew 300nm XC today and still same issues. I have now checked everything I can think of and personal opinion is something internal to the radio. Perhaps the way they designed the auto-squelch.

I am in touch with another member of this forum who is having exact same issues. Beyond frustrated. Please send me a PM if you want to talk offline.
 
GTR200 issue

Well, Steve and and I have been comparing notes and we have the exact same problem. Oddly enough we just shared pictures of our cockpit configurations and they are almost identical. We both are running a GDU460, with a stack in the middle with a autopilot controller on top (507), the GTR200 in the middle, and a Garmin 375 on the bottom. Single radio setup with the GTR as the intercom. I’ve been in contact a little bit with Garmin but so far no luck. If anyone else out there is having the same issue please contact me or Steve T. We would love to compare notes and get to the bottom of this.
 
It looks like you've tried everything we've all suggested, so here's something even further "out there" to try... How about reorganizing where the radio is with respect to everything else in the panel? i.e. pull the tray, drop it down below everything and (temporarily) hang it there with a webbing strap or something. i.e. get it away from the rest of your avionics.

This requires that you have enough of a service loop in your wiring to accomplish this, of course.

Alternately, maybe pulling other things nearby out instead? What comes out easily? the Garmin 375, maybe?

And to be clear, what I think you'd be testing by doing this is the possibility that there is some RF somewhere leaking between devices and causing issues.
 
#Me Too

I just experienced this same issue yesterday for the first time while talking with CLT ATC. I had to turn off squelch to hear them after I realized what was happening and I remembered this thread. I had been in direct communication with ATC when all of a sudden started missing their calls.


I have a single G3, GTR200B, GNX375, GMC507. Radio is 3 months in service, 55 total hours.

Question:
Has anyone found the smoking gun on the squelch/receive issue?

On a different note:
Prior to the receive/squelch problem experience yesterday, I have been having numerous transmit issue regarding ATC asking me to repeat my initial transmission. This has been happening since first flight. I have tied different headsets, a HALO, BOSE X, Lightspeed, and now a CQ. This happens intermittently they seem to not understand my initial transmission and I usually follow up with a “how do you hear this transmitter?” ATC typically responds with 5x4 or 5x5, so I’m confused on what’s causing this issue. Recently I dropped the mic gain from default 5 to 4 to see if that will help, bit only have two flights since the adjustment
 
I just experienced this same issue yesterday for the first time while talking with CLT ATC. I had to turn off squelch to hear them after I realized what was happening and I remembered this thread. I had been in direct communication with ATC when all of a sudden started missing their calls.


I have a single G3, GTR200B, GNX375, GMC507. Radio is 3 months in service, 55 total hours.

Question:
Has anyone found the smoking gun on the squelch/receive issue?

On a different note:
Prior to the receive/squelch problem experience yesterday, I have been having numerous transmit issue regarding ATC asking me to repeat my initial transmission. This has been happening since first flight. I have tied different headsets, a HALO, BOSE X, Lightspeed, and now a CQ. This happens intermittently they seem to not understand my initial transmission and I usually follow up with a “how do you hear this transmitter?” ATC typically responds with 5x4 or 5x5, so I’m confused on what’s causing this issue. Recently I dropped the mic gain from default 5 to 4 to see if that will help, bit only have two flights since the adjustment

Hi Mark,

Check your PM’s
 
So that is three of us with the exact same issue. We have compared photos of our configuration and they are exactly the same. One GDU460 with a center stack of a GMC507, a GTR200, and a GNX375 - in that order. I can see 2 being a coincidence and 3? Something is wrong with this Garmin configuration.
 
So that is three of us with the exact same issue. We have compared photos of our configuration and they are exactly the same. One GDU460 with a center stack of a GMC507, a GTR200, and a GNX375 - in that order. I can see 2 being a coincidence and 3? Something is wrong with this Garmin configuration.

Since there are likely thousands of people using the very popular GMC 507, GTR 200, and GNX 375 with a G3X Touch system, having a few people with poor reception is probably not evidence of a problem with this combination of equipment.

Just as another point of comparison, I have a G3X Touch system with the GMA 245, GTR 200, GMC 507, and GNX 375 in my stack and don't have this problem. Admittedly, I have the GTR 200 and GNX 375 separated by the GMC 507.

LGEZRadioStack.png

Steve
 
GTR 200 Reception Issue

So that is three of us with the exact same issue. We have compared photos of our configuration and they are exactly the same. One GDU460 with a center stack of a GMC507, a GTR200, and a GNX375 - in that order. I can see 2 being a coincidence and 3? Something is wrong with this Garmin configuration.

We are taking a look at a radio from one of the problematic installations, to try and recreate the reported issue. We will pin down whether it is a configuration/setting issue, an installation issue or an equipment issue. At this time we do not know exactly what the problem is so we do not have any guidance for resolving the issue. We will make sure to respond here when we have everything sorted out.

Thanks,

Justin
 
Is it possible that the type of antenna is causing the issue? I noticed that the OP is using the Delta Pop antenna which presents as a short at DC vs the Comant/Cobham CI-12x which is an open...

Just thinking aloud...
 
Is it possible that the type of antenna is causing the issue? I noticed that the OP is using the Delta Pop antenna which presents as a short at DC vs the Comant/Cobham CI-12x which is an open...

Just thinking aloud...

All three of us have three different antennas.
 
We are taking a look at a radio from one of the problematic installations, to try and recreate the reported issue. We will pin down whether it is a configuration/setting issue, an installation issue or an equipment issue. At this time we do not know exactly what the problem is so we do not have any guidance for resolving the issue. We will make sure to respond here when we have everything sorted out.

Thanks,

Justin

Thanks Justin. I did get a email back today also. We’ve just been chasing this thing for months now and don’t seem to be getting any closer.
 
Is it possible that the type of antenna is causing the issue? I noticed that the OP is using the Delta Pop antenna which presents as a short at DC vs the Comant/Cobham CI-12x which is an open...

Just thinking aloud...

I switched to a comant with same results. Mark has a rami, and also has the same problem. So, its definitely not the antenna
 
We are taking a look at a radio from one of the problematic installations, to try and recreate the reported issue. We will pin down whether it is a configuration/setting issue, an installation issue or an equipment issue. At this time we do not know exactly what the problem is so we do not have any guidance for resolving the issue. We will make sure to respond here when we have everything sorted out.

Thanks,

Justin

Thanks Justin.
 
We are taking a look at a radio from one of the problematic installations, to try and recreate the reported issue. We will pin down whether it is a configuration/setting issue, an installation issue or an equipment issue. At this time we do not know exactly what the problem is so we do not have any guidance for resolving the issue. We will make sure to respond here when we have everything sorted out.

Thanks,

Justin

Justin/G3Xpert, I was the one that sent in the radio. We flew the aircraft today with the new radio installed. The new radio made no difference, we had a couple of instances of lost comm. Although like always, as soon as you deselect the squelch ATC was load and clear. No change so it doesn’t appear the GTR200 is the problem.
 
Justin/G3Xpert, I was the one that sent in the radio. We flew the aircraft today with the new radio installed. The new radio made no difference, we had a couple of instances of lost comm. Although like always, as soon as you deselect the squelch ATC was load and clear. No change so it doesn’t appear the GTR200 is the problem.

Radios have been known to interfere with each other in various ways due to internally generated oscillator frequencies, power supply noise etc..
I mentioned this before but have you tried turning off the 375?
 
Radios have been known to interfere with each other in various ways due to internally generated oscillator frequencies, power supply noise etc..
I mentioned this before but have you tried turning off the 375?

Hi Walt,

I will be trying this next week. Problem is, it turns off the transponder which becomes problematic when you’re using ATC. Will report back results
 
Radios have been known to interfere with each other in various ways due to internally generated oscillator frequencies, power supply noise etc..
I mentioned this before but have you tried turning off the 375?

Thanks Walt, yep the three of us have all talked about the 375 as being the problem. Especially since all three configs have the 375 and GTR right next to each other. We just haven’t had the opportunity to try it out yet, mostly because of the transponder in the 375 and ATC. But we will try this out soon.
 
Technically it is forbidden to turn off compliant ADS-B equipment any time or place when an equipped aircraft is operated. Dudley Do-right rant off, I would. The rules are onerous.
Just land at a pilot-controlled field outside of rule airspace and then pull the breakers on the 375 for testing purposes. Just saying. Land between pulling or activating the breakers so the FAA ADS-B red light computer doesn't send you a nasty gram.
 
Or just tell ATC you're having some issues with the transponder and need to 'reset' it and it may be offline for a few minutes. I'm sure they would be happy to accommodate.
 
Second time

So this happened to me again the other day on a flight from KGSO To KSSI. I missed several attempted calls from CHARLESTON approach. The reason I knew I had missed calls is when I finally did hear them, I could tell by the controller’s tone he wasn’t happy, so I queried him if we had missed any calls and he replied yes, that he had been trying to contact me over several times. My estimate is about 5-10 minutes from the time we had our initial check in until we had our missed call issue. These issues have all happened within 20-30 miles from the controlling agency.

All current software on all LRU’s
Rami antenna.

I’m going to try and start documenting what frequencies and distance this happens.

Now Im wondering if you miss ‘one” call many times controllers just come back to you minutes later,,having assumed your busy etc. However when you hear their second call, but you are unaware that you missed the first one. I’m now curious if that could be happening too.

Now I fly Paranoid and treat the gtr200 in busy airspace like the HF radio listening to static with squelch off.
 
Update

Just wanted to provide latest findings which are kind of interesting. Many thanks to wiscoav8tor for noticing it first.

With the same frequency tuned in BOTH ‘active’ and ‘stby’, and while monitoring ‘stby’ (again, same freq), the radio calls were sometimes ONLY received on the monitored ‘stby’ side! This was verified by observing RX next to the stby freq. It happened randomly and distance from the station was not a factor.

The saga continues as we continue gathering clues…
 
Carl are you saying you have seen this too?

No. My one and only experience with this radio demonstrated RF front end selectivity shortfalls. I cannot say I have seen this exact problem as the radio was not my primary comm in the RV-14 I ferried for a friend.

Carl
 
No. My one and only experience with this radio demonstrated RF front end selectivity shortfalls. I cannot say I have seen this exact problem as the radio was not my primary comm in the RV-14 I ferried for a friend.

Carl

Oh gotcha. The 3 of us having the issues all have IDENTICAL panels, right down to the placement of each component.
 
Oh gotcha. The 3 of us having the issues all have IDENTICAL panels, right down to the placement of each component.

Steve,

did you get any resolution to this? If so, was it with the new 9.0 update?

Was having the same issue, my setup is GMA245R, GTN650xi, GTR200.

Regards,

Don
 
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