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Poor reception flying toward station.

Hangar 1271

Well Known Member
I'm flying an RV-8 with a GTN650xi as comm 1 and PS Engineering 200A as comm 2. While flying away from an airport, I can receive fine on the GTN but when I get about 25+ miles out and turn around I can no longer hear ATC. They can hear me but I can't hear them. I have found the 200A will receive farther out so I turn comm 2 receive on for a while until I can hear ATC on comm 1. Both comms have the same type of Commant bent antenna and are about 25 in apart from each other on the belly of the plane. Any ideas? Thanks.
 
Try swapping the antennas (by moving the cables between the radios). That'll help isolate the issue.
 
Good idea. Someone also suggested turning off squelch to see if that is the issue. Much easier than pulling up the floor as a first step.
 
Any updates?

Curious if you have found a root cause and or fix.

I have the same issue with a new gtn 650xi (com1), with my RV8, and since day one. Com2 is a gtr 200.
I have rechecked wiring more times than I can remember. Grounds, both aircraft and shields are all matching the drawings. Pinout checked too. 100% sure now have all wiring correct. I've even replaced BNC connectors. Swapped antennas of course. Nothing seems to help.

Wondering if I need to change to "straight" whip antennas for at least the 650xi com1.

Curious if you have found a fix.
 
SNIP.

Wondering if I need to change to "straight" whip antennas for at least the 650xi com1.

You would need a very good instrumented test range to measure the very slight performance difference between a bent whip and a straight antenna. In other words there is no practical difference.

Look more toward that amazingly expensive 650XI and the associated install. I’d start with the “desense” connection (Garmin’s work around for an overloaded receiver front end when transmitting on the other radio). Make sure it is not in play when your are just using the 650XI. Try just pulling the GTR-200 out of the tray and see if the 650XI works better.

Carl
 
Squelch set to ‘0’ ? RG400?, crimped BnC connections? Ground plane resistance (I like to remove paint under antenna).
 
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Mr. Carl, Mr. Walt!! Thank you for your help!.
1. I've toyed with the RX Squelch, and Carrier Squelch in the 650xi. I seem to not "hear" its affect whether at "0" or at "100". Still trying to understand these settings and effects. Yes, RG400. I've not checked Ohms resistance. Guess I need to do this. I've done the typical Continuity check after crimping, but you have a point I need to look at for ground plane resistance. Interesting.

2. Appreciate hearing it likely may not be worth spending another $400 to change out my Rami bent whips for Straights. I have the ground clearance. Just wondered. Thanks. HOWEVER, I have been trying multiple times to get a straight brass tacks answer to this whole "desensitivity" function you mention. I have read about that. But asking questions to the almighty maker of this **** 650xi, I can't get an answer if I need the TX Interlock or any other wiring. I'm trying to get tribal wisdom on this. GTR200 calls for it. But "they" say the new 650xi units have it built in. Still, it seems like I can't get clear direction for my combo of 650xi -> gma 245R -> gtr 200. But Carl you might be on to something, I just don't know which wire or connections or where or how to affect this...properly.

Thank you for responding you two. I'm desperate for tribal wisdom. Info is NOT in the manuals. I don't have anything good to say about this 650xi, but I have been schooled to keep my mouth shut. So the verdict is still out. Would love to be proven otherwise.
 
I have found many shops don't bother to install the xmt intlk wiring, so I think that being the issue is unlikely, but possible.
On the 650 it would be connector P1003, pin 9. When you ground this pin it lowers the receiver sensitivity. The ground can be sourced from the GTR200 or from the key line out of the audio panel.
I've installed many 650/750 radios and have never had a complaint. Antenna location and installation are at the heart of good reciever functionality.
I personally use Comant straight antenna's whenever possible.
If you can swap the antenna cables at the radios and see if there is any change.

The GTN install manual explains how and what the squelch setting do, see page 6-43 for more info: (a "noisy" aircraft for example can effect sq operation).

COM Squelch Functionality
The GTN Xi COM receiver squelch silences the received audio when there is no signal detected above a specific power threshold. RX Squelch is the primary squelch and functions by calculating the ratio of the signal power to the background noise power then compares it to the set threshold. If other aircraft equipment generates noise that consists of pure tones, those tones may be interpreted as signals and used for the calculation. As a result, the squelch breaks when the corresponding channel is selected. In this case, increase the RX squelch percentage or isolate the noise source until the squelch breaks no longer occur.

Carrier Squelch is the secondary squelch and functions by calculating the signal power only and comparing it to the set threshold. If other aircraft equipment is generating noise of a more random nature (wideband), the combined power may cause squelch breaks on many channels. In this case, increase the carrier squelch percentage or isolate the noise source until the squelch breaks no longer occur.
 
Dan,

I suggest you start with the easy stuff:
- Swap antennas between Comm #1 and Comm #2. Easy enough and you can use a length of coax as a jumper if needed.
- Pull the GTR-200 out of the tray - any effect on the 650?
- Don’t get carried away with the whole ground plane thing. This is RF ground, not DC. Typically a star washer under the mounting screw nut is more than enough.
- Coax continuity is a good check - but it does not tell the RF story. For that you need an antenna analyzer. On the continuity check verify center pin to center pin on the coax, shield to shield and no continuity between the center pin and shield. Disconnect the coax before doing this.

Carl
 
Appreciate this.
That extra explanation of the two squelches help. I'll go try to apply this today and see what effects I get.
Yes, I have been staring at the 1003 connector Pin 9. I was shown a screenshot from a TSO install manual that showed that pin 9, but no where shows if I need to connect it. Well, I know that it is NOT connected. So perhaps I am fine. Thank you for explaining this. If I did want to ground it, what you said seems to resonate.
Okay. I will chew on this and see if I can make anything happen today.
Appreciate the focus on the antenna. I fear this is my problem. I fear my ground plane and proximity of the two Coms is my problem. They are 20" apart, mounted a few inches behind the wing spar center box. Not great. and definitely not the 18 sq inches ground plane area that the garmin manual asks for. I really wish today I mounted the two Coms on belly centerline.
* When I only had the gtr 200 com, my reception was FANTASTIC. But just adding this 650xi in May...it is useless and is vastly worse than the 200, and now that install has affected the 200 now. Its like 2 whole steps backwards. Now I don't have either COM working well, when the single one was before.
Darn though I am so very tempted to change out to straight whip antennas...you can tell I am reaching here.
I'll go to work on this.
Thanks. I'll report back if I find anything positive.
 
And thank you Carl. Okay. Will do.
I've made some changes/improvements...so I'll do the Comm swap again. Okay on pulling the gtr 200 out. Didn't think about that. Ok. Will do.
And I will go re check continuity like you spelled out here. I didn't do that check to that detail. This helps. Will do today.
 
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* When I only had the gtr 200 com, my reception was FANTASTIC. But just adding this 650xi in May...it is useless and is vastly worse than the 200, and now that install has affected the 200 now. Its like 2 whole steps backwards. Now I don't have either COM working well, when the single one was before.
Darn though I am so very tempted to change out to straight whip antennas...you can tell I am reaching here.
I'll go to work on this.
Thanks. I'll report back if I find anything positive.

Going to a straight antenna is not the answer. Those two antennas are just too close to each other, and interact in a bad way. Physically remove one antenna, test fly. If the radio with the (one) antenna now works properly, you found the problem. Relocate the other antenna to the top if able, otherwise a lot further back.
 
Going to a straight antenna is not the answer. Those two antennas are just too close to each other, and interact in a bad way. Physically remove one antenna, test fly. If the radio with the (one) antenna now works properly, you found the problem. Relocate the other antenna to the top if able, otherwise a lot further back.
I agree with Bob on this. If something doesn't work after you make a change, take the change out and see if the problem goes away. :cool:
 
TX Interlock Inputs

Mr. Carl, Mr. Walt!! Thank you for your help!.
1. I've toyed with the RX Squelch, and Carrier Squelch in the 650xi. I seem to not "hear" its affect whether at "0" or at "100". Still trying to understand these settings and effects. Yes, RG400. I've not checked Ohms resistance. Guess I need to do this. I've done the typical Continuity check after crimping, but you have a point I need to look at for ground plane resistance. Interesting.

2. Appreciate hearing it likely may not be worth spending another $400 to change out my Rami bent whips for Straights. I have the ground clearance. Just wondered. Thanks. HOWEVER, I have been trying multiple times to get a straight brass tacks answer to this whole "desensitivity" function you mention. I have read about that. But asking questions to the almighty maker of this **** 650xi, I can't get an answer if I need the TX Interlock or any other wiring. I'm trying to get tribal wisdom on this. GTR200 calls for it. But "they" say the new 650xi units have it built in. Still, it seems like I can't get clear direction for my combo of 650xi -> gma 245R -> gtr 200. But Carl you might be on to something, I just don't know which wire or connections or where or how to affect this...properly.

Thank you for responding you two. I'm desperate for tribal wisdom. Info is NOT in the manuals. I don't have anything good to say about this 650xi, but I have been schooled to keep my mouth shut. So the verdict is still out. Would love to be proven otherwise.

Here are a couple of relevant excerpts from the GTR 200 Installation Manual:

  • The antenna should be mounted a minimum of six feet from any DME or other COM antennas.
  • If simultaneous use of two COM transceivers is desired (split-COM or simul-comm), the COM antennas should be spaced for maximum isolation. A configuration of one topside antenna and one bottom side antenna is recommended.
  • CAUTION - If the COM antennas are mounted less than six feet apart with a direct line of sight between the antennas the non-transmitting radio could be damaged when the other radio transmits. An example of direct line of sight is both antennas mounted on the bottom or top surface of the aircraft. For metallic aircraft one antenna should be mounted on the bottom close to the front and the other on the top of the aircraft close to the tail such that the aircraft structure is between the two antennas. For composite aircraft additional shielding may be needed between top and bottom mounted COM antennas.

All that being said, these radios are being installed in smaller aircraft where such separation may be difficult to achieve. For that reason, the transmit interlock input should be used to mitigate any issues that can be caused by a marginal antenna installation. When active, the transmit interlock input ‘desenses’ the GTR 200/200B receiver when another communications radio is transmitting. This protects the COM receiver hardware from exposure to the adjacent transmitting radio.

As to the question of whether you need the transmit interlock connection, here are some excerpts from the relevant manuals:

  • From page 2-3 of the GTR 200 Installation Manual: "The GTR 200/200B requires a transmit interlock"
  • From page 3-9 of the GTN Xi Installation Manual: "The GTN does not require a transmit interlock, but other COM radios such as the GNS 430W may require it for split-COM operations."

The GTR explicitly calls this connection out as a requirement. The GTN Xi does not, but defers to the requirements of other COM radios, like the GNS 430W. Since the GTR 200 also specifically calls for this connection as a requirement, you would want to make this connection with the GTN Xi.

Thanks,

Justin
 
too close

Let me agree with what Bob, mothership and others have said re antenna separation. On Cessna factory antennas I have measured (Bird thruline) 3 watts into one radio from the OTHER 10 watt unit. And that distance is 4 or 5 feet, not 24 inches. I bet damage from too close comm antennas is likely not rare.

Put one on the top, one on the bottom.

An additional effect of inadequate separation will be antenna pattern distortion with nulls on some freqs in some directions making a less reliable system. Two same band antennas in the near field of each other can couple energy much stronger than the eyeball suggests.

Ron
 
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A lot of good discussion about the xmit interlock. The original post was a receive problem and there is no interlock active on receive. I’m very curious if the problem moved to the other side when the antenna connections were switched. Is it the antenna or the radio? Does the problem clear entirely with antennas swapped?


Can the OP say what’s different now?
 
Update

Posting an update here, in helpful spirit, in response the likewise help those of you that have shared. Thx!
The popping feedback problem is fixed. However the range issue of only the 650xi's Com is NOT fixed yet.
1. The popping feedback, after 4 months of painful effort, is finally fixed. The smoking gun found was discovered when very methodically doing ground runup - "mag" checks. 4 months ago when I supposedly so called "finished" this IFR upgrade, at that time I also changed all spark plugs. Unrelated but simply it was time. Last week I pulled all spark plugs, noticed some spark residue and visual defects on the 'tips" where the boots connect that seemed alarming, most of which I can reasonably attribute to the type of spark plugs....the ones I put in had the screw-on tips. Long story short NAPA did an order switch-a-roo on me back in May and did not say anything. I did notice it right away then, but in naivety I very gently squeezed the screw on tips in effort to make them secure. Order receipt from NAPA confirms they sent the non-solid tip version instead. Anyways, not important. But bottomline is now I instaled the "Solid Tip" spark plugs, AND quadruply ensured this time the plug cable boots positively clicked into place and the boot was positively squeezed down on entirely. Result, the Right Side Mag that caused the Popping, is no longer now.
Lessons learned and case closed.

2. However the range reception is still 1/3rd of the GTR200 Com's range. So this week I am trying to tackle this. Wednesday I have an appointment at a Garmin avionics shop to help me check the VSWR.

Lastly, I have acted upon much of the advice here from Walt, Carl, Justin, and Bob. Or at least gave serious consideration. So thank you! Your help (street smarts / tribal wisdom) is a big deal. That said:
A.) I HAVE swapped antennas. 4 times. None of those swaps did the problem follow. During all 4 antenna swaps, everything continues to point to the 650xi as suspect.
B.)Last week after finding the Right EMag as the source of popping, I did try to isolate by removing the Antenna physically off the airplane belly. I even pulled the GTR200 out of its rack. During flight test I furthermore tested power Off and On of that circuit, additionally I slide the gtr200 back in and powered it On and back Off, all the while testing range reception of the 650xi's Com(1). Still yet the range is barely 30nm but really just 15mn reliably.

In comparison, this Saturday I reinstalled the 2nd antenna, reinstalled the GTR200, multiple checks I can consistently and reliably and predictably pick up both WX and comms throughout the entire bandwidth from 118 to 132 at MORE than 92 miles out.

This is where I am at today. See if I can get a 2nd win this week.
 
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Those two antennas are just too close to each other, and interact in a bad way. Physically remove one antenna, test fly. If the radio with the (one) antenna now works properly, you found the problem. Relocate the other antenna to the top if able, otherwise a lot further back.
Did you physically remove, not just disconnect, the GTR200 antenna and do a test flight as Bob recommended? This will confirm/eliminate an antenna proximity issue before attempting something else.
 
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One key point not discussed. Antenna proximity to another antenna, unless inches away, how close will have not practical effect on reception. As the problem here is reception when both radios are in the receive mode, antenna separation is not the problem.

I’ve flown with two belly bent whip antennas on three RVs, spacing between 20” and 30”. Never a problem even when transmitting on one while receiving on the other. The caveat however is your experience will also be dependent on your choice of radios.

Curious - the only hard antenna problem I had was on the 90 degree connector I used for the GTN-650 BNC connector at the radio. The problem was found when ringing out the coax and wingtip antenna as a system. The problem was I left a small “spike” on the center connector to coax solder joint. When the protective cap was installed the spike shorted to ground. 20 seconds with a soldering iron and all was well. You’d think with more than 50 years of making antennas and coax runs I’d know better. This proves the point of always ringing out antenna systems with the right instruments.

Ground plane. Don’t get wrap around this dimension. There is no rule the ground plane must be a perfect circle. Just look at helicopter comm antennas mounted out on the tail boom. The antenna is looking for a counterpoise, not a ground plane. Again on a well instrumented antenna range you can measure the difference in radiation patterns between size and dimensions of counterpoise installs. But for our need this is in the grass.

Last recommendation - any chance you can swap out the 650 with someone else's radio?

Carl
 
As I posted:
Did you physically remove, not just disconnect, the GTR200 antenna and do a test flight as Bob recommended? This will confirm/eliminate an antenna proximity issue before attempting something else.

Systematic troubleshooting, to fix anything, requires one step at a time. :cool:
 
Galin, Carl,
1. Yes I physically removed the antenna totally off the airplane. This action made the gtn 650xi radio Com-1 as the only Com and Com antenna.
No change.
2.Carl, no I have not had that opportunity yet of borrowing to swap out 650 units. Tomorrow (wednesday) I am supposed to have an appointment at a Garmin avionics shop. So we will see what they find out.
 
A lot of good discussion about the xmit interlock. The original post was a receive problem and there is no interlock active on receive. I’m very curious if the problem moved to the other side when the antenna connections were switched. Is it the antenna or the radio? Does the problem clear entirely with antennas swapped?


Can the OP say what’s different now?

I was hoping the original poster would have replied too perhaps with a finding.
But as for me, 1. No the 1/3rd range issue of the gtn 650xi did NOT move any of the times I swapped antenna coax connections. 2. No the problem does NOT clear up with swapping antennas, ...furthermore when I totaly removed the 2nd Com, the gtr 200 out of its rack, pulled its breaker, AND removed its antenna from the plane, it did not change.
 
Sounds like you have an issue with the GTN650. Either that or you have an exceptionally good GTR200 and a slightly below average GTN650.

:confused:
 
I would have suggested removing the gtn antenna, entirely, and see if the GTR returns to its previous good performance. If no then likely its ‘front end’ was damaged by overload.
 
I would have suggested removing the gtn antenna, entirely, and see if the GTR returns to its previous good performance. If no then likely its ‘front end’ was damaged by overload.

I appreciate your thinking.
Sorry. Much of this is hard to explain, chronologically and or what not. But the GTR 200 Com-2 has always been fine (great) on range of reception. Only issue was the popping, but last week found that out to be the ill spark plugs with screw tops, and maybe possibly ill pushed on plug wire boots. But anyways, the popping root cause has been found and fixed. Both radios are finally "popping" free.

However, I appreciate what you are eluding to with the "damaged front end".
Right now I am waiting for a reply from Garmin on how the heck to do the connections for the transmit interlock that they and another person directed me to connect. Problem is there are ZERO drawings that speak anything remotely related to the 650xi to the gma245R audio p, and the gtr 200. I possibly deduced the wiring, but not going into the bowels of 7th level of **** of removing the panel to add & pin those wires until someone of authority and experience gives instruction or validates my wiring interconnect sketch, or better yet Garmin addresses something of the like.
I've had the entire panel out of this 8 three times now. Just not going back in to the **** of this panel until I get a proven solution.
 
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Straightforward: run a single wire from the ‘interlock’ pin on the GTN to the push to talk wire going into the GTR. When the PTT line goes to ground, the GTR can transmit and the GTN will have reduced sensitivity.
I wonder if the gtn interlock pin is accidentally grounded?
 
Wiring Guidance

I appreciate your thinking.
Sorry. Much of this is hard to explain, chronologically and or what not. But the GTR 200 Com-2 has always been fine (great) on range of reception. Only issue was the popping, but last week found that out to be the ill spark plugs with screw tops, and maybe possibly ill pushed on plug wire boots. But anyways, the popping root cause has been found and fixed. Both radios are finally "popping" free.

However, I appreciate what you are eluding to with the "damaged front end".
Right now I am waiting for a reply from Garmin on how the heck to do the connections for the transmit interlock that they and another person directed me to connect. Problem is there are ZERO drawings that speak anything remotely related to the 650xi to the gma245R audio p, and the gtr 200. I possibly deduced the wiring, but not going into the bowels of 7th level of **** of removing the panel to add & pin those wires until someone of authority and experience gives instruction or validates my wiring interconnect sketch, or better yet Garmin addresses something of the like.
I've had the entire panel out of this 8 three times now. Just not going back in to the **** of this panel until I get a proven solution.

Both your GTR 200 and GTN 650Xi have an interlock input. When this input is active, the receiver in desensitized. You want to desensitize a radio's receiver when the adjacent radio is transmitting, so you connect the transmit interlock input of either radio to the mic key of the adjacent radio.

Page 25-6 of the AU revision of the G3X Touch Installation Manual includes an example of how this is accomplished for a GNS 430. In this example, the Com 1 Mic Key Output from the audio panel is wired to both the Mic Key input of the GNS 430 (to activate the transmitter on the GNS 430) and the transmit interlock input of the GTR 200 (to desensitize the GTR 200 receiver). In your installation, you will need to splice into the wire for the mic key input of the GTN 650 Xi (GTN 650 Xi - pin 11 on P1003) to create a parallel connection to the GTR 200's Interlock Input (GTR 200 - pin 5 on P2001).

To simplify things a little bit, the GTR 200 radio has both and transmit interlock input and output. The transmit interlock output can be used in place of tying into the adjacent radio's mic key input. The transmit interlock output from the GTR 200 (GTR 200 - pin 4 on P2001) is connected directly to the transmit interlock input of the GTN 650 Xi (GTN 650 Xi - pin 9 on P1003).

Thanks,

Justin
 
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I was hoping the original poster would have replied too perhaps with a finding.
But as for me, 1. No the 1/3rd range issue of the gtn 650xi did NOT move any of the times I swapped antenna coax connections. 2. No the problem does NOT clear up with swapping antennas, ...furthermore when I totaly removed the 2nd Com, the gtr 200 out of its rack, pulled its breaker, AND removed its antenna from the plane, it did not change.

Check the squelch settings. I had the same problem. To ident the problem in my plane, I hit the knob button on the upper left to activate open squelch and I could hear the radio transmissions. I didn't realize I had a problem until I'd get a handoff and checkin with a new approach controller and didn't hear anything back. So I narrowed the problem down to squelch.

The Xi appears to have a default squelch of like 57%... which for most applications is way too high.

Try this:

CONFIG mode
COM
Rx Squelch mode: Basic
Rx Squelch: 15% (down from 57%)

save config, reboot, test fly, report back.
 
BobTurner: No the pin 9 transmit interlock of gtn 650xi is empty, i.e. no pin or wire there.

Justin G3xpert: Thank you! Okay. I see that drawing now of that Rev.AU g3x manual. I was using what looks like the similar drawing from the gtr 200 manual. Appreciate you looking at this. I did not understand that the transmit interlock OUT could be used in place of... Okay. I will go pull the panel and run these wires now. I was confused because I had a photo of a drawing from a TSO version 650xi install manual page 11-32 that stumped me on a connection between that pin 9 and a pin 30 of audio panel. I am going to ignore that. I'll follow what you said here.
THANK YOU for looking into this and responding.

NTex, I have already worked with those squelch settings for both ends of the ranges, with no improvement, but thanks for sharing....I will write these settings down and apply them as needed to see if any help as well.
 
back to the drawing board.

Update: Last week before leaving for a long flight, I was able to get the Transmit Interlock connections done between the gtn 650xi and the GTR 200. Pin11 to Pin5, and Pin9 to Pin4, respectively for both wires. (I just ran a 2 wire shielded pair between the two units, terminated the shield to back-shell & ONLY at one end: at the GTR 200.
Results, no change. Unfortunately. The 650xi's COM-1 is still working, i.e. TX seems to be fine (honestly I have not tested how far out a tower can hear me), but RX is still the same terrible range of reception. I don't receive anything until approximately 15-ish Nmiles away. Still yet the gtr 200 has fantastic range.

This week I am buying a antenna SWR meter to find out what my VSWR. (can't seem to get into a shop). And one shop is directing me to change the RX Squelch to ADVANCED, and adjust the Low Med and High of the 25khz and 8.33kHz. settings.
Will go up today for some test flights to see if any changes. I have zero high expectations for any of this.
Also, will keep trying to get into an avionics shop somewhere. This is annoying it is this hard finding someone willing and able to work on an experimental and reasonably soon.

Fingers crossed.
 
Too bad you're not closer, we're equipped to do both VSWR and receiver sensitivity testing with some really nice test equipment.
Folks underestimate the value of a local resource when building a panel.
(I also have a 650xi in stock.)
 

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..."Folks underestimate the value of a local resource when building a panel. ", Right On about that one!
I might take you up on this. Will see how this battle plays out here. I go to Tulsa periodically anyways. Its not out of my scope to pop down your way. Appreciate your feed backs for sure.
 
Agree with Walt here. This is EAB, working out problems is supposed to be fun. But if it becomes not fun, time to call in a pro.
One more suggestion: do you know anyone with a known good 650, who would let you swap it into your panel? This would quickly localize the problem to either your antenna/coax/connectors, or the 650 itself.
 
Hey Dan, any update to your reception issue? I am having the exact same problem w/ my Garmin SL40 and about to start the troubleshooting process.
 
Nope, No improvement with the gtn 650xi's Com.

Hey Dan, any update to your reception issue? I am having the exact same problem w/ my Garmin SL40 and about to start the troubleshooting process.

Sorry. I've not been on here in a while. I have given up. No, this gtn 650xi's Com still sucks. I don't even use this "gosh darn" $14,000 gtn 650xi. Not happy about it. But I can't find an issue.
1. I did buy a Nano Antenna analyzer. I have not checked the antennas, cause I am so frustrated: pulling everything out and pulling that floor up. I just don't have the energy for it right now. I highly doubt it is that. I have started looking at other RV-8s when I get a chance and I continue to see similar placements under the belly. Anyways, still need to see what the vswr is.
2. I have had the panel entirely out of the plane a half dozen times. I have pin checked all D-sub connectors and wiring more times than fingers on my hands.
Unless someone gives me something specific to check that I have not, then I am not going back into the panel.
3. A neighbor friend repeatedly tells me he thinks I have an issue with the audio panel. I have the GMA 245R. But I have no idea or clue how to check or troublshooot the audio panel.

So, no good progress. As of today I absolutely hate the gtn 650xi. The Com issue with it is still a flippin problem. Not a happy garmin customer at all right now.

Frustrated.
Dan
 
Sorry. I've not been on here in a while. I have given up. No, this gtn 650xi's Com still sucks. I don't even use this "gosh darn" $14,000 gtn 650xi. Not happy about it. But I can't find an issue.
1. I did buy a Nano Antenna analyzer. I have not checked the antennas, cause I am so frustrated: pulling everything out and pulling that floor up. I just don't have the energy for it right now. I highly doubt it is that. I have started looking at other RV-8s when I get a chance and I continue to see similar placements under the belly. Anyways, still need to see what the vswr is.
2. I have had the panel entirely out of the plane a half dozen times. I have pin checked all D-sub connectors and wiring more times than fingers on my hands.
Unless someone gives me something specific to check that I have not, then I am not going back into the panel.
3. A neighbor friend repeatedly tells me he thinks I have an issue with the audio panel. I have the GMA 245R. But I have no idea or clue how to check or troublshooot the audio panel.

So, no good progress. As of today I absolutely hate the gtn 650xi. The Com issue with it is still a flippin problem. Not a happy garmin customer at all right now.

Frustrated.
Dan

My .02 is find someone on your field, EAA chapter,… that has the 650 or the 245 and swap for a flight. Does the issue follow the gear. There may be radios that are slide in replacements to the 650 slot that you can test with as well.
 
Since transmit is okay I doubt the antenna is the issue. To check the audio panel, pull the connector off the back (look for bent pins), pull two pins swapping the #1 com audio in with the #2 com audio in. If the problem now is the formerly good radio you know the problem is in the audio panel. The easiest check is still to find a loaner 650 and swap it in for yours.
 
Trying to perform null aural ELT localization in a training mission for search and rescue, I have to say it is a lot more difficult with a GTN 750 than anything else I worked with. Seems there is some sort of auto squelch that makes reception sensitivity very low and not always the same. With squelch off, we lose ELT signal more than 10NM from the source. With squelch activated, range is only about 1 to 2 miles when at 1000 feet and it varies too much. From 2000 feet, range is …. Lower instead of higher. At 6000 feet, ELT signal cannot be heard with squelch activated.

That to say I would look into squelch settings for this issue.
 
In the last week I have dove back into this finally with this new year and a new attitude. It seems like this last Saturday I got a little bit of a win. I still have one or two electrical gremlins. But in the 650xi's config, in the Com Settings, I changed the RX Squelch Setting to "Advanced". This opened up not just 3 but actually 6 settings, a Low, Med, and High for the radio bandwidth. ALSO, I just noticed for which I think might have been some of the issue, that there was also the "Carrier" squelch settings if you scrolled down in that new advanced menu! I did not see those until this trouble shoot time. Meaning those 3 Carrier settings likewise as the RX Squelch. Prior to now, I had changed the RX up to 95%. The Carrier was still at the garmin default of 57%. I dropped all 3 settings of both groups down to 5 %. In the last two days of test flying, settling frequencies one-to-one on each Com, the result now seems to be now that I have the same RX range, as well as the TX ranges. Also, today I called a Center that was 100nm away, result was both the GTR200 and the GTN650xi received seemingly equally good, and clarity report back was 5/5 clarity.
Honestly I have changed so damn much; Rx squelch setting up n down, and changed out a couple wires, and fixed a ground that I yanked out fumbling with this crap, plus there is more, and again so many config settings changes, that I don't know what is the smoking gun here. I suspect this recent change that worked is either the Carrier Squelch, OR the RX Squelch.... because I changed all these down and to be the same prior to the last two recent flights....I just don't know which was the fix. But one or both of those did some sort of improvement.
Still doing more testing, but right now I am at least CONSIDERING going back to using the gtn 650xi, and its Com as my primary Com1. Verdict is still out. Still fighting another gremlin, 4 weeks ago was flying an ILS and my audio panel went nuts and shut off. At home I checked all wiring, and found nothing. This has not reoccured. I roll my eyes in frustration, but I guess we will see how this plays out.

Summary, what I can figure out is now, at least it seems, that the 650xi's Com settings need to be in Advanced, and ALL 6 settings need to be set all at 5 %.
 
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Check the squelch settings. I had the same problem. To ident the problem in my plane, I hit the knob button on the upper left to activate open squelch and I could hear the radio transmissions. I didn't realize I had a problem until I'd get a handoff and checkin with a new approach controller and didn't hear anything back. So I narrowed the problem down to squelch.

The Xi appears to have a default squelch of like 57%... which for most applications is way too high.

Try this:

CONFIG mode
COM
Rx Squelch mode: Basic
Rx Squelch: 15% (down from 57%)

save config, reboot, test fly, report back.
Glad you got it fixed.

I think what was posted a few months ago would have worked. Advanced squelch can come with other issues too.
 
Glad you got it fixed.

I think what was posted a few months ago would have worked. Advanced squelch can come with other issues too.
I must admit in all fairness that you are absolutely correct. Both your reply, and a reply from Walt. The common denominator here is I am a complete electrical idiot. And should never have done this IFR avionics upgrade. I do owe thanks to you for your help. After the earlier replies I just still was fuzzy minded in that I still did not quite understand what you and Walt were trying to tell me. To be frank... I still even yet today don't quite understand the difference between the RX vs Carrier, or how to cause and effect trouble shoot from symptoms. But in the end here I do owe you and Walt and Mr Bob Turner thank you's. Not much else I can say.
 
I must admit in all fairness that you are absolutely correct. Both your reply, and a reply from Walt. The common denominator here is I am a complete electrical idiot. And should never have done this IFR avionics upgrade. I do owe thanks to you for your help. After the earlier replies I just still was fuzzy minded in that I still did not quite understand what you and Walt were trying to tell me. To be frank... I still even yet today don't quite understand the difference between the RX vs Carrier, or how to cause and effect trouble shoot from symptoms. But in the end here I do owe you and Walt and Mr Bob Turner thank you's. Not much else I can say.
No worries at all. I think Garmin has a problem with the default squelch settings on the Xi series radios.

I'd double the advanced settings though, and restore them to defaults.

Just the basic squelch should do the trick...start at 15% and work your way down 1-2% at a time until it's acceptable. I think zeroing out every setting might have some issues of their own . Glad you solved the problem though, I know how frustrating it can be to have high $$$ equipment not performing as specifies.
 
Just a note...... You have two antennas mounted 25 inches apart which happens to be 1/4 wavelength at 120Mhhz.
I think you made a two element Yagi. Hmmmm
 
No worries at all. I think Garmin has a problem with the default squelch settings on the Xi series radios.

I'd double the advanced settings though, and restore them to defaults.

Just the basic squelch should do the trick...start at 15% and work your way down 1-2% at a time until it's acceptable. I think zeroing out every setting might have some issues of their own . Glad you solved the problem though, I know how frustrating it can be to have high $$$ equipment not performing as specifies.
"double the advanced settings though, and restore them to defaults.". Humm? Now I am really confused. Humm? I will ponder this. But Umm....I really don't know about this.... I think I see what you are saying but..... Humm. K. I will think about this. Not sure I quite follow.
 
Just a note...... You have two antennas mounted 25 inches apart which happens to be 1/4 wavelength at 120Mhhz.
I think you made a two element Yagi. Hmmmm
Yeah well I'm not the only one doing this. And I see it on airplanes at nearly every fly-in I go to.I mean seriously, this is like the first or second thing my eyes look for on EVERY airplane now. Plus I checked with 3...yes I queried three, professional shops about this....all 3 said, after I explained my symptoms, it is not a problem. So my hands are in the air on this one.
 
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"double the advanced settings though, and restore them to defaults.". Humm? Now I am really confused. Humm? I will ponder this. But Umm....I really don't know about this.... I think I see what you are saying but..... Humm. K. I will think about this. Not sure I quite follow.
That's what I get for typing on my phone, apologies.

I meant to say restore the advanced settings to default, but only manipulate the basic squelch as outlined above.

Cheers
 
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