GNS-530W NAVCOM Troubleshooting

[FLYFST]

Anyone out there with experience troubleshooting NAV/COMM radio issues with the GNS-530W and willing to provide troubleshooting advice?  I am experiencing some problems with my installation and want to troubleshoot as much as I can before handing over to avionics shop.

thanks in advance - Hank

[MB65E]

What issues are you having?

-Matt

[FLYFST]

Issue is with reception on NAV #1 (low to poor) compared to NAV #2 (good) on KX-155.  Doing air-to-air checks between them at ~20 NM yields a difference of ~2 degree, after confirming I can hear the identifier on both.  However, on some larger distances < 40NM and above minimum reception altitude, I do not get the audio identifier on Nav #1 but the station ID, radial and distance show on the GNS-350 VLOC window.  Sometimes I do not get the NAV flags on NAV #1 and the correct ID shows on the GNS-530, but I can tell it is just not tracking the signal as in trying to intercept or follow a victor airway.  Nav #2 generally identifies the station at the same conditions, I can hear the station audio ID tones, and works correctly.

[Htmlkid]

Anyone have a trick for sticky buttons on the 530 vs sending it to Garmin for $1200

[squeaky.stow]

@Bob Weber is worth a call. He has twice saved me a lot of money by helping me determine that a major problem was actually a minor one and easy to fix in-house. 

webairconsulting.com. 

 

[FLYFST]

[mention=17747]Bob Weber[/mention] is worth a call. He has twice saved me a lot of money by helping me determine that a major problem was actually a minor one and easy to fix in-house. 
webairconsulting.com. 
 

Thanks, I will


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[takair]

If I read this right, your 530 has inferior performance as compared to the 155?  Do you have blade antennas on the tail?  Did the issue start suddenly or degrade over time?  Simple starting point might be swapping the Coax on the antenna duplexer and see if the problem changes sides.  Other things to look for is degraded coax connections, including on the back of the rack.

[FLYFST]

If I read this right, your 530 has inferior performance as compared to the 155?  Do you have blade antennas on the tail?  Did the issue start suddenly or degrade over time?  Simple starting point might be swapping the Coax on the antenna duplexer and see if the problem changes sides.  Other things to look for is degraded coax connections, including on the back of the rack.

Yes I have blade antennas and the issue has been developing over time. Baker Avionics also suggested swapping the coax to see if the issue moves to Nav #2. Thanks for the suggestion! Where should I expect to find the antenna duplexer? By the GNS or in the tail close to the antennas?


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[takair]

Just now, FLYFST said:

Yes I have blade antennas and the issue has been developing over time. Baker Avionics also suggested swapping the coax to see if the issue moves to Nav #2. Thanks for the suggestion! Where should I expect to find the antenna duplexer? By the GNS or in the tail close to the antennas?


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Tough call.  Likely near the front, behind the panel, so that they don’t have to run dual coax the length of the plane. Been a long time since I was behind the panel of a J.  

[FLYFST]

Tough call.  Likely near the front, behind the panel, so that they don’t have to run dual coax the length of the plane. Been a long time since I was behind the panel of a J.  

Thanks will look there first. That is one cramped space in the J.


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[carusoam]

Before throwing in the towel and going to the shop...

Expect light corrosion can always be an issue...

Cleaning connections to the antenna and wires along the way...

Ground planes can get really crummy over time...

Which antenna is on top, which is on the bottom.... and where the diplexer is.... often  a tail mounted device.  Do a search around here there will be pics....

If you can find the problem, you can save a lot of time that the shop will be doing...

You get to learn your plane once.... a good value...

When the shop is done, they probably won’t remember your bird for very long....

PP thoughts only, not a mechanic...

Best regards,

-a-

[FLYFST]

Thank you! I plan to start the research this weekend.


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[Bob Weber]

1. Rebond the NAV antennas. Inspect the coax, probably RG 58. I generally found the "diplexer" for a blade or "towel bar" array in the tail. We would then use a splitter behind the panel to feed the NAV/GS inputs. I can guide you here if you would like 616 822 1999

[FLYFST]

Thanks for reaching out Bob, I will give you a call later today to discuss further, after 1430 EST if you are available.  I just flew a couple of short flights to collect more troubleshooting data and my results appear to be inconclusive. 

[FLYFST]

1 hour ago, FLYFST said:

Troubleshooting update.

Acting on the advise of Baker Avionics and Takair, thanks to both, I swapped the Nav #1 and Nav #2 coax cables coming out of the Comant CI-505 coupler in the instruments panel near the NAVCOMs and flew a quick check flight.   The problem DID NOT move to Nav #2 which was one possibility, but the reception on NAV #1 did improve some.  NAV #1 (GNS-530W) was able to provide station ID and NAV guidance to a station 57.5 NM away, but that was not as consistent as the guidance from NAV #2 (KX-155).  Next troubleshooting step is to follow the suggestions of Carusoam and Bob Weaver (thanks to both) and clean the multiple coax cable connectors in the cockpit and empennage, as well as checking for corrosion and cleaning the connections of the blade antennas to the vertical tail.  I found the antenna diplexer located in the lower empennage, below the horizontal stabilizer and appears to be the original 1990 installation.

I'm searching for and hope someone can provide pictures (or where to find them) of how the two blade antennas mount on the vertical tail so I have a reference to reinstall them; there is nothing in the IPC or Maintenance Manual.  They have no external markings, so I am assuming the P/N and M/N will be somewhere on the base of the antenna and visible after removing them, but they look identical to these:

https://www.aircraftspruce.com/catalog/avpages/120200gsl.php

 

 

[Stan]

Don't want to muddy the waters, but I a similar issue, except it was on the Com side.

Can read the post and maybe it will be of some help.

GNS 530W Com issues

My Com issue went back to when I had an Electronics International CGR-30 installed.  

Found the GNS530 Nav and Com antenna cables switched. The GPS and G/S cables are ok. The Nav antenna cable was reconnected correctly.

The Com1 Coax was open from the cable to the Antenna. The Com antenna SWR check was good.

Suspect bad cable or loose connection behind the panel.  A new cable was fabricated from the back of the 530 to the pigtail. 

Hope all goes well and from the replies your on track, for me it was rather (no VERY) frustrating, swapped antennas, looked for corrosion issues, tracking coax, etc.  Works as it should now. 

 

 

[FLYFST]

Don't want to muddy the waters, but I a similar issue, except it was on the Com side.
Can read the post and maybe it will be of some help.

GNS 530W Com issues

My Com issue went back to when I had an Electronics International CGR-30 installed.  
Found the GNS530 Nav and Com antenna cables switched. The GPS and G/S cables are ok. The Nav antenna cable was reconnected correctly.

Thanks Stan, interesting read and I’m glad you solved your problem.

My Nav #1 problem has developed over time and I cannot trace its origin back to any maintenance event, so the most likely cause appears to be corrosion developing in the connectors, antennas, diplexer or power combiner. I am working my way slowly and eliminating components before giving up and taking to an avionics shop.

One new thing I noticed today is that the reception on Nav #1 seems worse when flying away from a distant VOR and stronger when flying to the VOR. The KX-155 Nav #2 works well in both directions.

All the best - Hank


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[jaylw314]

Have you tried removing and reseating the 530W unit in the rack?  I was having NAV reception issues, and when the avionics shop pulled it out (for something else), they found a piece of wire lace caught in the antenna plug.  Removing the debris it solved my problem

[philiplane]

corrosion doesn't develop in modern connectors because they are gold plated. Older King radios used tin plated connectors where re-racking the radio would wipe the contacts clean and solve problems. Coax pins & sockets are gold plated, along with everything in the GNS530 rack connections. 

Because your other radio shares the same antenna & connections up to the panel mounted splitter, Odds are the 530 has a weak nav receiver and it will need repair by Garmin.

[FLYFST]

Because your other radio shares the same antenna & connections up to the panel mounted splitter, Odds are the 530 has a weak nav receiver and it will need repair by Garmin.

Yes, sending the unit to Garmin may be in my future, but before committing to that I am investigating other possible sources since the problem has developed over time.

The loss in performance was easy to miss since I normally use NAV #1 in GPS mode and only switch to VLOC for ILS or LOC approaches, and by then the airplane is close to the station. It is only when I try using NAV #1 in VLOC mode to intercept and follow an airway that the problem becomes evident.

Interestingly, the unit does better flying to a station than flying from a station. In recent tests, flying at or above the MRA on the airway, the GNS350 was able to ID and display the station details at 57.5 NM, but without also getting the audio ID the navigation information is simply not reliable.

Thankfully my KC-155 NAV #2 performs well and it drives a second G/S, so I can use it to navigate and fly instrument approaches, just not coupled to the autopilot.

Thanks - Hank


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[carusoam]

Interesting that you can see a difference to vs. from the station...

There is a tail that may be throwing a shadow between the station and the antenna...

I don’t think I know of this shadow effect being very noticeable normally....
 

I stopped using my nav radios for long distances after I found them following the scalloped lines with precision... where the GPS does a very good job flying the magenta line...  
 

Got any pics of your antenna and your tail? Or know which antenna you have?

I think we have a choice of three...

• V
• towl bar
• blade

PP thoughts only, not a CFI....

Best regards,

-a-

[takair]

11 hours ago, FLYFST said:

 

Yes, sending the unit to Garmin may be in my future, but before committing to that I am investigating other possible sources since the problem has developed over time.

The loss in performance was easy to miss since I normally use NAV #1 in GPS mode and only switch to VLOC for ILS or LOC approaches, and by then the airplane is close to the station. It is only when I try using NAV #1 in VLOC mode to intercept and follow an airway that the problem becomes evident.

Interestingly, the unit does better flying to a station than flying from a station. In recent tests, flying at or above the MRA on the airway, the GNS350 was able to ID and display the station details at 57.5 NM, but without also getting the audio ID the navigation information is simply not reliable.

Thankfully my KC-155 NAV #2 performs well and it drives a second G/S, so I can use it to navigate and fly instrument approaches, just not coupled to the autopilot.

Thanks - Hank


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Hank

have you tried a few different VORs?  Try various frequencies to see if it might not be only a single frequency or range of frequencies.  This may then help point at the radio of the install.  Someone mentioned the rack.  There is a ground lug on the back that can be used as a central ground.  I found they degrade over time and found an independent airframe ground is better.  Usually you see audio degradation with that ground failing, but who knows.  Might be another thing for the list.

[FLYFST]

Interesting that you can see a difference to vs. from the station...
There is a tail that may be throwing a shadow between the station and the antenna...
I don’t think I know of this shadow effect being very noticeable normally....
 
I stopped using my nav radios for long distances after I found them following the scalloped lines with precision... where the GPS does a very good job flying the magenta line...  
 
Got any pics of your antenna and your tail? Or know which antenna you have?
I think we have a choice of three...

• V
• towl bar
• blade

PP thoughts only, not a CFI....
Best regards,
-a-

I will be doing more test flying to better document the difference in reception between flying to and from. Like you, I follow the magenta line, but periodically refresh my VOR navigation skills and equipment, which led me to discover all is not well with NAV-1, so now I am investigating to find and resolve.

You asked for some pictures, so here you go. I will not know for sure until I remove the antennas to clean and reestablish the ground plane, but they appear to be Comant CI 120-G/S. The two coax cables from the antenna come together in the lower tail cone at a CI 120-3 Power Combiner. From there a single coax comes into the cockpit and connects to a CI 505 Diplexer, that has two VOR outputs and a G/S output. The G/S cable goes to a splitter, one end to NAV-1 and the other to NAV-2.







The antenna mounting appears well sealed and there is no movement of either antenna. The top of the right antenna started to delaminate approx 7 years ago so I placed some transparent tape on it that has remained there since, and I did not notice any before/after NAV performance change since then. While possible, I doubt the problem is that antenna. When I swapped the diplexer outputs at the cockpit and did a quick flight check, the problem in NAV-1 did not move to NAV-2, which continued to work well, but the NAV-1 reception did improve some.





My hope remains that I will find the problem to be connector corrosion or antenna ground plane problems or both, but expect sending the unit to Garmin may be the eventual fix.


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[FLYFST]

Hank
have you tried a few different VORs?  Try various frequencies to see if it might not be only a single frequency or range of frequencies.  This may then help point at the radio of the install.  Someone mentioned the rack.  There is a ground lug on the back that can be used as a central ground.  I found they degrade over time and found an independent airframe ground is better.  Usually you see audio degradation with that ground failing, but who knows.  Might be another thing for the list.

I have tried three distant VORs, ORL 112.2, CRG 114.5 and MLB 110.0, plus nearby OMN 112.6. No problems with navigation to/from OMN or with performing air-to-air checks, which have remained consistent at 0-2 degrees difference. Navigation reception from ORL 112.2 is worst. Navigation to CRG 114.5 and MLB 110.0 are better, but NAV-2 (KX-155) is always stronger than NAV-1 (GNS530).

One curious and concerning thing is that when using NAV-1, the GNS will ID the station and display the radial and distance. When in the VLOC mode the GNS is driving the HSI and that shows the proper to/from indication, the NAV flag does not show, all of which indicates proper Nav performance. BUT, when far from the station I do not receive the audio ID and without it present, the navigation performance is not reliable or just plain wrong even though the GNS is showing the station identified and the HSI flags are indicating proper operation.

Thanks for suggesting the central ground lug on the back that can degrade over time. I will add that to my to check list.

Thanks again


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[carusoam]

great pics, Hank!
 

What are the lines on the blade antenna?

Is that just dirt on the plastic tape?

Or is the tape holding it together?

I don’t think I have any tape on my leading edges of the same type of antenna...

But, I’m not tall enough to put an eyeball on it either...  

Best regards,

-a-