GNS 530W Com issues

[Stan]

Need some Com advice:  I have a 1989 201 with the Com 1 being a GNS 530W.

It was in to Garmin twice this year:  1^st being a clicking/tapping issue that got progressively louder as the unit warmed (fixed).  Then the 2^nd being a com board replacement for this ongoing issue:

I have transmission / receiving issues talking to anyone over approx. 5 miles.  This began in 01/20 after the unit came back from Garmin for the 1^st issue.  As an example; I had/have problems over Warrenton, VA., calling Potomac Approach (PA), heading inbound to KHEF (Manassas, VA.).  (This is the Washington DC Special Flight Restricted Airspace)  I sometimes can hear them (sometime garbled) but they cannot hear me.  Warrenton to KHEF 12 miles, Warrenton to PA antenna is approx., 25 miles (I called PA to find out where their antenna was located). This also continues inbound as I tried the HEF tower from about the 5 mile point and the tower could not hear my transmission. My Com 2, a KX155 works fine. 

We switched antennas, still an issue, metered the power (probably wrong terminology), still an issue, moved a Stratus 3 and associated USB power cable off the panel, still an issue.  Finally sent it back to Garmin, and they replaced the com board.  Installed it yesterday and flew this morning, it worked fine on the ground and in the air, when told to contact PA outbound, they (PA) answered my initial call but they were weak and garbled (PA antenna at that point is approx., 15 miles).  They did not answer any repeated calls.  I switched to com 2, again with no issues.

I can live with it temporarily, however after troubleshooting and sending it back to Garmin, it is very frustrating.  Anyone have any thoughts?

[chriscalandro]

Swap it for the Avidyne slide in replacement.

[Jerry 5TJ]

Since #2 radio is good I wouldn't mess with it, not even for troubleshooting purposes.

It is possible there are coax and/or coax connector issues with the 530. 

The antenna connectors for the Garmin 530 antennas are type BNC female.  There are four of them.

Make sure that the com and nav and glideslope (g/s) connectors have not been swapped.  

If someone has confused them that could ruin the comm performance.

If that's not it, then carefully measure the comm antenna coaxial cable performance. 

[MB65E]

Similar issue with my 530w. I primarily use my 155 if I want to talk with someone. I can receive fine on the 530 clearly but transmitting produces a really strange side tone after the mic is depressed over 3 seconds. 
Interested in your findings!

I have swapped antennas and coax cables with no improvement. 

-Matt

 

[Stan]

Jerry,

That makes sense, as I had an Electronics International CGR-30 installed then all this started.

The 530 was out for service (issue #1) and the back of the 530 tray was moved around and they may have been swapped.

Also yesterday during he install (or reinstall #2) the tech said the glide slope indicator was slow or hesitant to come down on the HSI.

Thanks, appreciate the tips, will follow up when we address this.

[carusoam]

See if @Alan Fox has any insight..?  (Garmin radio age challenge)

Best regards,

-a-

[jamesm]

The weak part of the transmission, Could it be the the com "mic gain" setting?  providing that this is not  a new issue and didn't happen during a  new installation. 

I don't  know if GNS series  uses  there mechanical  adjustment for the mic gain setting later models have the mic gain controlled through software. Also  the newer unit use configuration module not part of the unit (it's located in the connector back shell) to  the keep settings. So in theory  you could switch them out between airplanes with out having to reconfigure them every time. at least that is my understanding. though I am not too sure how Garmin has done this in the GNS series. But in the GNC355 (GPS/COM) it is user  settable .

The problem that  I have been having is that the GNC355 is weak transmission  (it usually only one  tower controller that lets me know). the other problem is that it wouldn't retain the mic and some of the audio settings but the other setting were fine. I go into settings menu and  change the  mic gain settings to -6db  . Anything mic gain setting above 0db I would be  a little  leery.   I would suspect you start getting feed back with a mic gain above 0db  which is not good.

  It seems weird though  my other radio GNC255 (Nav/Com)  has it mic gain  set at -12db never has a problem with that mic gain setting.   Avionics guy told the -12db for mic gain is  what they set it for when they do installations.  

Hope this helps.

Good luck.

James '67C

[Stan]

Jerry,

Again thanks for the advice.  It does go 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 is 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.  Works as it should now. 

Sorry for the delay in the follow up.

[jlunseth]

Some unexpected things to think of. The older Garmin GNS series came in 28 volt and sometimes the installer had to use a converter to step the current down. Some of the converters would take awhile to “reload,” in other words a first transmission would be fine, or a first part of a transmission, but then the converter could not supply power and the later part would be bad. Needs a different converter that does not fade.

Pull all the portable charging devices and try it, see if any of them are causing interference.

I have perennially had trouble with the ability of my 430AW to receive, and it is an AW, 16 watt transmitter (obviously, that is outgoing power not receiving, but you would think the radio quality would be higher than the standard unit, its not). Had it back to Garmim a couple of times early on, and got a substitute unit at one point. I have an old King, don’t even remember the model number, that is my go to. 

I am planning on adding a GTN750Xi to the panel, keeping the 430AW and getting rid of some older stuff, including that King. But I have some serious concerns about the quality of the Garmin radios and I keep hearing about these issues. Gives me pause. I have the most trouble out in the west where transmitters are far apart, especially if there is weather, and especially at very low or very high altitudes.