GTX345 Bluetooth signal - SOLVED

[Lee A.]

So last year had the GTX345R installed in my Acclaim S.  

With 4 people and bags the signal was there but unusable in the pilots seat.  

Solution:

GTX345 has a single vent hole which is also, per Garmin, where the Bluetooth signal escapes the fully shielded LRU box.  A sticker on the unit states to install with the vent hole on top.  However, other Garmin instructions indicate installation with the vent hole on top or bottom is acceptable.  My unit was installed by Hartsell Avionics in Tyler, TX with the hole down.  So no chance of signal escaping.  

 

I will also also state I have factory air conditioning.  

 

Flipping the unit unit over and installing a passive repeater antenna system fixed the signal issue.  Keep in mind flipping the unit over is an extensive job, several hours of labor and reprogramming the unit.  

 

The passive antenna system makes makes no electrical connection with any of the planes systems.  Nor does it use power.  

 

An inexpensive WiFi antenna was secured within 1” of the vent hole to capture signals.  This was connected to low loss transmission cable which was fed behind the trim panels to another antenna near the pilots left hand.  

 

Works great.  We have 4 Bluetooth headsets operating in the plane and now my iPad picks up the GTX345 signal perfectly.  

 

The secret to making Ing a passive repeater work is to keep antennas close as possible.  

[aggiepilot04]

Sounds like somewhat of a hack, but a cheaper hack than buying a FlightStream 210. Thanks for sharing...I may wind up going this route as well.


Sent from my iPhone using Tapatalk

[aggiepilot04]

Did you try either flipping the 345 -OR- running the wire?  Just curious if both are necessary.  And maybe that’s why the plexiglass O2 door has worked for others but not me?  Because maybe others have the unit flipped?

[Lee A.]

Unfortunately I have not had a chance to disable the passive repeater system to determine which of the 2 interventions helped....or both.  

 

Just St glad the thing works finally after paying the money for it and paying TWICE for installation.  

[Lee A.]

Here is the cable and antennas I used.  In my installation I used the 10dbi antenna at the GTX345. 

 

[buddy]

Thanks, I’ve been trying to solve the problem too. I installed the plexiglass O2 door and thought I solved the problem but after one flight I couldn’t connect using my iPad Air 2. I went flying with a friend of mine yesterday and he brought along his mini 2 iPad which is just a little smaller than mine and that connected to my 345R no problem. The next time I’m down at the hangar I will check the location of the vent hole.

[buddy]

I just got back from the hangar and it looks like the vent hole your talking about was installed with the hole down. I’d like to pull the unit out and make sure it has a vent hole on the bottom but not sure how, any ideas?

[Lee A.]

Here are s

[Lee A.]

Here are some photos after installing passive repeater antenna   

[Jeff_S]

Yeah, I have a similar setup in my Ovation with factory A/C. I simply removed the Oxygen access door entirely. It now lives in the seat-back pocket of one of the passenger seats. The signal works fine even with some bags in the back, although if I have full baggage the signal does get blocked. In that case, I simply fire up the portable Stratus 2 that I've had for awhile (belts and suspenders, you know!) and that fills the void.  Much cheaper and easier than rewiring the whole thing.

My A/P was not too concerned about removing the Oxygen access door, but his only thought was that it might allow some carbon monoxide into the cabin. I have a portable CO detector that I activate on every flight, and have never detected anything, so I don't feel this is a problem.

[Txbyker]

I used Buddy’s plexi fix and connect ok.  I thought the antenna is behind the Garmin sticker.  Regardless, it aims for the side of the tail.  If the tray was parallel to the tail perhaps it would work.  

Russ 

[Jerry 5TJ]

Documentation for some other similar Garmin transponders (3X5 for one)  does claim the Bluetooth antenna is under the label.  

As an old RF guy I will opine the signal is not coming through that drain hole — look up “waveguide beyond cutoff” if you’re curious why.  

[PaulM]

On 10/6/2018 at 9:19 PM, Lee A. said:

GTX345 has a single vent hole which is also, per Garmin, where the Bluetooth signal escapes the fully shielded LRU box.

 

7 hours ago, Jerry 5TJ said:

Documentation for some other similar Garmin transponders (3X5 for one)  does claim the Bluetooth antenna is under the label.

Jerry is right,

  Feel under the blue "GARMIN" label on the front of the unit.   There is a notch (hole) that is covered by the sticker, that is the official way for the bluetooth signal to radiate.   2.4GHZ is a 3.125CM quarter wave..  which is about what that notch feels like. 

(This is clear in the GTX45R install manual which is the non TSO'ed version of the 345R... same hardware) 

3.12 Bluetooth Considerations (GTX 45R Only)

For optimal connectivity with a GTX 45, the Bluetooth antenna must point towards the passenger area of

the aircraft. This is identifiable by the Garmin logo sticker. Due to aircraft obstructions, Bluetooth

performance may be limited.

 

So I would suggest moving the 10db antenna to that area.  

I was going to test the passive repeater with a pair of Cushcraft S204912P antennas, but all of my N connector hardline is currently in a point to point wifi system... Plenty of PL239.. no spare N gear. 

I've ordered those ALFA antennas, the cable and a F-F bulkhead connector and will test that out. 

 

Edited October 8, 2018 by PaulM

[Lee A.]

Good info.  I may move that antenna.  

[aggiepilot04]

@PaulM did you get good results with the same antenna?  Haven’t had a chance to try this out yet, but confirmed that my 345 is mounted the same direction as Lee’s.  Debating on acquiring/testing a new iPad mini with my existing configuration vs. the passive antenna approach.  The iPhone X does not work, so I kinda doubt that a new device will change anything.

[JimK]

Here is what worked for me to fix the poor GTX345R bluetooth signal in the cockpit when the 345 is mounted behind the baggage compartment.  It involves two steps but resulted in excellent reception and I can now get all the FIS-B weather products as well as TIS-B traffic on my iPad which is mounted to the yoke in my Ovation 3GX.  Also, I didn't have to add an antenna or reposition my transponder like some forum participants have recommended.

Step 1: Replacing the aluminum oxygen bottle access panel in the aft bulkhead of the baggage compartment with a plastic one (thanks to someone else on this forum for suggesting that) improved my bluetooth signal to the point where I could at least pair my iPad to the GTX345R but the signal was not good enough to stay connected all time nor good enough to receive all that ADS-B had to offer.
Step 2: Remove the mylar covering on the aft side of the baggage compartment carpeted panel only in the area where it mates to the new plastic panel installed in step 1.  I cut through the mylar covering with a razor blade only about 1/16" deep into the foam insulation.  I used a putty knife to constantly separate the foam from the mylar, while I was removing the mylar, in order to leave as much of the foam insulation intact as possible. 

Be ready for some work.  The mylar is really stuck well to the foam.

Please see the attached pics

.

[buddy]

Jim, I also found another way to get a better Bluetooth connection on your iPad If you still have an intermittent connection after installing the plexiglass door. Start your airplane up and switch on your avionics master (my avionics comes on automatically with the G1000’s) if you don’t see traffic right away on ForeFlight I go to my settings, Bluetooth you’ll probably see that your GTX345R is NOT connected. Next turn your Bluetooth off then back on and tap on your GTX345R to reconnect. Please let me know after you’ve flown a few times that you are still  receiving a good  Uninterrupted Bluetooth signal and if you are I will remove the Mylar also.

[carusoam]

Great details and pics, Jim!

The Mylar is a metalized polyester (PET) film...

It essentially works like aluminum foil while blocking out all or most of the radio signals....

The aluminum is only a few atoms thick but just enough to work similar to solid foil.

Thanks for sharing that hidden detail...

That is a big observation!

Best regards,

-a-

[JimK]

Update per Buddy's request - I've been flying for a couple of months now with the Plexiglass access panel and the Mylar removed from the back of the insulation over the panel.  I always get a consistent, strong signal to my iPad from the GTX345R.  Never has failed to pair when I start the airplane and never has disconnected in flight.

[Danb]

My iPad mini picked up the signal fine until last week. The plane just came out of annual plus had surefly installed. My IPad Pro did pick up the signal, I had full baggage in the back. Any suggestions 

[carusoam]

7 hours ago, Danb said:

My iPad mini picked up the signal fine until last week. The plane just came out of annual plus had surefly installed. My IPad Pro did pick up the signal, I had full baggage in the back. Any suggestions 

Dan,

Looks like Siri might have changed the didn’t to a did...?

Or, I just didn’t understand your Question... 

How is the sure fly operating so far?

Best regards,

-a-

 

[Danb]

On 9/15/2020 at 8:56 PM, carusoam said:

Dan,

Looks like Siri might have changed the didn’t to a did...?

Or, I just didn’t understand your Question... 

How is the sure fly operating so far?

Best regards,

-a-

 

Ant the surefly seems fine, my starts are a little better although they were fine before, seems a little smoother at altitude subjective so who knows, I generally burn 18.8 to 19 gph block to block including climb out. These two five hour flights depicted just under 18 gph block to block, only two flights so far. Temps all were good at 13,000 my highest cht was 377-380, all temps stayed under 400 on climbing to fl 13 with cowl flaps open. Hopefully these remain same. Surefly is priced competitively so swapping from the mag seems worthwhile. Anthony there’s one for you in the factory that 310hp monster you fly is waiting 

[irishpilot]

man, I must be lucky. I never have issues connecting to my GTX345 and I've stuffed the Bravo full of bags and people and still connected.

 

However, after reading this thread, it sounds like signal blocking is a problem.

 

Sent from my Pixel 3a using Tapatalk

 

 

 

 

[PaulM]

I had the passive antenna pair routed to behind the pilot sidewall.  It will perhaps disconnect once a flight, but isn't related to the people or bags in the back.   So, not perfect, but better.  I keep the stratus as a backup so I always have a valid ADSB signal. 

[carusoam]

Many challenges came from the aluminized sheet of insulation, blocking the signals...

Some planes got the aluminized version, others didn’t...

I looked to see what insulation I had on that wall.... I haven’t found any there yet...  

Best regards,

-a-