GTN 650 reception range.

[johncuyle]

I know there have been a couple threads on the topic in the past but they're a little old by now, so rather than necro one I figured I'd start a new one to see what the latest knowledge is. I recently had a GTN 650 installed by a reputable Garmin dealer. It works quite well in every way and I'm very happy with the work except for one issue. Reception range is appallingly short. How short? Yesterday I was overflying OLM at 7500' and couldn't receive ATIS.

 

I don't know how this compares to the king it replaced because the radio was partially inop when I purchased the plane, but performance is considerably worse than COM2 (another old King) and, well, not being able to reliably receive from a mile and a half just isn't acceptable for a COM period.

 

Have others with the same issue found acceptable resolutions? The display on my old King is going out and it is going to be replaced sooner or later, and I'm terrified I won't have a reliable radio.

 

 

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[Bob - S50]

Ours seems to work OK.  I never use the GTN for ATIS though, I use #2 instead.  I was on the way from Hoquiam back to Auburn today at 3500'.  Because of a ridge line I was about on the Olympia 225 at 10 before Seattle Approach could hear me.  Once I got past the ridge it worked fine all the way home.

[johncuyle]

Ours seems to work OK.  I never use the GTN for ATIS though, I use #2 instead.  I was on the way from Hoquiam back to Auburn today at 3500'.  Because of a ridge line I was about on the Olympia 225 at 10 before Seattle Approach could hear me.  Once I got past the ridge it worked fine all the way home.

I've only had it for a couple months and I haven't used com on the GTN much because I can't reliably hear all the traffic in the pattern at Arlington while I'm ten miles out. I've been forcing myself to try to use it the last few flights to try to get enough information to help diagnose the problem, often tuning both radios to hear what I'd otherwise miss.


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[Bob - S50]

Could also be an antenna issue.  You might try swapping antenna's if that is feasible and see if that makes a difference.

[Marauder]

I know there have been a couple threads on the topic in the past but they're a little old by now, so rather than necro one I figured I'd start a new one to see what the latest knowledge is. I recently had a GTN 650 installed by a reputable Garmin dealer. It works quite well in every way and I'm very happy with the work except for one issue. Reception range is appallingly short. How short? Yesterday I was overflying OLM at 7500' and couldn't receive ATIS.
 
I don't know how this compares to the king it replaced because the radio was partially inop when I purchased the plane, but performance is considerably worse than COM2 (another old King) and, well, not being able to reliably receive from a mile and a half just isn't acceptable for a COM period.
 
Have others with the same issue found acceptable resolutions? The display on my old King is going out and it is going to be replaced sooner or later, and I'm terrified I won't have a reliable radio.
 
 
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Wow! I thought I was reading my post on the topic. I have a soon to be 5 year old GTN. The only problem I had with it has been an open squelch issue that turned out to be caused by the JPI 900.

Earlier this year I had the ADS-B upgrade done and shortly afterwards, the annual. I started flying the plane for the month between avionics work and annual. I began noticing the range for transmitting was really short. It became really pronounced on an IPC where 5 different ATC facilities couldn't hear me. I could hear them though.

Took the plane back to the avionics shop and found that the KX-99 portable radio adapter in that antenna line was failing. They removed it, did some ground tests and the obligatory SWR measurements to confirm the fix. When heading back home, I noticed the reception was terrible. I had the GTN and GNC 255 on the same frequency and I could see the 255 Rx light come on but nothing on the GTN. I could only pick something up with the squelch open.

I flew it a few more times before the annual and confirmed it was not receiving well. At the annual, I had them check the BNC and cable. They weren't able to find anything obviously wrong.

Looking around with my borescope, I saw that when they installed my new GTN, they kept the same RG-58 antenna wire (despite asking them to replace it). I'm in the process of removing the RG-58 and installing RG-400 with a new CI-196 antenna.

My original antenna and wiring is original to the plane. I'm hoping that this will correct the issue.


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[ArtVandelay]

I also have GTN650 and GNC255 combo. My avionics guy replaced the antenna wiring which they said is SOP, but I kept my antennas. All ATIS are not equal, some I have to be within 25 miles, others I can receive 75 miles away. The 255 and 650 seem about equal in performance.
Wiring gets old (corrosion), on boats they used tinned wire to prevent corrosion, I would have avionics shop hook up a portable antenna and have you take a test flight, it should be easy to do.

[kmyfm20s]

All my problems with my Garmin stack where a result of the original installer(from previous owner)using generic coaxial connectors instead of Garmin connectors.

[Bryan]

I have a GTN750, which is essentially the same unit.  We have no trouble picking up ATIS from 40+nm.  I don't think it is your GTN causing the issue.  Coax or Antenna.

Agree, had a GPS issue with my GTN for IFR approaches and turned out to be a connector issue early on for mine.

[Oscar Avalle]

I had a similar problem and it was the antenna and the connectors. The unit should be able to receive and transmit form more than 40 miles.


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[Brandontwalker]

No complaints with reception on my 650. Had problems with the GPS signal dropping out, but that turned out to be interference from the ELT. A $50 filter fixed that.


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[jetdriven]

DEfinately run RG400 cable to all the com, nav, and gps. The cable crimper is 20$ from amazon or ebay and the connectors are about 5$ each from Mouser. 

[Marauder]

4 hours ago, jetdriven said:

DEfinately run RG400 cable to all the com, nav, and gps. The cable crimper is 20$ from amazon or ebay and the connectors are about 5$ each from Mouser. 

That is exactly what I am up to currently. The shop that installed my GTN was told explicitly to replace all wiring. They left the RG-58. The best price I found for RG-400 is Aircraft Spruce. The BNC connectors are all in the $7 - $8 range from all the suppliers (Newark, Allied, Mouser, Chief, Aircraft Spruce). 

As Byron, points out you want to find a decent crimper. I would also add pick up a coax cutter that can handle the 3 cuts you need and practice some cuts as well. The RG-400 is silver coated copper stranded cable. The general misconception is that you can crimp the center conductor on with the 0.068" crimp. You can, but to take full advantage of the stranded wire, you should solder it on. Crimping is fine if you are using straight up RG-58 with a solid core copper conductor. 

The attached picture is the correct center conductor for attaching to RG-400. The hole is where you should be placing the solder. There is a high priced special solder adapter that heats the connector uniformly, but making sure you heat the connector to around 370 degrees and flow 60/40 solder (rosen not acid flux) will work fine.

 

[milotron]

If I recall, Aircraft spruce will provide preterminated cables to your length/connector configuration also. 

[jetdriven]

Ebay has sellers who part with rg400 by the foot.  Everything I crimped. Very rarely is anything soldered in a modern airplane. For example, it takes an engineering order to solder something on a Boeing. It stiffens the wire and it get brittle and snaps at the edge of the solder.  Just pull test it before snapping the BNC or TNC plug on. 

[donkaye]

I have a 750/650 combo.  I use the 750 for AIR Communications and the 650 for Ground, ATIS and Clearance.  That means I Get the ATIS in the air from the 650.  At 15,000 feet coming into Ogden for the Eclipse I picked up the ATIS at least 100 nm out.  This is comparable to my old KX 155 that I used for the same purpose.  I've noticed no range problems on either radio and I don't not have the higher powered GTNs.