GTN VHF

[rotorman]

I get longer range reception on my old King KY197 than on my GTN 650. The GTN shop that installed the unit has checked the antenna and the box settings but no joy. Anyone else find this on his GTN?

[RLCarter]

Output wattage has a lot to due with it... my guess is the Garmin is much lower

[kortopates]

Maybe swapping antenna coax leads between the King KY197 and the  GTN 650 would be more informative in isolating the issue. The GTN's have great radios so I'd doubt it's there unless yours has a real issue.

[bradp]

Ground plane, shield state, antenna SWR, and whether there is 50 year old RG-58 has as much or more impact on radio performance than the box itself. Also remember this is probably the most painful troubleshooting because the problem can reside anywhere from the box to the panel to the coax to the antenna etc. 

There was a comment about the wattage of the GTN vs the King box - shouldn’t matter on the receive end.  

Useful troubleshooting you can do to narrow down where your issue is or where 

Is your radio getting correct power (14/28V)?

Are your connectors properly sedated (I had one radio problem  track to a screw that worked it’s way loose on the back of my audio panel)? 
 

Is your coax old/linked/bent, is the shield disrupted, are your connectors corroded? Swap the coax at the back of the panel. Problem track? Swap the coax at the antenna if nearby.  Problem Track? I’ve had bad connectors I’ve found, a piece of shield that was incorporated into the center conductor /connector connection with a bad crimp etc.  coax is tricky sometimes. 
 

What’s your antenna SWR? I have a little digital meter from amazon that was <$50 and the bees knees. Remember if you’re Transmitting without an antenna or dummy load you risk damaging some radios. Be very careful- know what you’re doing when disconnecting radios.  
 

Do you have a clean /bare / uncorroded ground plane for your antenna? 

Hope this is helpful   
 

brad 

 

[ilovecornfields]

5 minutes ago, bradp said:

Are your connectors properly sedated

You’re not bringing the propofol home from work, are you?

[bradp]

Just now, ilovecornfields said:

You’re not bringing the propofol home from work, are you?

Just got the kids to sleep.  It’s easier at work.  I guess that’s Dr Freud being paged right there. :-)

[bradp]

Also back to the OP - sometimes one radio will have better reception than the other based on antenna location.  My KX-170B always had better reception than my 430 for years and years even though my go to radio was the 430.  The reason was twofold - SWR was better on the back roof antenna compared to the front; also the wings shield reception for certain ground transmitters.   Now I have a GNC 255 as com2.  It’s attached to the back roof antenna and I swapped the coax to a belly mounted antenna for the 430.
 

This way I can talk to CNC/GND/TWR on com2 and swap to the belly mounted antenna on com1 once airborne.  I really like this setup and have had almost zero issues with hearing or being heard. 

[rotorman]

4 minutes ago, ilovecornfields said:

You’re not bringing the propofol home from work, are you?

Beyond my pay grade. Sorry.

[Ragsf15e]

35 minutes ago, bradp said:

Also back to the OP - sometimes one radio will have better reception than the other based on antenna location.  My KX-170B always had better reception than my 430 for years and years even though my go to radio was the 430.  The reason was twofold - SWR was better on the back roof antenna compared to the front; also the wings shield reception for certain ground transmitters.   Now I have a GNC 255 as com2.  It’s attached to the back roof antenna and I swapped the coax to a belly mounted antenna for the 430.
 

This way I can talk to CNC/GND/TWR on com2 and swap to the belly mounted antenna on com1 once airborne.  I really like this setup and have had almost zero issues with hearing or being heard. 

This is a real good point, and often overlooked.  Definitely think about where your antenna is and where is the person you’re talking to - above or below or masked by your wing?  The two antennas are often far apart to prevent conflict (top/bottom is common).  So the one that works best on the ground often doesn’t work as well in the air.  They can be masked by the fuselage, wings, shoved close to the ground, etc.  

Thinking about this can help get proper reception (usually on the ground) from challenging locations on an airfield.

I guess I might think about this first before I go too far troubleshooting... could be a simple antenna swap between the two radios.

[flyboy0681]

I have the same issue when listening from a distant transmitter. On my unit if I listen without squelch, I can make out the transmission, but usually switch to the KX 165  by that point.

[Marauder]

I get longer range reception on my old King KY197 than on my GTN 650. The GTN shop that installed the unit has checked the antenna and the box settings but no joy. Anyone else find this on his GTN?

My GTN 650 also had a shorter range than my older Narco. When the Narco failed, I put in a 16W GNC 255B just to make sure I had the range.

I finally was able to get better performance out of the GTN when I replaced the RG58 with new RG400. Night and day difference



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[rotorman]

To add some clarification with respect to  some of the comments. I had two KY 197 that performed equally well. No difference. When the GTN was installed, the coax to was replaced and the antena was not. Immediately I had no reception without breaking squelch with a station on approach frequency at a Class B airport that I had used regularly for years.  So I think that pretty much eliminates the antena and the cable. 

[Marauder]

To add some clarification with respect to  some of the comments. I had two KY 197 that performed equally well. No difference. When the GTN was installed, the coax to was replaced and the antena was not. Immediately I had no reception without breaking squelch with a station on approach frequency at a Class B airport that I had used regularly for years.  So I think that pretty much eliminates the antena and the cable. 

From my experience, the GTN never performed as well as my old King 170B, MX-170B or even the Narco 12D+.

I would make sure the shop did a SWR on it with the new cable and existing antenna. This will eliminate a poorly made up BNC connector. Yes, I had one of those issues when I had new RG400 installed on the Nav side. Also, verify they install RG400 instead of putting in more RG58.

Also, not sure if you remember, but when the GTN units first came out they had a lot of open squelch issues. They did several firmware updates as well as having shops adjust the squelch setting. I would verify those updates are current.

To be honest, I think the GTNs are a bit more susceptible to interference and I believed they played around with the firmware and squelch settings to get this issue controlled and it may resulted in decreased range.



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[rotorman]

1 hour ago, Marauder said:

 

From my experience, the GTN never performed as well as my old King 170B, MX-170B or even the Narco 12D+.

I would make sure the shop did a SWR on it with the new cable and existing antenna. This will eliminate a poorly made up BNC connector. Yes, I had one of those issues when I had new RG400 installed on the Nav side. Also, verify they install RG400 instead of putting in more RG58.

Also, not sure if you remember, but when the GTN units first came out they had a lot of open squelch issues. They did several firmware updates as well as having shops adjust the squelch setting. I would verify those updates are current.

To be honest, I think the GTNs are a bit more susceptible to interference and I believed they played around with the firmware and squelch settings to get this issue controlled and it may resulted in decreased range.



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You are correct. The early ver of the GTN did have a squelch problem that was really aggravating. I remember fooling with the setting. Then the installer fooled with the setting, and then Garmin came clean and fixed it with the next version. But even during that time with the squelch issue I was having the same problem problem with range reception on same frequency In the same place in my flight. Perhaps Bob-S50 could chime in here. We fly out of the same airport. I'm pretty sure he has a GTN installed.