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  #1  
Old 01-01-2019, 05:33 PM
azflyer21 azflyer21 is offline
 
Join Date: Nov 2016
Location: Scottsdale AZ
Posts: 113
Default WAAS GPS Antenna Install Questions

I see the most common place to install the GPS antenna is top-side just behind the rear window.

-Where did you install yours?
-If installed top-side behind rear window, where did you run the wires?

Thanks
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  #2  
Old 01-01-2019, 06:20 PM
mturnerb mturnerb is offline
 
Join Date: Apr 2015
Location: Ponte Vedra, FL
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Quote:
Originally Posted by azflyer21 View Post
I see the most common place to install the GPS antenna is top-side just behind the rear window.

-Where did you install yours?
-If installed top-side behind rear window, where did you run the wires?

Thanks
Top side, aft of rear window. I routed cable down the back side of the baggage bulkhead, using nylon clamps (drilled a couple of holes to mount these), then through the mid-fuse bulkhead).

Some photos here:

https://turnerb14a.blogspot.com/2018...-antennas.html
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  #3  
Old 01-02-2019, 04:52 AM
Skysailor Skysailor is offline
 
Join Date: May 2011
Location: Atlanta, GA
Posts: 174
Default Inside cowling

Consider mounting it at the top of the firewall inside the cowling. Mine is there on the RV4. Much shorter and easier antenna run. I have a very small shelf just wide enough for two antennas. The WAAS GPS antenna for a GNS 480 and one for the Dynon Skyview sit on it right beside each other. Reception is excellent. Testing revealed it was the same as mounting on top of the fuselage. I like that they are not visible as well.
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  #4  
Old 01-02-2019, 05:13 AM
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ronschreck ronschreck is offline
 
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Location: Gold Hill Airpark (NC25), NC
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Quote:
Originally Posted by Skysailor View Post
Consider mounting it at the top of the firewall inside the cowling. Mine is there on the RV4. Much shorter and easier antenna run. I have a very small shelf just wide enough for two antennas. The WAAS GPS antenna for a GNS 480 and one for the Dynon Skyview sit on it right beside each other. Reception is excellent. Testing revealed it was the same as mounting on top of the fuselage. I like that they are not visible as well.
I have four GPS antenna mounted in this manner, including the WAAS GPS for ADS-B. Never had a problem. The heat under the cowling doesn't seem to bother them and they pick up satellites just as easily as an external mount.
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  #5  
Old 01-02-2019, 06:26 AM
BillL BillL is offline
 
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Location: Central IL
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Default +1 again

Quote:
Originally Posted by ronschreck View Post
I have four GPS antenna mounted in this manner, including the WAAS GPS for ADS-B. Never had a problem. The heat under the cowling doesn't seem to bother them and they pick up satellites just as easily as an external mount.
I only have 3 antenna. Shut down and sitting yields the highest temps. I have data somewhere if you need it.
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  #6  
Old 01-02-2019, 07:23 AM
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Walt Walt is offline
 
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Default -2

If the antenna is for an IFR navigator consider following the manufactures advice to achieve the best results. The old "I did it this way and haven't had any problems" doesn't really work for me personally or profssionally, especially not interested in testing this theory when in the soup on an LPV approach.

If the antenna is for something other than an IFR navigator, then it probably isn't that important and failure won't pose a serious risk to my health so mount it wherever you want.
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  #7  
Old 01-02-2019, 07:37 AM
vic syracuse vic syracuse is offline
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I'm with Walt on this one. IFR navigators should be mounted in compliance with the instructions. I always put the WAAS antenna for these on the outside.

Yes, I know---it slows the airplane down by 25 knots.

Vic
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  #8  
Old 01-02-2019, 08:11 AM
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kbalch kbalch is offline
 
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Location: Clermont, FL
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Default

Quote:
Originally Posted by Skysailor View Post
Consider mounting it at the top of the firewall inside the cowling. Mine is there on the RV4. Much shorter and easier antenna run. I have a very small shelf just wide enough for two antennas. The WAAS GPS antenna for a GNS 480 and one for the Dynon Skyview sit on it right beside each other. Reception is excellent. Testing revealed it was the same as mounting on top of the fuselage. I like that they are not visible as well.
I did it this way years ago on my -8. It worked great, but that was a VFR-only installation. For the new -14A, which will have a very complete IFR package, I'm not willing to deviate from the manufacturer's published installation guidelines.

I'm happy to experiment on some things, but nav reception in hard IFR isn't one of them.
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  #9  
Old 01-02-2019, 08:39 AM
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az_gila az_gila is offline
 
Join Date: Jan 2005
Location: 57AZ - NW Tucson area
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Exclamation Cable length

Quote:
Originally Posted by Skysailor View Post
Consider mounting it at the top of the firewall inside the cowling. Mine is there on the RV4. Much shorter and easier antenna run. I have a very small shelf just wide enough for two antennas. The WAAS GPS antenna for a GNS 480 and one for the Dynon Skyview sit on it right beside each other. Reception is excellent. Testing revealed it was the same as mounting on top of the fuselage. I like that they are not visible as well.
If it is a GTN or GNS Garmin unit then a short cable run is not recommended...

GPS antennas listed in Section 3.3 require a cable loss between 1.5 dB and 6.5 dB. If RG-142B or RG-400 is used, 1.5 dB equates to a length of approximately 6.5 feet of cable with a connector on each end. RG-142B or RG-400 cable can be used as long as the length is less than 35 feet. For longer lengths, use low-loss double or triple-shielded, 50Ω coaxial.
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