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Antenna Locations

OneTwoTree

OneTwoTree

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So ...... I need to mount a GA 57X and a GA 35 antenna, and I've run out of room in the center tunnel. SO, my question is can these antenna's be mounted in the front turtle deck, (red or yellow locations) right before the canopy. (Top tail cone is not available because I have a comm antenna there, and the previously metioned room issue in the center tunnel.) Also I do not want to mount under the engine cover, because most people feel that is unacceptable if you are going to use these antenna's for IFR purposes, and I will be doing that! TIA for any help!
 

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Can you keep the 8? inches or so distance requirement, you'll probably have to offset, one yellow, one red. In mine there is room up there for it I think. I put my com antennas on the bottom slots, so I put these two receivers on the back top. I just ran all the rg400 over the weekend, and didn't run out of room, I guess it's because you put the com2 and transponder back there and have to run all that wire/coax back?
 
an alternate method...

IMG_0855.JPGIMG_0840.JPGIMG_0854.JPGIMG_0886.JPG

There is a bit of a masking to the rear, perhaps 10° longitudinally and 5° in elevation, but I haven't observed any limitations or degradation in EPU, HDOP, VDOP, etc.

RAIM and other predictive outages (SAPT) aren't any more extensive due to this location.
 
Brian,

Did you add extra coax on the GPS antenna feed to meet the minimum length when using a Garmin GPS navigator?
How do you seal for water intrusion?

Carl
 
lipper03 said:
Can you keep the 8? inches or so distance requirement, you'll probably have to offset, one yellow, one red. In mine there is room up there for it I think. I put my com antennas on the bottom slots, so I put these two receivers on the back top. I just ran all the rg400 over the weekend, and didn't run out of room, I guess it's because you put the com2 and transponder back there and have to run all that wire/coax back?
Click to expand...
Actually Comm2 and transponder helps being in the tailcone. Its running all the oxygen tubes for the Muntain high system that is killing me.
 
Carl Froehlich said:
Brian,

Did you add extra coax on the GPS antenna feed to meet the minimum length when using a Garmin GPS navigator?
How do you seal for water intrusion?

Carl
Click to expand...

I experimented with "just enough" RG-400 to run between the GPS antenna and GTN 650xi, and I flew it that way for a bit over 2 years (150 hours), then I used a 3dB attenuator in-line (MicroCircuits HAT-3A+), then I coiled up 2m of RG-400 to get to the required 1.5dB to 6.5dB loss needed for the GPS receiver. I didn't really see a difference any which way, but I am running with the requisite length of RG-400 as prescribed by the installation guide now so whomever I sell the airplane to doesn't have to explain to some overly pedantic IA why the cable isn't long enough... :)

I used Vaseline to seal the edges. I figured it was easier to shed water than to try and build a submarine.
 
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Walt said:
I prefer to use the small dash mounted puck antennas for G3X and XM.
Click to expand...
I don’t understand why everyone doesn’t dash mount them. Seems ideal. Is it an aesthetics thing?
 
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I always mount the SkyView GPS receiver/antenna on the glare shield (covered with a dark cloth to prevent glare). The GTN-650 goes on the top of the fusleage aft of the cabin. Considering the problems I had with my first GTN-650 build when it first came out (I was an early adopter and got to go through all the Garmin growing pains) I go to great length to not have a repeat and move the antenna away.

Both comm antennas go on the belly. I do not buy into the “the tower cannot hear you without a top mounted antenna” thing. I’ve never had a problem.

Carl
 
Carl Froehlich said:
Both comm antennas go on the belly. I do not buy into the “the tower cannot hear you without a top mounted antenna” thing. I’ve never had a problem.

Carl
Click to expand...
Same here. I've had com antennas on the belly of several airplanes for many years and never had a problem reaching the tower when on the ground.
 
Me: Comdat on top (GPS/Com), 2nd com on bottom.
Plenty of history on bleed problems with antennas next to each other on the belly.
I've had blocked ground communication when I used to have bottom mounted antennas hence why I now have one on top.
 
I
OneTwoTree said:
So ...... I need to mount a GA 57X and a GA 35 antenna, and I've run out of room in the center tunnel. SO, my question is can these antenna's be mounted in the front turtle deck, (red or yellow locations) right before the canopy. (Top tail cone is not available because I have a comm antenna there, and the previously metioned room issue in the center tunnel.) Also I do not want to mount under the engine cover, because most people feel that is unacceptable if you are going to use these antenna's for IFR purposes, and I will be doing that! TIA for any help!
Click to expand...
n buying a combination gps / comm antenna and placing on top aft of canopy
 
Walt said:
Me: Comdat on top (GPS/Com), 2nd com on bottom.
Plenty of history on bleed problems with antennas next to each other on the belly.
I've had blocked ground communication when I used to have bottom mounted antennas hence why I now have one on top.
Click to expand...
I'm doing the same. Decided long ago that highest priority for me is to place antenna where they have best chance to work well.
 
Mikeyb said:
I don’t understand why everyone doesn’t dash mount them. Seems ideal. Is it an aesthetics thing?
Click to expand...
I put GPS antennas on the glareshield of my RV-8A and they worked well there, but depending on lighting conditions you can sometimes see reflections off the inside of the canopy even if you paint them flat or low gloss black. On the RV-14 I don't plan to have anything on the glareshield to keep it 'clean' but also to make sure I can jettison the canopy if needed. I'm always amazed walking the flight line at OSH how many people have a wire bundle and/or coax going up to the glareshield/canopy with no means of quick disconnect, rendering the canopy jettison practically useless. If I decide to run any wiring for a lighting strip or canopy latch warning, I plan to use a connector that faces upward just below the glareshield and verify that it can be easily yanked apart if you ever need to pull the handle...
 
czechsix said:
I put GPS antennas on the glareshield of my RV-8A and they worked well there, but depending on lighting conditions you can sometimes see reflections off the inside of the canopy even if you paint them flat or low gloss black.
Click to expand...
The instructions on the GA-35 are explicit about "do not paint". I'm sure this is more out of an abundance of caution but I'd like to know more about it since I plan to do the same thing.
 
skirting_virga said:
The instructions on the GA-35 are explicit about "do not paint". I'm sure this is more out of an abundance of caution but I'd like to know more about it since I plan to do the same thing.
Click to expand...
IMO the GA35 is a little big for the glareshield and not optimum, I put it on the aft fuselage.
 
skirting_virga said:
The instructions on the GA-35 are explicit about "do not paint". I'm sure this is more out of an abundance of caution but I'd like to know more about it since I plan to do the same thing.
Click to expand...
The materials in the paint could absorb or reflect RF energy -- and the wrong color of paint can cause the amp electronics to overheat.
 
skirting_virga said:
The instructions on the GA-35 are explicit about "do not paint". I'm sure this is more out of an abundance of caution but I'd like to know more about it since I plan to do the same thing.
Click to expand...
For a SkyView (and I assume G3X GPS antenna/receiver) this is no need to paint. Just cover with some dark cloth, tucking the edges under the antenna to hold (see photo). I’ve done this for all the SkyView installs over the years.

But do not put a GPS antenna for something like a Garmin GTN-650 on the glare shield. Garmin install instructions provide guidance on what they want you to do to mitigate known issues. For RVs this translates to the Garmin GPS Navigator antenna mounted on the top skin aft of the cockpit. For the RV-8 a good spot is just aft of the rear seat but still under the canopy. This allows for the canopy to slide as needed.

Carl
 

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Carl Froehlich said:
For a SkyView (and I assume G3X GPS antenna/receiver) this is no need to paint. Just cover with some dark cloth, tucking the edges under the antenna to hold (see photo). I’ve done this for all the SkyView installs over the years.

But do not put a GPS antenna for something like a Garmin GTN-650 on the glare shield. Garmin install instructions provide guidance on what they want you to do to mitigate known issues. For RVs this translates to the Garmin GPS Navigator antenna mounted on the top skin aft of the cockpit. For the RV-8 a good spot is just aft of the rear seat but still under the canopy. This allows for the canopy to slide as needed.

Carl
Click to expand...
Thanks for that clarification. I really wanted to put it on the glare shield and not punch a hole in the plane, but I have to abide by good practices with respect to a certified navigator.

As for a glare shield antenna, not mounted for the purposes of a certified IFR navigator as in your example, how is the avionics vent/fan location? Does the motor electric field cause problems for that?
 
Carl Froehlich said:
I always mount the SkyView GPS receiver/antenna on the glare shield (covered with a dark cloth to prevent glare). The GTN-650 goes on the top of the fusleage aft of the cabin. Considering the problems I had with my first GTN-650 build when it first came out (I was an early adopter and got to go through all the Garmin growing pains) I go to great length to not have a repeat and move the antenna away.

Both comm antennas go on the belly. I do not buy into the “the tower cannot hear you without a top mounted antenna” thing. I’ve never had a problem.

Carl
Click to expand...
You wouldn't believe the JETS PC24, CL35, Sf50's that I get on a daily basis that I can't talk to. MD'80's used to be real bad at the gate. On clearence delevery I would always have to ask them to use the top antenna. And then by magic, I could hear them.
 
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