RV8 Comm Antenna Locations

[sellis]

Now that Google searches no longer return VAF search results I'm having a hard time finding what I'm looking for. I'm sure this has been discussed, but I am trying to find the best location for dual comm antennas on the -8. Both will be Garmin comms with CI-122 antennas. All I see in the G3X and GTN install manuals is that 6' separation is best but 3' is adequate and that there needs to be a min 18"x18" metal plane at the base. It looks like most people are putting them underneath, parallel to each other and spaced maybe 3' apart. Any other thoughts, suggestions, or concerns would be appreciated. I know a top comm is desirable for ground communications but I assume is impossible on the -8. And while we're at it, what about the GPS antenna location? It looks like there are several options there. Thanks in advance for the advice!

 

[PilotjohnS]

I put mine on the bottom skin near the landing gear weldment. Works fine. Never found an issue even thou one is not “on top of fuse. The only concern is poking ones eyes out when crawling under to clean. I always put a wad of blue tape on the end. There is just enough room to make the min distance separation. But i did have to remove the paint under the antenna hardware when i re installed after plane was painted .

 

[John RV8]

Mine are both on the bottom of the fuselage slightly aft of the main spar. You can see them in this photo. (Taken by the fine folks at the Petit Jean Fly-in). If you zoom in a little bit. I’ve not had any issues talking to ATC while on the ground. My only GPS antenna is on the glareshield

 

[RV7 To Go]

Single Comm on the belly but if I had 2 it would be the same as the photo above. I Put my GPS on the deck just behind the canopy track. Lots of clearance when the canopy slides back. I could have put it on the deck under the canopy and just offset it to one side of the track, but I like symmetry whenever possible.

 

[Pilot8]

Mine are both on the bottom of the fuselage slightly aft of the main spar. You can see them in this photo. (Taken by the fine folks at the Petit Jean Fly-in). If you zoom in a little bit. I’ve not had any issues talking to ATC while on the ground. My only GPS antenna is on the glareshield View attachment 78838

Same location my 8- slightly aft of carry through with a doubler. I can take measurements and photos if OP interested.

 

[sellis]

All very helpful! Thanks for the replies. And a picture is worth a thousand words. Measurements as well! I would be grateful if you had time to get those for me Sam.

 

[Foghorn]

<snip> Now that Google searches no longer return VAF search results I'm having a hard time finding what I'm looking for.

The search engine DuckDuckGo.com works great.

 

[chrispratt]

Single comm antenna plus transponder antenna on belly just behind forward spar -- one on each side of belly; No issues in 20 years of flying. Two GPS antennas (painted matte black) on glareshield where I never notice them. And one WAAS antenna for ADS-B on the turtle deck just behind the back seat.

 

[Pilot8]

All very helpful! Thanks for the replies. And a picture is worth a thousand words. Measurements as well! I would be grateful if you had time to get those for me Sam.

Same setup on right side. The floor is out for a ground up panel rebuild- going Garmin.

 

[Brent]

mine are similar to the blue aircraft photo (John RV8) I have not had a problem with COM on the ground. GPS antenna just ahead of the canopy track behind the pax seat. ABS B each side behind pax seat. ELT between the two seats.
Everything operates as expected.

 

[sellis]

Again, this is all helpful. Thanks for the replies!

 

[ATC_RV8OR]

Location for second com antenna

I will be adding a second com radio in the near future and seem to be very limited on the location of the second antenna. I have a 8A and the existing antenna is located directly below the rear passengers stick. It would appear that the only place to go is aft on the belly and stick with the...

vansairforce.net

Antenna placement

I’m putting in two com antennas and a transponder/adsb antenna. I want to put the com antennas in the footwells. How far back from the spar must it be to not interfere with the pushrod for the ailerons? I assume if I’m aft of the pushrod hole all is good? And does the depth of the footwell get...

vansairforce.net

Antenna locations

I'm having a rough time locating my antennae. I have my 2 Comm antennae in the typical location, wide as can be, just aft of the wing spar. I am using the Delta-Pop Bent Red Tails (http://www.deltapopaviation.com/VHF_Com_Antennas.html) for these. I need to locate the two Delta-Pop...

vansairforce.net

Antenna conundrum

I am going with two bent whip antennas near the wing spar under the foot wells like I have seen on many RV-8s. My issue is with the transponder antenna. I have not paid attention to where RV-8 drivers are putting these, so please tell me where you put yours and QC what I have pictured below...

vansairforce.net

RV-8 dual comm antenna installation

The GTN-6XX install manual states that for best performance, a second comm antenna should be mounted at least six feet from the GTN comm antenna. For those with GTN-650 installations and a second comm also installed, how are your comm antennas positioned? The only practical surface to mount a...

vansairforce.net

Comm ant

Ok , did the search , read about 4 pages . Now my question , answers from flyers only please . Thinking of locating the comm and transponder antenna between the wing and fuselage forward of the rear spar , one on each side . Easy to access from the top at a latter date. Any feedback would...

vansairforce.net

The consensus seems to be dual comm antennas as far apart as possible under the 8. Minimal or no issues with ground comm. it will not be the minimum distance per most manufacturers.

 

[Skykingbob]

I placed my Comm antennas where everyone else does....as far to the left and right as possible. The GPS antenna I decided to put on
the turtledeck under the canopy area. Here are some pics of my mount....granted.....it may be a bit over the top when I could have used
four spacers for the screws to hold it down.....but it's a sickness of mine.....too many years doing machining.

I feel having it on the turtle deck minimizes the shadowing of the fuselage and gives it a great view of the sky.

 

[sellis]

Location for second com antenna

I will be adding a second com radio in the near future and seem to be very limited on the location of the second antenna. I have a 8A and the existing antenna is located directly below the rear passengers stick. It would appear that the only place to go is aft on the belly and stick with the...

vansairforce.net

Antenna placement

I’m putting in two com antennas and a transponder/adsb antenna. I want to put the com antennas in the footwells. How far back from the spar must it be to not interfere with the pushrod for the ailerons? I assume if I’m aft of the pushrod hole all is good? And does the depth of the footwell get...

vansairforce.net

Antenna locations

I'm having a rough time locating my antennae. I have my 2 Comm antennae in the typical location, wide as can be, just aft of the wing spar. I am using the Delta-Pop Bent Red Tails (http://www.deltapopaviation.com/VHF_Com_Antennas.html) for these. I need to locate the two Delta-Pop...

vansairforce.net

Antenna conundrum

I am going with two bent whip antennas near the wing spar under the foot wells like I have seen on many RV-8s. My issue is with the transponder antenna. I have not paid attention to where RV-8 drivers are putting these, so please tell me where you put yours and QC what I have pictured below...

vansairforce.net

RV-8 dual comm antenna installation

The GTN-6XX install manual states that for best performance, a second comm antenna should be mounted at least six feet from the GTN comm antenna. For those with GTN-650 installations and a second comm also installed, how are your comm antennas positioned? The only practical surface to mount a...

vansairforce.net

Comm ant

Ok , did the search , read about 4 pages . Now my question , answers from flyers only please . Thinking of locating the comm and transponder antenna between the wing and fuselage forward of the rear spar , one on each side . Easy to access from the top at a latter date. Any feedback would...

vansairforce.net

The consensus seems to be dual comm antennas as far apart as possible under the 8. Minimal or no issues with ground comm. it will not be the minimum distance per most manufacturers.

Thanks for these threads! Exactly what I have been unable to find. I tried DuckDuckGo but with only minimal improvement. I just need to learn a new search technique on the forums.

 

[sellis]

I placed my Comm antennas where everyone else does....as far to the left and right as possible. The GPS antenna I decided to put on
the turtledeck under the canopy area. Here are some pics of my mount....granted.....it may be a bit over the top when I could have used
four spacers for the screws to hold it down.....but it's a sickness of mine.....too many years doing machining.

I feel having it on the turtle deck minimizes the shadowing of the fuselage and gives it a great view of the sky.

View attachment 78946View attachment 78949View attachment 78950View attachment 78951View attachment 78952

Pics are great. Thank you!

 

[ATC_RV8OR]

Thanks for these threads! Exactly what I have been unable to find. I tried DuckDuckGo but with only minimal improvement. I just need to learn a new search technique on the forums.

I can’t find a lot of things that I used to with google search. The search on VAF is not as quick or easy. I feel like I’ve lost a lot of information that used to be easier to find but is now in an abyss

 

[Skykingbob]

Pics are great. Thank you!

Thanks.....sorry but I put one pic twice. I meant to put a pic of how I routed the coax cable. I used the canopy rail screws (longer ones) to attach the adel clamps
to hold the coax. I ran it from the GPS to the back and as shown to the GPS antenna.

 

[sellis]

Thanks.....sorry but I put one pic twice. I meant to put a pic of how I routed the coax cable. I used the canopy rail screws (longer ones) to attach the adel clamps
to hold the coax. I ran it from the GPS to the back and as shown to the GPS antenna.


View attachment 79086

Some serious engineering you have done with this! This is also helpful. Thanks again!

 

[Skykingbob]

Some serious engineering you have done with this! This is also helpful. Thanks again!

Like I said......it's a sickness
If you go to my Kitlog link in my signature you can use "Control F " on the site and search the logs for this and other things. There are
a lot of other good VAF posters with good Kitlogs that can be searched for reference during your build.

 

[sellis]

Garmin GPS antenna on the turtledeck under the canopy with no bracket - on my previous RV-8:

View attachment 79296

Or take a look at Paul Dye’s method of mounting on an RV-8 taking into account the turtledeck’s curvature:

Mounting On a Curve - KITPLANES

A long time ago, when homebuilders began installing Garmin 430s—the most popular IFR GPS/nav/com of the day—we were mostly left on our own to install the somewhat large GPS antenna. Garmin’s most important instruction was “DO NOT PAINT,” as proclaimed on the antenna itself. Many of us decided...

www.kitplanes.com

Very clean install. And I just read this article! Thank you!

 

[DeltaRomeo]

My antennae farm. Pic taken today. COMM antennae on bottom of aircraft

Downside doing this way is on an LPV approach to the north (northern hemisphere), when you get to the maltese cross the nose pitches down and the fuse blanks out the WAAS signal (was told one of the sats it needs is low on the horizon). Downgraded approach to LNAV. Lost the LPV annunciation. I may have got something wrong with this, but I did see the LPV note go away when doing an LPV to the north.

 

[sellis]

My antennae farm. Pic taken today. COMM antennae on bottom.
View attachment 79365
Downside doing this way is on an LPV approach to the north (northern hemisphere), when you get to the maltese cross the nose pitches down and the fuse blanks out the WAAS signal (was told one of the sats it needs is low on the horizon). Downgraded approach to LNAV. Lost the LPV annunciation. I may have got something wrong with this, but I did see the LPV note go away when doing an LPV to the north.

Interesting setup. That looks like it would work perfectly, especially with the new satellites that have been launched recently. I'm surprised you have a block in coverage. But I also know very little about the GPS network!

 

[Ralph Inkster]

Only belly com issue I’ve ever run into is airframe blocks transmissions directly up, for those times you want to tell that Baron 1000’ above you that you are overtaking (undertaking?) him…

 

[sellis]

Only belly com issue I’ve ever run into is airframe blocks transmissions directly up, for those times you want to tell that Baron 1000’ above you that you are overtaking (undertaking?) him…

Haha! I'll keep that in mind!