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  #1  
Old 04-08-2021, 04:51 PM
Desert Rat Desert Rat is offline
 
Join Date: Aug 2018
Location: 50-50 Wichita KS & Scottsdale AZ
Posts: 570
Default School me on antenna locations

Hi guys-

It's time to start thinking about putting down the baggage floors, which means that it's also time to quit kicking this down the road and to get serious about planning antenna placement and cable routing.

The following magic boxes are on my wish list
G3x 2 screen system
GTN650
GTR20 remote comm (comm 2)
GTX45R remote transponder.

There is obviously some other stuff as well, but not pertinent to the question at hand.

What I'm thinking at this point is 2 delta pop bent comm antenna side by side in the general vicinity of the seat pans, a data/transponder antenna under the baggage floor or just aft of the baggage bulkhead, IFR GPS antenna on top of the tailcone, archer VOR antenna in the wingtip.

questions;

I get that it is more ideal to have comm 2 on top, but I don't like the look on such a small airplane and see lots of RV's out there with both comms underneath. Has anyone who's gone this way actually, personally, experienced problems talking to ground or clearance delivery with a belly mounted antenna?

Is there any real difference between a TED antenna and a sooper dooper blade UAT antenna like the one delta pop sells?

I've done the searches, but I'm just looking for real world operational history from those who have gone before. Bonus points for pictures!

Terry
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Terry Shortt
AGI, CFI, CFII, MEI, A&P, Janitor
RV7 Empennage & Wing done
Fuselage in process
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  #2  
Old 04-08-2021, 05:09 PM
Walt's Avatar
Walt Walt is offline
 
Join Date: Aug 2005
Location: Dallas/Ft Worth, TX
Posts: 6,018
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I put a 'Comdat' antenna on top, combination GPS/Com.
Had enough times of blocked communication on the ground to change it up.
Also the benefit of not overloading the com inputs is good.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #3  
Old 04-08-2021, 05:16 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,947
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Quote:
Originally Posted by Desert Rat View Post
. SNIP

I get that it is more ideal to have comm 2 on top, but I don't like the look on such a small airplane and see lots of RV's out there with both comms underneath. Has anyone who's gone this way actually, personally, experienced problems talking to ground or clearance delivery with a belly mounted antenna?

Is there any real difference between a TED antenna and a sooper dooper blade UAT antenna like the one delta pop sells?
A comm antenna on top is truely ugly. Don’t do it. The concept that the tower cannot hear you on the ground violates basic RF propagation rules. VHF line of sight is by no means “if I can’t see you I cannot talk to you”. All three of my RV builds had both bent whip comm antennas on the bottom of the fuselage - never a problem over the last 20 years.

Get the blade XPDR and ADS-B antennas - they just look right on an RV.

Do not mount your ELT antenna on top, put it under the empennage fairing. That area is the most likely to survive if you flip over. The new 406 ELTs work very well like this.

Carl
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  #4  
Old 04-08-2021, 05:21 PM
Walt's Avatar
Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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Quote:
Originally Posted by Carl Froehlich View Post
A comm antenna on top is truely ugly. Don’t do it. The concept that the tower cannot hear you on the ground violates basic RF propagation rules. VHF line of sight is by no means “if I can’t see you I cannot talk to you”. All three of my RV builds had both bent whip comm antennas on the bottom of the fuselage - never a problem over the last 20 years.

Carl
I guess my experience in contrary to yours, or my plane doesn't know about the propagation rules?
And I think someone just called my airplane 'ugly'
But I get it, I've always valued function over looks.



And OMG, what's this... it can't be....a straight antenna (lower VSWR) on the bottom centered for best ground plane and clear of obstructions.



(Front blade is ADSB in via GDL50R, aft blade is xpdr which is mounted in rear)
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154

Last edited by Walt : 04-08-2021 at 05:31 PM.
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  #5  
Old 04-08-2021, 05:23 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Walt View Post
I guess my experience in contrary to yours.
And I think someone just called my airplane 'ugly'
Yep - I should have picked my words much better.....

Carl
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  #6  
Old 04-08-2021, 05:25 PM
Desert Rat Desert Rat is offline
 
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Location: 50-50 Wichita KS & Scottsdale AZ
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Walt, I'm building a slider and incorporating a super tracks extension, so I think a upper mount might have to go further back than yours? Also, 800 bucks for an antenna? holy cow!

I think that it does look nice though, I'll have to give it some thought.

What did you mean by not overloading the comm input?
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AGI, CFI, CFII, MEI, A&P, Janitor
RV7 Empennage & Wing done
Fuselage in process
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  #7  
Old 04-08-2021, 05:42 PM
Walt's Avatar
Walt Walt is offline
 
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Quote:
Originally Posted by Desert Rat View Post
Walt, I'm building a slider and incorporating a super tracks extension, so I think a upper mount might have to go further back than yours? Also, 800 bucks for an antenna? holy cow!

I think that it does look nice though, I'll have to give it some thought.

What did you mean by not overloading the comm input?
With both coms on the bottom best not to forget hook up the interlock connection between coms which desensitizes the receiver when the other one keys up. Usually results in a loud squeal from the radio not being used.
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Walt Aronow, DFW, TX (52F)

EXP Aircraft Services LLC
Specializing in RV Condition Inspections, Maintenance, Avionics Upgrades
Dynamic Prop Balancing, Pitot-Static Altmeter/Transponder Certification
FAA Certified Repair Station, AP/IA/FCC GROL, EAA Technical Counselor
Authorized Garmin G3X Dealer/Installer
RV7A built 2004, 1900+ hrs, New Titan IO-370, Bendix Mags
Website: ExpAircraft.com, Email: walt@expaircraft.com, Cell: 972-746-5154
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  #8  
Old 04-08-2021, 05:43 PM
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Mel Mel is offline
 
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Location: Dallas area
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Both com antenna's on my -6 just forward of the main spar couple inches inboard of the fuselage sides. Almost 30 years old and still working great. Never had a problem communicating with ground control or tower.
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Recipient of Tony Bingelis Award and Wright Brothers Master Pilot Award
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  #9  
Old 04-08-2021, 06:09 PM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
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Location: Dogwood Airpark (VA42)
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Quote:
Originally Posted by Walt View Post
With both coms on the bottom best not to forget hook up the interlock connection between coms which desensitizes the receiver when the other one keys up. Usually results in a loud squeal from the radio not being used.
But I suggest this is a problem mostly associated with radio in use. For example, the GTR-200 radio exhibits this problem - so much that Garmin has this line you connect between the GTN-650 and the GRR-200 to desensitize the GTR-200 when transmitting on the GTN-650. I found this out the hard way when flying an RV-14A (not mine). The GTR-200 was useless to monitor a secondary frequency as it did this squeal. Note - I consider the line between the GTN-650 and the GTR-200 a bandaid as it will, by definition, eliminate the capability of pilot talking on Comm #1 and co-pilot talking on Comm #2 (split mode). In short - I evaluate the GTR-200 as having a less than perfect front end.

I never had this problem using the Dynon radio as comm #2 and the GTN-650 as comm #1.

Carl
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  #10  
Old 04-08-2021, 06:20 PM
Thermos's Avatar
Thermos Thermos is offline
 
Join Date: Jan 2005
Location: KASH
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Default

Quote:
Originally Posted by Desert Rat View Post
What I'm thinking at this point is 2 delta pop bent comm antenna side by side in the general vicinity of the seat pans, a data/transponder antenna under the baggage floor or just aft of the baggage bulkhead, IFR GPS antenna on top of the tailcone, archer VOR antenna in the wingtip.
This is almost exactly what I have, the only exception is that my transponder antenna is just aft of the firewall between the exhaust outlet and gear leg. I don't have as much time on my airplane as other folks on this thread but so far I've had no real issues with my installation. There are some frequency pairs between my GTN-650 and GTR-20 which will occasionally create interference to one radio when the other is transmitting, but that was a risk I accepted when I installed both antennas on the bottom and isn't a huge issue for me. Comms on the ground are fine even when I don't have line of sight to the tower, but your mileage may vary. My Archer-style nav antenna works great so far.

A couple of things to look out for WRT your GTX-45R are minimum physical separation and maximum coax length between the LRU and antenna. Both numbers are in the install guide. Max length varies with the kind of coax you choose; I used RG-400 which means a max coax length of 8ish feet and that drove the location of my transponder (under the panel) and the antenna. No reason why you couldn't put them elsewhere, just keep the distances in mind.

A TED antenna would probably work fine, but Don Pansier puts a lot of effort into building and testing his antennas for top performance and that was worth the extra $ to me. Plus, he's a fellow RV builder and a great guy to boot. And I'm absolutely certain that my streamlined transponder antenna gives me at least 5 knots more speed.

HTH

Dave
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Last edited by Thermos : 04-08-2021 at 06:34 PM.
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