A aviation & planes forum. AviationBanter

If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below.

Go Back   Home » AviationBanter forum » rec.aviation newsgroups » Soaring
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Locating Transponder Antenna on top of the fuselage instead of under it.



 
 
Thread Tools Display Modes
  #51  
Old December 31st 19, 01:10 AM posted to rec.aviation.soaring
5Z
external usenet poster
 
Posts: 405
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

On Monday, December 30, 2019 at 6:44:50 AM UTC-8, Dan Marotta wrote:
In the absence of antenna diversity, I'm pretty sure all general
aviation factory built aircraft have the transponder antenna on the
bottom of the aircraft.Â* I would think the manufacturers must know
something.


When transponders first came out, the only receiver/interrogator was ground based. So anything certificated prior to TCAS, would definitely have the antenna on the bottom.
Then TCAS came along, and now ADS-B. These will interrogate/receive from any direction. So to be visible from any direction, one should probably have an antenna on top as well as bottom... And satellite based ADS-B likely demands it.
I'm sure Darryl has all the gory technical details :-) But my guess is that unless told otherwise, and considering cost of certification, etc., putting the antenna "where it's always been" is why it's on the bottom. :-)

5Z
  #52  
Old December 31st 19, 01:19 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 2,124
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

On Monday, December 30, 2019 at 10:34:25 AM UTC-5, wrote:
UH, as I said in my earlier post it was way easier to install on the turtle deck than down by the gear. In my 27, it took less than 4 hours from start to finish including the transponder and power routing. The longest portion was the routing of the antenna cable up through the tunnel to the panel, not alot of room in there I didnt crimp on the bnc to that end until after I fished it up to the panel. I mounted the blade as far back as I could possibly reach in the fuselage which is close to the junction of the flap and wing.

CH


I was thinking about the first message. Ventus CM would be an easy bottom install in the front of the engine bay.
Re '27. I did one behind the gear before the Schleicher tech note came out. Behind the gear was painful. The Schleicher TN installs through the oxygen cylinder area which is easy peasy.
I like to put ugly stuff where it shows less.
FWIW
UH
  #53  
Old December 31st 19, 02:19 AM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 100
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

Thanks all for the great response and information !
I will contact Schenpp Hirth and get information/drawing about the fuselage top location option.
Don't want to drill holes in the fuselage before that....
Dan
  #54  
Old December 31st 19, 01:17 PM posted to rec.aviation.soaring
India November[_2_]
external usenet poster
 
Posts: 31
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

Although the faired blade antenna has a theoretical drage coefficient less than a rod, in practice you have to align the blade with the local flow in the area of the attachment point. If the blade is not parallel with the streamlines, I suspect it potentially could add more drag than a plain ole' rod.
  #55  
Old December 31st 19, 01:19 PM posted to rec.aviation.soaring
India November[_2_]
external usenet poster
 
Posts: 31
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

Please let us know what you learn. I am thinking of an xponder install on my D2b.
  #57  
Old December 31st 19, 06:04 PM posted to rec.aviation.soaring
[email protected]
external usenet poster
 
Posts: 100
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

I will let you know what I found and what decided.
Dan
  #58  
Old January 1st 20, 03:32 PM posted to rec.aviation.soaring
India November[_2_]
external usenet poster
 
Posts: 31
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

I am thinking of the theoretical advantage in drag coefficient of a blade vs rod antenna which holds for any speed.
  #59  
Old January 1st 20, 09:36 PM posted to rec.aviation.soaring
MNLou
external usenet poster
 
Posts: 271
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

On Wednesday, January 1, 2020 at 8:32:48 AM UTC-6, India November wrote:
I am thinking of the theoretical advantage in drag coefficient of a blade vs rod antenna which holds for any speed.


Assuming, as previously stated, that the blade antenna is aligned with the airflow around the fuselage at that point.

I would think that the drag of a misaligned blade antenna could be significantly higher than the perfect alignment drag.

For that reason, I'm personally going with a rod and ball antenna. The manufacturer's recommendation for mounting a transponder antenna is in an area where I have no idea how the air really flows.

Does anyone know if the difference between a perfectly aligned blade antenna and a rod and ball antenna is at all significant at, say, 100 kts airspeed?

Lou
  #60  
Old January 1st 20, 09:43 PM posted to rec.aviation.soaring
Dan Marotta
external usenet poster
 
Posts: 4,601
Default Locating Transponder Antenna on top of the fuselage instead ofunder it.

Just anecdotal evidence here, but my Stemme came with a rod and ball
transponder antenna under the nose bowl.Â* I mounted a blade type antenna
about 6 inches aft of that for the Flarm B.Â* I haven't noticed any
difference in flying qualities, drag, etc.Â* Maybe it's measurable but
who cares?Â* I'm not in contention for a world record or title.

On 1/1/2020 1:36 PM, MNLou wrote:
On Wednesday, January 1, 2020 at 8:32:48 AM UTC-6, India November wrote:
I am thinking of the theoretical advantage in drag coefficient of a blade vs rod antenna which holds for any speed.

Assuming, as previously stated, that the blade antenna is aligned with the airflow around the fuselage at that point.

I would think that the drag of a misaligned blade antenna could be significantly higher than the perfect alignment drag.

For that reason, I'm personally going with a rod and ball antenna. The manufacturer's recommendation for mounting a transponder antenna is in an area where I have no idea how the air really flows.

Does anyone know if the difference between a perfectly aligned blade antenna and a rod and ball antenna is at all significant at, say, 100 kts airspeed?

Lou


--
Dan, 5J
 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
PowerFlarm Antenna Locations on Carbon Fuselage Dan Marotta Soaring 9 August 15th 19 08:38 PM
ASW27 Trasponder Antenna Installation Inside Fuselage. Paul Birkett Soaring 45 January 8th 18 04:31 AM
ASW-24 - Transponder Cable Routing in Fuselage [email protected] Soaring 6 February 3rd 15 06:00 PM
Transponder Antenna Placement Fuselage Bottom - Minimize Damage?Exact Location WaltWX[_2_] Soaring 9 January 20th 15 12:00 AM
Transponder and antenna Paolo Soaring 1 March 6th 04 04:32 AM


All times are GMT +1. The time now is 07:58 PM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 AviationBanter.
The comments are property of their posters.