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

Well here is a link to a picture of a Ventus with the transponder antenna located as per Schempp Hirth.
Seems to work well only is straight flight. In any banking flight, the antenna is shadowed by the fuselage and/or wings.
Maybe a location on the turtledeck is better ?

https://www.airliners.net/photo/-/Sc...HgcaJ1/QJ2lC9A

Dan

On Saturday, December 28, 2019 at 9:23:02 PM UTC-8, wrote:
Well here is a link to a picture of a Ventus with the transponder antenna located as per Schempp Hirth.
Seems to work well only is straight flight. In any banking flight, the antenna is shadowed by the fuselage and/or wings.
Maybe a location on the turtledeck is better ?

https://www.airliners.net/photo/-/Sc...HgcaJ1/QJ2lC9A

Dan

Thanks for the photo, ouch yep that looks like a dopey position, if above is the only other practical option I'd do that.

I think while Darryl's suggestion will work quite well, it is more
effort than is required.Â* The BNC connector and the nut and washer of a
rod antenna will provide the necessary electrical connection to the
ground plane.Â* With a blade antenna, the mounting studs will make a good
mechanical connection.

In my former LAK-17a, I used an aluminum square cut to the dimensions
specified in the antenna installation sheet and rolled it over an oxygen
tank to match the internal curvature of the fuselage aft of the landing
gear.Â* I glued it in place with contact cement knowing that the studs
and BNC would make a good mechanical and electrical connection.Â* It
worked great!Â* I mounted the antenna offset to one side for two
reasons;Â* first, the joint line of the fuselage halves was thicker than
the length of the studs and BNC, and second, it insured that the blade
antenna would not catch on the ramp when loading and unloading the
fuselage in the trailer.

On 12/28/2019 7:43 PM, Darryl Ramm wrote:
On Saturday, December 28, 2019 at 4:10:30 PM UTC-8, wrote:
"Pay attention to the proper ground plane installation with any of the standard external transponder 1/4 wave antenna. That is very important."
Can the ground Plane be inside a carbon fibre fuselage for an external blade type antenna ?
Dan
The ground plane you install would normally be inside the CF fuselage. And the antenna manufacture or glider manufacturer should provide instructions on how to do this properly. A part of the point of that aluminium plate or foil tape ground plane is to help with a good connection to the coax cable ground. In some cases you might scuff the inside of the fueslage to help make additional electrical connection to the carbon fibre weave. *Follow the directions your glider manufacturer provides.* A plate especially can also help provide a good solid surface for antenna lock washers to engage with. Clearly here the CF will act in part as a ground plane (even without a good direct electrical connection, but by backing it with a better conductor with good connection to the coax you are helping things along).


--
Dan, 5J

On Saturday, December 28, 2019 at 8:55:37 AM UTC-8, jfitch wrote:
On Saturday, December 28, 2019 at 12:26:15 AM UTC-8, Tango Whisky wrote:
My transponder hs 250 W output, no way I would want that any place near my head or my balls.

The normal location (recommended by many manufacturers) just ahead of the gear doors is much closer to your balls than an L2 in the nosecone (or the instrument pod), if that worries you. Probably less than 2' away. I always wear tin foil underwear to match my tin foil hat. But my transponder antenna is in the nosecone and works perfectly as tested by external radiated power and FCC ADS-B out reports.

But you don't wear tin-foil socks, do your toenails grow faster during soaring season? Would like to get a bit more information on the tin-foil hat, I think I need one. I have my transponder antenna in the fin works great, no need for time foil panties.

On Sunday, December 29, 2019 at 9:15:03 AM UTC-8, Jonathan St. Cloud wrote:
On Saturday, December 28, 2019 at 8:55:37 AM UTC-8, jfitch wrote:
On Saturday, December 28, 2019 at 12:26:15 AM UTC-8, Tango Whisky wrote:
My transponder hs 250 W output, no way I would want that any place near my head or my balls.

The normal location (recommended by many manufacturers) just ahead of the gear doors is much closer to your balls than an L2 in the nosecone (or the instrument pod), if that worries you. Probably less than 2' away. I always wear tin foil underwear to match my tin foil hat. But my transponder antenna is in the nosecone and works perfectly as tested by external radiated power and FCC ADS-B out reports.

But you don't wear tin-foil socks, do your toenails grow faster during soaring season? Would like to get a bit more information on the tin-foil hat, I think I need one. I have my transponder antenna in the fin works great, no need for time foil panties.

There's not much point in the tin foil hat, when 5G is deployed we will be dying and/or mutating by the 10s of thousands. I read that on the internet, so I'm certain it's true.

In the Ventus picture, you can see that the antenna is about half the distance to the pilots privates than it would be up in the nose cone.

jfitch wrote on 12/29/2019 9:53 AM:
On Sunday, December 29, 2019 at 9:15:03 AM UTC-8, Jonathan St. Cloud wrote:
On Saturday, December 28, 2019 at 8:55:37 AM UTC-8, jfitch wrote:
On Saturday, December 28, 2019 at 12:26:15 AM UTC-8, Tango Whisky wrote:
My transponder hs 250 W output, no way I would want that any place near my head or my balls.

The normal location (recommended by many manufacturers) just ahead of the gear doors is much closer to your balls than an L2 in the nosecone (or the instrument pod), if that worries you. Probably less than 2' away. I always wear tin foil underwear to match my tin foil hat. But my transponder antenna is in the nosecone and works perfectly as tested by external radiated power and FCC ADS-B out reports.

But you don't wear tin-foil socks, do your toenails grow faster during soaring season? Would like to get a bit more information on the tin-foil hat, I think I need one. I have my transponder antenna in the fin works great, no need for time foil panties.

There's not much point in the tin foil hat, when 5G is deployed we will be dying and/or mutating by the 10s of thousands. I read that on the internet, so I'm certain it's true.

In the Ventus picture, you can see that the antenna is about half the distance to the pilots privates than it would be up in the nose cone.

Since it's quarter wave antenna, I'm guessing the radiation pattern means a lot
less power is radiated to the pilot than a dipole in the nose cone.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Friday, December 27, 2019 at 5:22:04 PM UTC-8, wrote:
I put mine on a turtle deck on my ASW 27 and it works fine no issues with anyone seeing me or even worrying about it I really like the fact that it's there and was really easy to install compared to down by the gear

Long ago someone (I believe from Arizona) posted here about doing some research by talking to folks very familiar with FAA radar design about putting the transponder antenna on top of the fuselage. The conclusion was that if very near and above the radar site, the signal *might* be blocked. Other than that, it should be fine. Since we do a lot of turning, the antennal will be blocked for times anyway.

One reason for a transponder is to be seen by large aircraft TCAS, it's more likely they will be descending on a collision course, so having the antenna on top is a better idea....

5Z

On Sunday, December 29, 2019 at 9:53:24 AM UTC-8, jfitch wrote:
On Sunday, December 29, 2019 at 9:15:03 AM UTC-8, Jonathan St. Cloud wrote:
On Saturday, December 28, 2019 at 8:55:37 AM UTC-8, jfitch wrote:
On Saturday, December 28, 2019 at 12:26:15 AM UTC-8, Tango Whisky wrote:
My transponder hs 250 W output, no way I would want that any place near my head or my balls.

The normal location (recommended by many manufacturers) just ahead of the gear doors is much closer to your balls than an L2 in the nosecone (or the instrument pod), if that worries you. Probably less than 2' away. I always wear tin foil underwear to match my tin foil hat. But my transponder antenna is in the nosecone and works perfectly as tested by external radiated power and FCC ADS-B out reports.

But you don't wear tin-foil socks, do your toenails grow faster during soaring season? Would like to get a bit more information on the tin-foil hat, I think I need one. I have my transponder antenna in the fin works great, no need for time foil panties.

There's not much point in the tin foil hat, when 5G is deployed we will be dying and/or mutating by the 10s of thousands. I read that on the internet, so I'm certain it's true.

In the Ventus picture, you can see that the antenna is about half the distance to the pilots privates than it would be up in the nose cone.

And uh.... not relevant... the pilot is inside his carbon fiber partial faraday cage cockpit, and (agreeing with Eric) the pattern from the 1/4 wave antenna with groundplane shields the pilot from the antenna.

Over a beer some time: details of teaching assistants punking male students in their undergrad physics lab classes into wearing aluminium foil "mini skirts" during a _very_ low power microwave experiment. Oh so well done.

The Jonker website says that they are putting both the transponder antenna and the Flarm antenna in the vertical tail. Any reports on how that is working out?

5Z wrote on 12/29/2019 10:11 AM:
On Friday, December 27, 2019 at 5:22:04 PM UTC-8, wrote:
I put mine on a turtle deck on my ASW 27 and it works fine no issues with anyone seeing me or even worrying about it I really like the fact that it's there and was really easy to install compared to down by the gear

Long ago someone (I believe from Arizona) posted here about doing some research by talking to folks very familiar with FAA radar design about putting the transponder antenna on top of the fuselage. The conclusion was that if very near and above the radar site, the signal *might* be blocked. Other than that, it should be fine. Since we do a lot of turning, the antennal will be blocked for times anyway.

One reason for a transponder is to be seen by large aircraft TCAS, it's more likely they will be descending on a collision course, so having the antenna on top is a better idea....

Near airports, airliners are descending and ascending; in between they are above
18K. In our area, the C-17s cruise high and low; the low ones (2000' agl) are
never a problem, but the other ones do cross our normal altitudes at least twice
each flight. I'm skeptical that they are mostly descending, but I think their TCAS
can easily detect us when they get within a few miles, regardless of the
top/bottom location.


--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1