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Transponder and ADSB antennae question.

 
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Robert Reed



Joined: 22 Oct 2009
Posts: 270
Location: Dallas/Ft.Worth

PostPosted: Sat Jun 23, 2018 7:34 pm    Post subject: Transponder and ADSB antennae question. Reply with quote

I am in the process of locating best place to install the transponder and ADSB antennae. I have been building for way too long and as a result some things planned years ago are no longer viable. I initially installed two Archer NAV antennae, one in each wing. Now I see little or no need for either antennae and have no plans to install other than GPS.

My question is rather I could disconnect the coax to those antennae, install the transponder and ADSB in the wing bottom and use the existing coax? I can’t remove the NAV antennae since I bonded them to the underside of the wing top. Will the old antennae interfere with the transponder or ADSB? Any other issues to consider? If I later decide to install a NAV system will it interfere with either unit?

Bob Reed


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PostPosted: Sat Jun 23, 2018 8:48 pm    Post subject: Transponder and ADSB antennae question. Reply with quote

Robert,

<< disconnect the coax to those antennae, install the transponder and ADSB
in the wing bottom and use the existing coax? I can’t remove the NAV
antennae since I bonded them to the underside of the wing top. Will the old
antennae interfere with the transponder or ADSB? Any other issues to
consider >>

First a confusion. Vanilla ADSB units have only one combined
ADSB/transponder antenna. Why do you need two?

Second confusion. Archer antennas need a metal wing to act as a
counterpoise. How are the Archer antennas bonded inboard of the wing tip.
Either you have a non-metal wing with no counterpoise or you have a shielded
antenna. Obviously there is something here I don't understand.

Potential problems:

By the wing bottom I assume you mean the bottom at the center of the
wingspan. Besides the extra complexity of a remote ADSB unit vs. a panel
mount you are faced with the manufacturers limit on cable length, usually
about 10 feet, because of cable signal attenuation.

Most of ADSB is still ground based. Thus the ADSB antenna needs a 360
degree view of the ground to function fully. At the wing tip much of the
ground (even half) is blocked. This will result in spotty performance and
whines from ATC each time your transponder signal drops out.

ADSB/transponder antennas are ground plane type. A short spike is mounted
on an 8 inch or so circle/octagon/etc. Mounting this antenna with the spike
horizontal and facing outward would shield the antenna from any conducting
metal inboard. But this also guarantees maximum signal blockage. Mounting
the ground plane on the bottom of the wingtip with the spike protruding
downward would work better.

If it were me, I'd mount the antenna on the bottom of the fuselage. On my
Sportsman, it is mounted to the underside of the fuselage cage with the
spike protruding through the fiberglass fuselage shell about 1 inch.

Tom Kuffel

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Robert Reed



Joined: 22 Oct 2009
Posts: 270
Location: Dallas/Ft.Worth

PostPosted: Sun Jun 24, 2018 5:39 am    Post subject: Transponder and ADSB antennae question. Reply with quote

Bob Reed
Sent from my iPhone

Quote:
On Jun 23, 2018, at 11:47 PM, The Kuffels <kuffel(at)cyberport.net> wrote:




Robert,

<< disconnect the coax to those antennae, install the transponder and ADSB in the wing bottom and use the existing coax? I can’t remove the NAV antennae since I bonded them to the underside of the wing top. Will the old antennae interfere with the transponder or ADSB? Any other issues to consider >>

First a confusion. Vanilla ADSB units have only one combined ADSB/transponder antenna. Why do you need two?

The Dynon transponder and ADSB units do not share the same antenna and are required to be separated.

Quote:
Second confusion. Archer antennas need a metal wing to act as a counterpoise. How are the Archer antennas bonded inboard of the wing tip. Either you have a non-metal wing with no counterpoise or you have a shielded antenna. Obviously there is something here I don't understand.

The Archer antenna are designed to be installed in a non-metal location on inside of wing. Yes I have a composite wing.


Quote:
Potential problems:

By the wing bottom I assume you mean the bottom at the center of the wingspan. Besides the extra complexity of a remote ADSB unit vs. a panel mount you are faced with the manufacturers limit on cable length, usually about 10 feet, because of cable signal attenuation.


I have an inspection panel on the bottom of the the wing about two feet from wing root that allows access to wing bolts and the NAV antenna connectors. That would also give me easy access to install the antenna for transponder on one side and adsb on the other while still needing only a short lead to each

Quote:
Most of ADSB is still ground based. Thus the ADSB antenna needs a 360 degree view of the ground to function fully. At the wing tip much of the ground (even half) is blocked. This will result in spotty performance and whines from ATC each time your transponder signal drops out.

ADSB/transponder antennas are ground plane type. A short spike is mounted on an 8 inch or so circle/octagon/etc. Mounting this antenna with the spike horizontal and facing outward would shield the antenna from any conducting metal inboard. But this also guarantees maximum signal blockage. Mounting the ground plane on the bottom of the wingtip with the spike protruding downward would work better.

If it were me, I'd mount the antenna on the bottom of the fuselage. On my Sportsman, it is mounted to the underside of the fuselage cage with the spike protruding through the fiberglass fuselage shell about 1 inch.

Tom Kuffel


Tom, I did my homework on the best locations and because there’s other issues with the fuselage locations I was trying to find a better place. My question was will a disconnect antenna interfere with the transponder or ADSB. You answered everything but.


Thanks
Quote:

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user9253



Joined: 28 Mar 2008
Posts: 1311
Location: Riley TWP Michigan

PostPosted: Sun Jun 24, 2018 5:40 am    Post subject: Re: Transponder and ADSB antennae question. Reply with quote

Like Tom said, you only need one antenna if you are installing a new ADS-B transponder. If you are installing an older transponder along with an ADS-B adapter, then two antennas are required. Of course the GPS requires its own antenna mounted with a view of the sky in all directions. The transponder has a maximum coax length. The GPS antenna has both a minimum and a maximum coax length. That is if it has coax. Some GPS units have the antenna and receiver all in one.
It it unlikely the Archer antennas will interfere with either the transponder or GPS antennas.
If you have not purchased an ADS-B transponder yet, you might consider the APPAREO STRATUS ESG or the GARMIN GTX335. The Stratus ESG comes with a USB power outlet.


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user9253



Joined: 28 Mar 2008
Posts: 1311
Location: Riley TWP Michigan

PostPosted: Sun Jun 24, 2018 5:44 am    Post subject: Re: Transponder and ADSB antennae question. Reply with quote

I think that confusion about the number of antennas is because some brands have one antenna for both transmitting and receiving and other brands have two separate antennas. Have you already decided to go with all Dynon?

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Robert Reed



Joined: 22 Oct 2009
Posts: 270
Location: Dallas/Ft.Worth

PostPosted: Sun Jun 24, 2018 5:58 am    Post subject: Transponder and ADSB antennae question. Reply with quote

I am installing the Dynon Skyview system with their transponder and ADSB systems (both in and out) which use two antenna. The GPS antenna is the new 2020 compliant and mounted on top of fuselage with an older backup on the inside of fiberglass top.

I would mount the transponder and ADSB antenna inside the fuselage but I don’t have the room to satisfy the distance from one of my COM antenna and keep the distance between the two antenna to be installed.

I think you did answer my question which was would the disconnected antenna interfere.

Thanks
Bob Reed
Sent from my iPhone

Quote:
On Jun 24, 2018, at 8:40 AM, user9253 <fransew(at)gmail.com> wrote:



Like Tom said, you only need one antenna if you are installing a new ADS-B transponder. If you are installing an older transponder along with an ADS-B adapter, then two antennas are required. Of course the GPS requires its own antenna mounted with a view of the sky in all directions. The transponder has a maximum coax length. The GPS antenna has both a minimum and a maximum coax length. That is if it has coax. Some GPS units have the antenna and receiver all in one.
It it unlikely the Archer antennas will interfere with either the transponder or GPS antennas.
If you have not purchased an ADS-B transponder yet, you might consider the APPAREO STRATUS ESG or the GARMIN GTX335. The Stratus ESG comes with a USB power outlet.

--------
Joe Gores




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Robert Reed



Joined: 22 Oct 2009
Posts: 270
Location: Dallas/Ft.Worth

PostPosted: Sun Jun 24, 2018 6:06 am    Post subject: Transponder and ADSB antennae question. Reply with quote

Yes I have decided to go with the Dynon for many reasons but most important being single source has always proven to be the best approach when possible. They have integrated all of their units in the system making installation easier. Most important is if there’s a problem I have only one number to call and they can’t claim it is the other company at fault.

Bob Reed
Sent from my iPhone

Quote:
On Jun 24, 2018, at 8:44 AM, user9253 <fransew(at)gmail.com> wrote:



I think that confusion about the number of antennas is because some brands have one antenna for both transmitting and receiving and other brands have two separate antennas. Have you already decided to go with all Dynon?

--------
Joe Gores




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=481167#481167











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Kellym



Joined: 10 Jan 2006
Posts: 1548
Location: Sun Lakes AZ

PostPosted: Sun Jun 24, 2018 6:44 am    Post subject: Transponder and ADSB antennae question. Reply with quote

OK, I have the Dynon Skyview ADS-B in and out. The Archer antennas are
unlikely to interfere, assuming they are in the wing tips and the new
antennas will be close to the fuselage.
However, given you have composite wings, you will have to install a
ground plane for each antenna.
To quote from the Dynon install manual:
"When a conventional aircraft monopole antenna is used it relies on a
ground plane for correct behaviour. For ideal performance the ground
plane should be very large compared to the wavelength of the
transmission, which is 275 mm. In a metal skinned aircraft this is
usually easy to accomplish, but is more difficult in a composite or
fabric skinned aircraft. In these cases, a metallic ground plane should
be fabricated and fitted under the antenna.
The ground plane should be as large as you can sensibly make it. Because
it is a function of the wavelength of the transmission,
*the smallest practical ground plane for a transponder is a square
around 120mm per side(approx 4.75in); as the size increases the
performance improves until the ground plane is around 700mm (27.5in)on
each side*.
Anything much larger than that size is unlikely to show significant
further improvement."

You need that size ground plane for each ADS-B antenna, unless used on a
metal skinned aircraft. So ground plane will likely be as much a factor
as spacing from com antenna.
As a PS, your Archer antennas would not have worked, unless there is a
version I am unaware of. They were designed for a *metal* wing with
composite wingtips. The metal wing is required for grounding. I have one
in each wing tip of my Vans RV.

On 6/24/2018 6:37 AM, Robert Reed wrote:
Quote:




Bob Reed
Sent from my iPhone

> On Jun 23, 2018, at 11:47 PM, The Kuffels <kuffel(at)cyberport.net> wrote:
>
>
> Robert,
>
> << disconnect the coax to those antennae, install the transponder and ADSB in the wing bottom and use the existing coax? I can’t remove the NAV antennae since I bonded them to the underside of the wing top. Will the old antennae interfere with the transponder or ADSB? Any other issues to consider >>
>
> First a confusion. Vanilla ADSB units have only one combined ADSB/transponder antenna. Why do you need two?

The Dynon transponder and ADSB units do not share the same antenna and are required to be separated.

> Second confusion. Archer antennas need a metal wing to act as a counterpoise. How are the Archer antennas bonded inboard of the wing tip. Either you have a non-metal wing with no counterpoise or you have a shielded antenna. Obviously there is something here I don't understand.



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PostPosted: Sun Jun 24, 2018 6:46 am    Post subject: Transponder and ADSB antennae question. Reply with quote

Robert,

My mistake. Whenever someone talks about Archer antennas I think of the
wingtip versions.

<< My question was will a disconnect antenna interfere with the transponder
or ADSB. You answered everything but. >>

Perhaps the meaning of "shield the antenna from any conducting metal
inboard." is not clear. I was answering a broader question. The ground
plane of a ground plane type antenna shields the antenna from all metal
behind it: antennas, coax, bolts, attach fittings, etc.

If you have Archer Model 5 transponder antennas, things are a little
different. The fat elements end, furthest away from the cable connector,
needs to be as far from other metal as possible.

In any event, the likelihood of any interference with a disconnected
cable/antenna is minimal. With line-of-sight communication almost anything
will work satisfactorily.

Tom Kuffel
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Robert Reed



Joined: 22 Oct 2009
Posts: 270
Location: Dallas/Ft.Worth

PostPosted: Sun Jun 24, 2018 12:32 pm    Post subject: Transponder and ADSB antennae question. Reply with quote

Bob Reed
Sent from my iPhone

Quote:
On Jun 24, 2018, at 9:45 AM, The Kuffels <kuffel(at)cyberport.net> wrote:



Robert,

My mistake. Whenever someone talks about Archer antennas I think of the wingtip versions.


Archer makes a number of different antenna. I have two different Archer COM Antenna, one installed in vertical stabilizer and one on fuselage side. Archer also had two different NAV antenna one for composite wings and one that fit into a fiberglass wing tip. I also have the Archer transponder antenna but it’s not usable with Dynon transponder.
Quote:
<< My question was will a disconnect antenna interfere with the transponder or ADSB. You answered everything but. >>

Perhaps the meaning of "shield the antenna from any conducting metal inboard." is not clear. I was answering a broader question. The ground plane of a ground plane type antenna shields the antenna from all metal behind it: antennas, coax, bolts, attach fittings, etc.

If you have Archer Model 5 transponder antennas, things are a little different. The fat elements end, furthest away from the cable connector, needs to be as far from other metal as possible.

In any event, the likelihood of any interference with a disconnected cable/antenna is minimal. With line-of-sight communication almost anything will work satisfactorily.

Tom Kuffel


I didn’t think there would be an issue but antenna are not in my area of expertise. Dynon instructions for the transponder specifically said to keep the antenna three feet from NAV or COM antenna. Since I don’t need both NAV antenna the wing root seems to satisfy the requirements if the disabled antenna will not cause a problem.

Too many antenna and too little space.
Quote:
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Robert Reed



Joined: 22 Oct 2009
Posts: 270
Location: Dallas/Ft.Worth

PostPosted: Sun Jun 24, 2018 12:46 pm    Post subject: Transponder and ADSB antennae question. Reply with quote

Archer produced several different antenna for both composite and metal aircraft. The NAV antenna I used were designed to be imbedded within the wing and not the wing tip. Mine were bonded to the inside of the wing top.

I am very aware of the ground plane and is part of the problem trying to find space. The ground plane for the ELT was a real issue to find room to install.

Sounds like there’s no problem if the NAV antenna is not installed and further research indicates the ADSB in will not have a problem with an active NAV.

Bob Reed
Sent from my iPhone

Quote:
On Jun 24, 2018, at 9:43 AM, Kelly McMullen <kellym(at)aviating.com> wrote:



OK, I have the Dynon Skyview ADS-B in and out. The Archer antennas are unlikely to interfere, assuming they are in the wing tips and the new antennas will be close to the fuselage.
However, given you have composite wings, you will have to install a ground plane for each antenna.
To quote from the Dynon install manual:
"When a conventional aircraft monopole antenna is used it relies on a ground plane for correct behaviour. For ideal performance the ground plane should be very large compared to the wavelength of the transmission, which is 275 mm. In a metal skinned aircraft this is usually easy to accomplish, but is more difficult in a composite or fabric skinned aircraft. In these cases, a metallic ground plane should be fabricated and fitted under the antenna.
The ground plane should be as large as you can sensibly make it. Because it is a function of the wavelength of the transmission,
*the smallest practical ground plane for a transponder is a square around 120mm per side(approx 4.75in); as the size increases the performance improves until the ground plane is around 700mm (27.5in)on each side*.
Anything much larger than that size is unlikely to show significant further improvement."

You need that size ground plane for each ADS-B antenna, unless used on a metal skinned aircraft. So ground plane will likely be as much a factor as spacing from com antenna.
As a PS, your Archer antennas would not have worked, unless there is a version I am unaware of. They were designed for a *metal* wing with composite wingtips. The metal wing is required for grounding. I have one in each wing tip of my Vans RV.

> On 6/24/2018 6:37 AM, Robert Reed wrote:
>
> Bob Reed
> Sent from my iPhone
>> On Jun 23, 2018, at 11:47 PM, The Kuffels <kuffel(at)cyberport.net> wrote:
>>
>>
>>
>>
>> Robert,
>>
>> << disconnect the coax to those antennae, install the transponder and ADSB in the wing bottom and use the existing coax? I can’t remove the NAV antennae since I bonded them to the underside of the wing top. Will the old antennae interfere with the transponder or ADSB? Any other issues to consider >>
>>
>> First a confusion. Vanilla ADSB units have only one combined ADSB/transponder antenna. Why do you need two?
> The Dynon transponder and ADSB units do not share the same antenna and are required to be separated.
>> Second confusion. Archer antennas need a metal wing to act as a counterpoise. How are the Archer antennas bonded inboard of the wing tip. Either you have a non-metal wing with no counterpoise or you have a shielded antenna. Obviously there is something here I don't understand.
>





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