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Antenna grounding

 
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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Wed Jun 08, 2016 8:16 am    Post subject: Antenna grounding Reply with quote

I am Installing two Com Bent whip antennas on the belly of my RV8.  These are the Comant Brand sold by Stien and others.  I have fabricated backing plates with nutplates on them for ease of installation and to beef up the area.  I am planing to bond the plates to the inside of the skin.  No rivets and actually better support is my theory.  I will leave off the bonding agent near the 4 mounting screw holes to attempt to get a good ground.  Just to be sure I was considering making a short grounding strap from the the backup plate to the air frame inside. 
Will this extra ground cause me any issues.  If the back plate were riveted it wouldn't  be necessary, 
Also,  I f any one has used these antennas they come with a thin cork gasket.  N0 instructions (there are none on their web site).  Most people I know just use a sealant on the base of the antenna perimeter. 
Thanks


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PostPosted: Wed Jun 08, 2016 8:38 am    Post subject: Antenna grounding Reply with quote

Michael

I am building an 8 as well. What you describe is exactly what I was thinking about doing.

If you can post some pictures. Also What structural adhesive were you planning to use? I am thinking about using PRC. ( same a fuel tank sealant) as it will
create a waterproof seal, is strong and will not create any corrosion issues later
Craig

Quote:
On Jun 8, 2016, at 12:14 PM, Michael Lazarowicz <tllaz330(at)gmail.com> wrote:

I am Installing two Com Bent whip antennas on the belly of my RV8. These are the Comant Brand sold by Stien and others. I have fabricated backing plates with nutplates on them for ease of installation and to beef up the area. I am planing to bond the plates to the inside of the skin. No rivets and actually better support is my theory. I will leave off the bonding agent near the 4 mounting screw holes to attempt to get a good ground. Just to be sure I was considering making a short grounding strap from the the backup plate to the air frame inside.

Will this extra ground cause me any issues. If the back plate were riveted it wouldn't be necessary,

Also, I f any one has used these antennas they come with a thin cork gasket. N0 instructions (there are none on their web site). Most people I know just use a sealant on the base of the antenna perimeter.

Thanks


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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Wed Jun 08, 2016 9:12 am    Post subject: Antenna grounding Reply with quote

I have researched this bonding issue quite a bit.  T  Aviation industry has long used a product called Hysol.  Its expensive unless you can find it tin little packs. 
Click Bond makes a great adhesive that is available in small packs from " the Flight Shop"  There about $1:50 each and you don't have to worry about the mixing ratios.
There is  another alternative that comes from West System EPOXY.  zits called G-FLex and you can get it online or most Marine supply houses.  I used it to bond the hinges to my cowl.  G- Flex was devolved to bond dissimilar material  that expand and contract   at different temps.  Regular Epoxy will crack over time because it gets way to brittle .  G Flex  is even used to repair Aluminum boats.  It comes in two forms.  Thickened and regular.  You want the thickened.  Its a 50/50 mix. 
I will use the click bond because it is removable if need be with heat. 
There is also a You tube on G-flex where they show how it can be used to patch even under water. 
Hope this all helps
On Wed, Jun 8, 2016 at 12:36 PM, Craig Reding <clr(at)redingaviation.com (clr(at)redingaviation.com)> wrote:
Quote:
--> AeroElectric-List message posted by: Craig Reding <clr(at)redingaviation.com (clr(at)redingaviation.com)>

Michael

I am building an 8 as well.  What you describe is exactly what I was thinking about doing.

If you can post some pictures. Also What structural adhesive were you planning to use? I am thinking about using PRC.  ( same a fuel tank sealant) as it will
create a waterproof seal, is strong and will not create any corrosion issues later


Craig

> On Jun 8, 2016, at 12:14 PM, Michael Lazarowicz <tllaz330(at)gmail.com (tllaz330(at)gmail.com)> wrote:
>
> I am Installing two Com Bent whip antennas on the belly of my RV8.  These are the Comant Brand sold by Stien and others.  I have fabricated backing plates with nutplates on them for ease of installation and to beef up the area.  I am planing to bond the plates to the inside of the skin.  No rivets and actually better support is my theory.  I will leave off the bonding agent near the 4 mounting screw holes to attempt to get a good ground.  Just to be sure I was considering making a short grounding strap from the the backup plate to the air frame inside.
>
> Will this extra ground cause me any issues.  If the back plate were riveted it wouldn't  be necessary,
>
> Also,  I f any one has used these antennas they come with a thin cork gasket.  N0 instructions (there are none on their web site).  Most people I know just use a sealant on the base of the antenna perimeter.
>
> Thanks



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user9253



Joined: 28 Mar 2008
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Location: Riley TWP Michigan

PostPosted: Wed Jun 08, 2016 9:13 am    Post subject: Re: Antenna grounding Reply with quote

If the backing plates are square with a nutplate in each corner, then tightening the screws will bring the corners into contact with the aircraft skin. No additional grounding is needed. A thin film of grease under each corner will prevent corrosion. The grease will not prevent metal to metal contact because the grease will be forced out under screw pressure. Grease will keep air and water and contaminants out.

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PostPosted: Wed Jun 08, 2016 10:24 am    Post subject: Antenna grounding Reply with quote

What's wrong with rivets?  Why not at least a rivet in each corner? Then you get the electrical bond you need.

I'd consider the cork gasket optional, but some type of seal is needed between antenna base & skin.
Charlie
-------- Original message --------
From: Michael Lazarowicz
Date:06/08/2016 12:14 PM (GMT-05:00)
To: aeroelectric-list(at)matronics.com
Subject: AeroElectric-List: Antenna grounding
I am Installing two Com Bent whip antennas on the belly of my RV8.  These are the Comant Brand sold by Stien and others.  I have fabricated backing plates with nutplates on them for ease of installation and to beef up the area.  I am planing to bond the plates to the inside of the skin.  No rivets and actually better support is my theory.  I will leave off the bonding agent near the 4 mounting screw holes to attempt to get a good ground.  Just to be sure I was considering making a short grounding strap from the the backup plate to the air frame inside. 
Will this extra ground cause me any issues.  If the back plate were riveted it wouldn't  be necessary, 
Also,  I f any one has used these antennas they come with a thin cork gasket.  N0 instructions (there are none on their web site).  Most people I know just use a sealant on the base of the antenna perimeter. 
Thanks


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PostPosted: Wed Jun 08, 2016 4:54 pm    Post subject: Antenna grounding Reply with quote

At 11:14 AM 6/8/2016, you wrote:
Quote:
I am Installing two Com Bent whip antennas on the belly of my RV8. These are the Comant Brand sold by Stien and others. I have fabricated backing plates with nutplates on them for ease of installation and to beef up the area. I am planing to bond the plates to the inside of the skin. No rivets and actually better support is my theory. I will leave off the bonding agent near the 4 mounting screw holes to attempt to get a good ground. Just to be sure I was considering making a short grounding strap from the the backup plate to the air frame inside.Â

WAayyyyy too much overkill . . . just rivet the
doubler to the a/c with appropriate rivets around
the periphery. Rivets swell up in the properly
drilled hole making a GAS-TIGHT connection between
itself and the mated materials. No other bonding
is necessary. The antenna should come with a gasket
or you can replace the gasket with a thin bead
of electronic (non-acid) rtv or just some E6000
wherein you wipe off the 'squeeze out' after the
mounting hardware is tightened.

http://tinyurl.com/6rwodso



Bob . . .


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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Wed Jun 08, 2016 8:35 pm    Post subject: Antenna grounding Reply with quote

Ok I give .  I will rivet it.  

I have a weird one for you Bob.  I have been struggling to mount my antennas the proper distance from each other and comply with other Garmin restrictions .  After a lot of back and forth with Garmin I made sure my transponder antenna was three feet from the transponder as required in their installation manual.  I sent them a picture of where everything was and their tec guy said he was " concerned" about how close my transponder antenna is to the magnatomiter .  The antenna in question is on the belly and is about 11 inches below the manotomiter.  
There are no restrictions in the magnatomiter installation that says it has to be any specific distance from the transponder antenna.   I know they are concerned about magnetism near the unit.  Why would they care about the antenna?

On Wednesday, June 8, 2016, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
At 11:14 AM 6/8/2016, you wrote:
Quote:
I am Installing two Com Bent whip antennas on the belly of my RV8.  These are the Comant Brand sold by Stien and others.  I have fabricated backing plates with nutplates on them for ease of installation and to beef up the area.  I am planing to bond the plates to the inside of the skin.  No rivets and actually better support is my theory.  I will leave off the bonding agent near the 4 mounting screw holes to attempt to get a good ground.  Just to be sure I was considering making a short grounding strap from the the backup plate to the air frame inside.Â

   WAayyyyy too much overkill . . . just rivet the
   doubler to the a/c with appropriate rivets around
   the periphery. Rivets swell up in the properly
   drilled hole making a GAS-TIGHT connection between
   itself and the mated materials. No other bonding
   is necessary. The antenna should come with a gasket
   or you can replace the gasket with a thin bead
   of electronic (non-acid) rtv or just some E6000
   wherein you wipe off the 'squeeze out' after the
   mounting hardware is tightened.

http://tinyurl.com/6rwodso



  Bob . . .


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PostPosted: Thu Jun 09, 2016 6:48 pm    Post subject: Antenna grounding Reply with quote

I have a weird one for you Bob. I have been struggling to mount my antennas the proper distance from each other and comply with other Garmin restrictions . After a lot of back and forth with Garmin I made sure my transponder antenna was three feet from the transponder as required in their installation manual.

Which transponder are we talking about?

I sent them a picture of where everything was and their tec guy said he was " concerned" about how close my transponder antenna is to the magnatomiter . The antenna in question is on the belly and is about 11 inches below the manotomiter.

There are no restrictions in the magnatomiter installation that says it has to be any specific distance from the transponder antenna. I know they are concerned about magnetism near the unit. Why would they care about the antenna?

A transponder's output is not 'magnetic' in the
sense that it would upset the calibration of a
compass. However, the peak power output is on
the order of 100 to 150 watts which CAN disturb
the electronics associated with a magnetometer.

If you're already installed, leave it and do
flight tests to see if a transponder making
replies to ground stations has any observable
effect on displayed magnetic heading values.

I suspect it will not but it's easy to check.





Bob . . .


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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Fri Jun 10, 2016 5:14 am    Post subject: Antenna grounding Reply with quote

Hi Bob,
It is Garmins GTX 23.  I know of one installation at least where the magnetometer is close ( about 2 feet form the antenna) and there are no problems.  That RV8 has been flying for 2 years.  I will have the ability to switch the ADSB antenna with the Transponder antenna and get it 4. 5 feet from the magnetometer.  The problem is then the Transponder antenna is less than a foot from the GTX23 unit.
After hounding Garmin about their requirement that the GTX23 box itself be located  3 feet (not 3 feet of coax) from the transponder antenna I ended up with the transponder antenna 3 feet away and putting the ADSB less than a foot from the box.  If it does not work out I can switch the antennas with out too much work later.
After pressing the Garmin people one of their guys checked with the Transponder person at Garmin and they indicated they THOUGHT  what really was required was at least 3 feet of Coax. 
There is a Check that I will run on the magnetometer when it is up and running.  One with the G3X and one with PC software that Garmin gave me a link to.  

Thanks for all your help
Mike

On Thu, Jun 9, 2016 at 10:47 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
I have a weird one for you Bob.  I have been struggling to mount my antennas the proper distance from each other and comply with other Garmin restrictions .  After a lot of back and forth with Garmin I made sure my transponder antenna was three feet from the transponder as required in their installation manual.

  Which transponder are we talking about?

I sent them a picture of where everything was and their tec guy said he was " concerned" about how close my transponder antenna is to the magnatomiter .  The antenna in question is on the belly and is about 11 inches below the manotomiter. 

There are no restrictions in the magnatomiter installation that says it has to be any specific distance from the transponder antenna.   I know they are concerned about magnetism near the unit.  Why would they care about the antenna?

  A transponder's output is not 'magnetic' in the
  sense that it would upset the calibration of a
  compass. However, the peak power output is on
  the order of 100 to 150 watts which CAN disturb
  the electronics associated with a magnetometer.

  If you're already installed, leave it and do
  flight tests to see if a transponder making
  replies to ground stations has any observable
  effect on displayed magnetic heading values.

  I suspect it will not but it's easy to check.
 




  Bob . . .


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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Fri Jun 10, 2016 5:24 am    Post subject: Antenna grounding Reply with quote

One other question if you cont mind.  I am using RG400 for my ADSB and with all this antenna location I may have to add about 6 " to the ADSB cable.  Its already about 12 feet long.  This is just ADSB in so not transmission.  How much will I loose if I extend the cable with a interconnect fitting ?  I got into this long length because of the transponder being in the back. 
Mike
On Thu, Jun 9, 2016 at 10:47 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
I have a weird one for you Bob.  I have been struggling to mount my antennas the proper distance from each other and comply with other Garmin restrictions .  After a lot of back and forth with Garmin I made sure my transponder antenna was three feet from the transponder as required in their installation manual.

  Which transponder are we talking about?

I sent them a picture of where everything was and their tec guy said he was " concerned" about how close my transponder antenna is to the magnatomiter .  The antenna in question is on the belly and is about 11 inches below the manotomiter. 

There are no restrictions in the magnatomiter installation that says it has to be any specific distance from the transponder antenna.   I know they are concerned about magnetism near the unit.  Why would they care about the antenna?

  A transponder's output is not 'magnetic' in the
  sense that it would upset the calibration of a
  compass. However, the peak power output is on
  the order of 100 to 150 watts which CAN disturb
  the electronics associated with a magnetometer.

  If you're already installed, leave it and do
  flight tests to see if a transponder making
  replies to ground stations has any observable
  effect on displayed magnetic heading values.

  I suspect it will not but it's easy to check.
 




  Bob . . .


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PostPosted: Sat Jun 11, 2016 11:25 am    Post subject: Antenna grounding Reply with quote

At 08:20 AM 6/10/2016, you wrote:
Quote:
One other question if you cont mind. I am using RG400 for my ADSB and with all this antenna location I may have to add about 6 " to the ADSB cable. Its already about 12 feet long. This is just ADSB in so not transmission. How much will I loose if I extend the cable with a interconnect fitting ? I got into this long length because of the transponder being in the back.Â

6 inches? The losses added by 6" plus
connector to an existing 12' run cable
would be difficult to measure much less
observe in practice.

A 12' length of RG400 will toss off about
40% of your transmit/receive signals at
transponder frequencies . . .

http://tinyurl.com/hdphfdv

. . . again, probably not enough to be
observed in practice. But at Beech, we'd use
something more like LMR-400 for a loss of
about 15%. There are probably sellers
on eBay that would custom assemble a
cable for you.

What model transponder are we talking about.
I like to read the wordage in the manual
associated with antenna locations.


Bob . . .


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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Sat Jun 11, 2016 12:13 pm    Post subject: Antenna grounding Reply with quote

Hi Bob,
I am not speaking of the Transponder antenna.  Mine will bee around 40" long with RG400.  What referring to is the ADSB inn on The Garmin GRT39.remote  I does not specify or give any antenna lengths. max or minimum.  Teh RV8 bottom make mounting all this stuff 2  Comm antennas one transponder antenna and on ADSB Antenna.  Basically Garmin wants them all 3feet or better apart.  Since I mounted the transponder box itself a GTS 23ES in back I am fighting the distance Garmin wants between the Unit and the Transponder antenna 3 feet.  To add tomy problem I have the Magnetometer in the tail and as I mentioned previously Garmin has concerns  that my transponder antenna  may be too close to the Magnetometer. 
I have it set up so I can switch the cables of the ADSB antenna and the Transponder antenna. The transponder is no big deal but my ADSB unit is up front and I already have it run.  I was just  a small amount short if I do the switch, so I was wondering if I was stretching the limits of the length of the ADSB in. 
In the End I will just hook it up and do the checks .  Just trying to keep the crawling in back and re routing of wire to a minimum. 
The units are Transponder GTS 23ES,

                       ADSB          GRT39 R
Thanks
On Sat, Jun 11, 2016 at 3:23 PM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
At 08:20 AM 6/10/2016, you wrote:
Quote:
One other question if you cont mind.  I am using RG400 for my ADSB and with all this antenna location I may have to add about 6 " to the ADSB cable.  Its already about 12 feet long.  This is just ADSB in so not transmission.  How much will I loose if I extend the cable with a interconnect fitting ?  I got into this long length because of the transponder being in the back. 

   6 inches?  The losses added by 6" plus
   connector to an existing 12' run cable
   would be difficult to measure much less
   observe in practice.

   A 12' length of RG400 will toss off about
   40% of your transmit/receive signals at
   transponder frequencies . . .

http://tinyurl.com/hdphfdv

   . . . again, probably not enough to be
   observed in practice. But at Beech, we'd use
   something more like LMR-400 for a loss of
   about 15%.  There are probably sellers
   on eBay that would custom assemble a
   cable for you.

   What model transponder are we talking about.
   I like to read the wordage in the manual
   associated with antenna locations.


  Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1906
Location: Riley TWP Michigan

PostPosted: Sat Jun 11, 2016 3:34 pm    Post subject: Re: Antenna grounding Reply with quote

Another RV-8 builder posted:
Quote:
I previously installed my transponder antenna under the RV 8 baggage floor on the left side. I mounted my Navworx ADSB antenna next to the innermost inspection cover on the right wing. This gave me the suggested 5 foot distance between the two and minimized cable length. Works like a charm.
Don
http://www.vansairforce.com/community/showpost.php?p=788980&postcount=12

Manufacturer's lawyers probably specify the minimum distance between various aircraft antennas. And that distance is probably greater than necessary.

Bob, how far apart should a 1090 MHz transmitting antenna be from a 978 MHz receiving antenna? And how far should a transponder antenna be from a com antenna? Thanks


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PostPosted: Sun Jun 12, 2016 7:03 am    Post subject: Antenna grounding Reply with quote

Quote:

Bob, how far apart should a 1090 MHz transmitting antenna be from a 978 MHz receiving antenna? And how far should a transponder antenna be from a com antenna? Thanks

That can only be quantified in the lab and even then, there
are dozens of intertwined variables. The two systems are first
qualified to some agreed upon design goals. Then powers that
be will get their heads together to recommend installation
parameters that are unlikely to exceed limitations identified
in the design goals.

ARC used to want our VHF comm antennas 4 or 5 feet
apart . . . but we stuck pairs of them on top of
the high-wing Cessnas barely 24 inches apart and
similarly spaced from the glide-slope and ADF
sense antennas.

Engineers and marketing people often WISH for
one thing . . . while the folks who have to make
it all fit and work find out what the real limits
are. Recommendations are seldom tucked up tightly
to real lines in the sand . . .

I suspect you're correct in the idea that some committee
of cognizant individuals probably sat down knowing
that 2 feet was enough and then doubled it. I think the
risks to hardware due to proximity are minimal . . . the
biggest concern is for degraded performance. So do the
best you can then try it out.


Bob . . .


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Laz



Joined: 04 Jan 2016
Posts: 30

PostPosted: Sun Jun 12, 2016 7:21 am    Post subject: Antenna grounding Reply with quote

When talking of com antennas .  How do you deal with a bent whip?  Distance from base or from the tip?

On Sunday, June 12, 2016, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
Quote:
Quote:

  Bob, how far apart should a 1090 MHz transmitting antenna be from a 978 MHz receiving antenna?  And how far should a transponder antenna be from a com antenna?  Thanks

  That can only be quantified in the lab and even then, there
  are dozens of intertwined variables. The two systems are first
  qualified to some agreed upon design goals. Then powers that
  be will get their heads together to recommend installation
  parameters that are unlikely to exceed limitations identified
  in the design goals.

  ARC used to want our VHF comm antennas 4 or 5 feet
  apart . . . but we stuck pairs of them on top of
  the high-wing Cessnas barely 24 inches apart and
  similarly spaced from the glide-slope and ADF
  sense antennas.

  Engineers and marketing people often WISH for
  one thing . . . while the folks who have to make
  it all fit and work find out what the real limits
  are. Recommendations are seldom tucked up tightly
  to real lines in the sand . . .

  I suspect you're correct in the idea that some committee
  of cognizant individuals probably sat down knowing
  that 2 feet was enough and then doubled it. I think the
  risks to hardware due to proximity are minimal . . . the
  biggest concern is for degraded performance. So do the
  best you can then try it out.


  Bob . . .


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PostPosted: Sun Jun 12, 2016 7:23 am    Post subject: Antenna grounding Reply with quote

Quote:
I have it set up so I can switch the cables of the ADSB antenna and the Transponder antenna. The transponder is no big deal but my ADSB unit is up front and I already have it run. I was just a small amount short if I do the switch, so I was wondering if I was stretching the limits of the length of the ADSB in.Â

probably not . . .


Quote:
In the End I will just hook it up and do the checks . Just trying to keep the crawling in back and re routing of wire to a minimum.Â

sounds like a plan . . .


Bob . . .


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