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Toroid beads/VOR antenna design

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berkut13(at)berkut13.com
Guest

Posted: Mon Oct 27, 2014 6:48 am Post subject: Toroid beads/VOR antenna design

Thanks!  Very helpful discussion.  Yes, the ferrites are for future COM 

antennas being imbedded in composite structure where size does matter.



The below brings up a different question I have about a retrofit VOR/GS 

antenna I need to install as well:   A traditional 'T' shaped (with a slight 

angle in the two radials) VOR antenna can not be utilized given the physical 

constraints of the area it must be installed.  There are really no other 

options for mounting given the aircraft's shape and construction materials. 

The two radials for the antenna will be in-line, no angle, horizontal and 

mounted in a newly formed conduit drilled into the leading edge foam of a 

small airfoil skinned with fiberglass.   The radials will likely be solid 

conductor wire or copper foil attached to a small wooden dowel for rigidity 

during installation and soldered to the coax.  I plan to construct a balun 

out of coax as described below.  This part is all rather straightforward.



The issue is: There is insufficient depth (fore/aft) in the area to run the 

feed line coax sway from the radials to form the bottom of the 'T' so the 

feed line coax must run parallel to and in close proximity of the (shield 

connected) "lower" radial at least it's full length before being able to 

re-direct away.  Imagine a fully built "antenna of a stick" set being 

inserted into a horizontal 5/8"dia conduit hole, then capping off the hole 

with only the feed coax sticking out, then running to the radio.  The end of 

the "lower" radial can be right at the end of the conduit hole, or it can be 

installed deeper into the structure if different design parameters dictate.



So, antenna gurus, the questions become: Will this sub-optimal antenna 

config perform acceptably as a receive only antenna?  Is there something 

else I can do to make it more efficient given the space constraints, or is 

there even a different antenna design more applicable to this install?



You input is appreciated.



-James

--

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Oct 27, 2014 11:14 am Post subject: Toroid beads/VOR antenna design

At 09:47 2014-10-27, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: <berkut13(at)berkut13.com>



 Thanks!  Very helpful discussion.  Yes, the ferrites are for future COM antennas being imbedded in composite structure where size does matter.



 The below brings up a different question I have about a retrofit VOR/GS antenna I need to install as well:   A traditional 'T' shaped (with a slight angle in the two radials) VOR antenna can not be utilized given the physical constraints of the area it must be installed.  There are really no other options for mounting given the aircraft's shape and construction materials. The two radials for the antenna will be in-line, no angle, horizontal and mounted in a newly formed conduit drilled into the leading edge foam of a small airfoil skinned with fiberglass.   The radials will likely be solid conductor wire or copper foil attached to a small wooden dowel for rigidity during installation and soldered to the coax.  I plan to construct a balun out of coax as described below.  This part is all rather straightforward. 	


    Any 'morphing' of geometry from the center-fed

    dipole driven with coax at right angles will

    result in a degradation of performance in terms

    of pattern and impedance matching. The closest

    anyone has come to an elegant end-fed dipole in

    the airplanes was the Miracle Antenna brand 

    "air-whip", end-feed dipole antenna with the

    toroidal common mode choke we discussed earlier

    this past week.



 [img]cid:.0[/img]



 [img]cid:.1[/img]



 

    You could string this style antenna out under a

    leading edge but you still have to deal with the common-

    mode choke 'lump' . . .



    I note that Miracle Antennas seems to have

    closed the doors. Aircraft Spruce doesn't offer

    the antennas any more and the website is black.



    They were in business for a lot of years and ejoyed

    some good reviews by their ham-radio clients.

    It seems that their demise is based more on business

    issues than product performance issues.



    The big problem with development of the

    lead edge vor antenna is the inconvenient

    packaging process that involves cut-n-try

    experiments on a device buried under

    layers of Fiberglas.



    It follows that what ever lies underneath that

    layer of glass and epoxy should be a low-risk

    configuration . . . it's damned hard to change

    if you don't like it.



    This seems like an ideal application for an active

    antenna. This is a relatively short (on the order of

    6 to 12 inches long attached to a very compact

    amplifier right at the end of the coax feedline.

    It takes a little fussing to get dc voltage out

    to the amplifier on the coax but this could well

    be a VERY compact solution to a receive-only antenna

    for VOR that eliminates the geometry issues that

    arise when you try to put a center fed dipole into

    a leading edge.   



 

   Bob . . .

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jluckey(at)pacbell.net
Guest

Posted: Mon Oct 27, 2014 12:01 pm Post subject: Toroid beads/VOR antenna design

You may already be aware but thought I would mention it - Have you read Bob Archer's stuff on antennas?  I think is company is called Sportcraft Antennas.  A quick google should find his website.

FYI,

-Jeff



 

     On Monday, October 27, 2014 12:37 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:

  

  



   At 09:47 2014-10-27, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: <berkut13(at)berkut13.com>



 Thanks!  Very helpful discussion.  Yes, the ferrites are for future COM antennas being imbedded in composite structure where size does matter.



 The below brings up a different question I have about a retrofit VOR/GS antenna I need to install as well:   A traditional 'T' shaped (with a slight angle in the two radials) VOR antenna can not be utilized given the physical constraints of the area it must be installed.  There are really no other options for mounting given the aircraft's shape and construction materials. The two radials for the antenna will be in-line, no angle, horizontal and mounted in a newly formed conduit drilled into the leading edge foam of a small airfoil skinned with fiberglass.   The radials will likely be solid conductor wire or copper foil attached to a small wooden dowel for rigidity during installation and soldered to the coax.  I plan to construct a balun out of coax as described below.  This part is all rather straightforward. 	


    Any 'morphing' of geometry from the center-fed

    dipole driven with coax at right angles will

    result in a degradation of performance in terms

    of pattern and impedance matching. The closest

    anyone has come to an elegant end-fed dipole in

    the airplanes was the Miracle Antenna brand 

    "air-whip", end-feed dipole antenna with the

    toroidal common mode choke we discussed earlier

    this past week.



 [img]cid:1.659687060(at)web184906.mail.gq1.yahoo.com[/img]



 [img]cid:2.659687060(at)web184906.mail.gq1.yahoo.com[/img]



 

    You could string this style antenna out under a

    leading edge but you still have to deal with the common-

    mode choke 'lump' . . .



    I note that Miracle Antennas seems to have

    closed the doors. Aircraft Spruce doesn't offer

    the antennas any more and the website is black.



    They were in business for a lot of years and ejoyed

    some good reviews by their ham-radio clients.

    It seems that their demise is based more on business

    issues than product performance issues.



    The big problem with development of the

    lead edge vor antenna is the inconvenient

    packaging process that involves cut-n-try

    experiments on a device buried under

    layers of Fiberglas.



    It follows that what ever lies underneath that

    layer of glass and epoxy should be a low-risk

    configuration . . . it's damned hard to change

    if you don't like it.



    This seems like an ideal application for an active

    antenna. This is a relatively short (on the order of

    6 to 12 inches long attached to a very compact

    amplifier right at the end of the coax feedline.

    It takes a little fussing to get dc voltage out

    to the amplifier on the coax but this could well

    be a VERY compact solution to a receive-only antenna

    for VOR that eliminates the geometry issues that

    arise when you try to put a center fed dipole into

    a leading edge.   



     Bob . . .

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berkut13(at)berkut13.com
Guest

Posted: Mon Oct 27, 2014 1:22 pm Post subject: Toroid beads/VOR antenna design

Bob,

  

 Based on what you have indicated, this type of â€œair whipâ€ antenna would  work very well in this area â€“  small airfoil leading edge D-section (carbon  spared, glass skinned canard in this case).    I can feed the  antenna portion of the assembly into the foam conduit and the choke can reside  inside the fuselage area, either just outside the airfoil skin, or I can build a  small access box for it.  If an â€œactiveâ€ box is required, electrical is  readily available in this area too.  All of this can be done without  affecting the external airfoil surface and thus easy to implement and  potentially to remove and service.

  

 Can you point me to some more specific info on how to build this type of  antenna and choke?

  

 Thanks!

 -James

  

  

  

  

    

  From: Robert L. Nuckolls, III (nuckolls.bob(at)aeroelectric.com) 

 Sent: Monday, October 27, 2014 2:13 PM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: Re: Re: Toroid beads/VOR antenna  design

  



 At  09:47 2014-10-27, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message    posted by: <berkut13(at)berkut13.com>



The below brings up a    different question I have about a retrofit VOR/GS antenna I need to install as    well:   A traditional 'T' shaped (with a slight angle in the two    radials) VOR antenna can not be utilized given the physical constraints of the    area it must be installed.  	


  

    "air-whip", end-feed dipole antenna with the

   toroidal common  mode choke we discussed earlier

   this past week.



[img]cid:FF9923CCB41F469AA35A22968198A6F6(at)DEFIANT2600[/img]

   You could string this style antenna out  under a

   leading edge but you still have to deal with the  common-

   mode choke 'lump' . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 28, 2014 7:15 am Post subject: Toroid beads/VOR antenna design

At 16:20 2014-10-27, you wrote:

 	  Quote: 	
		  Bob,



Based on what you have indicated, this type of 

â€œair whipâ€ antenna would work very well in 

this area –  small airfoil leading edge 

D-section (carbon spared, glass skinned canard 

in this case).    I can feed the antenna portion 

of the assembly into the foam conduit and the 

choke can reside inside the fuselage area, 

either just outside the airfoil skin, or I can 

build a small access box for it.  If an 

â€œactiveâ€ box is required, electrical is 

readily available in this area too.  All of this 

can be done without affecting the external 

airfoil surface and thus easy to implement and 

potentially to remove and service.



Can you point me to some more specific info on 

how to build this type of antenna and choke?


	


   Not sure this is the best way to go. Assume you are

   glassing a 'conduit' into the leading edge of the

   surface under consideration. What is the inside diameter

   of the proposed conduit? How long? Do I presume correctly

   that the 'radio end' of the conduit is accessible after

   assembly such that any antenna slipped into it could

   be repaired/modified at a later time?



   Bob . . .

berkut13(at)berkut13.com
Guest

Posted: Tue Oct 28, 2014 7:55 am Post subject: Toroid beads/VOR antenna design

This is actually a retrofit as the original structure was built by the owner 

without any VOR or GS antenna(s).  Horizontal, antenna space on this 

aircraft is limited to this area only.



The hope is not to "glass" an antenna into/onto the structure, but to insert 

one into a conduit that was bored into the internal foam (about 5/8"dia, 

about 5ft long) of the leading edge D-section on one side of the canard. 

The radio end would protrude from the structure into the nose of the 

aircraft either as a coax connector, pig tail, or I can create an internal 

box for a choke/circuitry/etc.   The original idea was to put a dipole in 

this area as I described earlier, but it sounds like there would  too much 

degradation in performance having the center feed coax+balun parallel and 

very close to one of the elements.   Removal would simply be a reverse of 

the insert - pull it out/stick it in with a little glass cut/repair at the 

feed end.



I'm trying to avoid the traditional retrofit which is to glass (permanently) 

a copper foil dipole onto the center bottom surface of the canard.  This too 

is sub-optimal as the radials will extend onto the external airfoil surface, 

the antenna is blocked/surrounded by rudder pedals/hydraulic 

pump/relays/battery/etc and previous installations in this area have been 

low performance.  The canard is carbon spared, so the traditional V shape of 

the antenna is extremely flat (almost straight) anyway being limited to the 

3.5" in front of the spar.    I have had good results with shallow V dipoles 

in the hollow D-sections of molded canards with about 3" separation between 

radials and coax run....but of course, that is not an option here.



Thoughts?



-James

--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Oct 28, 2014 12:26 pm Post subject: Toroid beads/VOR antenna design

I'm trying to avoid the traditional retrofit which is to glass 

(permanently) a copper foil dipole onto the center bottom surface of 

the canard.  This too is sub-optimal as the radials will extend onto 

the external airfoil surface, the antenna is blocked/surrounded by 

rudder pedals/hydraulic pump/relays/battery/etc and previous 

installations in this area have been low performance.  The canard is 

carbon spared, so the traditional V shape of the antenna is extremely 

flat (almost straight) anyway being limited to the 3.5" in front of 

the spar.    I have had good results with shallow V dipoles in the 

hollow D-sections of molded canards with about 3" separation between 

radials and coax run....but of course, that is not an option here.



   The legacy "v" shape was more cosmetic than physically

   or electrically beneficial. The straight dipole in your

   leading edge would be just fine.



   I'm thinking about an "active" antenna. An electrically

   'short' antenna (less than 1/4 wave) can be an effective

   receiving antenna . . . but it's not resonant . . . meaning

   that the thing is a pretty hi impedance source of energy

   not well suited to piping that energy into a 50-ohm

   coax.



   A work-around has roots that go WWwaaayyy back in radio

   receiving history with earliest practical roots demonstrated

   in car radios. Antennas on cars might be little more than

   1 meter long yet expected to perform in the capture of

   signals having wavelengths in the neighborhood of 200-400

   meters.



   In the instance before us, it's quite possible to get

   a 'resonant' antenna capable of delivering energy into

   a 50-ohm coax . . . the problem is physical layout

   limits that we've discussed. But suppose we consider a

   'short' antenna . . . say about 1/10th wavelength at

   115 Mhz or 10" long.



   A simple amplifier can be crafted to go on the antenna

   end of the coax that will improve the short antenna's

   ability to deliver energy into the coax.  It takes about

   8 components on a board about 1/2 x 3/4 inch. You not

   only run your normal RG coax out to this board, you run

   a 22AWG wire connected to 14V.



   Now your overall antenna is less than a foot long and

   doesn't need the "counter-poise" that turns a 1/4

   wave monopole into a dipole of twice the length.



   I've got some other antenna work to do in the next few

   weeks and I thought I would fiddle with an active

   antenna amplifier for VOR/LOC/GS. Could you bore a hole

   in your canard leading edge foam to accept a 1" piece

   of thinwall pvc pipe about 15" long?  If so, we may

   well be able to craft an antenna that would slip into

   the pipe and just lay there.

   Bob . . .

berkut13(at)berkut13.com
Guest

Posted: Tue Oct 28, 2014 3:07 pm Post subject: Toroid beads/VOR antenna design

A small, active antenna is just fine as I would have room for a circuit 

board on the end of the whip (inboard end) and have power available a few 

inches away.



I donâ€™t think I can get 1"dia in there.  The D section is quite small in 

aspect, and there are wooden dowels running fore/aft in the middle of the 

foam from the construction process - I had to bore in front of those.  The 

foam conduit already exists now, I bored it from the tip inboard.  I will 

plug/repair the outboard conduit hole in the tip, and although it could be 

used for initial installation, I would not consider it to be an access or 

service point in the future as it would affect the external surfacing/paint.



In this case, and ideally, the antenna portion would be flexible enough to 

bend 90degrees (not sharply) to be fed down and into the foam conduit 

(inboard to outboard) -  it is not a direct shot into the conduit from the 

inboard end.  There is a plunge cut box in the bottom inboard skin/foam for 

access to the LE foam conduit.  This area will also will be the exit point 

for the antenna pigtail/connection.  The antenna would just lay in the foam 

conduit, and the circuit board can be supported or secured in the access box 

area.



If you anticipate working on an antenna design as you describe, I will table 

this issue for a few weeks and move forward with other items.  I am working 

to get this particular aircraft in the air in the Dec'14/Jan'15 timeframe 

and am on track to do so.   Obviously, it canâ€™t fly until the holes in the 

canard are repaired (preferably with antenna installed).  



So you know, the antenna will be connected to a Garmin 650 radio that has a 

VOR/GS splitter internally and has only the one coax connection.



Thanks for all your help!

-James

--

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Oct 29, 2014 7:30 am Post subject: Toroid beads/VOR antenna design

At 18:01 2014-10-28, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: <berkut13(at)berkut13.com>



 A small, active antenna is just fine as I would have room for a circuit board on the end of the whip (inboard end) and have power available a few inches away.



 I donâ€™t think I can get 1"dia in there.  The D section is quite small in aspect, and there are wooden dowels running fore/aft in the middle of the foam from the construction process. 	




    I'm not sure I have a clear mental image of your configuration.



    Q: If the antenna portion of the proposed installation were

       a 15-25" long, say stiff rod with the 'amplifier' stuck to

       the inboard end, would you be able to install such a device?



    It occurs to me that while many builders have described the

    boring of a hole through the foam under a composite structure,

    it might be possible to simply push the antenna portion of

    the device into the foam. The resulting hole would be no

    larger than what the antenna itself produced.



  	  Quote: 	
		  In this case, and ideally, the antenna portion would be flexible enough to bend 90degrees (not sharply) to be fed down and into the foam conduit (inboard to outboard) -  it is not a direct shot into the conduit from the inboard end. 	


    This is the unclear part. The 'antenna' portion the

    system need not be straight, rigid or any particular

    shape. It ultimately DOES want to have some geometric

    length in the horizontal plane (this is the e-field probe

    portion of its physics) but something of a curve or zig-zag

    isn't especially detrimental.



    So the goal is to get SOME conductor in a mostly horizontal

    orientation. The 'active' portion of the installation is

    an etched circuit board with a handful of surface mount

    components on it. I'm thinking something on the order of

    3/4" square. It would be fitted with a length of RG coax

    and a 14v power supply wire soldered on. The antenna connection

    could be a short pigtail that attached to the end of

    the conductor of choice installed in the foam.

 [img]cid:.0[/img]



  	  Quote: 	
		  So you know, the antenna will be connected to a Garmin 650 radio that has a VOR/GS splitter internally and has only the one coax connection. 	


    This is a 'broadband' design which should perform

    well at both VOR/LOC and GS frequencies. Parts

    not already on hand have been ordered. I'm going

    to set up a little 'antenna range' experiment in

    the back yard in the next few weeks. I can massage

    this active antenna project at the same time.



 

   Bob . . .

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berkut13(at)berkut13.com
Guest

Posted: Wed Oct 29, 2014 10:42 am Post subject: Toroid beads/VOR antenna design

Again, thank you for your help here.

  

 I have private emailed you with some photos of the projectâ€™s canard to help  better describe the mounting challenges.    For everyone else â€“  just imagine a surf board laying on the floor (perpendicular) in front of you,  mark off a 2â€™ wide section in the center, and you need to install a horizontal  antenna into the long side edge of board left or right of the center  section;  you can only access that center section you just marked off, and  you canâ€™t violate the external surfaces other than the center  section.   Fun, eh?

  

 Had I to do it over with this new antenna style in mind...yes, a ridged rod  could be inserted into the foam (at a slight angle from horizontal) but it would  need to have a spade point on the end, and be able to be chucked into a drill  while inserting for the length you are describing.  The standard blue foam  is easy to penetrate an inch or two, but beyond that the friction builds  rapidly.  This would be quite difficult if the amp was attached to the  element.  It would be much easier to just use a slightly larger dia rod  with a spade tip to bore a path through the skin and into the foam for the  antenna to be inserted into later â€“ again, at a slight angle from  horizontal.

  

 -James

  

  

  

    

  From: Robert L. Nuckolls, III (nuckolls.bob(at)aeroelectric.com) 

 Sent: Wednesday, October 29, 2014 10:29 AM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: Re: Re: Toroid beads/VOR antenna  design

  



 At  18:01 2014-10-28, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message    posted by: <berkut13(at)berkut13.com>



A small, active antenna is    just fine as I would have room for a circuit board on the end of the whip    (inboard end) and have power available a few inches away.



I donÃ¢Â€Â™t    think I can get 1"dia in there.  The D section is quite small in aspect,    and there are wooden dowels running fore/aft in the middle of the foam from    the construction process. 	




   I'm not sure I have a  clear mental image of your configuration.



   Q: If the antenna  portion of the proposed installation were

      a  15-25" long, say stiff rod with the 'amplifier' stuck  to

      the inboard end, would you be able to  install such a device?



  

   [quote][b]

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