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Mike Whisky

Joined: 05 Jun 2006
Posts: 336
Location: Switzerland

Posted: Sun Nov 01, 2009 1:32 pm Post subject: First successful test of windscreen antenna

I just wanted to share my first positive experience with the windscreen antenna taped to the center bar. I tested it by holding the center bar at the right angle and attached my handheld radio to it. I had no problems listening to Zurich tower although being inside a concrete building.



I glued the strip to the bar and covered it with black tape (see attached photos)



Cheers

Michael

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_________________
RV-10 builder (flying)
#511

pitts_pilot(at)bellsouth.
Guest

Posted: Sun Nov 01, 2009 2:32 pm Post subject: First successful test of windscreen antenna

I will have two radios, and I plan on putting the antennas in each side 

windshield post in the fiberglass top.    Not the most ideal place 

....no good ground plane right there ..... but it's better than letting 

them hang outside, or horizontal as in the wingtips.  I have a friend 

with an RV-6 that removed his antenna that was stuck to the center bar.

Linn



Michael Wellenzohn wrote:

 	  Quote: 	
		   



 I just wanted to share my first positive experience with the windscreen antenna taped to the center bar. I tested it by holding the center bar at the right angle and attached my handheld radio to it. I had no problems listening to Zurich tower although being inside a concrete building.



 I glued the strip to the bar and covered it with black tape (see attached photos)



 Cheers

 Michael



 --------

 RV-10 builder (avionics, wiring)

 #511





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p 70494#270494





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recapen(at)earthlink.net
Guest

Posted: Sun Nov 01, 2009 6:37 pm Post subject: First successful test of windscreen antenna

Help me with this please - I had one similar - on the windscreen.  Had it 

tested by a bunch of HAM radio guys - they said it was too short causing the 

SWR to be bad.  I had made it longer in hopes of cutting it doen during 

testing.  It seemed to receive OK  but couldn't get anyone to hear me.....



How long is yours?

Have you tried it in flight?

What led you to taping it to the center post?

Is it insulated from the center post only by the paint?



Thanks,

Ralph Capen

RV6A N822AR (at) N06 39hrs

Collecting a bunch of -10 parts already......



---

jdalmas(at)yahoo.com
Guest

Posted: Mon Nov 02, 2009 6:01 am Post subject: First successful test of windscreen antenna

The antenna should be 1/2 wavelength long.  



So, at 122.7 MHz, and with a speed of light at 3 x 10**8 m/sec, 1/2 of the wavelength is 1.22m or about 48inches.



Check out this website for way more info....



http://k9erg.tripod.com/theory.htm

John Dalmas

RV10 397

working on instrument panel

--- On Sun, 11/1/09, Ralph E. Capen <recapen(at)earthlink.net> wrote:



[quote] From: Ralph E. Capen <recapen(at)earthlink.net>

 Subject: Re: First successful test of windscreen antenna

 To: rv10-list(at)matronics.com

 Date: Sunday, November 1, 2009, 9:30 PM

 

 "Ralph E. Capen" <recapen(at)earthlink.net>

 

 Help me with this please - I had one similar - on the

 windscreen.  Had it 

 tested by a bunch of HAM radio guys - they said it was too

 short causing the 

 SWR to be bad.  I had made it longer in hopes of

 cutting it doen during 

 testing.  It seemed to receive OK  but couldn't

 get anyone to hear me.....

 

 How long is yours?

 Have you tried it in flight?

 What led you to taping it to the center post?

 Is it insulated from the center post only by the paint?

 

 Thanks,

 Ralph Capen

 RV6A N822AR (at) N06 39hrs

 Collecting a bunch of -10 parts already......

 

 ---

Kellym

Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ

Posted: Mon Nov 02, 2009 6:42 am Post subject: First successful test of windscreen antenna

Most aircraft antennas start with 1/4 wavelength, not 1/2. So 24" is 

more likely to fit the space available.



john dalmas wrote:

[quote] 

 

 The antenna should be 1/2 wavelength long.  

 

 So, at 122.7 MHz, and with a speed of light at 3 x 10**8 m/sec, 1/2 of the wavelength is 1.22m or about 48inches.

 

 Check out this website for way more info....

 

 http://k9erg.tripod.com/theory.htm

 

 

 John Dalmas

 RV10 397

 working on instrument panel

 

 

 --- On Sun, 11/1/09, Ralph E. Capen <recapen(at)earthlink.net> wrote:

 

> From: Ralph E. Capen <recapen(at)earthlink.net>

> Subject: Re: First successful test of windscreen antenna

> To: rv10-list(at)matronics.com

> Date: Sunday, November 1, 2009, 9:30 PM

> 

> "Ralph E. Capen" <recapen(at)earthlink.net>

>

> Help me with this please - I had one similar - on the

> windscreen.  Had it 

> tested by a bunch of HAM radio guys - they said it was too

> short causing the 

> SWR to be bad.  I had made it longer in hopes of

> cutting it doen during 

> testing.  It seemed to receive OK  but couldn't

> get anyone to hear me.....

>

> How long is yours?

> Have you tried it in flight?

> What led you to taping it to the center post?

> Is it insulated from the center post only by the paint?

>

> Thanks,

> Ralph Capen

> RV6A N822AR (at) N06 39hrs

> Collecting a bunch of -10 parts already......

>

> ---

_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD

AirMike

Joined: 27 Feb 2007
Posts: 514
Location: Nevada

Posted: Mon Nov 02, 2009 7:58 am Post subject: First successful test of windscreen antenna

I was advised by Aerotronics in Billings Mt and at least one other avionics shop to just use a regular external antenna (which I did) for the COM. I was able to buy a used Cessna Commant antenna at OSH two years ago for about $30-$35. It works flawlessly. I did however use the same installation as Michael for the NAV antenna. As I recall it is 24 or 25 inches long. I bought the Van's product which is essentially a piece of copper foil glued to the headliner just behind the windshield. Connect it with a piece of coax cable run thru the steel cabin support strut I tested it's reception yesterday over the Fallon, NV  - Hazen VOR. I got good reception on all points of the compass. I was worried about the reception driving away from the VOR when the tail cone blankets the signal, but it worked fine.

_________________
See you OSH '18
Q/B - sold.

Bob Turner

Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA

Posted: Mon Nov 02, 2009 11:25 am Post subject: Re: First successful test of windscreen antenna

Use a half wavelength if you cut the wire in the middle, and feed each side with the coax (center to one side, braid to the other).



Use a quarter wave length if you mount the feed end over a "ground plane" (a large conducting surface - maybe the glare shield is large enough). Attache the center conductor to the wire, the braid to the ground plane.



Either of these gives a reasonable match to 50 ohm coax. But nearby metal may change the match by quite a bit, so don't be surprised if taping to the cabin support bar doesn't match all that great. Or maybe it will, all depends on the details. The fact that the cabin support bar is not perpendicular to the glare shield will change things, too.



Modern receivers are very sensitive and will work with lousy antennas. The real test is if the tower can hear you when you transmit (especially with a low powered hand held). I can receive quite well on my handheld inside the cabin of a 182 with just the little rubber duckie antenna; but only transmit about 3 miles with this arrangement.

_________________
Bob Turner
RV-10 QB

Mike Whisky

Joined: 05 Jun 2006
Posts: 336
Location: Switzerland

Posted: Mon Nov 02, 2009 1:37 pm Post subject: Re: First successful test of windscreen antenna

My antenna strip is about 23 inches long but plus the cable its more like 24

reception is good but I didn't try to transmit yet.

The center bar is powder coated in flat black on top of the original gray.

Mike

_________________
RV-10 builder (flying)
#511

Phil White

Joined: 10 Jan 2006
Posts: 45
Location: Downers Grove, IL

Posted: Mon Nov 02, 2009 6:43 pm Post subject: Re: First successful test of windscreen antenna

Because the center post is attached to the airframe, it is grounded.  Having your antenna tightly attached to a grounded piece will probably de-tune it significantly, or at the least cause an odd radiation pattern on transmit.

  I expect you will not find this antenna to work at all well.



  It is recommended that you install the foil strip type on the inside of the fiberglass roof, where it is away from the metal of the airframe.  Comm antennas need to be vertically polarized, so the best location is on the door post immediately behind the door.  I have such a foil antenna for my handheld installed there, and it works well.  (But for the main Comm, I rely on an external Comant on the belly, cause I know it will work well.)

Phil in IL, finishing at rotary engine install

pitts_pilot(at)bellsouth.
Guest

Posted: Mon Nov 02, 2009 7:07 pm Post subject: First successful test of windscreen antenna

Phil White wrote:

 	  Quote: 	
		   

 

 Because the center post is attached to the airframe, it is grounded.

 Having your antenna tightly attached to a grounded piece will

 probably de-tune it significantly, or at the least cause an odd

 radiation pattern on transmit. I expect you will not find this

 antenna to work at all well.

 

 It is recommended that you install the foil strip type on the inside

 of the fiberglass roof, where it is away from the metal of the

 airframe.  Comm antennas need to be vertically polarized, so the best

 location is on the door post immediately behind the door.

Or in front of the door.  I'm going to try that place first.
	


Linn

do not archive



   I have

 	  Quote: 	
		   such a foil antenna for my handheld installed there, and it works

 well.  (But for the main Comm, I rely on an external Comant on the

 belly, cause I know it will work well.) Phil in IL, finishing at

 rotary engine install

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p 70659#270659

Phil.Perry(at)netapp.com
Guest

Posted: Tue Nov 03, 2009 9:00 am Post subject: First successful test of windscreen antenna

I'm glad someone finally said something.  Every time I typed a response,

I sounded like a jack ass so I just deleted my message.  But I'll just

come right out and say it.  That's a lousy lousy choice for an antenna

location. Listening and transmitting are two separate things.  To prove

my point, try attaching a coat hanger as an antenna and see how well it

will work to listen on - you'll be surprised at how well it works.

Shoot, even aluminum foil works for rabbit ears to receive television

stations.



I've designed and built several antennas over the years and can speak

from many years of experience and personal mistakes.  So of those were

pretty creative like loading up a metal rain gutter as an antenna, a

flagpole, even an entire building.



There's absolutely no chance of that antenna ever tuning because of the

antennas position relative to the metal bar.  But that did give me an

idea that'll probably still not work - but it's might be worth a shot.

That is to swap the steel bar out with a composite one.  That might get

it, but you're still going to have some significant metal that could

interfere.



Another concern is with all that RF literally right on top of your

panel.  EFIS, GPS, Engine Sensors (electronic) are all running right

there.  Not to mention the RF will light up everything "inside" the

cockpit too.  I've experienced my share of RF burns from touching metal

nearby a transmitting antenna - they're painful.



I apologize for sounding really negative, but I've been down this path

before.  There are many better places to put an antenna but none any

worse.



Phil



--

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Tue Nov 03, 2009 10:51 am Post subject: First successful test of windscreen antenna

Phil, don't feel like that.



Few of us builders have considered timely issues on RF signal

propagation and effective communication/navigation for future flight,

when building the RV-10 early in the process.  The correct time to

identify components, select the correctly effective antenna and place it

on the airframe in the right location is early in the planning. Far

earlier than most have admitted.  A wise builder does not need to spend

the money on the avionics but should have a solid idea of manufacturer,

model and placement of antennas.



Horizontal/Vertical polarity, proper ground plane installation, doubler

plates to accept the load and a solid transmitting radiation pattern

just might be beyond the casual builder.  Before those who like to

criticize pipe in, I will offer a solution.  Talk to Stein.  Visit your

favorite avionics shop that will repair your components and plan for the

build rather than learning late in the completion.



Most of the time the components are selected far too late, mounted

structurally unwisely and fail to radiate a safe and effective signal

when needed most.



Skin mapping is a foreign word to most RV-10 builders.  Few understand

the bio-physics of being a rear seat navigator in a Navy EA-6B.

Antennae arrays, mega wattage and lots of RF can fry valued private

parts.  Anyone remember the cellphone scare of brain tumors years ago

from having the working end of the antenna so close to gray matter?



Any ham should have access to an SWR meter and the correct pigtail to

test your transmitted Wave.  Some will even be able to plot the

effectiveness during broadcast. Others might get the antenna tuned at

one end of the spectrum and loose the opposite. Tuning can be an art

form. Aviation is about tradeoffs.  Others will opt for a Garmin 530

which doubles the watts being shoved out the tuned end of the final

installation.  When the pipe is the wrong length, when the ground plane

is ineffective, when the RF signal is masked externally by other

materials such as Plexiglas, fiberglass, carbon or aluminum the output

circuitry on the transmitter can take an expensive dump at the worst

time.  Chasing kinked coax or improper crimped connections can be even

more challenging.



Get on board early in the build - learn from others.  And thanks for

your perspective.

Don't forget to support Matt during the month of November!



John

W7COX



--

Phil.Perry(at)netapp.com
Guest

Posted: Tue Nov 03, 2009 1:17 pm Post subject: First successful test of windscreen antenna

I think you agreed with me, John.  



I agree with everything you said.  Find someone who's been down the path

before and get their advice.  It'll save countless weeks of chasing

gremlins and you'll end up with a more efficient and trouble free

antenna system.



Phil





--

rv10builder(at)verizon.ne
Guest

Posted: Tue Nov 03, 2009 1:17 pm Post subject: First successful test of windscreen antenna

Phil;

Somehow I missed the reason for your apology. You used your experience to 

relay to people that the idea is not a good one, there are many on this 

forum who have no clue if it will work until it's tested, specifically me.. 

that is why I hold the feedback from all those builders who relay what has 

worked for them. You have opened the dialog to have others give their 

perspective, you have basically serve the group well in doing so.. so no 

idea why the apology.

If you're apologizing for stating a fact based on experience, which it 

sounds you're doing, keep it coming, not apologizing, but giving your 

feedback so we don't follow in something that wont work..

Thanks!

Pascal



--------------------------------------------------

From: "Perry, Phil" <Phil.Perry(at)netapp.com>

Sent: Tuesday, November 03, 2009 8:47 AM

To: <rv10-list(at)matronics.com>

Subject: RE: Re: First successful test of windscreen antenna



[quote] 



 I'm glad someone finally said something.  Every time I typed a response,

 I sounded like a jack ass so I just deleted my message.  But I'll just

 come right out and say it.  That's a lousy lousy choice for an antenna

 location. Listening and transmitting are two separate things.  To prove

 my point, try attaching a coat hanger as an antenna and see how well it

 will work to listen on - you'll be surprised at how well it works.

 Shoot, even aluminum foil works for rabbit ears to receive television

 stations.



 I've designed and built several antennas over the years and can speak

 from many years of experience and personal mistakes.  So of those were

 pretty creative like loading up a metal rain gutter as an antenna, a

 flagpole, even an entire building.



 There's absolutely no chance of that antenna ever tuning because of the

 antennas position relative to the metal bar.  But that did give me an

 idea that'll probably still not work - but it's might be worth a shot.

 That is to swap the steel bar out with a composite one.  That might get

 it, but you're still going to have some significant metal that could

 interfere.



 Another concern is with all that RF literally right on top of your

 panel.  EFIS, GPS, Engine Sensors (electronic) are all running right

 there.  Not to mention the RF will light up everything "inside" the

 cockpit too.  I've experienced my share of RF burns from touching metal

 nearby a transmitting antenna - they're painful.



 I apologize for sounding really negative, but I've been down this path

 before.  There are many better places to put an antenna but none any

 worse.



 Phil



 --

Phil.Perry(at)netapp.com
Guest

Posted: Tue Nov 03, 2009 1:38 pm Post subject: First successful test of windscreen antenna

Hi Pascal,



I never sent my original e-mail because I couldn't figure out how to

communicate the issue without sounding really really rude or offensive

and that's not my goal.  So those messages got typed and then I deleted

them.



But Phil White cracked the door enough for me to open up for a few

seconds.



As John Cox mentioned, go find a ham who has been around for awhile and

ask them to visit your project for a few hours.  If they're the

old-school type who built their own antennas and transceivers (AKA:

home-brew type), they'll jump right on the project and be able to

provide very valuable experience, tools, and measuring equipment.



I've heard that antennas operate on FM.  That's not really true, there's

a science to it.



I'll let you figure out what FM is.  



Phil





--

deej(at)deej.net
Guest

Posted: Tue Nov 03, 2009 1:51 pm Post subject: First successful test of windscreen antenna

On 11/03/2009 04:38 PM, Perry, Phil wrote:

 	  Quote: 	
		   I've heard that antennas operate on FM.  That's not really true, there's

 a science to it.



 I'll let you figure out what FM is.  



   


	


    Another hint - our aviation COM radios work on AM frequencies

(Amplitude Modulation).  You can find info on AM at

<http://en.wikipedia.org/wiki/Amplitude_modulation> and FM at

<http://en.wikipedia.org/wiki/Frequency_modulation> if you are

interested in learning more.



    <http://www.arrl.org/> is a good place to start if you want to learn

about antenna construction.



fyi



-Dj



-- 

Dj Merrill - N1JOV

Glastar Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Grumman Yankee Driver N9870L - http://deej.net/yankee/

Phil.Perry(at)netapp.com
Guest

Posted: Tue Nov 03, 2009 2:06 pm Post subject: First successful test of windscreen antenna

Yes, I should clarify.



The particular version of FM I was referring to is a certain type of

______ Magic that can only be found in the urban dictionary.  It is the

type of magic that avionic technicians frequently use to neuter

electronic gremlins from ever reproducing.  This phrase is commonly

found on military flight lines.  



Phil



--

MauleDriver(at)nc.rr.com
Guest

Posted: Tue Nov 03, 2009 2:32 pm Post subject: First successful test of windscreen antenna

Freakin' Magic 'eh?



do not archive



Perry, Phil wrote:

[quote] 



 Yes, I should clarify.



 The particular version of FM I was referring to is a certain type of

 ______ Magic that can only be found in the urban dictionary.  It is the

 type of magic that avionic technicians frequently use to neuter

 electronic gremlins from ever reproducing.  This phrase is commonly

 found on military flight lines.  



 Phil



 --

Mike Whisky

Joined: 05 Jun 2006
Posts: 336
Location: Switzerland

Posted: Tue Nov 03, 2009 2:40 pm Post subject: Re: First successful test of windscreen antenna

Hi Phil,



since I am the one who started the topic I thank you for sharing your insides here. I couldn't find any "real" answer before in the forum. My COM 1 is an external antenna and I thought that the com 2 would be fine on the center bar. Having read your statements above will change my installation.



Cheers

Mike

_________________
RV-10 builder (flying)
#511

Phil.Perry(at)netapp.com
Guest

Posted: Tue Nov 03, 2009 3:44 pm Post subject: First successful test of windscreen antenna

Hey Mike,



I really didn't want to come across negatively.



Just looking at the airplane and thinking of creative places to install

a copper tape antenna, I'd suggest running a tape (or even wire) in the

vertical section aft of the main doors.  This is the vertical area

(inside the cabin top) that is between the aft windows and the main

door.  You'll be able to maintain vertical polarization by installing

here.  Measuring my cabin top, I have around 30 inches vertical area for

the antenna to run inside at this location.  About 22 inches of space

above the aluminum airframe - a key number as you'll see in the next

paragraph.



Just doing some quick math, you'll only need an antenna length of 22.11

inches to tune the antenna to 127mhz.  (Middle of 118mhz - 136mhz

range).  You can ground the braid to the fuselage (There's a really nice

longeron right there) and attach the center conductor to the copper

tape/wire.  The base of the tape should be above the aluminum airframe,

so braid goes to the frame and the center conductor goes directly into

the vertical tape.  (Does any of that make sense?)



You'll stand a better chance of getting a resonant antenna in this

location.  I'm still a little concerned with that much RF being radiated

inside the cockpit, but it may not matter.  Only testing the transmitter

with the avionics up and running will really tell the truth.



For your benefit, when calculating the antenna length you can use this

simple formula to get the quarter wavelength of the antenna.  Quarter

wavelength = 234/(frequency in mhz)



The antenna I described is essentially a 1/2 wavelength antenna being

composed of a 1/4 wavelength radiating element (copper tape).  The other

1/4 wavelength of the antenna is being made up from the aluminum

structure of the fuselage.



Let me know if I can help.



Phil

--

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