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Antenna placement

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rparigor(at)SUFFOLK.LIB.N
Guest

Posted: Tue Jan 23, 2007 10:54 am Post subject: Antenna placement

Have a few questions about antenna placement for our Europa (fiberglass).



The Advanced Aircraft Electronics L2 Transponder antenna came with a piece

of balsa to mount it on. What is idea here? Bond the antenna to balsa,

then balsa to fiberglass?



As far as the fore and aft position of Transponder antenna, 2 available

positions are ~ 5 feet behind pilot, or ~ 8 feet behind pilot. 5 feet will

allow a slight lower position in flight, but is closer to the motor. Which

choice is preferable of the 2?



As far as the left and right position of the transponder antenna, there is

an ~ 2" thin wall aluminium pitch tube running fore and aft. I could mount

the antenna direct under this tube by ~ 2" that would make for a

friendlier movement about. Or I can displace it to one side 6 (8 feet) or

12 inches (5 feet). What would preference be?



I will have Advanced Aircraft Electronics 5T antenna mounted just behind

the baggage bay bulkhead. It will be powering a Vertex 700 panel mounted

hand held. I will mount it bent 90 degrees where approx 1/2 is vertical,

and half will be on the roof horizontal(to work equal bad on both nav and

Com). Talking to Advanced they said it will provide approx 70% of the

performance on both Nav and Com compared to proper straight orientation,

and be far better than rubber ducky antenna with 90 degree bend.



Any comments from those who have done this 90 degree bend?



I want to place my ELT whip antenna (ACK EO1)vertical inside fuse, where

it will be diagonal from the center of 90 degree bend of Advanced 5T

antenna by about 18 inches. 



Will this close proximity potentially cause any receive or transmit

problems for Vertex? 



If I were to test the ACK and had the vertex on, could this close

proximity cause harm the the Vertex?



Other info:

Transponder antenna will be either 2 or 5 feet aft of ELT antenna

Primary Com antenna is a Bob Archer in top of rudder



Thx.

Ron Parigoris

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N6030X(at)DaveMorris.com
Guest

Posted: Tue Jan 23, 2007 11:33 am Post subject: Antenna placement

I'm only going to comment on a small part of this.  As a ham operator 

with a few decades of experimentation with antennas (primarily HF, 

but also some VHF), I've seen most everything you can do right and 

wrong with antennas.



First of all, almost nothing you have described here is going to have 

a *huge* impact.  The bad effects you might achieve will be 

minor.  When you are 50 miles from an ATC comm station trying 

desperately to raise someone, the minor impacts could become more 

significant, but for 99% of your flying, it won't matter too 

much.  So, here are a few thoughts:



Try to keep all antennas a quarter wavelength away from other metal 

that is in the same plane (not airplane, geometric plane).  In feet, 

that's about 234 / Frequency in Megahertz.  Run coax feeders 90 

degrees away from the antenna as far as possible to prevent 

interference.  Receivers will work with any piece of wire and you'll 

be able to hear *something*, but when you get the wire length exactly 

right and you have no interference with surrounding metal, you'll be 

rewarded with a really nice strong signal and low noise.



Putting a 90 degree bend in the antenna will screw up its SWR.  That 

may only affect your reception by 3db, but it could potentially cause 

your solid state, computer controlled transmitter to automatically 

reduce its output power.  I'm not sure.  You'll have to try it 

out.  When you're flying in New Mexico over an area where you can't 

raise ATC even at 8500 feet and the terrain is fiercely hostile (for 

instance here: 

http://www.davemorris.com/Photos/Mooney%20N6030X%20Shiprock%20NM/IMG_2098.jpg) 

, you'll want as good a transmitter as you can get.  So, the question 

becomes, are you going to need NAV out in the boonies more than COM, 

or vice versa.  My guess is you're going to have a darn nice GPS on 

board, and you may never use your handheld NAV function on the 

radio.  So, optimize it for COM if that applies to you.



If the ELT antenna is 18 inches minimum from the COM antenna, that's 

not the ultimate in separation, but it will be adequate.  I doubt 

you'd be able to tell the difference if you moved it a full quarter 

wavelength away.  It may affect the radiation lobes, causing them to 

be oriented more forward and aft, and giving you less effectiveness 

off the wingtips, but it will be so miniscule you probably won't 

notice the difference unless you are way far from the ground 

station.  When you test the ELT, turn down the volume in the Vertex, 

or just unplug it.  It won't harm it, but you won't like the noise.



Aircraft that have a non-metal tail cone about 31 inches in diameter 

can take advantage of my Morris Com Loop antenna, which is a full 

wavelength loop mounted on the fuselage wall.  It provides slight 

gain, greater immunity to noise, and requires no ground plane.

http://www.davemorris.com/MorrisComLoop.cfm



Dave Morris

www.N5UP.com

www.N6030X.com

At 11:54 AM 1/23/2007, you wrote:

 	  Quote: 	
		  I will have Advanced Aircraft Electronics 5T antenna mounted just behind

the baggage bay bulkhead. It will be powering a Vertex 700 panel mounted

hand held. I will mount it bent 90 degrees where approx 1/2 is vertical,

and half will be on the roof horizontal(to work equal bad on both nav and

Com). Talking to Advanced they said it will provide approx 70% of the

performance on both Nav and Com compared to proper straight orientation,

and be far better than rubber ducky antenna with 90 degree bend.



Any comments from those who have done this 90 degree bend?



I want to place my ELT whip antenna (ACK EO1)vertical inside fuse, where

it will be diagonal from the center of 90 degree bend of Advanced 5T

antenna by about 18 inches.



Will this close proximity potentially cause any receive or transmit

problems for Vertex?



If I were to test the ACK and had the vertex on, could this close

proximity cause harm the the Vertex?

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glastar(at)gmx.net
Guest

Posted: Tue Jan 23, 2007 10:17 pm Post subject: Antenna placement

rparigor(at)SUFFOLK.LIB.NY.US wrote:

 	  Quote: 	
		   



 Have a few questions about antenna placement for our Europa (fiberglass).



 The Advanced Aircraft Electronics L2 Transponder antenna came with a piece

 of balsa to mount it on. What is idea here? Bond the antenna to balsa,

 then balsa to fiberglass?

Ron, shape the Balsa so it conforms to the shape of your fuselage, epoxy 
	


it to the fuselage, glue the antenna on the balsa (blades are straight) 

cover blades and balsa with a layer of glass going also on the fuselage 

shell.



That's what we did on several Glastar's and it worked out great.



br Werner

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