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icubob(at)newnorth.net
Guest

Posted: Thu Feb 09, 2006 3:33 pm Post subject: antennas

hi all,

 I have several antennas to install. My elt requires a ground plane. Tim at b and c was very helpful with my questions but i question leads to 5 more. Is there any way around a ground plane for the elt? If not, any suggestions on how to make it in my wood/cloth fuselage? At first i thought numerous strips of thin copper way the way to go but that looks like just more fasteners. Can a very thin sheet be laid down in the fuse. bottom? It wouldnt exactly be flat with all the woodworking to go around.

  Also, my dipole comm must be vertical. No more than 45 deg slant. is 30 deg vastly better than 45 deg and is 15 deg vastly better than 30 deg. Are these slanted antennas going to noticeably going to affect transmission/ reception that much anyway?

  Anyone want to volunteer a phone number to me off list? i have more questions every time i get one answered.

          Thanks in advance, bob noffs

nuckollsr(at)cox.net
Guest

Posted: Thu Feb 09, 2006 3:46 pm Post subject: antennas

At 05:30 PM 2/9/2006 -0600, you wrote:



 	  Quote: 	
		  



hi all,

  I have several antennas to install. My elt requires a ground plane. Tim 

 at b and c was very helpful with my questions but i question leads to 5 

 more. Is there any way around a ground plane for the elt? If not, any 

 suggestions on how to make it in my wood/cloth fuselage? At first i 

 thought numerous strips of thin copper way the way to go but that looks 

 like just more fasteners. Can a very thin sheet be laid down in the fuse. 

 bottom? It wouldnt exactly be flat with all the woodworking to go around.


	


      If it's wood and fabric, I'd go with a vertical dipole wrapped

      around the inside surface of the fuselage. Perhaps on side opposite

      your comm dipole cited below and separated some fore/aft as well . . .



 	  Quote: 	
		     Also, my dipole comm must be vertical. No more than 45 deg slant. is 30 

 deg vastly better than 45 deg and is 15 deg vastly better than 30 deg. 

 Are these slanted antennas going to noticeably going to affect 

 transmission/ reception that much anyway?


	




      No . . . the lion's share of antenna performance happens

      in the first 25% of length each side of center (about 5")

      meaning that things you do with the last 15" per side are

      not terribly critical. Get as much of the center section for

      both antennas as vertical as practical, then wrap the ends

      around the inside surface of the fuselage.



      They'll drop in center frequency as you "fold" them so you

      MIGHT want to check them with an SWR/Antenna analyzer and

      trim them for optimum.



 	  Quote: 	
		     Anyone want to volunteer a phone number to me off list? i have more 

 questions every time i get one answered.


	


      Let's do it on the list. If your questions are worth

      asking, then they're worth sharing too.



      Bob . . .

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Thu Feb 09, 2006 4:30 pm Post subject: antennas

bob noffs wrote:



 	  Quote: 	
		    Is there any way around a ground plane for the elt? 


	


No.



 	  Quote: 	
		   If not, any suggestions on how to make it in my wood/cloth fuselage? 


	


Most anything will do. You want some strips of copper or wire that are

the same length as the ELT antenna, i.e. 1/4 wave at 121.5 MHz (about

25" or so). A flat piece of metal 25" in radius or larger would work.

And it may be oddly shaped.



 	  Quote: 	
		   Can a very thin sheet be laid down in the fuse. bottom? 


	


Certainly. That would be fine.



 	  Quote: 	
		   It wouldnt exactly be flat with all the woodworking to go around.


	


That doesn't matter.



 	  Quote: 	
		     Also, my dipole comm must be vertical. No more than 45 deg slant. is 30 deg vastly better than 45 deg and is 15 deg vastly better than 30

deg.
	




The closer you are to vertical, the better it will work but anything

will work after a fashion, even horizontal. Just try to get it as

vertical as possible.



 	  Quote: 	
		   Are these slanted antennas going to noticeably going to affect transmission/ reception that much anyway?


	


Odds are, no, you won't notice the difference.



 	  Quote: 	
		     Anyone want to volunteer a phone number to me off list? i have more questions every time i get one answered.


	


If I have time I would answer your questions.



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

nuckollsr(at)cox.net
Guest

Posted: Thu Feb 09, 2006 6:11 pm Post subject: antennas

Guess I forgot to ask if you had a dual freq ELT . . . I guess all the

new ones are. In this case, the ground plane under a stock antenna is

necessary. But since it's a dual freq, one might argue that two sets of

radials would be good . . . one set tuned for 121.5 (24") and another

set optimized for 406 (7.3"). Hmmm . . . maybe a 7.3" radius piece of

copper foil with a few 20" legs soldered to the edge. The single dipole

I suggested would not be suited for dual frequency use (although one

COULD be crafted . . . it would probably be more trouble than it's worth).



  Bob . . .

At 05:30 PM 2/9/2006 -0600, you wrote:



 	  Quote: 	
		  



hi all,

  I have several antennas to install. My elt requires a ground plane. Tim 

 at b and c was very helpful with my questions but i question leads to 5 

 more. Is there any way around a ground plane for the elt? If not, any 

 suggestions on how to make it in my wood/cloth fuselage? At first i 

 thought numerous strips of thin copper way the way to go but that looks 

 like just more fasteners. Can a very thin sheet be laid down in the fuse. 

 bottom? It wouldnt exactly be flat with all the woodworking to go around.


	


      If it's wood and fabric, I'd go with a vertical dipole wrapped

      around the inside surface of the fuselage. Perhaps on side opposite

      your comm dipole cited below and separated some fore/aft as well . . .



 	  Quote: 	
		     Also, my dipole comm must be vertical. No more than 45 deg slant. is 30 

 deg vastly better than 45 deg and is 15 deg vastly better than 30 deg. 

 Are these slanted antennas going to noticeably going to affect 

 transmission/ reception that much anyway?


	




      No . . . the lion's share of antenna performance happens

      in the first 25% of length each side of center (about 5")

      meaning that things you do with the last 15" per side are

      not terribly critical. Get as much of the center section for

      both antennas as vertical as practical, then wrap the ends

      around the inside surface of the fuselage.



      They'll drop in center frequency as you "fold" them so you

      MIGHT want to check them with an SWR/Antenna analyzer and

      trim them for optimum.



 	  Quote: 	
		     Anyone want to volunteer a phone number to me off list? i have more 

 questions every time i get one answered.


	


      Let's do it on the list. If your questions are worth

      asking, then they're worth sharing too.



      Bob . . .

BigD(at)DaveMorris.com
Guest

Posted: Thu Feb 09, 2006 7:56 pm Post subject: antennas

In theory, the amount of loss varies as the cosine of the angle difference 

between the transmitting and receiving antennas.  At a 45 degree angle, you 

lose 3dB, which is somewhat noticeable, because it is actually 1/2 of the 

power lost.  At 90 degrees, it is over 20dB loss, which is substantial.



In practice, the signals bounce around and may not arrive at your antenna 

perfectly vertically polarized to begin with, but it doesn't hurt to make 

it as close to vertical as possible.  The problems will mainly show up when 

you're a long way away from the ground station.  When you're close, it 

won't make much difference.



Dave Morris



At 05:30 PM 2/9/2006, you wrote:

 	  Quote: 	
		  



   Also, my dipole comm must be vertical. No more than 45 deg slant. is 30 

 deg vastly better than 45 deg and is 15 deg vastly better than 30 deg. 

 Are these slanted antennas going to noticeably going to affect 

 transmission/ reception that much anyway?

icubob(at)newnorth.net
Guest

Posted: Fri Feb 10, 2006 4:12 am Post subject: antennas

hi all,

  i have gotten quite a bit of info from the responses to my questions. i now am confident i can mount my comm antenna and transponder and they will work. the elt with a ground plane still has me stalled though. will have more questions about that , just wanted to let everyone know how helpful the responses were. gotta go make donuts now.

                  bob noffs

brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Fri Feb 10, 2006 6:59 am Post subject: antennas

Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 

 Guess I forgot to ask if you had a dual freq ELT . . . I guess all the

 new ones are. 


	


The old ones are too. They operate at 121.5 MHz and 243 MHz.



 	  Quote: 	
		   In this case, the ground plane under a stock antenna is

 necessary. But since it's a dual freq, one might argue that two sets of

 radials would be good . . . one set tuned for 121.5 (24") and another

 set optimized for 406 (7.3"). Hmmm . . . maybe a 7.3" radius piece of

 copper foil with a few 20" legs soldered to the edge. The single dipole

 I suggested would not be suited for dual frequency use (although one

 COULD be crafted . . . it would probably be more trouble than it's worth).


	


And a tuned 1/4 wave counterpoise (radials) for 121.5 MHz is totally

useless at 243 MHz. Good point about having two sets of radials.



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Fri Feb 10, 2006 7:28 am Post subject: antennas

Responding to an AeroElectric-List message previously posted by: "bob noffs" 

<icubob(at)newnorth.net>



2/10/2006



Hello Bob, Dare I post some heresy? Will the gummint sic its watch dogs on 

me? Will the electromagnetic radiation purists on the list rise up in total 

fury to slap me down? Well, I'll take a chance.



Suppose that the gummint, in its infinite wisdom, mandated that every 

aircraft carry 3 pounds of butter and a container of maple syrup just in 

case the survival situation after crashing resulted in a supply of pancakes 

as the available food supply. Would you insist on carrying genuine maple 

syrup or would an imitation be good enough for you?



Maybe an ELT is a little more useful than butter and maple syrup in a crash 

situation, but I sure as hell wouldn't place my entire faith in being found 

and rescued in one of the garden variety ELT's that we are mandated to 

carry. My point is that obsessing over antenna ground plane details is 

wasted time.



Nobody knows exactly what attitude their aircraft will be in when it 

finishes crashing. The ELT antenna could end up pointing directly down at, 

and a few inches from, the surface of the earth. How much difference would a 

perfect ground plane, if one could construct one, make in that situation?



Here is my thinking:



1) To be legal, buy one of the garden variety ELT's that we are mandated to 

carry. Install it securely in the proper location in the proper attitude 

with regard to its deceleration sensor. Fasten on the wire antenna that came 

with the ELT and don't obsess over ground planes or what the antenna's 

attitude will be when you finish crashing. Go fly.



2) If you want to take some truly effective steps for rescue after crashing 

you can, and probably should to the degree that you are concerned and 

considering routes of flight, do some or all of the following.



2A) Always carry a hand held VHF comm radio with a battery supply that you 

KNOW to be capable of extended operation.



2B) Always carry a cell phone with a battery supply that you KNOW to be 

capable of extended operation.



2C) Purchase and carry a PLB http://www.equipped.com/faq_plb/default.asp



2D) Carry a tough plastic container of water -- size your choice. My 

experience with even short time rescued people is that they experienced an 

almost mentally debilitating thirst shortly after crashing.



2E) Carry a knife of enough size and sturdiness to punch through / crack 

your plastic windows and canopy.



I am sure that other posters will add their favorite / essential crash 

survival items, but obsessing over these items falls into the same category 

of time wasting like obsessing over ground planes. Take what you deem to be 

reasonable precautions to be rescued after a survivable crash and then 

proceed to fly worry and guilt free (and legal).



OC



PS: If you have the bank account to afford one of the new 406 Mhz ELT's, go 

for it.



<< hi all, I have several antennas to install. My elt requires a ground 

plane. Tim at b and

c was very helpful with my questions but i question leads to 5 more. Is 

there

any way around a ground plane for the elt? If not, any suggestions on how to

make it in my wood/cloth fuselage? At first i thought numerous strips of 

thin

copper way the way to go but that looks like just more fasteners. Can a very

thin sheet be laid down in the fuse. bottom? It wouldnt exactly be flat with

all the woodworking to go around.....skip.....Thanks in advance, bob noffs>>

BobsV35B(at)aol.com
Guest

Posted: Fri Feb 10, 2006 7:41 am Post subject: antennas

Good Morning OC,  



I know the rules say no "me too" messages, but you have presented the same  

arguments that I would like to present, but was afraid to send due to the  

flaming I would get had I done so!

 

Very well done.

 

Do Not Archive

 

Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



 

In a message dated 2/10/2006 9:31:26 A.M. Central Standard Time,  

bakerocb(at)cox.net writes:



2/10/2006



Hello Bob, Dare I post some heresy? Will the gummint  sic its watch dogs on 

me? Will the electromagnetic radiation purists on  the list rise up in total 

fury to slap me down? Well, I'll take a  chance.



Suppose that the gummint, in its infinite wisdom, mandated that  every 

aircraft carry 3 pounds of butter and a container of maple syrup  just in 

case the survival situation after crashing resulted in a supply of  pancakes 

as the available food supply. Would you insist on carrying  genuine maple 

syrup or would an imitation be good enough for  you?



Maybe an ELT is a little more useful than butter and maple syrup  in a crash 

situation, but I sure as hell wouldn't place my entire faith in  being found 

and rescued in one of the garden variety ELT's that we are  mandated to 

carry. My point is that obsessing over antenna ground plane  details is 

wasted time.



Nobody knows exactly what attitude their  aircraft will be in when it 

finishes crashing. The ELT antenna could end  up pointing directly down at, 

and a few inches from, the surface of the  earth. How much difference would a 

perfect ground plane, if one could  construct one, make in that situation?



Here is my thinking:



1)  To be legal, buy one of the garden variety ELT's that we are mandated to  

carry. Install it securely in the proper location in the proper attitude  

with regard to its deceleration sensor. Fasten on the wire antenna that  came 

with the ELT and don't obsess over ground planes or what the  antenna's 

attitude will be when you finish crashing. Go fly.



2) If  you want to take some truly effective steps for rescue after crashing 

you  can, and probably should to the degree that you are concerned and  

considering routes of flight, do some or all of the following.



2A)  Always carry a hand held VHF comm radio with a battery supply that you  

KNOW to be capable of extended operation.



2B) Always carry a cell  phone with a battery supply that you KNOW to be 

capable of extended  operation.



2C) Purchase and carry a PLB  http://www.equipped.com/faq_plb/default.asp



2D) Carry a tough plastic  container of water -- size your choice. My 

experience with even short time  rescued people is that they experienced an 

almost mentally debilitating  thirst shortly after crashing.



2E) Carry a knife of enough size and  sturdiness to punch through / crack 

your plastic windows and  canopy.



I am sure that other posters will add their favorite /  essential crash 

survival items, but obsessing over these items falls into  the same category 

of time wasting like obsessing over ground planes. Take  what you deem to be 

reasonable precautions to be rescued after a  survivable crash and then 

proceed to fly worry and guilt free (and  legal).



OC

pwmac(at)sisna.com
Guest

Posted: Fri Feb 10, 2006 9:06 am Post subject: antennas

Curious why you did not mention a sat phone? They save lives all the time 

all that is needed is a list of appropriate phone numbers. Cost is coming 

down all the time and even used hand sets are available. Save your self 

instead of depending on the system.

Regards, Paul

=============

At 02:28 AM 2/10/2006, you wrote:

 	  Quote: 	
		  



Responding to an AeroElectric-List message previously posted by: "bob noffs"

<icubob(at)newnorth.net>



2/10/2006



Hello Bob, Dare I post some heresy? Will the gummint sic its watch dogs on

me? Will the electromagnetic radiation purists on the list rise up in total

fury to slap me down? Well, I'll take a chance.



Suppose that the gummint, in its infinite wisdom, mandated that every

aircraft carry 3 pounds of butter and a container of maple syrup just in

case the survival situation after crashing resulted in a supply of pancakes

as the available food supply. Would you insist on carrying genuine maple

syrup or would an imitation be good enough for you?



Maybe an ELT is a little more useful than butter and maple syrup in a crash

situation, but I sure as hell wouldn't place my entire faith in being found

and rescued in one of the garden variety ELT's that we are mandated to

carry. My point is that obsessing over antenna ground plane details is

wasted time.



Nobody knows exactly what attitude their aircraft will be in when it

finishes crashing. The ELT antenna could end up pointing directly down at,

and a few inches from, the surface of the earth. How much difference would a

perfect ground plane, if one could construct one, make in that situation?



Here is my thinking:



1) To be legal, buy one of the garden variety ELT's that we are mandated to

carry. Install it securely in the proper location in the proper attitude

with regard to its deceleration sensor. Fasten on the wire antenna that came

with the ELT and don't obsess over ground planes or what the antenna's

attitude will be when you finish crashing. Go fly.



2) If you want to take some truly effective steps for rescue after crashing

you can, and probably should to the degree that you are concerned and

considering routes of flight, do some or all of the following.



2A) Always carry a hand held VHF comm radio with a battery supply that you

KNOW to be capable of extended operation.



2B) Always carry a cell phone with a battery supply that you KNOW to be

capable of extended operation.



2C) Purchase and carry a PLB http://www.equipped.com/faq_plb/default.asp



2D) Carry a tough plastic container of water -- size your choice. My

experience with even short time rescued people is that they experienced an

almost mentally debilitating thirst shortly after crashing.



2E) Carry a knife of enough size and sturdiness to punch through / crack

your plastic windows and canopy.



I am sure that other posters will add their favorite / essential crash

survival items, but obsessing over these items falls into the same category

of time wasting like obsessing over ground planes. Take what you deem to be

reasonable precautions to be rescued after a survivable crash and then

proceed to fly worry and guilt free (and legal).



OC



PS: If you have the bank account to afford one of the new 406 Mhz ELT's, go

for it.



<< hi all, I have several antennas to install. My elt requires a ground

plane. Tim at b and

c was very helpful with my questions but i question leads to 5 more. Is

there

any way around a ground plane for the elt? If not, any suggestions on how to

make it in my wood/cloth fuselage? At first i thought numerous strips of

thin

copper way the way to go but that looks like just more fasteners. Can a very

thin sheet be laid down in the fuse. bottom? It wouldnt exactly be flat with

all the woodworking to go around.....skip.....Thanks in advance, bob noffs>>

n395v

Joined: 10 Jan 2006
Posts: 450

Posted: Sat Feb 11, 2006 6:26 am Post subject: Re: antennas

absolutely marvelous info filled discussion. Read the whole thread this am and learned a lot.

_________________
Milt

jmfpublic(at)comcast.net
Guest

Posted: Sat Feb 11, 2006 10:04 pm Post subject: antennas

The problem of the ELT anntenna in a wood and fabric plane, or a composite one, is discussed in Jim Weir's RST anntenna book.  He suggests two dipoles, driven by the same coax, and that is what I plan to do.  The ground plane is best suited for an aluminum plane.  The configuration looks like the letter X with one pair of legs about 1/3 of the other.  I don't recall the exact dimenions, something on the order of 7 inches and 21 inches.  Jim Weir suggests copper tape, but I prefer 0.032 or 0.016 thick brass as being much easier to handle and solder.  This is available in the hardware store in widths of 1/4, 1/2, 3/4, and 1 inch.  Best to tune this with an antenna analyser, of course.



Jim Foerster, J400, wiring

nuckollsr(at)cox.net
Guest

Posted: Sun Feb 12, 2006 8:46 pm Post subject: antennas

At 10:02 PM 2/11/2006 -0800, you wrote:



 	  Quote: 	
		  

<jmfpublic(at)comcast.net>



The problem of the ELT anntenna in a wood and fabric plane, or a composite 

one, is discussed in Jim Weir's RST anntenna book.  He suggests two 

dipoles, driven by the same coax, and that is what I plan to do.  The 

ground plane is best suited for an aluminum plane.  The configuration 

looks like the letter X with one pair of legs about 1/3 of the other.  I 

don't recall the exact dimenions, something on the order of 7 inches and 

21 inches.  Jim Weir suggests copper tape, but I prefer 0.032 or 0.016 

thick brass as being much easier to handle and solder.  This is available 

in the hardware store in widths of 1/4, 1/2, 3/4, and 1 inch.  Best to 

tune this with an antenna analyser, of course.



Jim Foerster, J400, wiring


	


   That would work too. Thanks for tossing that into the pile!



   Bob . . .

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