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CJohnston(at)popsound.com
Guest

Posted: Mon Nov 27, 2006 10:37 am Post subject: transponder antenna placement

Hey all - 



I was perusing the archives looking for info on the transponder antenna

placement, and I ran across mentions of microwaves cooking private

parts.  Really?  Come on...  really?  I'm looking at spots to mount the

antenna, and under the pilot / copilot seats seems like the best bet for

me.  The tunnel is out, because I made a false floor that goes from the

firewall to the spar and I don't want any penetrations there.  I was

thinking the transponder antenna under the copilot and the avidyne/ryan

traffic antenna under the pilot seat.  I've already got comms under the

rear passenger seats, and navs in the wingtips.  Is the transponder

really going to do a number on me or my copilot under the seats?

Inquiring minds want to know...



cj

#40410

fuse

www.perfectlygoodairplane.net

Rick S.

Joined: 12 Feb 2006
Posts: 347
Location: Las Vegas

Posted: Mon Nov 27, 2006 10:54 am Post subject: transponder antenna placement

Chris,



I have heard both....that it is harmful microwave energy from William Curtis who's electronic knowledge I trust and that it's bunk. I mounted mine on the bottom right side between the battery and the right sidewall behind the baggage bulkhead. It's outta the way, it is a long coax run but at least it's not near the nads, rumor or not  



Rick S.

40185

_________________
Rick S.
RV-10
40185

indigoonlatigo(at)msn.com
Guest

Posted: Mon Nov 27, 2006 11:10 am Post subject: transponder antenna placement

How do you like 'em- sunny side up, over easy, hard boiled or poached. 

Scrambled is not an option.



Seriously, what kind of material would be needed to stop the radiation?



Inquiring organs want to know.



John G.



Do Not Archive

 	  Quote: 	
		  From: "Chris Johnston" <CJohnston(at)popsound.com>

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

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

Subject: transponder antenna placement

Date: Mon, 27 Nov 2006 10:36:33 -0800






Hey all -



I was perusing the archives looking for info on the transponder antenna

placement, and I ran across mentions of microwaves cooking private

parts.  Really?  Come on...  really?  I'm looking at spots to mount the

antenna, and under the pilot / copilot seats seems like the best bet for

me.  The tunnel is out, because I made a false floor that goes from the

firewall to the spar and I don't want any penetrations there.  I was

thinking the transponder antenna under the copilot and the avidyne/ryan

traffic antenna under the pilot seat.  I've already got comms under the

rear passenger seats, and navs in the wingtips.  Is the transponder

really going to do a number on me or my copilot under the seats?

Inquiring minds want to know...



cj

#40410

fuse

www.perfectlygoodairplane.net

jesse(at)itecusa.org
Guest

Posted: Mon Nov 27, 2006 11:18 am Post subject: transponder antenna placement

I can't speak to the sperm-count effect of the Transponder antenna, but if

you're out of the baby-making stage, then that might not matter anyway.

Let's go ahead and get the do not archive tag here.



I put mine on the tunnel just aft of the firewall, which allows for a very

short wiring run and keeps it away from the other cables and antennas.  I

have the comms under the pilot and copilot.  The main thing I would

recommend, if you are comfortable putting it under your seat, would be that

you have at least 30-36 inches between it and the comms, which shouldn't be

a big problem.  Also, I understand that it is a good idea to keep the cable

run separate from your other antennas.



Jesse Saint

I-TEC, Inc.

jesse(at)itecusa.org

www.itecusa.org

W: 352-465-4545

C: 352-427-0285



--

bcondrey

Joined: 03 Apr 2006
Posts: 580

Posted: Mon Nov 27, 2006 11:30 am Post subject: Re: transponder antenna placement

Chris,



Below is from an exchange on this subject on the AeroElectric list - short version is that there isn't an issue.



Bob



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



Message:  #10129 Date:  Mar 10, 2003 From:  "Robert L. Nuckolls, III" <bob> Subject:  Re: defending the "familiy jewels" . . . 

>

>A transponder antenna that close to your passengers "private parts"

>might not be the best thing to do. The radiation may do some damage.

>

>Rino



   A hangar myth. Folks have looked at the

   peak output power rating of a transponder (100 to 250W)

   and tried to make a connection between a desire to

   make one's airplane visible to a distant radar receiver

   and cooking meat.



   When you buy a microwave, it too is rated in the

   hundreds of watts . . . but CONTINUOUS duty. A

   good 700W microwave will boil a cup of water in

   about 2 minutes. (Remember the traveler's immersion

   heaters in the hardware store? They're 300W heaters

   and take about 4 minutes to boil a cup of water).

   If you measure the current draw of this machine,

   it will be on the order of 8-9 amps or 1000W total

   input.



   Your transponder draws about 1.5 amps while being

   interrogated for a total input power of 18W. The

   output comes in the form of a series of 0.5 uSec

   pulses in respond to an interrogation that represent

   a string of binary numbers representing either your

   squawk code (mode A) or altitude (mode C). Assuming

   you are interrogated once per second (quite often)

   your average output power for a 250W transponder

   is on the order of 250W x 20 pulses x 0.0000005

   seconds/1 second or 2.5 milliwatts per second.

   This isn't going even going to warm up much less cook

   anything.



   Another fallacy of the myth concerns body parts

   most sensitive to microwave radiation . . . turns

   out that your eyes are the most vulnerable . . .

   but the story isn't nearly so interesting to

   really macho pilots. None the less, there are

   folks who have armor-shielded their seat bottoms

   in deference to this myth. The story was REALLY

   popular about 15 years ago in the heyday of

   the Long-Ezs



   Here's a post I did on a canard pusher list

   server about 5 years ago:



 > Location away from the pilot/co-pilot is also

 >recommended but over ten feet requires a different cable. Yes?? I was

 >thinking about locating it aft of the pilot in the baggage area. Is that

 >distance safe?



   A totally bogus recommendation. A few years back, someone observed

   that their transponder was rated for 200 watts output . . . 1/3rd

   that of the family microwave. Our hero was immediately concerned for

   preservation of the family jewels and proceeded to line the bottom

   of his composite seat pan with aluminum foil. What he failed to

   understand was that his RF coffee warmer and popcorn popper was

   rated in continuous watts while the transponder was in peak watts.

   The average power output from a transponder is less than 1 watt . . .

   BTW, the eyes are about 100 times more sensitive to the effects of

   microwave heating than are any deep organs . . . you'll go blind

   you quit making babies.



        Bob . . .

AV8ORJWC

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

Posted: Mon Nov 27, 2006 11:33 am Post subject: transponder antenna placement

This goes along with the original scientific studies used in 1983, when

cell phones were first sold that said everyone was going to get brain

tumors on the side closest the antenna on your hand-held.



I think it led to a lot of brain dead teenagers but no tumorous growths

in their adult life - yet.  However, there are a lot of EA-6B Naval

Aviators that swear their love life was curtailed by the errant

electrons bouncing off the gold electroplated canopies from all that

jamming they did for Uncle Sammy.



Rick I would think the Air Force used similar stories on the girls in

your day.  Just don't forget about Blue Nads from those forward NACA

ducts.



John Cox

40600

--

CJohnston(at)popsound.com
Guest

Posted: Mon Nov 27, 2006 11:39 am Post subject: transponder antenna placement

Does the placement of the transponder antenna need to be as far forward

as possible, or am I making that up?  I feel like I read that or heard

that somewhere.  If I can put the antenna behind the bulkhead I'd love

it!  is there a good argument (besides longer coax run) against putting

the antenna back there?



cj

#40410

fuse

www.perfectlygoodairplane.net





do not archive 

--

dlm46007(at)cox.net
Guest

Posted: Mon Nov 27, 2006 12:10 pm Post subject: transponder antenna placement

Why worry? I have been flying light airplanes for thirty plus years and 4000 

hours with the transponder antenna just below my seat. I had three healthy 

children in my 20s and two healthy children in my 50s , the last at 55.

---

Tim(at)MyRV10.com
Guest

Posted: Mon Nov 27, 2006 12:18 pm Post subject: transponder antenna placement

If your com's are under the rear seats, having these antennas

so close may not be a good thing.  I'm no expert, but I

do think they want 30+ inches or something like that, so

the more the better.  The other suggestion of under

the tail seems OK though, despite the long cable run.

I opted to keep that cable short and put it in the tunnel.

Not sure if you could just do a penetration in your

false floor and grommet it to seal it up, but if you can

find a way to get it there, it's not a bad spot.  Don't

put it way up right by the exhaust though....leave it back

a little.



Tim Olson - RV-10 N104CD - Flying

do not archive

Chris Johnston wrote:

 	  Quote: 	
		   

 

 Hey all - 

 

 I was perusing the archives looking for info on the transponder antenna

 placement, and I ran across mentions of microwaves cooking private

 parts.  Really?  Come on...  really?  I'm looking at spots to mount the

 antenna, and under the pilot / copilot seats seems like the best bet for

 me.  The tunnel is out, because I made a false floor that goes from the

 firewall to the spar and I don't want any penetrations there.  I was

 thinking the transponder antenna under the copilot and the avidyne/ryan

 traffic antenna under the pilot seat.  I've already got comms under the

 rear passenger seats, and navs in the wingtips.  Is the transponder

 really going to do a number on me or my copilot under the seats?

 Inquiring minds want to know...

 

 cj

 #40410

 fuse

 www.perfectlygoodairplane.net

Tim(at)MyRV10.com
Guest

Posted: Mon Nov 27, 2006 12:20 pm Post subject: transponder antenna placement

I think you're making it up.  On my old certified plane it was back

behind the step area, under the tail.



Tim Olson - RV-10 N104CD - Flying

do not archive

Chris Johnston wrote:

[quote] 

 

 Does the placement of the transponder antenna need to be as far forward

 as possible, or am I making that up?  I feel like I read that or heard

 that somewhere.  If I can put the antenna behind the bulkhead I'd love

 it!  is there a good argument (besides longer coax run) against putting

 the antenna back there?

 

 cj

 #40410

 fuse

 www.perfectlygoodairplane.net

 

 

 

 

 do not archive 

 --

Rick S.

Joined: 12 Feb 2006
Posts: 347
Location: Las Vegas

Posted: Mon Nov 27, 2006 12:26 pm Post subject: transponder antenna placement

Well many a night we did radar ops checks and had to actually transmit, I never did trust those cones set out in front. I saw a guy throw a wad of steel wool out in front and watched it burst into flames...yeah I know not so smart in a slightly explosive enviroment but that convinced me that those invisible radio waves really could do some damage if they were powerful enough. That was almost as exciting as throwing a cement brick into an F-100 afterburner and watcing the force of full AB throw the brick a good 400 feet. The noise and vibrations off that AB was enough to make you feel sick to your stomach. All BTW you could not "see"



Some truth to the term that what you can't see CAN hurt you. Of couse that leads to why there is an eye patch on the stick of the Victor alert birds.....



Rick S.

40185



do not archive

_________________
Rick S.
RV-10
40185

Rick S.

Joined: 12 Feb 2006
Posts: 347
Location: Las Vegas

Posted: Mon Nov 27, 2006 12:34 pm Post subject: transponder antenna placement

lol....but how many Tails do they have David!!  



Rick S.

40185



do not archive

_________________
Rick S.
RV-10
40185

rvbuilder(at)sausen.net
Guest

Posted: Mon Nov 27, 2006 12:59 pm Post subject: transponder antenna placement

Sounds like a good episode of Mythbusters.  Adam can put his nads in a

microwave and Jamie can sit on a transponder antenna while being

regularly interrogated or pushing ident.  ROFLMAO!



Seriously though, I don't think anyone has ever done a serious study on

this.  In reality any potential health issues are probably pretty small.

You probably get more rads from the solar radiation at 15,000 feet than

from the transponder.  I still wouldn't put it right under my seat

though.  The biggest issue in placement is keeping the antenna lead as

short as possible.



Michael Sausen

-10 #352 fuselage 



--

dlm46007(at)cox.net
Guest

Posted: Mon Nov 27, 2006 1:02 pm Post subject: transponder antenna placement

Since we met when I visited your garage you will have to judge for yourself

---

indigoonlatigo(at)msn.com
Guest

Posted: Mon Nov 27, 2006 1:22 pm Post subject: transponder antenna placement

Under the seat however, the moicrowaves would be going through several 

layers of metal to find your privates, unless your a low hanger.



DO not archive

[quote]From: "RV Builder (Michael Sausen)" <rvbuilder(at)sausen.net>

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

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

Subject: RE: Re: transponder antenna placement

Date: Mon, 27 Nov 2006 14:59:20 -0600




<rvbuilder(at)sausen.net>



Sounds like a good episode of Mythbusters.  Adam can put his nads in a

microwave and Jamie can sit on a transponder antenna while being

regularly interrogated or pushing ident.  ROFLMAO!



Seriously though, I don't think anyone has ever done a serious study on

this.  In reality any potential health issues are probably pretty small.

You probably get more rads from the solar radiation at 15,000 feet than

from the transponder.  I still wouldn't put it right under my seat

though.  The biggest issue in placement is keeping the antenna lead as

short as possible.



Michael Sausen

-10 #352 fuselage



--

Rick S.

Joined: 12 Feb 2006
Posts: 347
Location: Las Vegas

Posted: Mon Nov 27, 2006 1:24 pm Post subject: transponder antenna placement

I knew that!! I didn't take notice though.   



Rick S.



do not archive

_________________
Rick S.
RV-10
40185

billderou(at)yahoo.com
Guest

Posted: Mon Nov 27, 2006 1:49 pm Post subject: transponder antenna placement

The antenna placement recommendations from Garmin are:

  1. place antenna 3 feet (physical measurement) from transponder unit

  2. cable no longer than 8.8 feet of RG-400 (to handle the high power)

  3. 30 inches (physical measurement) from any com antenna

  4. Try to maximize distance from landing gear leg when placing under the seat to minimize

      holes in pattern. Mine is too close but it works correctly.

   

  Bill DeRouchey

  billderou(at)yahoo.com (billderou(at)yahoo.com)

  Flying with a few pit stops

  



"John W. Cox" <johnwcox(at)pacificnw.com> wrote:

  [quote]--> RV10-List message posted by: "John W. Cox" 



This goes along with the original scientific studies used in 1983,  when

cell phones were first sold that said everyone was going to get brain

tumors on the side closest the antenna on your hand-held.



I think it led to a lot of brain dead teenagers but no tumorous growths

in their adult life - yet. However, there are a lot of EA-6B Naval

Aviators that swear their love life was curtailed by the errant

electrons bouncing off the gold electroplated canopies from all that

jamming they did for Uncle Sammy.



Rick I would think the Air Force used similar stories on the girls in

your day. Just don't forget about Blue Nads from those forward NACA

ducts.



John Cox

40600

--

AV8ORJWC

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

Posted: Mon Nov 27, 2006 1:49 pm Post subject: transponder antenna placement

"Rads on the Nads".  A new section for Tim on the RV U site.  Leave it

to Michael to get us all ROFLMAO.

John Cox

40600

Do not Archive



--

pitts_pilot(at)bellsouth.
Guest

Posted: Mon Nov 27, 2006 6:45 pm Post subject: transponder antenna placement

Not having to do any testing myself ...   ..... I'll side with bunk! 

 First of all, the energy just isn't there, and the average energy is 

way lower than that so ..... make your own assessment.  Lets face it 

... microwave ovens work on the resonant frequency of water molecules. 

 I haven't a clue what that frequency really is, but the transponder 

frequency probably isn't anywhere close.  I'd liken it to the cell 

phone/tumor thingy.

Linn

do not archive .... because I just may be blowing smoke!



Rick wrote:



 	  Quote: 	
		  



Chris,



I have heard both....that it is harmful microwave energy from William Curtis who's electronic knowledge I trust and that it's bunk. I mounted mine on the bottom right side between the battery and the right sidewall behind the baggage bulkhead. It's outta the way, it is a long coax run but at least it's not near the nads, rumor or not  



Rick S.

40185

wv4i(at)bellsouth.net
Guest

Posted: Tue Nov 28, 2006 3:46 am Post subject: transponder antenna placement

My comm and xpdr antennas in my RV6 are roughly 30" apart, have no 

problem, are located under the seat area, etc. The avionics are basic 

King 76 and 97 series. Keep in mind that the radiation patterns of 

antennas so located are mostly directed away from the aircraft (and you) 

by the aircraft skin, the latter which provides an RF ground plane. 

Metal between you and any RF emission is better. Further away is also 

better, as the strength of the RF field decreases with the square of the 

distance. The antennas' distance apart recommendation goes mostly to RF 

interference and to a lesser extent the possibility of detuning one 

antenna by virtue of its proximity to the other. Rather than get into 

all the theory and math behind the recommendations, BEST to just follow 

the recommendations and move on (or take up ham radio like me). The 

other issue that arises, besides inter station interference, is the 

possibility of pumping too much RF into a nearby receiver front end of a 

2nd radio/xpdr, while transmitting on 1st. This can damage the receiver, 

but mostly only an issue with similar avionics, i.e. xpdr vs xpdr, comm 

vs comm, etc.. Also, Bob Nuckolls' points re effective radiated power, 

pulsed, duration, etc. are well taken (know he'll sleep easier now). 

Radar is, as John C noted, a different story, while pulsed, is in 

MEGAwatts, and also at very harmful frequencies, but it is highly 

directive, AWAY from aircraft. Softer body tissue is most vulnerable to 

RF exposure. Last, when considering antenna placement location, SIMPLY 

consider the most often direction of the target station from the 

aircraft, and seek the best, practical, unobstructed, line of sight 

antenna location, thereby avoiding nulls. Nav antennas in wing tips, 

okay if you must, but one in each wing tip then, would be better, re nulls.



Ready to put out the flames here.......as always.



Link McGarity

#40622



do not archive

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