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AirMike
Joined: 27 Feb 2007
Posts: 514
Location: Nevada
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 Posted: Thu Aug 21, 2008 5:16 pm Post subject: Glowing genitles and three headed babies |
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I am trying to decide where to place my transponder antenna. I was told by another builder that it emits quite a bit of radiation and that it should not be placed (very conveniently and easily) under the front seats.
My avionics tech told me "no problem - not an issue". No appreciable amount of radiation.
Since I need to decide the placement pretty soon , does anybody have a comment on radiation and transponders. I do not want my Grandkids to have 8 toes, three heads, and an IQ of 63.
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Q/B - sold. |
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rv10builder(at)bellsouth.
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| Posted: Thu Aug 21, 2008 6:22 pm Post subject: Glowing genitles and three headed babies |
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Mike,
The aluminum skin on the belly of the aircraft will provide more than
ample protection between the antenna and your...ahem...jewels. Besides,
the duty cycle/PEP of transponder transmissions isn't really a threat to
human tissues as much as it is to adjacent antennas of other avionics.
That's where your real concern should be and plan accordingly.
Brian
Nashville
N104BS Flying
AirMike wrote:
| Quote: |
I am trying to decide where to place my transponder antenna. I was told by another builder that it emits quite a bit of radiation and that it should not be placed (very conveniently and easily) under the front seats.
My avionics tech told me "no problem - not an issue". No appreciable amount of radiation.
Since I need to decide the placement pretty soon , does anybody have a comment on radiation and transponders. I do not want my Grandkids to have 8 toes, three heads, and an IQ of 63.
--------
OSH '08 or Bust (busted) be there in "09
Q/B Kit - exited cabin top/door purgatory
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=199856#199856
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wcurtis(at)nerv10.com
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| Posted: Thu Aug 21, 2008 6:27 pm Post subject: Glowing genitles and three headed babies |
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Put it in the tunnel by your feet. This is where I will put mine: http://nerv10.com/wcurtis/90Electrical/antenna.html
The good new is that aluminum does provide ~some~ shielding from radio waves. With a composite aircraft, you would definately have to worry.
This is one of the reasons I have one of my comm antennas on the fuselage top. I know most put both on the belly for looks. Think of when you are operating out of towered fields and are using ground communications or god forbit land hard off airport and rip out the belly antennas. Even in my Cessna with BOTH comm antennas on the top, occasionally, depending on my position on the field, there are issues communicating with ground and clearance. I can't imagine this being any better with both comm antennas on the belly.
William
http://nerv10.com/wcurtis/
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billderou(at)yahoo.com
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| Posted: Thu Aug 21, 2008 6:47 pm Post subject: Glowing genitles and three headed babies |
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The transponder antenna emits 250w of power and is the most powerful transmitter in the plane. One problem is the antenna transmitting back into the transponder unit and also transmitting into the COM antennas. Check your installation specifications for your transponder and com radios - it should provide guidance on the transponder antenna.
The Garmin 330 specs 8 feet of coax from the antenna back to the unit and the Garmin 430 specs greater than 36 inches from com antenna to transponder antenna. So you need to study both units to determine placement.
BTW if you are using a bent whip underneath the belly for COM then the VSWR (range) will be much better if you install the antenna aft of the trailing edge. This location sets up the transponder to be installed underneath the seats or just behind the firewall in the tunnel. I was originally concerned that the transponder antenna would be close to the exhaust tubes and soak up too much heat if installed all the way forward in the tunnel but this turned out to be not a problem.
Bill DeRouchey
N939SB, flying
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AirMike
Joined: 27 Feb 2007
Posts: 514
Location: Nevada
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| Posted: Thu Aug 21, 2008 7:17 pm Post subject: Glowing ...... |
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Knowing about the separation and the ground control issue, I have placed my com antenna (vertically - facing up) at the rear of the fuse almost to the tail cone fairing (just over the pitch control unit)
Might try the Archer or the Vans Nav antenna in the wing tip rather than the more effective cat whiskers on the tail
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Q/B - sold. |
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ron.mcgann(at)baesystems.
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| Posted: Thu Aug 21, 2008 7:36 pm Post subject: Glowing genitles and three headed babies |
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Bill is spot on. Review the documentation for your unit. The position relative to your cohoneys is not relevant given:
1. the antenna cannot be too close to the transponder unit,
2. the antenna cannot be too close to obstructions eg gear legs,
3. the natenna cannot be too close to other antennas
4. the length of RG400 cable between the xpdr and antenna should not exceed a given length (or an alternate cable is required)
I have deliberately exlcuded distances etc because I don't know what Xpdr you plan to use - the above were ceratinly considerations for my GTX 327.
For the record, I have one belly mount comm whip under the pilot seat and the XPDR antenna is close to the centreline just aft of the rear wing spar/fuse carrythrough that meets the requirements above, as best I could.
cheers,
Ron
187 paint prep
[quote] From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of Bill DeRouchey
Sent: Friday, 22 August 2008 12:17 PM
To: rv10-list(at)matronics.com
Subject: Re: Glowing genitles and three headed babies
The transponder antenna emits 250w of power and is the most powerful transmitter in the plane. One problem is the antenna transmitting back into the transponder unit and also transmitting into the COM antennas. Check your installation specifications for your transponder and com radios - it should provide guidance on the transponder antenna.
The Garmin 330 specs 8 feet of coax from the antenna back to the unit and the Garmin 430 specs greater than 36 inches from com antenna to transponder antenna. So you need to study both units to determine placement.
BTW if you are using a bent whip underneath the belly for COM then the VSWR (range) will be much better if you install the antenna aft of the trailing edge. This location sets up the transponder to be installed underneath the seats or just behind the firewall in the tunnel. I was originally concerned that the transponder antenna would be close to the exhaust tubes and soak up too much heat if installed all the way forward in the tunnel but this turned out to be not a problem.
Bill DeRouchey
N939SB, flying
----- Original Message ----
From: AirMike <Mikeabel(at)Pacbell.net>
To: rv10-list(at)matronics.com
Sent: Thursday, August 21, 2008 6:16:30 PM
Subject: Glowing genitles and three headed babies
--> RV10-List message posted by: "AirMike" <Mikeabel(at)Pacbell.net (Mikeabel(at)Pacbell.net)>
I am trying to decide where to place my transponder antenna. I was told by another builder that it emits quite a bit of radiation and that it should not be placed (very conveniently and easily) under the front seats.
My avionics tech told me "no problem - not an issue". No appreciable amount of radiation.
Since I need to decide the placement pretty soon , does anybody have a comment on radiation and transponders. I do not want my Grandkids to have 8 toes, three heads, and an IQ of | Quote: |
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"'>http://www.matronics.com/Navigator?RV10-List
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matronics.com
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ricksked(at)embarqmail.co
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| Posted: Thu Aug 21, 2008 8:16 pm Post subject: Glowing genitles and three headed babies |
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Guys,
You need to think about some positive points...having been exposed to many a bad chemical I've grown a small tail...granted..it's shocking but I can tell you, there's nothing like a tail...nobody ever doubts when your happy...cause your tails "wags", if your scared...it goes between your legs...when a good bird is near...it stands up...given all the benefits of mutation due to radiation from our transmitters...fear not...you can get a tail too!! Once you learn to put the "fly" of your underwear towards the back...to allow room for your tail...all is good...The down side is, you don't need to use the fly in your underwear up front anymore...seems when you grow a tail...the portion that used to protrude in the front...shrivels up and falls off, but heck your tail still wags!!!
Rick Sked
40185
do not achive
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AirMike
Joined: 27 Feb 2007
Posts: 514
Location: Nevada
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| Posted: Thu Aug 21, 2008 9:33 pm Post subject: Glowing gonads , tails , and argumentum ad absurdum |
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Thanks for the educational and amusing responses. I checked the archive on this topic and found out that this topic had been hashed before in November of 06.
Of the interesting comments:
How do you like 'em- sunny side up, over easy, hard boiled or poached.
Scrambled is not an option. Inquiring organs want to know.
From Mr. Jesse Saint:
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.
From the ultimate guru : Robert L. Nuckolls, III
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
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Q/B - sold. |
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