Wanted: Transponder antenna

[Grandpa B.]

I'm starting the fabrication of a new boot cowl for the Champ project. The
transponder antenna got wiped off the bottom during the groundloop (no, I
didn't do it!), so I gotta get a new one.

I've seen the 'bargain' version in AS&S for $22 or so. Are they useful, or
should I spend the ~$60 for a decent one?

Anybody have one laying around that they no longer need?

Jon B.

[David O]

"Grandpa B." <never.mind> wrote:

>I'm starting the fabrication of a new boot cowl for the Champ project. The
>transponder antenna got wiped off the bottom during the groundloop (no, I
>didn't do it!), so I gotta get a new one.
>
>I've seen the 'bargain' version in AS&S for $22 or so. Are they useful, or
>should I spend the ~$60 for a decent one?
>
>Anybody have one laying around that they no longer need?
>
>Jon B.



I'll give you one anecdotal data point. I bought the $22 "TED"
transponder antenna from Aircraft Spruce a few years back. It seemed
well constructed and my transponder signal is apparently getting out
as I've had no complaints of dropouts from ATC.

David O -- http://www.AirplaneZone.com

[Paul Lee]

There is nothing wrong with the $22 one. Only for fast birds,
you may want an aerodynamic shaped one.
Composite projects can even build the $22 jobs into wings, etc.

"Grandpa B." <never.mind> wrote in message >...
> I'm starting the fabrication of a new boot cowl for the Champ project. The
> transponder antenna got wiped off the bottom during the groundloop (no, I
> didn't do it!), so I gotta get a new one.
>
> I've seen the 'bargain' version in AS&S for $22 or so. Are they useful, or
> should I spend the ~$60 for a decent one?
>
> Anybody have one laying around that they no longer need?
>
> Jon B.
>

[Rich S.]

"Paul Lee" > wrote in message
m...
> There is nothing wrong with the $22 one. Only for fast birds,
> you may want an aerodynamic shaped one.
> Composite projects can even build the $22 jobs into wings, etc.

Hey! Don't forget us wood and fabric types. I was going to install mine
under my seat, but then I thought about possible radiation effects on the
family jewels. I mentioned this to my wife who poo-pooed my concern. So I
put it under her seat.

Rich S.

[David O]

"Rich S." > wrote:


>Hey! Don't forget us wood and fabric types. I was going to install mine
>under my seat, but then I thought about possible radiation effects on the
>family jewels. I mentioned this to my wife who poo-pooed my concern. So I
>put it under her seat.
>
>Rich S.

My transponder antenna is under my Long EZ pilot seat under an
aluminum ground plane disk with aluminum foil glued to the underside
of the seat as added protection for the "jewels". I don't know how
effective the shield is but I'm out of the kid making biz anyway
(hopefully). :)

David O -- http://www.AirplaneZone.com

[- Barnyard BOb -]

>I was going to install mine
>under my seat, but then I thought about possible radiation effects on the
>family jewels. I mentioned this to my wife who poo-pooed my concern. So I
>put it under her seat.
>
>Rich S.
++++++++++++++++++++++++++++++

Any new additions to the family since?



Barnyard BOb

[Rich S.]

"- Barnyard BOb -" > wrote in message
...
>
>
> >I was going to install mine
> >under my seat, but then I thought about possible radiation effects on the
> >family jewels. I mentioned this to my wife who poo-pooed my concern. So I
> >put it under her seat.
> >
> >Rich S.
> ++++++++++++++++++++++++++++++
>
> Any new additions to the family since?

No, but after a long cross-country, I can use her as a night light. ;o)

Rich S.

[Paul Lee]

AFAIK the tranponder antenna should be 8+ feet away from warm bodies.

"Rich S." > wrote in message >...
> "Paul Lee" > wrote in message
> m...
> > There is nothing wrong with the $22 one. Only for fast birds,
> > you may want an aerodynamic shaped one.
> > Composite projects can even build the $22 jobs into wings, etc.
>
> Hey! Don't forget us wood and fabric types. I was going to install mine
> under my seat, but then I thought about possible radiation effects on the
> family jewels. I mentioned this to my wife who poo-pooed my concern. So I
> put it under her seat.
>
> Rich S.

[Jerry Springer]

And where would you be getting that information from? Don't know many small
single engine airplanes that would meet that requirement.

Jerry

Paul Lee wrote:
> AFAIK the tranponder antenna should be 8+ feet away from warm bodies.
>
> "Rich S." > wrote in message >...
>
>>"Paul Lee" > wrote in message
m...
>>
>>>There is nothing wrong with the $22 one. Only for fast birds,
>>>you may want an aerodynamic shaped one.
>>>Composite projects can even build the $22 jobs into wings, etc.
>>
>>Hey! Don't forget us wood and fabric types. I was going to install mine
>>under my seat, but then I thought about possible radiation effects on the
>>family jewels. I mentioned this to my wife who poo-pooed my concern. So I
>>put it under her seat.
>>
>>Rich S.

[Rob Turk]

"Paul Lee" > wrote in message
m...
> There is nothing wrong with the $22 one. Only for fast birds,
> you may want an aerodynamic shaped one.
> Composite projects can even build the $22 jobs into wings, etc.
>

You may not want to do that. It works for COM but may not work for
transponders. They work on pretty high frequencies (around 1000MHz) and it
doesn't take much to shield such signals. The composit may not be a problem,
but your paint or even wet conditions may stop the signal from getting out.

Rob

[Jim Weir]

Are you guessing on this, repeating an OWT, or do you have first hand hard data?

Jim



"Rob Turk" >
shared these priceless pearls of wisdom:

->You may not want to do that. It works for COM but may not work for
->transponders. They work on pretty high frequencies (around 1000MHz) and it
->doesn't take much to shield such signals. The composit may not be a problem,
->but your paint or even wet conditions may stop the signal from getting out.
->
->Rob
->



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Big John]

Jim

The Radom's we used in military were transparent to the radar
frequencies. You couldn't just take a can of Krylon and paint them. If
damaged, was a special way of repairing.

There must be data available on effect of glass, cloth and paints,
etc., on RF transmission/reception?

I haven't taken time for a Google search but might be something amoung
Radoms, RF attenuation, etc

Hughes Aircraft, who made the fighter radar I used, might have some
attenuation figures someplace if you can get to the right person.

Have a good Turkey day out there in the land of Fruits and Nuts <G>
..

Big John

Know you didn't start thread but others will read this post and thread
will go on and on and on...............

On Wed, 26 Nov 2003 09:20:27 -0800, Jim Weir > wrote:

>Are you guessing on this, repeating an OWT, or do you have first hand hard data?
>
>Jim
>
>
>
>"Rob Turk" >
>shared these priceless pearls of wisdom:
>
>->You may not want to do that. It works for COM but may not work for
>->transponders. They work on pretty high frequencies (around 1000MHz) and it
>->doesn't take much to shield such signals. The composit may not be a problem,
>->but your paint or even wet conditions may stop the signal from getting out.
>->
>->Rob
>->
>
>
>
>Jim Weir (A&P/IA, CFI, & other good alphabet soup)
>VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
>http://www.rst-engr.com

[Cy Galley]

Where or how did you come up with 8 foot? References Please

"Paul Lee" > wrote in message
om...
> AFAIK the tranponder antenna should be 8+ feet away from warm bodies.
>
> "Rich S." > wrote in message
>...
> > "Paul Lee" > wrote in message
> > m...
> > > There is nothing wrong with the $22 one. Only for fast birds,
> > > you may want an aerodynamic shaped one.
> > > Composite projects can even build the $22 jobs into wings, etc.
> >
> > Hey! Don't forget us wood and fabric types. I was going to install mine
> > under my seat, but then I thought about possible radiation effects on
the
> > family jewels. I mentioned this to my wife who poo-pooed my concern. So
I
> > put it under her seat.
> >
> > Rich S.

[Jim Weir]

Big John >
shared these priceless pearls of wisdom:

->Jim
->
->The Radom's we used in military were transparent to the radar
->frequencies. You couldn't just take a can of Krylon and paint them. If
->damaged, was a special way of repairing.

Exactly my point. There is a tremendous difference between C and X band radar
and low L band transponders. Making generalities such as the prior poster did
without having done the work is the worst sort of conjecture.

The answer is that you CAN take a can of Krylon of the correct mix and paint
them. You can't take just ANY can of Krylon without knowing what you are doing.
And the damage required baking to eliminate entrapped water before you glassed
the damage.

->
->There must be data available on effect of glass, cloth and paints,
->etc., on RF transmission/reception?

Yes, and we did it for Bellanca when we designed their internal antenna system.


Jim
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Grandpa B.]

Man, I didn't intend to start a fight...

I think I'll just buy the TED from AS&S; they're $19.95 in their on-line
catalog. I'll need other stuff, so the S&H won't hurt too bad.

Thanks RAH denizons for the assist!

Got one half of the 'boot' cowl cut, drilled, smoothed last night. I was a
bit dismayed by the un-evenness from the shears (regular scissors-type,
compound lever), but a lot of the waviness went away as I de-burred the edge
with 320 sandpaper. It looks quite nice.

Jon B.

"Cy Galley" > wrote in message
news:Ke6xb.315272$Fm2.330421@attbi_s04...
> Where or how did you come up with 8 foot? References Please
>
> "Paul Lee" > wrote in message
> om...
> > AFAIK the tranponder antenna should be 8+ feet away from warm bodies.
> >
> > "Rich S." > wrote in message
> >...
> > > "Paul Lee" > wrote in message
> > > m...
> > > > There is nothing wrong with the $22 one. Only for fast birds,
> > > > you may want an aerodynamic shaped one.
> > > > Composite projects can even build the $22 jobs into wings, etc.
> > >
> > > Hey! Don't forget us wood and fabric types. I was going to install
mine
> > > under my seat, but then I thought about possible radiation effects on
> the
> > > family jewels. I mentioned this to my wife who poo-pooed my concern.
So
> I
> > > put it under her seat.
> > >
> > > Rich S.
>
>

[Rob Turk]

"Jim Weir" > wrote in message
...
> Are you guessing on this, repeating an OWT, or do you have first hand hard
data?
>
> Jim
>

As a licensed ham operator I have sufficient experience with frequencies
around 1200 MHz. Those don't like their antenna's shielded by wet or painted
surfaces. Transponders are just over 1000MHz, it's reasonably safe to assume
they are equally influenced. I'm not saying it will never work (fwiw, GSM at
900MHz works in-door), but I do want to caution people that there are many
variables involved that could make it not work.

Contrary to COM signals (118-136MHz) you can't use just any CB or VHF SWR
meter to check out if the antenna matches at these frequencies. With the
transponder sending out pulses of 200+ Watts I wouldn't want to gamble
having a bad SWR and seeing that power end up ruining the transponder stage.
Better be safe and put the $22 antenna where it belongs; Outside.

Rob

[Jim Weir]

"Rob Turk" >
shared these priceless pearls of wisdom:

->"Jim Weir" > wrote in message
...
->> Are you guessing on this, repeating an OWT, or do you have first hand hard
->data?
->>
->> Jim
->>
->
->As a licensed ham operator

Jesus. A ham operator? Those are the credentials you come to the table with?

Amateur radio extra, first licensed in 1959. First 'phone with radar
endorsement, 1960. BS-Physics (Microwave option) 1967. MSEE CGS 1983, RF
option. Pacific Southwest Airlines (1963-1967) avionics and radar technician.
Teledyne Ryan Space Systems (1967-1973) Microwave Antenna Engineer. Founder and
CEO RST Engineering, with a world class reputation for hidden antennas in
nonconductive structures (1973 --) with approximately fifteen THOUSAND operating
antennas in plastic/wood/fabric aircraft including one hanging in the
Smithsonian.


I have sufficient experience with frequencies
->around 1200 MHz.

How long has it been since you fell off the turnip truck, feller? The ham bands
at 33 and 23 cm are 10% or so away from the transponder frequencies. Not too
far away, but far enough.



Those don't like their antenna's shielded by wet or painted
->surfaces.

First, the plural is "antennas", not the possessive. In the second place, this
is the first mistake of fact so far. That is just horsepuckey. Wet and paint
won't make squat for difference. And I've done and retained the engineering
data that says so.


Transponders are just over 1000MHz

1030 and 1090 to be exact. Betcha can't tell me without looking which one is
transmit and which one is receive.



, it's reasonably safe to assume
->they are equally influenced. I'm not saying it will never work (fwiw, GSM at
->900MHz works in-door), but I do want to caution people that there are many
->variables involved that could make it not work.

Yada, yada yada...


->
->Contrary to COM signals (118-136MHz) you can't use just any CB or VHF SWR
->meter to check out if the antenna matches at these frequencies. With the
->transponder sending out pulses of 200+ Watts I wouldn't want to gamble
->having a bad SWR and seeing that power end up ruining the transponder stage.
->Better be safe and put the $22 antenna where it belongs; Outside.


Izzat a fact? Then I guess I'd best trash my $50k worth of RF antenna test
equipment, because I surely wouldn't want to gamble my transponder on brothers
Hewlett and Packard's equipment and the results derived therefrom.

By the way, do the math before you post. That 200+ watts of transponder power
is peak pulse power. If you go through the calculation, you find that the
transponder output stage is running about 5 watts CW averaged over a couple of
seconds or so.

Now, to repeat what I've been telling my colleagues building airplanes for the
last 30 years...put the transponder antenna inside the plastic with a round or
(better yet) octagonal ground plane, shield the sensitive parts of your anatomy
with tinfoil, and go for it.

Jim


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Rob Turk]

Jim,

I'm truely disappointed about your response. If this newsgroup is about
showing off how big your dick is, go right ahead. I was under the impression
that the newsgroup was to discuss and provide help. None of the information
I gave is wrong, I provided a fair warning to think twice before putting a
UHF antenna enclosed inside a frame. You made it into a ****ing match. I
admire the knowledge you have, but the way you display it makes me sick.

Rob
(The Netherlands, not a native English speaker, sorry for any spelling
mistakes...).

"Jim Weir" > wrote in message
...
> "Rob Turk" >
> shared these priceless pearls of wisdom:
>
> ->"Jim Weir" > wrote in message
> ...
> ->> Are you guessing on this, repeating an OWT, or do you have first hand
hard
> ->data?
> ->>
> ->> Jim
> ->>
> ->
> ->As a licensed ham operator
>
> Jesus. A ham operator? Those are the credentials you come to the table
with?
>
> Amateur radio extra, first licensed in 1959. First 'phone with radar
> endorsement, 1960. BS-Physics (Microwave option) 1967. MSEE CGS 1983, RF
> option. Pacific Southwest Airlines (1963-1967) avionics and radar
technician.
> Teledyne Ryan Space Systems (1967-1973) Microwave Antenna Engineer.
Founder and
> CEO RST Engineering, with a world class reputation for hidden antennas in
> nonconductive structures (1973 --) with approximately fifteen THOUSAND
operating
> antennas in plastic/wood/fabric aircraft including one hanging in the
> Smithsonian.
>
>
> I have sufficient experience with frequencies
> ->around 1200 MHz.
>
> How long has it been since you fell off the turnip truck, feller? The ham
bands
> at 33 and 23 cm are 10% or so away from the transponder frequencies. Not
too
> far away, but far enough.
>
>
>
> Those don't like their antenna's shielded by wet or painted
> ->surfaces.
>
> First, the plural is "antennas", not the possessive. In the second place,
this
> is the first mistake of fact so far. That is just horsepuckey. Wet and
paint
> won't make squat for difference. And I've done and retained the
engineering
> data that says so.
>
>
> Transponders are just over 1000MHz
>
> 1030 and 1090 to be exact. Betcha can't tell me without looking which one
is
> transmit and which one is receive.
>
>
>
> , it's reasonably safe to assume
> ->they are equally influenced. I'm not saying it will never work (fwiw,
GSM at
> ->900MHz works in-door), but I do want to caution people that there are
many
> ->variables involved that could make it not work.
>
> Yada, yada yada...
>
>
> ->
> ->Contrary to COM signals (118-136MHz) you can't use just any CB or VHF
SWR
> ->meter to check out if the antenna matches at these frequencies. With the
> ->transponder sending out pulses of 200+ Watts I wouldn't want to gamble
> ->having a bad SWR and seeing that power end up ruining the transponder
stage.
> ->Better be safe and put the $22 antenna where it belongs; Outside.
>
>
> Izzat a fact? Then I guess I'd best trash my $50k worth of RF antenna
test
> equipment, because I surely wouldn't want to gamble my transponder on
brothers
> Hewlett and Packard's equipment and the results derived therefrom.
>
> By the way, do the math before you post. That 200+ watts of transponder
power
> is peak pulse power. If you go through the calculation, you find that the
> transponder output stage is running about 5 watts CW averaged over a
couple of
> seconds or so.
>
> Now, to repeat what I've been telling my colleagues building airplanes for
the
> last 30 years...put the transponder antenna inside the plastic with a
round or
> (better yet) octagonal ground plane, shield the sensitive parts of your
anatomy
> with tinfoil, and go for it.
>
> Jim
>
>
> Jim Weir (A&P/IA, CFI, & other good alphabet soup)
> VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
> http://www.rst-engr.com

[[email protected]]

Rob, when you really done it, it ain't bragging.

There are thousands - maybe 10's of thousands - of Jim's antennas
flying. He wrote the book on hidden aircraft antennas. Your
information is might be a reasonable extrapolation, but his is
empirical.

On Thu, 27 Nov 2003 08:04:37 +0100, "Rob Turk"
> wrote:

:Jim,
:
:I'm truely disappointed about your response. If this newsgroup is about
:showing off how big your dick is, go right ahead. I was under the impression
:that the newsgroup was to discuss and provide help. None of the information
:I gave is wrong, I provided a fair warning to think twice before putting a
:UHF antenna enclosed inside a frame. You made it into a ****ing match. I
:admire the knowledge you have, but the way you display it makes me sick.
:
:Rob
:(The Netherlands, not a native English speaker, sorry for any spelling
:mistakes...).
:
:"Jim Weir" > wrote in message
.. .
:> "Rob Turk" >
:> shared these priceless pearls of wisdom:
:>
:> ->"Jim Weir" > wrote in message
:> ...
:> ->> Are you guessing on this, repeating an OWT, or do you have first hand
:hard
:> ->data?
:> ->>
:> ->> Jim
:> ->>
:> ->
:> ->As a licensed ham operator
:>
:> Jesus. A ham operator? Those are the credentials you come to the table
:with?
:>
:> Amateur radio extra, first licensed in 1959. First 'phone with radar
:> endorsement, 1960. BS-Physics (Microwave option) 1967. MSEE CGS 1983, RF
:> option. Pacific Southwest Airlines (1963-1967) avionics and radar
:technician.
:> Teledyne Ryan Space Systems (1967-1973) Microwave Antenna Engineer.
:Founder and
:> CEO RST Engineering, with a world class reputation for hidden antennas in
:> nonconductive structures (1973 --) with approximately fifteen THOUSAND
:operating
:> antennas in plastic/wood/fabric aircraft including one hanging in the
:> Smithsonian.
:>
:>
:> I have sufficient experience with frequencies
:> ->around 1200 MHz.
:>
:> How long has it been since you fell off the turnip truck, feller? The ham
:bands
:> at 33 and 23 cm are 10% or so away from the transponder frequencies. Not
:too
:> far away, but far enough.
:>
:>
:>
:> Those don't like their antenna's shielded by wet or painted
:> ->surfaces.
:>
:> First, the plural is "antennas", not the possessive. In the second place,
:this
:> is the first mistake of fact so far. That is just horsepuckey. Wet and
:paint
:> won't make squat for difference. And I've done and retained the
:engineering
:> data that says so.
:>
:>
:> Transponders are just over 1000MHz
:>
:> 1030 and 1090 to be exact. Betcha can't tell me without looking which one
:is
:> transmit and which one is receive.
:>
:>
:>
:> , it's reasonably safe to assume
:> ->they are equally influenced. I'm not saying it will never work (fwiw,
:GSM at
:> ->900MHz works in-door), but I do want to caution people that there are
:many
:> ->variables involved that could make it not work.
:>
:> Yada, yada yada...
:>
:>
:> ->
:> ->Contrary to COM signals (118-136MHz) you can't use just any CB or VHF
:SWR
:> ->meter to check out if the antenna matches at these frequencies. With the
:> ->transponder sending out pulses of 200+ Watts I wouldn't want to gamble
:> ->having a bad SWR and seeing that power end up ruining the transponder
:stage.
:> ->Better be safe and put the $22 antenna where it belongs; Outside.
:>
:>
:> Izzat a fact? Then I guess I'd best trash my $50k worth of RF antenna
:test
:> equipment, because I surely wouldn't want to gamble my transponder on
:brothers
:> Hewlett and Packard's equipment and the results derived therefrom.
:>
:> By the way, do the math before you post. That 200+ watts of transponder
:power
:> is peak pulse power. If you go through the calculation, you find that the
:> transponder output stage is running about 5 watts CW averaged over a
:couple of
:> seconds or so.
:>
:> Now, to repeat what I've been telling my colleagues building airplanes for
:the
:> last 30 years...put the transponder antenna inside the plastic with a
:round or
:> (better yet) octagonal ground plane, shield the sensitive parts of your
:anatomy
:> with tinfoil, and go for it.
:>
:> Jim
:>
:>
:> Jim Weir (A&P/IA, CFI, & other good alphabet soup)
:> VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
:> http://www.rst-engr.com
:

[Rob Turk]

Here's my view of what happened:

1. Someone advises to just put the transponder antenna inside the frame.
2. I place a warning, basically saying there's more to it then just put it
in and forget about it.
3. Jim comes back and asks if I have any experience at all that supports my
warning, in a somewhat hostile way.
4. I respond that in my experience as ham operator I do have hands-on
experience working with this. I caution the group (not Jim..) that diagnosis
is harder than hooking up a cheap SWR meter.
5. Jim feels it necessary to dismiss my experience as bullsh*t, posts his
entire resume, posts his list of valuable equipment and bashes my spelling.

Nowhere did I say Jim was wrong. His 15.000 installed antennas certainly
prove it can be done. But that doesn't dismiss that an unknowing home
builder might make mistakes. The builder, or a follow-on owner may decide
it's fancy to put metallic paint on the plane. Or someone may think it's a
good idea to install an inspection hole next to the antenna, and use one of
these aluminum covers. Both will influence proper operation of the
transponder.

I think Jim's response is way out of proportion. I know Jim has plenty of
knowledge on the subject and I'm sure he'll agree that you can't just stick
the antenna anywhere you want without thinking things through. Therefor I
would have expected constructive comments from him, not all-out bashing.

Rob


> wrote in message ...
> Rob, when you really done it, it ain't bragging.
>
> There are thousands - maybe 10's of thousands - of Jim's antennas
> flying. He wrote the book on hidden aircraft antennas. Your
> information is might be a reasonable extrapolation, but his is
> empirical.
>
> On Thu, 27 Nov 2003 08:04:37 +0100, "Rob Turk"
> > wrote:
>
> :Jim,
> :
> :I'm truely disappointed about your response. If this newsgroup is about
> :showing off how big your dick is, go right ahead. I was under the
impression
> :that the newsgroup was to discuss and provide help. None of the
information
> :I gave is wrong, I provided a fair warning to think twice before putting
a
> :UHF antenna enclosed inside a frame. You made it into a ****ing match. I
> :admire the knowledge you have, but the way you display it makes me sick.
> :
> :Rob
> :(The Netherlands, not a native English speaker, sorry for any spelling
> :mistakes...).
> :
> :"Jim Weir" > wrote in message
> .. .
> :> "Rob Turk" >
> :> shared these priceless pearls of wisdom:
> :>
> :> ->"Jim Weir" > wrote in message
> :> ...
> :> ->> Are you guessing on this, repeating an OWT, or do you have first
hand
> :hard
> :> ->data?
> :> ->>
> :> ->> Jim
> :> ->>
> :> ->
> :> ->As a licensed ham operator
> :>
> :> Jesus. A ham operator? Those are the credentials you come to the table
> :with?
> :>
> :> Amateur radio extra, first licensed in 1959. First 'phone with radar
> :> endorsement, 1960. BS-Physics (Microwave option) 1967. MSEE CGS 1983,
RF
> :> option. Pacific Southwest Airlines (1963-1967) avionics and radar
> :technician.
> :> Teledyne Ryan Space Systems (1967-1973) Microwave Antenna Engineer.
> :Founder and
> :> CEO RST Engineering, with a world class reputation for hidden antennas
in
> :> nonconductive structures (1973 --) with approximately fifteen THOUSAND
> :operating
> :> antennas in plastic/wood/fabric aircraft including one hanging in the
> :> Smithsonian.
> :>
> :>
> :> I have sufficient experience with frequencies
> :> ->around 1200 MHz.
> :>
> :> How long has it been since you fell off the turnip truck, feller? The
ham
> :bands
> :> at 33 and 23 cm are 10% or so away from the transponder frequencies.
Not
> :too
> :> far away, but far enough.
> :>
> :>
> :>
> :> Those don't like their antenna's shielded by wet or painted
> :> ->surfaces.
> :>
> :> First, the plural is "antennas", not the possessive. In the second
place,
> :this
> :> is the first mistake of fact so far. That is just horsepuckey. Wet
and
> :paint
> :> won't make squat for difference. And I've done and retained the
> :engineering
> :> data that says so.
> :>
> :>
> :> Transponders are just over 1000MHz
> :>
> :> 1030 and 1090 to be exact. Betcha can't tell me without looking which
one
> :is
> :> transmit and which one is receive.
> :>
> :>
> :>
> :> , it's reasonably safe to assume
> :> ->they are equally influenced. I'm not saying it will never work (fwiw,
> :GSM at
> :> ->900MHz works in-door), but I do want to caution people that there are
> :many
> :> ->variables involved that could make it not work.
> :>
> :> Yada, yada yada...
> :>
> :>
> :> ->
> :> ->Contrary to COM signals (118-136MHz) you can't use just any CB or VHF
> :SWR
> :> ->meter to check out if the antenna matches at these frequencies. With
the
> :> ->transponder sending out pulses of 200+ Watts I wouldn't want to
gamble
> :> ->having a bad SWR and seeing that power end up ruining the transponder
> :stage.
> :> ->Better be safe and put the $22 antenna where it belongs; Outside.
> :>
> :>
> :> Izzat a fact? Then I guess I'd best trash my $50k worth of RF antenna
> :test
> :> equipment, because I surely wouldn't want to gamble my transponder on
> :brothers
> :> Hewlett and Packard's equipment and the results derived therefrom.
> :>
> :> By the way, do the math before you post. That 200+ watts of
transponder
> :power
> :> is peak pulse power. If you go through the calculation, you find that
the
> :> transponder output stage is running about 5 watts CW averaged over a
> :couple of
> :> seconds or so.
> :>
> :> Now, to repeat what I've been telling my colleagues building airplanes
for
> :the
> :> last 30 years...put the transponder antenna inside the plastic with a
> :round or
> :> (better yet) octagonal ground plane, shield the sensitive parts of your
> :anatomy
> :> with tinfoil, and go for it.
> :>
> :> Jim
> :>
> :>
> :> Jim Weir (A&P/IA, CFI, & other good alphabet soup)
> :> VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
> :> http://www.rst-engr.com
> :
>

[Morgans]

"Rob Turk" > wrote in message
...
> Here's my view of what happened:
>
> 1. Someone advises to just put the transponder antenna inside the frame.
> 2. I place a warning, basically saying there's more to it then just put it
> in and forget about it.
> 3. Jim comes back and asks if I have any experience at all that supports
my
> warning, in a somewhat hostile way.
> 4. I respond that in my experience as ham operator I do have hands-on
> experience working with this. I caution the group (not Jim..) that
diagnosis
> is harder than hooking up a cheap SWR meter.
> 5. Jim feels it necessary to dismiss my experience as bullsh*t, posts his
> entire resume, posts his list of valuable equipment and bashes my
spelling.
>
> Nowhere did I say Jim was wrong. His 15.000 installed antennas certainly
> prove it can be done. But that doesn't dismiss that an unknowing home
> builder might make mistakes. The builder, or a follow-on owner may decide
> it's fancy to put metallic paint on the plane. Or someone may think it's a
> good idea to install an inspection hole next to the antenna, and use one
of
> these aluminum covers. Both will influence proper operation of the
> transponder.
>
> I think Jim's response is way out of proportion. I know Jim has plenty of
> knowledge on the subject and I'm sure he'll agree that you can't just
stick
> the antenna anywhere you want without thinking things through. Therefor I
> would have expected constructive comments from him, not all-out bashing.
>
> Rob
>
The only point Jim made, in his own unique way is, that you are full of
****. He called you on it. Point, game, match.
--
Jim in NC

[George A. Graham]

On Wed, 26 Nov 2003, Jim Weir wrote:

> Now, to repeat what I've been telling my colleagues building airplanes for the
> last 30 years...put the transponder antenna inside the plastic with a round or
> (better yet) octagonal ground plane, shield the sensitive parts of your anatomy
> with tinfoil, and go for it.

I hate to agree with our former gubernatorial candidate, but he is right.
My little stick is under my seat, and works great without seeing the
daylight.

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[Paul Lee]

Sorry. Don't remember the source. Had it when I was installing the
antenna. Suppose I could find it if I spend hours of searching,
but don't have time for it now - just remember it off hand.

But I think the 8+ feet refers to the body being in direct
path of the radiation pattern. If you place it in such a way that your
body is on the other side of the ground plane or on other side of a metal
shield you should be OK.

Jerry Springer > wrote in message .net>...
> And where would you be getting that information from? Don't know many small
> single engine airplanes that would meet that requirement.
>
> Jerry
>
> Paul Lee wrote:
> > AFAIK the tranponder antenna should be 8+ feet away from warm bodies.
> >
> > "Rich S." > wrote in message >...
> >
> >>"Paul Lee" > wrote in message
> m...
> >>
> >>>There is nothing wrong with the $22 one. Only for fast birds,
> >>>you may want an aerodynamic shaped one.
> >>>Composite projects can even build the $22 jobs into wings, etc.
> >>
> >>Hey! Don't forget us wood and fabric types. I was going to install mine
> >>under my seat, but then I thought about possible radiation effects on the
> >>family jewels. I mentioned this to my wife who poo-pooed my concern. So I
> >>put it under her seat.
> >>
> >>Rich S.