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VE3LVO(at)rac.ca
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 Posted: Tue Dec 26, 2006 6:26 am Post subject: Pitot/antenna |
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Bob N has obviously taken great pains to discuss the meritsa of combining
the two........ The thing that bothers me is that a 'hoizontal' antenna
loses 20dB to a vertical one and 26 inches does not give great scope to
adapt both. the one exception would be if the pitot could be mostly vertical
base isolated in cloth skin.
Cheers,
Ferg Kyle
Europa A064 914 Classic
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sportav8r(at)gmail.com
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| Posted: Tue Dec 26, 2006 11:19 am Post subject: Pitot/antenna |
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I wonder if we could prototype a helically-loaded "rubber duck" comm
antenna and slip a polypropylene tube inside it with an L-bend at the
end to act as a pitot; encase the whole thing in a streamlined radome.
Interesting excercise. Bandwidth would inevitably suffer from the
physical shortening versus a quarter wave. A lossy loading coil would
give some feeble de-ice heat during Tx (just kidding.) A lot of work
to shave a half knot of speed penalty, but a fun excercise
nonetheless. If I weren't busy with other projects, it's just the
kind of thing I'd try.
Come to think of it, a full size transponder antenna would easily fit
in a very modest blade pitot housing...
-Bill B
On 12/26/06, Fergus Kyle <VE3LVO(at)rac.ca> wrote:
| Quote: |
Bob N has obviously taken great pains to discuss the meritsa of combining
the two........ The thing that bothers me is that a 'hoizontal' antenna
loses 20dB to a vertical one and 26 inches does not give great scope to
adapt both. the one exception would be if the pitot could be mostly vertical
base isolated in cloth skin.
Cheers,
Ferg Kyle
Europa A064 914 Classic
|
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nuckollsr(at)cox.net
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| Posted: Tue Dec 26, 2006 11:53 am Post subject: Pitot/antenna |
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At 02:18 PM 12/26/2006 -0500, you wrote:
| Quote: |
I wonder if we could prototype a helically-loaded "rubber duck" comm
antenna and slip a polypropylene tube inside it with an L-bend at the
end to act as a pitot; encase the whole thing in a streamlined radome.
Interesting excercise. Bandwidth would inevitably suffer from the
physical shortening versus a quarter wave. A lossy loading coil would
give some feeble de-ice heat during Tx (just kidding.) A lot of work
to shave a half knot of speed penalty, but a fun excercise
nonetheless. If I weren't busy with other projects, it's just the
kind of thing I'd try.
Come to think of it, a full size transponder antenna would easily fit
in a very modest blade pitot housing...
|
Cool! Hadn't considered that.
Hmmm . . . maybe better yet, slice metal pitot tube into
horizontal and vertical portions (right across
the knee joint). Materials that traverse the joint wound
have to be non-conductor -OR- fabricated in a way
that provides loading components for the comm antenna.
Now the horizontal portion becomes more of a minimally
radiating top-hat and the vertical mast enjoys majority
current flow in the right polarity.
THAT could work! Except for the inevitable distortion
in pattern that arises from a leading edge location
on wing, it might function rather well.
If I can get an IR&D activity spun up next year, I'll toss
that out on the table to see if some RF-inquisitive guys
might like to go mock that up in the lab. It would be an
easily crafted experiment.
Bob . . .
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sportav8r(at)gmail.com
Guest
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| Posted: Tue Dec 26, 2006 1:25 pm Post subject: Pitot/antenna |
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No reason I see why we can't have the pitot shaped like an inverted-T
rather than an L. That would allow more top (bottom) loading to be
added, and the "hat" would not radiate, thus negating any directivity
effects that would arise from the L-shape. The back of the T would be
strictly antenna-related and not needed for Pitot, of course.
I like it.
-Bill B
On 12/26/06, Robert L. Nuckolls, III <nuckollsr(at)cox.net> wrote:
| Quote: |
At 02:18 PM 12/26/2006 -0500, you wrote:
>
>
>I wonder if we could prototype a helically-loaded "rubber duck" comm
>antenna and slip a polypropylene tube inside it with an L-bend at the
>end to act as a pitot; encase the whole thing in a streamlined radome.
>Interesting excercise. Bandwidth would inevitably suffer from the
>physical shortening versus a quarter wave. A lossy loading coil would
>give some feeble de-ice heat during Tx (just kidding.) A lot of work
>to shave a half knot of speed penalty, but a fun excercise
>nonetheless. If I weren't busy with other projects, it's just the
>kind of thing I'd try.
>
>Come to think of it, a full size transponder antenna would easily fit
>in a very modest blade pitot housing...
Cool! Hadn't considered that.
Hmmm . . . maybe better yet, slice metal pitot tube into
horizontal and vertical portions (right across
the knee joint). Materials that traverse the joint wound
have to be non-conductor -OR- fabricated in a way
that provides loading components for the comm antenna.
Now the horizontal portion becomes more of a minimally
radiating top-hat and the vertical mast enjoys majority
current flow in the right polarity.
THAT could work! Except for the inevitable distortion
in pattern that arises from a leading edge location
on wing, it might function rather well.
If I can get an IR&D activity spun up next year, I'll toss
that out on the table to see if some RF-inquisitive guys
might like to go mock that up in the lab. It would be an
easily crafted experiment.
Bob . . .
|
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nuckollsr(at)cox.net
Guest
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| Posted: Tue Dec 26, 2006 6:17 pm Post subject: Pitot/antenna |
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At 04:25 PM 12/26/2006 -0500, you wrote:
| Quote: |
No reason I see why we can't have the pitot shaped like an inverted-T
rather than an L. That would allow more top (bottom) loading to be
added, and the "hat" would not radiate, thus negating any directivity
effects that would arise from the L-shape. The back of the T would be
strictly antenna-related and not needed for Pitot, of course.
I like it.
|
I've added it to my notebook of "cookies" to toss on the
table should I find an opportunity to suggest it in the
future.
Bob . . .
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phil(at)petrasoft.net
Guest
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| Posted: Fri Dec 29, 2006 12:10 pm Post subject: Pitot/antenna |
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That aft-end of the T could be closed with some small radially drilled
holes and used as the static port.
Godspeed,
Phil Birkelbach - Houston Texas
RV-7 N727WB
http://www.myrv7.com
Bill Boyd wrote:
| Quote: |
<sportav8r(at)gmail.com>
No reason I see why we can't have the pitot shaped like an inverted-T
rather than an L. That would allow more top (bottom) loading to be
added, and the "hat" would not radiate, thus negating any directivity
effects that would arise from the L-shape. The back of the T would be
strictly antenna-related and not needed for Pitot, of course.
I like it.
-Bill B
On 12/26/06, Robert L. Nuckolls, III <nuckollsr(at)cox.net> wrote:
>
> <nuckollsr(at)cox.net>
>
> At 02:18 PM 12/26/2006 -0500, you wrote:
>
> >
> <sportav8r(at)gmail.com>
> >
> >I wonder if we could prototype a helically-loaded "rubber duck" comm
> >antenna and slip a polypropylene tube inside it with an L-bend at the
> >end to act as a pitot; encase the whole thing in a streamlined radome.
> >Interesting excercise. Bandwidth would inevitably suffer from the
> >physical shortening versus a quarter wave. A lossy loading coil would
> >give some feeble de-ice heat during Tx (just kidding.) A lot of work
> >to shave a half knot of speed penalty, but a fun excercise
> >nonetheless. If I weren't busy with other projects, it's just the
> >kind of thing I'd try.
> >
> >Come to think of it, a full size transponder antenna would easily fit
> >in a very modest blade pitot housing...
>
> Cool! Hadn't considered that.
>
> Hmmm . . . maybe better yet, slice metal pitot tube into
> horizontal and vertical portions (right across
> the knee joint). Materials that traverse the joint wound
> have to be non-conductor -OR- fabricated in a way
> that provides loading components for the comm antenna.
>
> Now the horizontal portion becomes more of a minimally
> radiating top-hat and the vertical mast enjoys majority
> current flow in the right polarity.
>
> THAT could work! Except for the inevitable distortion
> in pattern that arises from a leading edge location
> on wing, it might function rather well.
>
> If I can get an IR&D activity spun up next year, I'll toss
> that out on the table to see if some RF-inquisitive guys
> might like to go mock that up in the lab. It would be an
> easily crafted experiment.
>
> Bob . . .
|
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nuckollsr(at)cox.net
Guest
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| Posted: Fri Dec 29, 2006 7:50 pm Post subject: Pitot/antenna |
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At 02:08 PM 12/29/2006 -0600, you wrote:
| Quote: |
That aft-end of the T could be closed with some small radially drilled
holes and used as the static port.
|
That kind of rings a bell for something I've seen before
although I'm sure the pitot-static tube was not also an
antenna. Great thought! I'll add that to the mix. A pitot-static
tube that is also a reasonably efficient antenna. I believe
that's doable.
Bob . . .
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sportav8r(at)gmail.com
Guest
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| Posted: Sat Dec 30, 2006 6:14 am Post subject: Pitot/antenna |
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Keep in mind, though, that with too much "top (bottom) hat" length,
you'll be concocting a shape that might have some ugly flutter
characteristics once excited. The vertical portion of such a
structure will need lots of torsional stiffness to keep things tame
under the wing.
Bill B
On 12/29/06, Robert L. Nuckolls, III <nuckollsr(at)cox.net> wrote:
| Quote: |
At 02:08 PM 12/29/2006 -0600, you wrote:
>
>
>That aft-end of the T could be closed with some small radially drilled
>holes and used as the static port.
That kind of rings a bell for something I've seen before
although I'm sure the pitot-static tube was not also an
antenna. Great thought! I'll add that to the mix. A pitot-static
tube that is also a reasonably efficient antenna. I believe
that's doable.
Bob . . .
|
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