Antenna under fabric in welded tube ship?

[Jon[_6_]]

I would like to put internal nav and comm antennas in a series 5
kitfox, which has a welded tube frame. Could reasonable performance
be obtain with elements on the inside surface of the fabric, but out
side the frame? Seems to me this is essentially mounting the antenna
very close to a so-so ground plane. How much loss and alteration of
the radiation pattern is likely? Would the situation improve by
minimzing runs parallel to the frame tubes?

Thanks!

Jon

[Morgans[_2_]]

"Jon" > wrote in message
...
>I would like to put internal nav and comm antennas in a series 5
> kitfox, which has a welded tube frame. Could reasonable performance
> be obtain with elements on the inside surface of the fabric, but out
> side the frame? Seems to me this is essentially mounting the antenna
> very close to a so-so ground plane. How much loss and alteration of
> the radiation pattern is likely? Would the situation improve by
> minimzing runs parallel to the frame tubes?

I'm no expert, and I am sure someone who is will chime in, but I don't think
that will work worth a darn.

If the antenna element within an antenna length of the frame, the fact that the
frame is a part of the ground plane will interfere with the signal, or something
along that effect.
--
Jim in NC

[RST Engineering]

You would get better performance with a piece of limp spaghetti inside a
copper septic tank.

Jim

--
"If you think you can, or think you can't, you're right."
--Henry Ford

"Jon" > wrote in message
...
>I would like to put internal nav and comm antennas in a series 5
> kitfox, which has a welded tube frame. Could reasonable performance
> be obtain with elements on the inside surface of the fabric, but out
> side the frame? Seems to me this is essentially mounting the antenna
> very close to a so-so ground plane. How much loss and alteration of
> the radiation pattern is likely? Would the situation improve by
> minimzing runs parallel to the frame tubes?
>
> Thanks!
>
> Jon

[Steve Foley]

"RST Engineering" > wrote in message
...
> You would get better performance with a piece of limp spaghetti inside a
> copper septic tank.
>
> Jim
>

What length spaghetti?

Also, would I need a field approval to install this, or is it electrically
connected to the landing light?


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

When the only tools you have are a dremel and a flat blade screwdriver,
everything looks like a rounded
off philips screw.

[MikeMl]

Jon wrote:
> I would like to put internal nav and comm antennas in a series 5
> kitfox, which has a welded tube frame. Could reasonable performance
> be obtain with elements on the inside surface of the fabric, but out
> side the frame? Seems to me this is essentially mounting the antenna
> very close to a so-so ground plane. How much loss and alteration of
> the radiation pattern is likely? Would the situation improve by
> minimzing runs parallel to the frame tubes?
>
> Thanks!
>
> Jon

Jon,

fact of life is that an antenna needs to approximate a dipole half a
wavelength long. You can cheat, and leave off half the dipole, and use
the aircraft structure as the other half dipole, however, that implies
that the 1/4 wavelength monopole is mounted PERPENDICULAR to the
airframe; not PARALLEL to it. I'm with Jim...

[MikeMl]

MikeMl wrote:
> Jon wrote:
>> I would like to put internal nav and comm antennas in a series 5
>> kitfox, which has a welded tube frame. Could reasonable performance
>> be obtain with elements on the inside surface of the fabric, but out
>> side the frame? Seems to me this is essentially mounting the antenna
>> very close to a so-so ground plane. How much loss and alteration of
>> the radiation pattern is likely? Would the situation improve by
>> minimzing runs parallel to the frame tubes?
>>
>> Thanks!
>>
>> Jon
>
> Jon,
>
> fact of life is that an antenna needs to approximate a dipole half a
> wavelength long. You can cheat, and leave off half the dipole, and use
> the aircraft structure as the other half dipole, however, that implies
> that the 1/4 wavelength monopole is mounted PERPENDICULAR to the
> airframe; not PARALLEL to it. I'm with Jim...

btw-on a less than 120MPH airplane, why bother trying to hide it?

[[email protected]]

On Apr 22, 10:33 am, Jon > wrote:
> Could reasonable performance
> be obtain with elements on the inside surface of the fabric, but out
> side the frame?
--------------------------------------------------------------------

Yes. But only when the control tower is also inside of the fabric
(but out side of the frame).

Seriously Jon, if you want to radiate a good signal create a counter-
poise (ie, a 'ground plane') and mount your radiating element in the
middle... outside of the fabric. If you're worried about drag, spring
for a composite antenna with a nicely streamlined cross-section.
Otherwise, do what everyone else does and use a hunka brass welding
rod in a BNC connector :-)

-R.S.Hoover
-(KA6HZF)

[[email protected]]

On Apr 22, 2:36 pm, "RST Engineering" > wrote:
> You would get better performance with a piece of limp spaghetti inside a
> copper septic tank.
>
> Jim

We have a '96 American Champion 7ECA in which the factory
installed the ELT antenna inside the aft fuse frame, with the
antenna's whip zip-tied to a diagonal upright to keep it away from the
elevator and rudder cables. I hope we never have to go looking for
this airplane.
This is the same outfit that sells airplanes with plugs in the
tank sump drain ports. Plugs instead of quick-drain vaves. Go figure.
We fixed that one immediately.

Dan