Dipole Transponder Antennas

Has anyone used a Dipole antenna on their transponder? I understand that
the dipole gives better coverage above where the "standard" antennas
usually only project down and to the sides. Aircraft Spruce carries
dipoles, they are a little spendy, but might be worth it. Any experience
out there?
-Tony Condon
Cherokee II N373Y

There are a number of people in this group who used dipole antennas.
I've got the L2 model from Advanced Aircraft Electronics in my ASW-19,
it was $99 if I remember right.

Because I have a fiberglass tail boom, all I had to do was glue the
dipole to the supplied strip of balsa, then glue the dipole into the
tail boom in a vertical position. No need for a ground plane at all,
and as you point out it radiates both upwards and downwards.

It seems to work very well, but I couldn't tell you just how much
better it performs than a monopole under the same circumstances. For
me its biggest advantage was the ease of installation.

-John

Tony Condon wrote:
Has anyone used a Dipole antenna on their transponder? I understand that
the dipole gives better coverage above where the "standard" antennas
usually only project down and to the sides. Aircraft Spruce carries
dipoles, they are a little spendy, but might be worth it. Any experience
out there?
-Tony Condon
Cherokee II N373Y

+1

Works great, easy to install. W & W has them too.

jcarlyle wrote:
There are a number of people in this group who used dipole antennas.
I've got the L2 model from Advanced Aircraft Electronics in my ASW-19,
it was $99 if I remember right.

Because I have a fiberglass tail boom, all I had to do was glue the
dipole to the supplied strip of balsa, then glue the dipole into the
tail boom in a vertical position. No need for a ground plane at all,
and as you point out it radiates both upwards and downwards.

It seems to work very well, but I couldn't tell you just how much
better it performs than a monopole under the same circumstances. For
me its biggest advantage was the ease of installation.

-John

Tony Condon wrote:
Has anyone used a Dipole antenna on their transponder? I understand that
the dipole gives better coverage above where the "standard" antennas
usually only project down and to the sides. Aircraft Spruce carries
dipoles, they are a little spendy, but might be worth it. Any experience
out there?
-Tony Condon
Cherokee II N373Y

I had the same experience with this antenna. In your wooden
ship this is just the ticket. I bought mine from Tim at Wings and
Wheels. Works great and is super easy to install.
Brian

At 20:36 14 April 2009, jcarlyle wrote:
There are a number of people in this group who used dipole
antennas.
I've got the L2 model from Advanced Aircraft Electronics in my
ASW-19,
it was $99 if I remember right.

Because I have a fiberglass tail boom, all I had to do was glue
the
dipole to the supplied strip of balsa, then glue the dipole into
the
tail boom in a vertical position. No need for a ground plane at
all,
and as you point out it radiates both upwards and downwards.

It seems to work very well, but I couldn't tell you just how
much
better it performs than a monopole under the same
circumstances. For
me its biggest advantage was the ease of installation.

-John

Tony Condon wrote:
Has anyone used a Dipole antenna on their transponder? I
understand that
the dipole gives better coverage above where the
"standard" antennas
usually only project down and to the sides. Aircraft Spruce
carries
dipoles, they are a little spendy, but might be worth it. Any
experience
out there?
-Tony Condon
Cherokee II N373Y

Thanks,

after seeing the ones that Tim has, it makes more sense. The antennas
that Aircraft Spruce carries are different, and I cant see as well how
they mount. Will be very easy to mount that antenna in the web of sticks
in the tail of the Cherokee.
-Tony Condon
Cherokee II N373Y

I have use an L2 in my LS8 for five years. Just slap it on the inside
of the fuse with velcro. Works super. Approach reads me clearly in
all orientations.

On Apr 14, 4:15*pm, Tony Condon
wrote:
Has anyone used a Dipole antenna on their transponder? I understand that
the dipole gives better coverage above where the "standard" antennas
usually only project down and to the sides. *Aircraft Spruce carries
dipoles, they are a little spendy, but might be worth it. *Any experience
out there?
-Tony Condon
Cherokee II N373Y

A dipole and a monopole with a proper groundplane both have
approximately the same pattern, both above and below the plane of the
groundplane. The whole idea of a 'groundplane' is to produce a
virtual mirror image of the monopole. Monopole/groudplane
combinations are particularly convenient for metal-skinned aircraft,
where the requisite groundplane is essentially free. A dipole
arrangement might be much simpler than a monopole/groundplane for a
glider.

Frank(TA)

Frank wrote:
On Apr 14, 4:15 pm, Tony Condon
wrote:
Has anyone used a Dipole antenna on their transponder? I understand that
the dipole gives better coverage above where the "standard" antennas
usually only project down and to the sides. Aircraft Spruce carries
dipoles, they are a little spendy, but might be worth it. Any experience
out there?
-Tony Condon
Cherokee II N373Y

A dipole and a monopole with a proper groundplane both have
approximately the same pattern, both above and below the plane of the
groundplane. The whole idea of a 'groundplane' is to produce a
virtual mirror image of the monopole. Monopole/groudplane
combinations are particularly convenient for metal-skinned aircraft,
where the requisite groundplane is essentially free. A dipole
arrangement might be much simpler than a monopole/groundplane for a
glider.

The patterns are different, and the bigger the ground plane, the bigger
the difference. The monopole with a large ground plane radiates only on
the side with the antenna. The "mirror image" you mention is just a
convenient way to think about how a conducting surface affects the
electric field. In practice, it blocks the field. Look up "Faraday
cage", as an example.

If a metal airplane needs a good signal on the top and the bottom, it
uses two antennas, one on each side. In Tony's wood and fabric glider,
the dipole is an good choice.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* "Transponders in Sailplanes" http://tinyurl.com/y739x4
* Sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org