Transponder Antennas

[HopePilot]

So it looks like my transponder antenna is ready to go. Both of my blade antennas have lost part of their plastic and were acting flaky in the rain. I was thinking of getting a Comant CI-105, but if there is something with less drag/smaller I'd love to hear about it. I still have a metal belly or I'd bury them in the belly.

[scottfromiowa]

I don't know what kind of antenna it is, but my transponder antenna is a small (couple inchs) with a small ball on the bottom....Works great. Wish I could be of more help. There ARE small antenna's out there.

[N601RX]

I've been needing one also. I found this one, seems to be the same size, but a little cheaper.

http://www.aircraftspruce.com/catalog/avpages/av74_ant.php?clickkey=4083

[Jerry 5TJ]

The short whip with a ball on the end is the cheapest type. See EBAY for ~$20 DME / Transponder antennas.

[scottfromiowa]

The short whip with a ball on the end is the cheapest type. See EBAY for ~$20 DME / Transponder antennas.

Yup, that's it. Mine works great. 25 bucks and a small footprint.

[Marauder]

Yup, that's it. Mine works great. 25 bucks and a small footprint.

Same on mine. Works great. Only problem I have had was self inflicted. Cleaning the belly you can snag your clothing on it and break it.

[jetdriven]

We changed the ball on a stick antennas for Comant Ci-105s and they work great, and less drag.

[M204ever]

Performancewise the blade prefered, for DME blade only, drag difference is neglible.

[tony]

I have the same antenna as scott, its works fine. Never had an issue.

http://www.ebay.com/itm/BRAND-NEW-Aircraft-Transponder-DME-Post-Antenna-/140824751998?pt=Motors_Aviation_Parts_Gear&hash=item20c9cf2f7e&vxp=mtr

[Piloto]

The Commant C105 is a good choice. It is the same one that was installed later on new Mooneys. The rod and ball antenna works equally well but is subject to performance degradation by accumulation of carbon/oil deposits and icing, so keep it clean. The blade type is essentially immune to icing and deposits. Unlike the rod which acts a static wick the blade shell keeps static electricity away thus reducing radio noise into the transponder/DME. If you are in the proximity of salt water definitely get the blade type. It is also less prone to corrosion.

José

[Marauder]

The Commant C105 is a good choice. It is the same one that was installed later on new Mooneys. The rod and ball antenna works equally well but is subject to performance degradation by accumulation of carbon/oil deposits and icing, so keep it clean. The blade type is essentially immune to icing and deposits. Unlike the rod which acts a static wick the blade shell keeps static electricity away thus reducing radio noise into the transponder/DME. If you are in the proximity of salt water definitely get the blade type. It is also less prone to corrosion.

José

Do you know if the transponder and DME antennae are interchangeable?

[Piloto]

Do you know if the transponder and DME antennae are interchangeable?

Yes they are. The truth is that the same antenna is applicable to either DME or Transponder. The DME frequency range is from 970 to 1220 MHz while transponder is 1030 & 1090 MHz.

José

[jetdriven]

Performancewise the blade prefered, for DME blade only, drag difference is neglible.

Believe it or not, a typical TED antenna reportedly has about 4 times the drag of a typical blade antenna. That data is taken from a soaring website that compared a RAMI rod & ball antenna (0.41 lbs drag) to a RAMI blade antenna (0.09 lbs drag) (both measured at 250 mph).

[larryb]

I still have a metal belly or I'd bury them in the belly.

Can you really mount it under the fiberglass belly? I really like that idea. Has anybody else done this?

[aviatoreb]

Believe it or not, a typical TED antenna reportedly has about 4 times the drag of a typical blade antenna. That data is taken from a soaring website that compared a RAMI rod & ball antenna (0.41 lbs drag) to a RAMI blade antenna (0.09 lbs drag) (both measured at 250 mph).

Very interesting! We need more of that - actual drag measurements in proper units.

Does anyone know the lbs of drag of your favorite mooney, say a factory original M20J?

[N601RX]

I've never saw a number before, but prop manufactures should be able to supply a rpm/thrust chart for any given pitch angle. The charts should be specified in lbs. In regards to the numbers above which was measured at 250mph my guess is that when slowed down to 180mph they would be negligible when compared to the drag of the plane.

[Piloto]

Can you really mount it under the fiberglass belly? I really like that idea. Has anybody else done this?

I would not recommend any antenna installation beneath the composite skin. The performance of the antenna degrades substantially and you could be invisible to TCAS equipped airplanes from above. The trade off between any speed gain (if any) and safety is not worth it.

José