broken Comant DME/transponder antenna

[stapler101]

I snapped the transponder antenna from the belly of my plane with a wash brush (don't ask!).
The wire was "soldered" to the flat metal antenna (metal is approx. 2" wide x 3" tall but is paper thin).
I used the word soldered above, but I don't know if it soldered or secured with some type of weld(?)
Anyone have a suggestion as to how I could reattach the wire?

 

[Skylane81E]

SOP is replacement of the antenna in our shop, no repairs attempted.

 

[stapler101]

thanks Ducan, I needed to fly this weekend so I was looking for a quick fix until I could get one ordered.
My local ap thinks he may have one, if not, I will get one ordered.

 

[Piloto]

Suggest replacing the antenna with a blade type like the comant C105 http://www.aircraftspruce.com/catalog/avpages/comant105.php Unlike the rod type antenna blade antennas are less susceptible to performance degradation by oil/dirt/ice/exhaust deposit accumulation at the antenna base. For longer performance the antenna should be away from the engine exhaust path. Exhaust gases are corrosive and create a conductive coat on the antenna that degrades its performance. Keep all belly antennas clean for best performance.

José

 

[John Collins]

Don't use the transponder with the antenna broken off. These antennas have a nasty habit of breaking and shorting out the transponder. The antenna is cheap, not so for the transponder repair.

 

[denverpilot]

It's not that they "short out" the transponder.

It's that the transponder is transmitting into a mismatched load and the resulting standing wave fries the final output RF transistor, often charring the nearby circuit board traces as the DC bias also jumps the gap to the ground plane of the board itself.

It lets the magic smoke out.

Definitely don't operate a transponder with a known antenna defect. It'll kill it more often than not.

A Comm radio with a known antenna defect can be powered up and you can see if you can hear anything on the broken antenna system but don't hit that transmit button. Could be instant toast, might survive if the "fold-back" circuit for power into a bad antenna is fast enough.

 

[stapler101]

thanks for the great input from all.

 

[flyingron]

Depends on the transponder. If you have a older cavity tube transponder (KT-76 or AT-50 or whatever), you can very much damage it with no antenna. If you've got a newer solid state unit like a Garmin, it just won't work but it shouldn't burn up. Those solid state finals on 14/28V won't get enough current through them to damage them even into a dead short or open.