Transponder AERIAL

[Maybe]

What alternatives are there to the rather expensive transponder aerials at our local shops? (starting at R500+)

There is a guy selling them in the states for $10. (R70) each?

Does anyone know of a local agent or place to get the aerials for less?

thanks

[German]

Go measure the length and make one with a piece of wire!

[Maybe]

Really that easy?

Has anyone done this before? a pic or two?

It would be great.....(I believe the wire would be much less than the local SA price on these antennas - R550+)


This is the one for R550:

TRANSPONDER stub-antenna.jpg (7.77 KiB) Viewed 2345 times

[ppakotze]

The antenna in the photo will work. Your metal aircraft will provide the groundplane for the antenna to work against. You could make it yourself, but the trick is to get that little whip supported properly against the vibration and airflow. In the photo it looks like the white dielectric is providing some of that function. You could even just solder the right length of copper wire to a BNC connector and then use some sort of aerodynamic radome (non electric covering) to protect your copper wire against the vibration and airflow. Just thinking out loud here, but you could use something as simple and light as polystyrene to the protection, but then the polystyrene itself would need some protection. I'll keep my eyes open for something. Do you need the same connector (BNC) as in the photo?

Regards
Pieter

[justin.schoeman]

Or just order one from the states. Ask the seller to just pop one in an international priority mail envelope (it is small enough). Will only cost around $3 for postage. Still works out a LOT cheaper than buying locally...

[Maybe]

Hi ppakotze,

Any transponder aerial will work...i just need one....new...second hand...anything!

Justin.schoeman,

thanks for the tip...I think it might just be the answer to go International....America is just so much cheaper on aviation parts...only in SA its considered as a richman sport!

Cool....anyone with a secondhand alt encoder?

[Kingfisher]

I spoke to a local antenna manufacturer, were busy working on it.
Will post info as soon as it becomes available.
I am also able to supply coaxial cable & connectors as well as whip type com's antennas

[ppakotze]

Hello again

Put this together today. Will bolt to a metal plate tomorrow and tune. Electrically it will be 100% mechanically it will bend when bumped, but could be straightened again and would still work. Have used similar construction techniques for a harsher environment in the past.

Thinking of a second prototype with a stiffer whip element. If this will work for you let me know. Its going to cost you at least a beer.

Sorry only cellphone pic.

Regards
P.

[Boet]

What ever you do, just put the bloody thing as far away from the cockpit as you possibly can. I understand that this item puts out seriaas microwaves. Do not want to microwave your fav body, do you?

[Maybe]

ppakotze......a bear I can afford
Keep me posted.


Boet....I aggree....I am considering another kid sometime
Mounting position...?? On the belly....as far away from cockpit?..close to the rudder....?

[justin.schoeman]

Mounting position...?? On the belly....as far away from cockpit?..close to the rudder....?

Not too serious - you are flying in a tin can, not a rag and tube . Gives you some nice good shielding.

[ppakotze]

Hello again

Mounted the antenna on a plate and trimmed it down to the right length for a transponder. Mounting position should be on the bottom of the aircraft. Shielding should not be a problem. (I still find it funny that people are quick to worry about 'microwaves' but happy to have their heads glued to a cellphone for hours on end.) For the antenna electrical performance you should mount it on the largest flattest piece of metal plate without obstruction. From the mechanical point of view you want to mount where there is the least risk of something hitting it.

Anyway antenna is performing well (-20dB return loss on TX and -15dB on receive). I did not bother optimising it too much as the installed antenna on your aircraft will behave slightly differently. I am in the Harties area, PM me if you want it.

Regards
P.