Author Topic: Transponder Aerial  (Read 2572 times)

drvale

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Transponder Aerial
« on: January 28, 2020, 07:21:52 pm »
I might be being a little dense here!
I have had a PAW from nearly the word GO and it has worked fine except the Transponder receiver aerial is located in one of the few vertical positions in the cockpit (its a Falco and everything is curved or has large chunks of metal or fuel tanks in the way to obstruct signals). This results in some blind spots, I also have had for a while a Garrecht VY-01 Transponder with ADS-B output and external aerial linked to an MGL EFIS, again has worked fine.
Question is: Is there any reason why I cannot T a BNC connector into my Transponder aerial and connect to the PAW as well (with of course suitable connectors). I realise the Garrecht outputs a thunk through the aerial but as it also receives and the aerial is external then it may give me a better reception.
I have explored putting the aerial in the wing but this is heading towards the 'too hard tray'.
Have looked through the forum and cannot see this topic having been raised before.
David Vale, G-OCAD

Admin

Re: Transponder Aerial
« Reply #1 on: January 28, 2020, 07:39:31 pm »
Connecting to your transponder antenna, will destroy the receiver in an instant
What about using the internal antenna its a dipole and pretty small

https://pilotaware.com/product/internal-1090-aerial/
« Last Edit: January 28, 2020, 07:42:05 pm by Admin »

drvale

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Re: Transponder Aerial
« Reply #2 on: January 28, 2020, 09:59:52 pm »
Thanks for quick response. thought that may be the case!  I do have a centre feed dipole aerial from the shop but no where to locate it easily to keep it vertical (even with its short length) unless its internal to the wood wing and that is a nightmare. A fuel tank and Lycoming would preclude the most obvious location and if placed in the rear fuselage the only accessible spot that is vertical is just below the rear fuel tank. Horizontal would be fine but of course that is really going to limit signal strength. It maybe that ADS-B is strong enough to cope with this on a short range i.e. 20 Nm but I don't know. Adding another external aerial is an option but us Falco chaps are very concerned in adding drag to our fast flying machines.
David Vale, G-OCAD

exfirepro

Re: Transponder Aerial
« Reply #3 on: January 28, 2020, 11:23:35 pm »
David,

You would get away with cutting a PAW 1090 whip (the type supplied with the ‘Classic), down to 69mm after which it would almost certainly fit on the coaming. As the 1090 side is RX only, It doesn’t need a ground plane - just watch for the base magnets if near the compass (or remove them).

There is a thread here, though some of the photos seem to have disappeared...

http://forum.pilotaware.com/index.php/topic,438.msg5661.html#msg5661

Hope this helps.

Regards

Peter

Ian Melville

Re: Transponder Aerial
« Reply #4 on: January 29, 2020, 07:10:08 am »
As the 1090 side is RX only, It doesn’t need a ground plane

Are you sure?

GeoffreyC

Re: Transponder Aerial
« Reply #5 on: January 29, 2020, 07:16:48 am »
David,

You would get away with cutting a PAW 1090 whip (the type supplied with the ‘Classic), down to 69mm after which it would almost certainly fit on the coaming. As the 1090 side is RX only, It doesn’t need a ground plane - just watch for the base magnets if near the compass (or remove them).

There is a thread here, though some of the photos seem to have disappeared...

http://forum.pilotaware.com/index.php/topic,438.msg5661.html#msg5661

Hope this helps.

Regards

Peter

I did the “cutting the classic antenna down to 69mm” approach as recommended in this article, and it works fine, but found that securing the classic antenna in place wasn’t easy.  My inspector didn’t like it and neither did I, Velcro, sticky pads, all tried but after a while it came loose again.

So I changed and tried the “MCX pigtail stripped back and stiffened with heatshrink”.  This worked perfectly, the antenna sticks straight up at the back of my classic and receives signals reliably.

Geoffrey

exfirepro

Re: Transponder Aerial
« Reply #6 on: January 29, 2020, 08:11:23 am »
As the 1090 side is RX only, It doesn’t need a ground plane

Are you sure?

Hi Ian,

I’m not saying it is ‘optimal’ without a ground plane, but I know of plenty which are working fine like this and siting on the coaming is generally high enough to minimise screening to the front from the engine. Traffic at lower altitude will of course be screened to a degree, but it is usually picked up at range we’ll before it gets into the ‘shadow’ of the engine.

Peter
« Last Edit: January 29, 2020, 08:18:34 am by exfirepro »

drvale

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Re: Transponder Aerial
« Reply #7 on: January 29, 2020, 08:16:22 am »
Thanks everyone, My original was a cut down whip aerial and it was impossible to place on the coaming without being in line of sight or being too close to the compass.
I am going to try some experiments this morning with the centre feed dipole and see if I can find somewhere that is going to work.
David Vale, G-OCAD

exfirepro

Re: Transponder Aerial
« Reply #8 on: January 29, 2020, 08:29:24 am »
David,

Most users don’t find the cut down whip distracting at all. It’s so thin you soon forget it’s there (and if you smooth the cut end you can leave the cap off the tip).

The magnets are very easy to remove by taking off the plastic cover on the base and prising them free. While you have the base off you can also cut back the co-ax to a tidy length and re-solder it in place, then after putting back the aluminium cap, carefully fill the base with hot glue or araldite to give a firm solid base for mounting - or fill it with silicone, which will also stick it to the coaming pretty effectively. (GeoffreyC)

Regards

Peter

drvale

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Re: Transponder Aerial
« Reply #9 on: January 30, 2020, 08:12:03 am »
Peter, thanks for this. I did have it before on the coaming and have changed the aerial for the centre feed dipole. It was not aesthetically pleasing sticking up in view. I bit the bullet yesterday and located it in the rear fuselage which meant a lot of contortion and bruises. Tested as well and gave a good signal. I also located the PAW aerial as well (centre feed ) about a foot from the 1090 aerial, unable to test that as located in France. The PAW aerial is not so important as most of my flying is in France and I only venture across the channel a couple of times a year. Hopefully it will be OK though.
David Vale, G-OCAD

exfirepro

Re: Transponder Aerial
« Reply #10 on: January 30, 2020, 08:49:43 am »
David,

Thanks for the update. Please keep us posted on how it goes.

Regards

Peter