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Avidyne TAS600 Traffic Advisory System

Ps @peter I wonder why our upper aerial has two blades but yours has only one?

Now retired from forums best wishes

The Avidyne TAS6xx system (which I believe is what was installed in the RAF Grobs, with a Sandel SN3500 EHSI for the traffic display) uses two 2-blade antennae. One has 2 blades side by side, and the other has 2 blades in front of one another and looks like a single blade.

They can be mounted either way up. I have the side by side one on the bottom.

If you have both looking like a single blade, that is totally wierd…

I think the Honeywell TAS system uses two antennae, both having side by side blades. Not sure why…

Administrator
Shoreham EGKA, United Kingdom

Upper is two and lower is one blade on ours. I wonder if having the two on top makes any difference?

Now retired from forums best wishes

It well might, because then both blades are getting a signal, without shielding from the blade in front of it.

There is a number of people here who know the answers

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

I think the Honeywell TAS system uses two antennae, both having side by side blades. Not sure why…

The Honeywell can be installed with two directional antennae (two blades, side by side), or with mixed directional and non directional (single blade, well, just single antenna, type DMNI50-9-2).

I have second option, which Cessna certified through SB/MK, directional being on top, non directional on the bottom.

I’ve had trouble with the directional one, which has failed in a vicious way: target would appear to the opposite where they actually were. Troubleshooting has been difficult, because system would not return any error. Replacing the top antenna solved this behavior.

Never had problem with target shading in the 12 o’clock position. Only sometimes disappearing when just below (for a second or two).

Last Edited by PetitCessnaVoyageur at 11 Dec 21:43

TAS is beautiful, but it is an expensive and complex system, which has costed quite much to maintain so far (I didn’t mention a recent failure of the KTA810 computer)

I am still looking at swapping the two antennae as mentioned above, to move the upper TAS antenna to the front.

The only other explanation for the lack of 12 o’clock sensitivity is a fault in the TAS box. The cabling was all done in RG400; I know because I free-issued the cable to the installer.

The only concern is that this will place the combined GPS+VHF (COM1/NAV1) antenna closer to the COM2/NAV2 antenna which is further back. Is there a known issue with these antennae being spaced by about 60cm?

Does anyone familiar with this system know what the test equipment for the TAS6xx looks like and what it actually does? Almost nobody seems to have this equipment.

Administrator
Shoreham EGKA, United Kingdom

I wonder if you are experiencing some sort of Fresnel effect? (As opposed to just a plain reflection/ diffraction issue).

I think swapping the antennas would be a good plan!

United Kingdom

My theory is that the TAS antenna is shielded by a combination of the curvature of the roof and the fat blob at the base of the COM1/NAV1/GPS antenna.

Unfortunately, over the past few years, nobody has been able to offer a credible input on this; one based on actual experience. Kyp’s input above proves it is not the curvature of the roof alone that’s doing it.

I don’t think it is a faulty TAS box because I get the full 15nm range on all other bearings. Especially from known-good transponder installations i.e. small and large jets.

The Annual is next week and we will find out if there is enough spare cable going to that TAS antenna to enable it being moved. I think there is; there is a sizeable coil of the stuff in the rear cavity of the plane. If not, we will have to replace all four cables which will be a big job.

I’ve merged several near-identical TAS6xx threads. Near the start of this new thread there are some interesting posts regarding how the directional resolution probably works (although nobody seems to actually know).

Incidentally I don’t understand why all four antenna cables have to be the same length. Surely the two going to the top antenna must be identical and the two going to the bottom antenna must be identical. If all four had to be identical then there would necessarily be an additional requirement for the two antennae to be vertically one above the other, precisely, which there isn’t.

Administrator
Shoreham EGKA, United Kingdom
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