Hi Peter,
Just read your post.
I am now beginning to wonder if the problem I have – Port / Starboard target swap overs (contacted you by e-mail) is also due to signal overload. I might try buying 4 off 2db or 3db in line BNC/BNC attenuators and plug them in at the processor box end and see what happens.
Will let you know how I get on.
Back in 2007 I had the TAS600 installed in my PA32 Lance II. It all worked well to start with but after 18 months it started producing targets that were on the wrong side of the aircraft. i.e. a target on the Port would show up on the Starboard side of the display (GNS530). Yet ground testing the TAS showed it all to be working correctly. Avidyne also had the Central processor unit back and bench testing found no fault. Several years later I was offered Avidynes Flexcare extended warranty for one year which I bought into and returned the Central processor unit for a second time. This time a fault was found and corrected. The unit has worked fine since; until about 2 months ago!!
Now I am experiencing the same problem again. What appears to be Port / Starboard target position swaps but not totally reliably! I also sometimes get ghost returns that follow me around as if I am in loose formation with someone off my starboard side by half a mile!!!
I would be very keen to hear of other forum members experience with the TAS600 equipment??
I have the other TAS … Skywatch TR497, but I know that calibbration of the antenna(s) is very important. I would also check all antenna connections. Most of the time it’s the antennas, AFAIK!
Very similar experience to yours, Peter.. But most of the time it works well.
I have not had it looked at, mainly because the system is still very accurate when there is a real threat that is nearby, calling out "traffic, x o’clock, less than one mile’’, also showing up as big yellow blob on the nav display.
We have the same left right issue with our TAS610 on the gns530. But our ex500 display and the aural warnings are not affected. One display was connected via arinc and the other via rs232. Thus I deactivated the traffic on the gns530 and no problems since. So the whole system is probably not broken but something is wrong with the interface.
In combination with GNS it could have to do with dual heading inputs, which causes the units to go wrong.
For the other units:
I would strongly advise you to have the system carefully inspected… Some installers don’t seem to have good RF knowledge, which can cause the units themself to fail. A TAS doest transmit and receive, a non working port can and will destroy the amplifier.
Fixed this problem for Commander on this forum
It would be weird to feed two different heading inputs to the TAS box. Who would do that? But yes I can see it might confuse it if it has crappy software.
The system uses the 2-blade antenna (the one which actually has two separately visible blades) to distinguish left/right. It’s possible that a marginal return might not allow the box to determine L/R reliably. This could be due to poor quality cable having been used. The “installer” who did mine (one of UK’s top two firms – I am not naming it because I have zero interest in litigation) and who did some potentially life-threatening bodges, didn’t want to use the proper RG400 cable so I bought it and free issued to them. The cables are quite long and are thus a prime candidate for picking up muck and also picking up stuff from each other given that they run close together for long distances.
The “one blade” antenna is actually two blades also but they are overmoulded to look like one blade. That one distinguishes front/back.
However, many GA planes have badly wired transponders also. I find that bizjets and airliners show up with 100% reliability, all the way out to the 15nm or whatever radius the TAS605 is supposed to support. Light GA targets are much less good and often there is no indication till a mile or less away.
It would be weird to feed two different heading inputs to the TAS box. Who would do that?
Not two different heading inputs to the TAS box, but one heading input to the GNS and one to the TAS box which interfered which eachother. Have had this issue one a single aircraft, which was quite hard to troubleshoot.
This could be due to poor quality cable having been used.
I do not think poor quality cable will cause operation as indicated. There should be a specified cable loss, with RG-400 (Which I use) you often have some overlength in these cables to meet the minimum cable loss. Cable loss AND cable length AND ground plane have to be done right for an good installation. Even while the manual calls out to have the lengths similair I always use a network analyzer with time domain measurement to measure the electrical length of each cable, and tune them to the same electrical length. Do note physical length and electrical length for coax cables are not the same thing, and can be different between batches and even within the same batch. Getting the electrical length right will assure the most accurate bearing indication possible.
However, many GA planes have badly wired transponders also. I find that bizjets and airliners show up with 100% reliability, all the way out to the 15nm or whatever radius the TAS605 is supposed to support. Light GA targets are much less good and often there is no indication till a mile or less away.
There is more then 10 dB difference between a legal lowest output and legal limit maximum output transponder, with airliners and bizjest having high power output, and in general use good quality coax cable. On GA aircraft, often RG-58 is used, and while totally not suited for the job, are within legal limit with this combination. Combine this with an old worn out RG-58 cable and you will have little power radiating from the antenna.
This is why I think good avionics testing is important. I know many customers don’t agree, and sometimes argue that it still functions, and they don’t get complaints. Your transponder might work radiating just 10 Watts, and have a lower receiver sensitivity due to coax loss, but still functional, will fail the test. Repair this kind of issues before your transponder gets damaged is less expensive on the long run, and better for everyone.
The same is true on the TAS-600 problems reported, it is worthwhile to troubleshoot, and fix it with a “cheap” RG-400 fix, or just new connectors while the TAS unit itself is still serviceable, instead of continue to fly till it fails and requires repair of the power amplifier at the factory.
Good change that this has happed to the topic starters TAS-600 as well… Problems which couldn’t be reproduced on the unit itself could have been caused by poor antenna connections, then later at the second time the unit could have been finally been damaged, repaired again, so it will work for a while, until it fails again due to poor connections. I can’t say this has happend to this TAS-600 but it is a plausible explanation IMHO.
What I find surprising is that the requirement for all four cables to be within 2cm of each other in length translates to a miniscule difference in attenuation, when you look at the RG400 spec at say 1GHz.
The box must be extremely sensitive to attenuation differences, for the direction finding to work.
That also means the connectors need to be very carefully assembled, because the insertion loss of a typical RF connector is comparable to maybe 20cm of the cable!
The tolerance on coaxial attenuators is way more than 5cm of RG400.
Jesse,
My DA42 came with TAS from the factory and I may assume that Diamond uses proper materials and does proper installation work. The system has been working fine for 6 years but now it starts failing intermittingly, in that it sometimes causes false indications and confuses left/right. Sometimes also shows a target moving way too fast. The fact that it does so intermittingly probably points at a bad connection, right? So I suppose the first points to inspect and reseat would be the connectors at the antenna’s side and the input connector to the pertinent G1000 LRU. Plane is in the shop, so might as well have it checked.. Any further ideas welcome, thanks in advance..
