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Trutrak/Mic Key problem

tkirk

tkirk

Active Member
I have the trutrak ADI-1 and have a problem. When I key the mic, the ADI indicator jumps down and holds until I release the mic key, then the indicator goes back to normal. Any one else experience this?

I have an SL40, a Bob archer wing tip antenna (left wing), and the trutrak servor is in the right wing. The servo and antenna (RG-400) wires are bundled together coming from behind the panel and down the firewall and then back to the spar where they split. Do I need to try to separate the servo and antenna wires, or is there another possilbe cause??
 
Similar

I have the TT DigiFlight II with altitude hold. When I was using the Archer wingtip antenna for comm, keying the mike would cause the TT to pitch up dramatically. For that and even better reasons (range and clarity) I switched to a Comant on the belly and the problem went away. It may not have been the Archer itself, but the way I ran the wires in proximity. The Comant wire is not in the same bundle as the TT, but the Archer wire was/is. I had the Archer checked for stray energy and all that technical stuff and it was OK, so my tentative conclusion is that the bundling of the wires was the real culprit. I did need the much better performance of the Comant, though, so I solved two for the price of one. I hope this helps.
 
At first I would not suspect RF interference but more on the side of a grounding issue. An improper ground some where in the system can wreak havoc on diagnosing goofy indicator problems. First I would make a temporary power cable just for the ADI. Both power and ground and connect it directly to a power source. Observe if this corrected the problem. If it does then you have somewhere to start.
Let us know how it works!
 
Trutrak

Thanks for the replies. I was already thinking about a belly mount for the same reasons you state.

As far as grounding, I will try a different harness but I don't think that will be the problem. I have a common ground block (48 tab from B&C) and was very careful connecting all of the grounds because I did not want any noise.
 
Also simular.

When I transmit on my SL30/wing tip antenna, I see my fuel level on my AFS engine monitor take a dip. The longer I talk the lower it goes. Some of the other sensors are also effected to a lesser degree.
Before I figured this out it gave me some tense moments. All thing would be going along fine and as I approached the airport area, I would transmit my location. The AFS would announce to me "fuel low". :( I would look over at the indicator and see that it was no longer green, but had turned yellow. The closer I got to the airport the lower my fuel would go, until on final it might be in the red. :eek:
By the time I had finished taxing it would be back in the green. :)
I haven't found the fix for this yet and don't have a problem on my 2nd radio, GNS430/bent whip. I just have been avoiding transmitting on the 1st radio.

Kent
 
TT A/P disconnect

I believe that somewhere in the TT documentation they warn against running the A/P disconnect wire (assuming you have one) in parallel with a COMM antenna wire. Running it across a COMM wire is OK.
 
Archer Com antenna wierdness

I too have an interesting phenomenon that seems to be associated with the Archer wingtip Com antenna.

When I key the mic to transmit, my Van's manifold pressure gauge and Van's Ammeter gauge go all the way off the scale :eek: The gauges return to normalcy when I release the mic switch. It seems to affect the gauges differently depending on which com frequency is selected. It happens with or without the engine running and with or without the alternator turned on and seems to have nothing to do with battery voltage.

The com antenna cable is bundled with the other instrument panel wiring until it gets to the center console and then runs into the wing with the nav light/strobe/landing light wires. I wonder if it is related to the antenna wire being bundled with the instrument panel wiring or if it is related somehow to the Archer com antenna itself :confused: .

I like the fact that my com antenna is hidden and not hanging in the slipstream, but I am toying with replacing it with an external whip on the belly. Does anyone have a feel as to whether the 'wierdness' with the Archer com is related to the antenna itself or due to wiring/bundling issues?
 
Talk about RF interference, I have an interesting experience. Last March I did first flight of a RV-6A. Each time I keyed the mike, the ELT got triggered. I heard the noise but was too busy to hunt it down. When I landed the FBO guy run over to inform me of the ELT transmission. On my second flight that day, I kept my finger closed to the remote ELT reset button. Each time I keyed the mike, I had to reset the ELT. Subsequently the owner reroute the cables and the problem went away (at least for the local UNICOM frequency).
 
PTT triggers off scale ammeter reading

AV8rDoc said:
When I key the mic to transmit, my Van's manifold pressure gauge and Van's Ammeter gauge go all the way off the scale :eek: The gauges return to normalcy when I release the mic switch. It seems to affect the gauges differently depending on which com frequency is selected.
Click to expand...
I have the same issue but only happens when I have the nav lights on. I get a full scale deflection of the ammeter when keying the PTT. I am using a belly mounted Comant whip antenna.
I thought it might be an RF interferance issue with the ammeter wire. I tried shielding the ammeter wire from the radio (it was routed directly behind it) and got very little effect.
Based on some of the suggestions here I may try checking the ground on the nav lights. They are grounded in the wing where as everything else is grounded at the firewall. I installed a couple of studs to put a grounding strap between the wing and the fuselage but did not install it due to very little ohms when checked with a ohm meter between the wing and the fuselage.
 
I separated the antenna wire from the bundle of wires coming from the panel and all the way down the FW, and the TT deflection was about 1/4 the amount it was before. The antenna wire is now separated from the other wires from the SL40 all the way to the wing root. At the wing root, the antenna wire joins the taxi light, position light, and future pitot heat wires in the wing. If I get some time, I think I will pull the antenna wire all the way out of the wing and separate from all other wires then reconnect to the SL30 and see if the problem goes away.

I also noticed that the ray allen trim indicator jumps from neutral to the bottom of the indicator when the mic is keyed (trim servo does not move).

BTW, I don't have an autopilot disconnect wire. Also, the antenna seems to be well grounded to the air frame as per the installation instructions.
 
I am telling you again to look for a ground problem. I feel more strongly that you have a ground problem with your radio now that you mentioned the ray allan indicator. I too had the indicator go nuts and also had the amp meter pull to the left when I keyed the mic. I also have a single ground block and I home ran all of the grounds back to this block and still had the problems all of you have mentioned. Before you pull all of your antenna wire out of the wing do a simple test by just running pos and gnd DIRECTLY from the TT to the battery. Key the mic and note the result.
Current flows from neg to positive and the radio pulls the most current when the mic is keyed. If the ground is not proper it will pull current anyway it can. It could be a connection directly behind the radio. Ground issues are a pain in the butt to track down.
 
Update

I finally had some time this evening, so I disconnected the TT harness and ran pos and neg wires from the TT directly to the battery. Even after doing this, I still have the same problem as before. I am not sure what I will do next, but I am leaning toward a belly whip antenna.
 
Grounding issues

Have seen this sort of issue several times in the commercial world. Every time it was associated to the antenna itself. Either a breakdown of the antenna windings, corrosion build up between the antenna and its connector or a corrosion build up breaking the ground of the antenna to the airframe. Try a little scotchbrite and contact cleaner yet?
 
Check coax connection at radio

Have you checked the coax connection at the back of the radio? It's a solder type connection, and a cold solder joint on the shield or center conductor could cause some RF to flow on the outside of the coax. I'd also double check the coax connection at the antenna, a bad connection on either the center conductor or shield will have the same effect.

Another old Ham trick is to coil up about five turns of coax in a 2" diameter loop right near the feed point of the antenna. That should de-couple the coax from the antenna, and keep reflected RF from flowing on the outside of the coax.

I would also look for a friend or neighbor that had an SWR meter to check the SWR (Standing Wave Ratio) of the antenna. A high SWR (depends on radio but ROT is 2:1) could certainly make RFI worse, and might even damage the radio.

If you only had to worry about power leads, you could put a bypass capacitor (.01uF) across the power leads right where they enter the device, but with all the other wires going to the servo, you still have plenty of avenues for the RF to get in. I'd call TRU-TRAK before putting a bypass capacitor on any other lines.

Finally, do you have strobe or nav light wires running right next to the antenna? The method of routing, and the location of the antenna ground vs. where these wires cross will have a big impact on the amount of RF that flows on them.

-Paige

RV-8A
 
Grounding at antenna

I'll throw my 2 cents in as well ... check the grounding at the antenna itself. I believe that Bob Archer says to have a good ground interface at the wingtip for his antenna. How are you grounding it?

Another test you can try is to use another coax, and transmit using the elt antenna, which is a 1/4 wave over the fuselage as a ground plane. Hopefully you also have a good ground on this one, if not, then make sure the surface where the nut is being tightened is clear of primer/paint. You want the antenna shield to be grounded well at the antenna.
 
I had the same problem with my 9A before first flight in '03. MP and ammeter would go wacky when ppt button pushed. Delayed first flight over a month. After removing panel numerous times, talking to anyone I could bug for opinions, I called Vans. I think it was Gus that explained to me that the gauges(steam) are simple electromagnetic 1950's technology, are not shielded, and are affected by close proximity to RF radiating from radio. He said they removed the ammeter gauge(have voltmeter only) and did not put mp gauge in the prototype 9A because "it would upset the passengers".

I also thought it was com ant, coax, ant location, bad ground, or maybe global warming. I guess it's just the 50's auto technology,as Gus said, and can be ignored ,or removed, or you can spend bigger bucks and buy new technology instruments. :(
 
Update?

I want to revive this thread because I am getting ready to install my autopilot servos and com/transponder antennas. It appears to me from reading this thread that the thing to avoid is running the com/xponder coax parallel with autopilot wires. They should cross at right angles to the extent possible.

What is less clear to me is whether there is a problem with locating the com/xponder antennas close to the autopilot servos. I am building an 8A wtih TT pitch and roll servos and want to mount the antennas (2 bent whips and a rod) on the centerline on the under-belly. I know I need antenna separation from each other (coms primarily). However, do I need to be careful how close the antennas are to the servos?

Also, for those of you who mounted an antenna on the centerline belly of an 8A... How did you deal with the lip down the middle where the two belly skins join?

Thanks,
 
Reading back through this thread, it seems to me that there may be a commonality with the Archer COM antenna. I'll add my data point: I WAS using an Archer wing tip antenna for COM2 and when I would transmit on some frequencies, the TruTrak autopilot would command a large pitch change. I abandoned the wing tip antenna for a Comant belly whip for better reception, and the issue is gone.
 
Comm radio interference issues

I am in agreement with Scott that at least some of what has been described in this thread seems to be related to the Archer wingtip com antenna. I ran an experiment: I disconnected the coax in my wingtip from the Archer com antenna and connected it to a standard whip antenna that I borrowed from a friend. I did not change and wiring/bundling in any way. Now when I trigger the PTT I get only a very very minor 'flick' of the ammeter and the manifold pressure gauge.:)

HMMMM..... now I am debating if I should reconsider placing a standard whip antenna on the belly and getting rid of the Arcgher wingtip com. I do like that extra 0.00001 knot advantage of the Archer wingtip antenna though! And the plane looks 'cleaner' for sure. I was planning to upgrade my engine instruments in the next few months to newer technolgy anyways, so if I no longer have the ammeter and MP gauge weirdness maybe i'll stick with the Archer com.... Decisions, decisions...:confused:

Ok- here's another question for the group that may be related: I have been using an ICOM A200 com with the Archer wingtip com. When transmitting in the air the sidetone and my transmissions at times sound all distorted, but it does not happen when transmitting on the ground. I think it is related to my microphone picking up high background noise in the cockpit during flight, but could it be related somehow to an RF interference issue from the Archer antenna? What do you guys think?
 
You may want to change anyway.

AV8rDoc said:
HMMMM..... now I am debating if I should reconsider placing a standard whip antenna on the belly and getting rid of the Arcgher wingtip com. I do like that extra 0.00001 knot advantage of the Archer wingtip antenna though! And the plane looks 'cleaner' for sure. I was planning to upgrade my engine instruments in the next few months to newer technolgy anyways, so if I no longer have the ammeter and MP gauge weirdness maybe i'll stick with the Archer com.... Decisions, decisions...:confused:
Click to expand...

I have the AFS2500 engine monitor and capacitive fuel sensors in the tanks. When I transmit on my Archer my fuel level drops. FAST.
Scared me the first couple of time this happened and I didn't know why. As I approached the airport and started broadcasting my position, my fuel started going away. It takes awhile with not transmitting before it reads correct again. The closer I got to the airport the lower my fuel was and the AFS 2500 started letting me know I had a problem "FUEL LOW". I was preparing myself for an engine out approach as the gauges were in the RED!

Now that I understand what is going on I don't use my #1 radio for transmitting. I will be installing another bent-whip on the belly this winter.

Kent
 
Last edited:
AV8rDoc said:
I am in agreement with Scott that at least some of what has been described in this thread seems to be related to the Archer wingtip com antenna. I ran an experiment: I disconnected the coax in my wingtip from the Archer com antenna and connected it to a standard whip antenna that I borrowed from a friend. I did not change and wiring/bundling in any way. Now when I trigger the PTT I get only a very very minor 'flick' of the ammeter and the manifold pressure gauge.:)
Click to expand...


HHMMMM...I wonder if there is a high VSWR on some installations of the Archer antenna. I am not questioning whether the design of the antenna was done properly. However, there are many installation variables that could be affecting the VSWR. High SWR means a stronger reflected wave which could be coupling over into other instrumentation. Personnally, I don't think I would install an Archer com antenna without checking the SWR. Then again I am an old ham radio guy...

So far I am not hearing that there is any potential problem with locating the com/xponder antennas near the AP servos. I'll wait for more folks to hopefully respond.

Thanks all,
 
Not sure, but.

apatti said:
HHMMMM...I wonder if there is a high VSWR on some installations of the Archer antenna. I am not questioning whether the design of the antenna was done properly. However, there are many installation variables that could be affecting the VSWR. High SWR means a stronger reflected wave which could be coupling over into other instrumentation. Personnally, I don't think I would install an Archer com antenna without checking the SWR. Then again I am an old ham radio guy...

So far I am not hearing that there is any potential problem with locating the com/xponder antennas near the AP servos. I'll wait for more folks to hopefully respond.

Thanks all,
Click to expand...

When I transmitted on the Archer in the hangar, my FM radio picked up a lot of static. Didn't happen when I used the bent-whip.
The Archer was about 10 ft from the radio that the whip was about 20.

Kent
 
apatti said:
So far I am not hearing that there is any potential problem with locating the com/xponder antennas near the AP servos. I'll wait for more folks to hopefully respond.
Click to expand...

Come to think of it, my COM1 (comant belly bent whip) antenna off of my 430W is almost directly below my pitch servo, NO problems.
 
There are two very certain ways you can get stray rf energy into your avionics. One is due to the fact that braided cable, even dual braid, emits rf energy through the spaces in the braid, both magnetic and electrostatic. Don't bundle low-level signals in with high power signals of any kind, rf or AC/DC, and use the best available cable for your radios, the low loss, high isolation Andrew FSJ1-50.
The other comes from reflections from the antenna due to an unbalanced load or the coax not leaving the antenna perpendicular will cause antenna currents to run down the outside of your coax. To get rid of this, put clamp-on ferrites over the cable close to the antenna. Radio Shack or JameCo.
 
The proximity of the ground below the plane when on the groud changes the radiation pattern of the antenna from what it is in free-space!
 
Some of these antennas are not balanced which will cause the aforementioned antenna currents on the outside of the coax which then enters the cockpit. This often shows up as squeels or distortion in transmission on some frequencies. Ferrites!!!
 
Trutrak/SL-30 interference

I have the same problem as so many others. I have the ADI Pilot II, an SL-30 and a Comant Antenna on the belly. Keying the mike with altitude hold engaged causes a pronounced pitch up. The liquid crystal display on the engine monitor also changes values as long as the mike key is depressed. Pitch servo wires are well separated from antenna coax. Have checked all grounds, remounted the antenna with a backing plate and plate nuts to improve the ground and have temporarily clipped jumper wires from all shields and grounds to the fuselage. Nothing works. Spoke to John at TruTrak and he was suprised to hear of a problem with the ADI Pilot. Apparently there were difficulties with provious models. He is working on some filters but is pretty busy with other projects. As a last resort I am going to have an avionics shop read the antenna with a wattmeter to see if there is excessive RF feed back.

Gordon Henry
(RV-7)
 
FYI.....I bought one of the Radio Shack ferrites, but saw no change. I have also ran +/- wires direct from battery with servo disconnected....no change. Is there a chance this might be a Tru Trak problem? The horizon needle on my ADI-I is scratching the glass, so I have to send it in to be repaired anyway. Maybe Tru Trak can check the filters then, too.

My fix was to install a belly mount, but have not done that yet. Now it sounds like it could be a waste of time and money.
 
One more data point

I had (have) two internal antennas in my Sportsman, both copper-foil dipoles with the ferrite beads. One is in the composite vertical stab, the other behind the baggage bay, where it's forced to make a very wide C shape as the top and bottom extremities curve with the fuse.

I've been fighting similar problems with my TruTrak DigiFlight IIVSGV...same pitch-up but only when transmitting on the lower third of the com band. I tried moving the coax away from the servos and wiring but that didn't help. I also had what I'd call poor reception on both antennas and even worse transmitting capability on the C-shaped antenna, as you'd expect.

Finally bit the bullet and installed external com antennas on top of the wing. Miraculous! Much better reception, no more autopilot interaction...all is finally right with the world. I have not seen a speed decrease, but I haven't more than a couple of data points on that. I'd give up a knot or two to be able to talk to ATC.

Wish I'd done this sooner.

--Marc

PS: My first TruTrak ADI also had the pitch bar rubbing the glass, circa early 2006. Seems to be a continuing problem.
 
For what it's worth,,
My (A project is till in the hangar and I have a similar issue of RF interference affecting the MAC Trim Indicators. I have an SL30, and a belly mounted, bent-whip comm antenna. I have checked all of the grounds, even re-ran a temp coax from the sl30 to the antenna in an effort to maximize the distance from the trim servos, relays, indicators, and wiring,,, all to no avail.

I was able to duplicate the interference using my handheld transmitter, as a sort of RF Probe,,, passing it over and near any of the Trim System components with the Tx button keyed. In my case, I was able to reproduce the symptoms in and around the relay deck's. I have both of them mounted aft of the pilot's stick, below the floor,,, using terminal strips to connect the myriad of wiring.

What I have not tried is to pull the airplane outside and away from the metal hangar.

Anyway, I have decided to live with it unless someone can give me a definitive solution.
Of course, when the day comes for the first flight, as one poster suggested,, that may "fix" the problem by providing airspace below the antenna and thus limiting any reflective action from the hangar floor.
 
Keying the mike makes the Tru Trak go mad!

It is now a year since the last post in this thread, but I am experiencing the exact problems you guys were having! I have an SL30 with a Belly whip antenna, that is exactly underneath the Tru Trak Pitch servo. When keying the mike, the servo pulls the stick back, a lot. The Dynons show no emotion at all when keying the mike. The voltage stays the same. As far as I can tell all ground connections are fine.

- I pulled the Disengage wire from the Tru Trak: no cure!
- Disconnected all the com wiring to the Intercom and used a jumper, to key the mike: no cure!
- I even disconnected the coax at the radio and antenna and used a coax, run well away from all other wiring: no cure!

Here is bunch of questions:

- What to do/test next?
- My plane is still in the garage (concrete floor with some rebar in it), could the signal be bouncing off the floor, causing this?
- Should the whip of the antenna be ?connected? with the center conductor of the coax? I do not get a reading on my ohm-meter when testing between the whip and the center conductor.
- How did all of you, complaining about this problem, a year ago, fix it?

Hope you guys can up with some answers.

Regards, Tonny.
 
Not an RV guy, but had exactly the opposite problem on my Lancair 235 a few years back - key the mike, nose pitched down! It was never awful, as the mike key was on the stick and after the first time I just "knew" to hold a little back pressure when talking.

Never found a solution. The model was a DCF-200 (which accepted analog signals, not NMEA).

I'm hoping it doesn't occur in my new Digiflight II VSGV in my 320 - first flight any day now.
 
Pilottonny said:
It is now a year since the last post in this thread, but I am experiencing the exact problems you guys were having! I have an SL30 with a Belly whip antenna, that is exactly underneath the Tru Trak Pitch servo. When keying the mike, the servo pulls the stick back, a lot. The Dynons show no emotion at all when keying the mike. The voltage stays the same. As far as I can tell all ground connections are fine.

- I pulled the Disengage wire from the Tru Trak: no cure!
- Disconnected all the com wiring to the Intercom and used a jumper, to key the mike: no cure!
- I even disconnected the coax at the radio and antenna and used a coax, run well away from all other wiring: no cure!

Here is bunch of questions:

- What to do/test next?
- My plane is still in the garage (concrete floor with some rebar in it), could the signal be bouncing off the floor, causing this?
- Should the whip of the antenna be ?connected? with the center conductor of the coax? I do not get a reading on my ohm-meter when testing between the whip and the center conductor.
- How did all of you, complaining about this problem, a year ago, fix it?

Hope you guys can up with some answers.

Regards, Tonny.
Click to expand...

Hi Tonny,

I will assume you have an ADI Pilot II. You also probably have the plastic casing on the unit. We now have a metal casing we can put on it for you at no charge. This eliminates the pitch up when the mike is keyed problem. Just give me a call or send me an email and I'll get you an RMA#. Thanks!
 
TruTrak still no cure!

Hello everybody,

As was promissed by TruTrak, they changed the casing of my ADI Pilot II from plastic to aluminium and sent it back. I installed the instrument today, gues what? no change! I realy hoped and expected that this would cure the problem.

What about the others that posted in this thread, how did you guys solve these problems? Most of the posts are more than a year old. Please let us know!

Lucas: I also sent you a private message.

Regards, Tonny.
 
RFI problems

I have had some experience with some of the problems listed on this thread.

Have the following installed in my 7...

SL-30
DigiFlt IIVS
Van's Gauges

I operate a HF ham radio in the aircraft as well and have the following advice...

The Van's ammeter is very sensitive. The wires between the gauge and the shunt block should be shielded or run a single coaxial wire instead. This will stop RF from creating current flow in the gauge feed wires during transmit. External comm antennas that are operating properly should not interfere with the ammeter in my exp. reguardless of the wire setup.

Com antennas should be mounted outside the airframe to aviod interference with avionics. "Rubber duck" antennas transmitting inside the airframe vastly increase chance of RFI.

Try not to mount your trutrak near your comm (or other) transmitter.

Make sure that your antenna is well grounded.

Use high quality coax to feed your comm transmitter. Cheap RG-58 can cause problems.

Ground all avionics to a single point to avoid ground loop problems.

Consider making a balun on your comm transmit line. RF can flow on the outside of the antenna feedline and cause interference. A cheap easy way to make a balun is to simply coil the coax about 5 turns in about a 1.5 inch diameter as close to the antenna as you can. This forms a RF choke that stops certain frequencies from traveling back up the coax shield and radiating interfering signals.

Some aircraft antennas will not have any electrical continuity from the whip to the center conductor of the connector as they may have an internal transformer or other impeadence matching device inside.

I have isolated all the RFI problems in my aircraft other than a slight pitch change when the autopilot is on when transmitting on 14mhz through a 65ft trailing antenna at 100 watts!

Good luck
 
I have this same problem with the ADI Pilot II in our CT. I will begin investigating the coax runs and connectors first, then will try the metal enclosure on the AP head.

TODR
 
Returned unit to Trutrack, awaiting return!

I had to send the Trutrak back again, still awaiting the return, after wich testing will continue. I am very pleased that TruTrak is not just leaving me in the cold with some stupid answer that I am doing something wrong, but are trying very hard to solve the problem.

Regards, Tonny.
 
A few years ago I had a RV-6 with a Rocky Mountain engine monitor installed. After I flew it a couple times, everytime I keyed the radio (KLX-125) the monitor went blank... A check with RM suggested I had RF bouncing around the cockpit. This was a simple check as I only had one radio. I replaced the BNC connector on the belly mounted antenna even though it looked OK and miracles of miracles...the problem went away. That RF is strange stuff !

Ed Booth, Trenton, SC
Builder and flyer RV-6, 7, 9,10
 
Keying the mic problem, still not solved!!!

Well folks,

I got the Trutrak back again, earlier this week and testing continued. I tried everything I could think of. Here are some samples:

- Connected power and ground directly to the battery and disconnected all wires except for the pitch servo ones. Problem still there!

- Used the ELT antenna, on top of the fuselage instead of the belly-whip antenna. Problem is less severe, but not solved. Maybe the ELT antenna is less powerful than the belly whip?

- Wrapped the whole unit in aluminum foil, including the front (the only plastic bit of the casing now). But that does not make any difference either. This shows how desperate I am!

You can imagine that I am without anymore ideas of what to test next. Anybody got any idea what is causing this? Could it be the surroundings of the aircraft, i.e. the fact that the plane is still in the garage?

I have all the other avionics and wiring finished now, but I do want to solve this problem before I carry on. If I need to change any of the wiring, now is the time to do it, while I still have good access to it.

I appreciate all you replies, please chime in and give us your thoughts on this!

Regards, Tonny.
 
In the USA

There are some folks who wear tin foil on their heads...something about aliens..have you tried that?..:)


Whay I would do is make up a new coax with new ends on it..like an exension cord and connect the radio directly to both the ELT and the whip antenna.I'm thinking RF is escapting your coax or connectors somehow.

Frank
 
New connectors and added ferites, still no cure!

Today I put two new connectors on the coax and also put ferites on both ends of the coax (got them of an old computer cable).
Also ran a separate temporary 12 V wire to the servo, well away from the coax.

I normally test on 123,45. After trying some lower and some higher frequencies it apears that the problem is biggest in the mid-range frequencies and completely gone in the low frequencies.

I do not understand this anymore, especially because it is only the Trutrak that reacts! I must have wasted at least 40 hours messing around with this and all to no avail!

Frank I already made up a coax and connected it directly from the SL30 to the belly whip, well away from all other wires (although it was TV-coax, I did not have any other spare coax).

I don't even want to think of ordering new coax, connectors and wires, ripping it all out and reroute it, only to find out that it has not cured the problem!

Regards, Tonny.
 
Antenna ground is OK

Norman,

Yes it is, it is attached with 4 stainless steel screws and I removed the paint to make sure it is properly grounded. The Ohm-meter does not show any resistence between the outside of the connector and the airframe. Also tried the ELT-Antenna. The ELT selftests the Antenna to be OK, so there can not be a problem with that antenna.

My antenna is installed under the AP-servo, but I have seen many pictures of the same setup and these people don't seem to have any problems.

I feared this was due to the fact that I have the servo wires in the same bundle with the coax, but other people have done this with no problem. Also when I tested with a separate coax, I kept it well away from all other wiring and the problem was still there.

I am now awaiting start of business in the USA and hope to hear from Trutrak.

Kind regards, Tonny.
 
Tonny,

Considering how many people have had this exact same issue (including me), I have to believe that something in the TruTrack system is subject to picking up and amplifying RF. As I said in my earlier post I had a similar problem, but my airplane pitched down instead of up - but then I remembered that in my installation I had followed the directions to reverse the direction of the pitch servo, so the problem then becomes identical to yours with the false command coming from the control head.

I also distinctly remember it happened more aggressively in different frequencies, so this also matches your description. In general, though, if I did not take manual control while transmitting it would depart from the correct attitude, and then over-correct once the transmit switch was released. It was almost as if some capacitor were "charging" while transmit was on, and "discharging" once the power was released.

Why this happens to some people and not others is a mystery, but that it happens to so many speaks of a design problem. In the way of these things (and I really like the TruTrack folks) it is probably something so small and innocuous that it has never occurred to them that whatever it is could POSSIBLY be the cause.

As I said before, I do really like their autopilots and have bought a second one. If I have the problem with this one, I will probably be bull-headed like before and just learn to anticipate and cope with it, while continuing to pester them for a fix.
 
As I read this thread, I was hoping that by Page 5 there would have been definitive resolution of this AP/Tx issue, but no.

I have an ADI Pilot II, SL-30 and Comant belly whip like others here. However, since I have yet to leave the ground, I haven't discovered any problems. I may have to play around with it before I fly for the first time.

FWIW, I do remember a cautionary note that Stein made regarding my TT unit. He specifically said that there was some issue with comm transmitting causing a pitch change in the AP, and that "TruTrak is working on a fix."

However, judging from the comments and experiences related on this thread, I wonder if TT is indeed working on a fix ...
 
Please test it!

Don,

Are the SL30 and AP installed and working yet?

If they are, all you need to do is: engage the AP, the stick should be solid. Than push the PTT button and see what happens. If nothing happens, you want to make sure the AP is working correct by lifting the tail up and the stick should move. Also you want a handheld or any other radio to check if the Radio is transmitting.

Let us know what you find out.

If Stein has said there is an issue with it, that means it is not something I am doing wrong, :) but it also means that it may be difficult to cure! :mad:

I am still hoping to get an answer from Lucas real soon now, because I need to get on to new tasks, but can't until this problem is cured.

Regards, Tonny.
 
Yes, Tonny, I need to check the systems. At this point, I just finished wiring and plumbing everything and am shifting my focus to body work -- you know, sanding and priming and sanding and priming and ... well, you understand.

However, I'll probably check things this weekend. I need to verify that my antenna connections are all sound (haven't figured out how best to do that) and I'll try the transmit-while-lifting-tail test and report back.
 
I too encountered the exact same problem.
ADI Pilot II, Commant Bent whip on the belly, SL-30 & Icom A210 both do it.

With altitude hold engaged, and key the mic and the pitch servo goes nuts. :eek:

I sent it back to TT and they removed the plastic casing and installed the newer aluminum box and if memory serves they said they added something else inside as well.

When it came back, I re-installed it (had to re-route pitot static lines because the ports on the back are now in a different location) and then turned it all back on to try it.

It still moves the pitch servo when the mic is keyed up, but to a much lesser degree than before. :(

So, it seems they are moving in the right direction, but still have more to fix.
 
Thanks guys for sharing this with us here. At least I know not to continue searching or start ripping out my wiring, I wasted to much time on this as it is.

I also had a bit of a strugle with the Pitot and static lines, because of the different location of the connections. But because I use the plastic tubes I could alter the tubing without to much hassle. Fortunately I had plenty of spare tubing.

BTW have you run your coax together with the Servo wires, or are they well apart?

Regards, Tonny.
 
Pilottonny said:
Don,

Are the SL30 and AP installed and working yet?

If they are, all you need to do is: engage the AP, the stick should be solid. Than push the PTT button and see what happens. If nothing happens, you want to make sure the AP is working correct by lifting the tail up and the stick should move. Also you want a handheld or any other radio to check if the Radio is transmitting.
Click to expand...

I'm gonna sound like a rainy day here - but I tried exactly that years back with my original, and the problem did not manifest on the ground.

Best test? Make sure that you have the autopilot "vertical torque" setting as low as you can set it and still have it provide enough torque to move the nose up and down as it should. Then, when you are airborne and the autopilot is on "Altitude Hold" key the mike - just be prepared to use a little force to keep the nose level.

You will know immediately if you have this issue.

If Stein has said there is an issue with it, that means it is not something I am doing wrong, :) but it also means that it may be difficult to cure! :mad:
Click to expand...

Amen! I used to think I was the only one - even flew out to the factory. To their credit, they spent most of a day; even replaced my unit; and went flying with me. It did not solve the problem.

Keep us posted on your results!

Bill
 
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