Icom A210 opens AM squelch when Skyview turns on

[cperry]

So, at 21hrs, I've resolved many of the Icom A210 noise issues, but still having one issue in particular. As soon as the skyview display turns on, the AM Squelch opens on my radio, which causes all sorts of random static as people hundreds of miles away from me are picked at as radio noise.

- Skyview filters have been installed.
- Ground wires have been checked, including one suggestion of disconnecting the audio ground wire
- I've removed power from all other systems in the aircraft except the skyview screen, dynon transponder, vpx, and radio.

One thing I've just realized I haven't tried is removing power from the dynon transponder...so, will try that to make sure its not the xpndr causing the interference (its mounted quite close to the radio, and it wouldn't be my first bad antenna install). But, cutting power to the screen alone does cause the interference to stop, and its a constant interfence, not intermitent, so I'm not sure how far that will take me.

Aside from that...any other ideas?

 

[Dynon]

The following is a reposting of previous advice we've given in this area....

So a bit of background on SkyView's RF qualitites: We performed tests at a fully certified lab that Boeing (we're in the Seattle area) also uses. SkyView meets/exceeds RTCA DO-160F, category H, for aviation COMM, NAV, and GPS bands. Cat H is the hardest to pass, for devices that are in direct view of an antenna. We did our tests with a full SkyView network with long cables, modules, servos, GPS antenna, battery, etc. As some people have found, the display by itself is "quieter" than a whole network, but the whole network does pass including all accessories and wiring.

Certification requirements do allow some noise output. No electronics are silent, and the standards do have noise limits. This is why you will see squelch level differences when you have a SkyView on vs. off. We're by no means claiming it does not output RF noise at all.

We have also tested a D100, and it also passes by a substantial margin. We have never heard of EMI issues with a D100, so it appears that some customer installations are more sensitive than the FAA requires.

RF interference can be a hard issue to track, and wiring configuration, antenna location, antenna ground-plane, and general dimensions and construction materials of the airplane can make a big difference. Even manufacturers of certified planes struggle with these problems. So we're thinking that some installations are more sensitive than others, which is why not every customer is experiencing issues.

As for specific troubleshooting steps:

It sounds like you have the filters for older SkyView displays that don't have EMI filtering built in. So that's good.

Next the first thing we would recommend trying would be to install a 50 ohm load on the radio, right at the back of the radio, instead of any antenna or coax. This should block all RF from the radio, but the radio will still draw power and create RF inside. Do you still get the noise? If so, your radio doesn't have great shielding. If not, try the dummy load in place of the antenna to test if it's getting in the coax.

Next, if that fixes it, then put the 50 ohm load at the end of the coax where the antenna goes. Does the problem come back?

Knowing these things will help isolate where the RF is getting out of the system and into the Dynon.

Next, know that noise often comes from the power input. If you have a battery, does it happen when it's running on battery and not master (pull the circuit breaker/fuse)?

Is it the network cables? Does it do it when they are all unplugged from the screen?

Plastic or metal plane?

Is it better or worse on some frequencies?

What kind of COM is in the plane, and how high do you need to turn the squelch up to make the noise go away?

Just moving the antenna isn't likely to help unless it's really close to the SkyView or components. As a point of reference, we don't have issues in testing with an antenna from an SL-30 ON TOP of an ADAHRS, so it's not as simple as just the antenna location, and a new one won't be any better if it's leaking out of the RF system somewhere else.

There is also a chance the issues are a really bad ground somewhere, and it's actually the power draw of the radio that is the issue, not the RF.

Finally, there is always a very small chance a specific screen is broken.

 

[cperry]

Thanks Dynon, some good ideas in there that I hadn't thought of yet, so I'll be looking into those things and will report back - especially using the dummy load to check the antenna cable, running Skyview from the backup battery, and checking different frequencies.

For everything else on the list:
- Tried with all DSAB connections disconnected from screen - no effect
- Metal plane
- Definately on 122.75, 123.2 and 126.7...will check the full range.
- Icom A210, squelch turned to max. This radio has been nothing but trouble, so it could well be the radio that is the problem, and not the skyview.
- Antenna is pretty far away from everything...will leave that for last
- Grounding...seems good...but will check again...2nd to last.
- Broken screen? Very last. Note this unit (002265) has been repaired, but I believe the issue was there before the repair as well. Perhaps we can take a look at the repair records to see what was done - that just might eliminate this possibility if everything that could be causing this has already been replaced.

 

[cperry]

Some new information...

- Problem is on all frequencies.
- When I disconnect Skyview from master power, and run off backup battery, the noise stops
- When I disconnect the radio antenna cable at the radio, the noise stops
- turning off power to the transponder, or anything else that was running had no effect.

So, with that...the one thing both skyview power and antenna have is a ground connection. The antenna I bought grounds the sheilding at the antenna. I've fairly certain the shielding is also grounded at the radio. Is this normal for a radio antenna? I can try disconnecting the ground at the antenna, but its a bit fo work...might this be a possibility?

 

[Dynon]

Well, what you've discovered so far is that it's the power wires that are going to SkyView that are radiating some RF energy. From there, it gets trickier. If you can move SkyView's power wires away from your radio's coax and antenna, that may help. The fact that it breaks squelch all the way up to the max setting is a bit extreme, unless the A210 doesn't have a very wide range (we don't have personal experience with the radio). It's possible that there's something up with your particular SkyView display, but it's not a sure thing either.

 

[rfazio1951]

CPerry, I've got a Skyview and an Icom A210 also. I also had trouble with the squelch on the radio. I complained to Icom and they had me send it in. I don't know what they did, but it is now perfect. Mine was set to the highest squelch I could and it would still give me static in the headsets. I noticed that once it warmed up it would be better and would squelch out the static most of the time. After I sent it in though it is just perfect. They supposidly adjusted something and I have the squelch down low and it is fine. Give them a call.

 

[cperry]

One thing I can try is plugging the screen into my future "EFIS-2" harness. Maybe I just need to fly from the right seat! lol

Thanks, Richard. I'll look into that as a possibilty as well.

Chris

 

[cperry]

...an update (been out of the country for two weeks).

I've managed to try a number of things, and got some interesting results. There are a couple of things I still plan to look into, so not screaming for more help just yet.
- plugged SV1000 into EFIS-2 harness, problem is still there
- plugged a friends SV1000 into my harness, problem goes away
- plugged a friends SL40 radio in place of my A210 with my SV1000, problem goes away.
- plugged my SV1000 into friends airplane with his SL40, problem goes away.
- haven't yet tried my SV1000/A210 in friends airplane (but this would help to confirm the problem is the airplane, not the equipment)
- connected only power wires from SV1000 directly to battery and moved screen physically far away from radio, problem is still there.
- disconnected antenna @ radio, and problem goes away.
There are a number of things yet to test on the antenna, so we're not finished yet.
Again...I'll keep this up to date.

 

[billythefish]

Hi, I have terminated at the radio - no additional noise.
Termination at the antenna - no additional noise.

I think this rules out the radio (shielding), the antenna feedline (and connections/terminations) and electrically-conducted RF.

Connecting the aerial: I bought a new antenna (a CI-121) and it's well grounded to the metal skin of the aircraft, near to the tail. Result: lots of noise, same as previous antenna, across all frequencies. So much so it renders the radio inoperable.

I think this means that the RF is so extreme that it's reaching the antenna at the back of the aircraft?

Any other ideas from anyone here?

Thanks.
=bill

 

[jakej]

Hey guys

Did you do as Richard Fazio suggested ? or try another A210 ?

Jake J

 

[cperry]

Was out testing again this weekend...disconnected the aircraft antenna, put on a new cable. With a terminator, no issue, but put an A24 antenna on, and problem comes back, even 10ft away from the aircraft (this sort of suggests to me that maybe the problem isn't actually the antenna - if it was, I would think I could get away from the noise, but its just constant in the headset).

BillS, looks like you and I have a similar issue.

As soon as the outside temps come up above -400, I'm going to try connecting my radio to a separate battery, and also try running the Skyview from a separate battery off its main harness...try to eliminate some part of the power system. Depending what that produces, might try running some grounds back directly to the battery.

I haven't tried having the squelch range adjusted -yet- as I don't want to risk losing radio transmissions that I do want to hear, which I suspect might happen if the noise from the power cables is stronger than the surrounding radio transmissions. I wish I had access to another A210 to try out, but everyone I know around here uses the SL40.

 

[billythefish]

Posted this on another thread by mistake...

Hi,

I have terminated at the radio - no additional noise.
Termination at the antenna - no additional noise.

I think this rules out the radio (shielding), the antenna feedline (and connections/terminations) and electrically-conducted RF.

Connecting the aerial: I bought a new antenna (a CI-121) and it's well grounded to the metal skin of the aircraft, near to the tail. Result: lots of noise, same as previous antenna, across all frequencies. So much so it renders the radio inoperable.

I think this means that the RF is so extreme that it's reaching the antenna at the back of the aircraft?

Any other ideas from anyone here?

Thanks.
=bill

 

[cperry]

Well, I can't think of any more conclusive test than this. I've hooked my Skyview screen to a battery on the coffee table, turned on my handheld Icom A24 radio with the squelch turned to max, then turned on the Skyview. With the radio a good 10ft from the Skyview screen, the squelch opens. Turn the skyview off, the squelch closes.

But...some new information. With the LCOM filter installed, if I wiggle the wire harness, the problem becomes intermittent. With the LCOM filter removed, the problem is constant. Might I just have a bad filter?

 

[cperry]

One more piece to the puzzle...if I connect all the ground wires AND ground the skyview case using one of the screws on the back of the unit, I only get radio noise with the antenna within about 2ft of the unit, even with no capacitance filter installed at all. This is quite acceptable. Also able to turn the squelch down considerably. So, a solution for me might be to put a more positive ground on the case, rather than just grounding the pins. This might also better explain the intermitentness (how spelled?) of the issue during flight. I'll try this out, and let the world know how it turned out for me.

 

[cperry]

I've spent the weekend doing some additional testing with my unit. Replacing the L-com filters had no additional positive effect (but definately an improvement with them vs without them). Also, adding a case ground to the SV1000 had no effect in the aircraft.

Some of the bench testing I've done suggests that this RF noise is propogating through the entire aircraft skin (metal airplane). With my antenna mounted through the skin, I just can't get it away from the noise. Supporting this theory, I couldn't get my handheld less than 12" from any point on the aircraft skin without it breaking squelch when set at a fairly conservative level. I would have expected the skin to sheild the antenna from wiring noise rather than propogate it.

I've got just a couple more things to try in the aircraft (a couple of wires situated near the antenna that I need to try to isolate). If that doesn't solve the problem, I'm probably going to have to talk about sending the unit back to have it checked.

 

[cperry]

Quote from me from above:
"- Antenna is pretty far away from everything...will leave that for last"

Well, here's last. Wow, what a bear! But finally, some success.  Previously, I hooked the SV1000 up to another battery, and as soon as I got close to the airplane, the squelch opened. Well, I did this again, but this time put the battery, wiring, and screen inside the airplane, and was able to turn the squelch down to about 70% without it opening. Based on this, tried isolating circuits again..but this time I physically disconnected them from the VPX rather than just turning them off. Also disconnected the sv-bus and the gps cable from the sv1000. All good (enough). Something about my antenna design: the signal cable is exposed for a few inches inside the aircraft skin. The aircraft seems to be able to shield the antenna itself from the noise, but with the signal cable exposed outside the shielding inside the skin, I suspect thats where its picking it up.

So, going to experiment with a BNC bulkhead fitting that will take the sheilding right to the aircraft skin. If that works, I'll replace the antenna with one that has a built-in BNC fitting rather than a pigtail. If that still doesn't work, I'll be rewiring to move some wires even farther away from the antenna to try to get some more aluminum between them and the antenna connection.

 

[cperry]

Problem solved:

I replaced my antenna, which uses a pigtail with about 3" of exposed (unshielded) signal wire on a terminal screw(see pic), with one that has a BNC connector moulded right into it, effectively bringing the antenna shielding through the aircraft skin.

So, yes, the skyview screen is a bit noisy, but in my case at least I'm able to overcome it. Here's some test results:
Old antenna: 136.0mhz, squelch set to max, squelch won't close. 123.2mhz, squelch set to max, squelch opens intermittently.
New antenna: 136mhz, squelch opens @ 90%, 123.2mhz, squelch opens @ -30%.

These new numbers a very acceptable, so can't wait for the wind to calm down so I can try it in the air!!!
;D