Wiring (RF interference) question
- Thread starter woxofswa
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We don't recommend having RF wiring that close to SkyView wiring. It's quite possible that there will be an issue of transmitted Radio Frequency (RF) energy getting into the SkyView Network. Wiring for homebuilt, even kits, is always on a case-by-case basis.
billythefish
New Member
I'm worried about RF output from the Skyview display, rather than coax interference to the SV network... I've found that my single SV display (not EMS or ADAHRS) is creating huge amounts of RF interference which disrupts even my ICOM handheld (tuned to a local ATIS on 131.35) up to 10 feet away! Has no-one else seen this? As a design decision, I can't sacrifice COM for Skyview...! 
If anyone here's got any ideas, in terms of possible underlying problems and remedies, I'd be very grateful. I don't want to put my Skyview display in a lead box or leave it on the ground! :-?
thanks
=bill
If anyone here's got any ideas, in terms of possible underlying problems and remedies, I'd be very grateful. I don't want to put my Skyview display in a lead box or leave it on the ground! :-?
thanks
=bill
- Joined
- Mar 23, 2005
- Messages
- 13,226
I'm worried about RF output from the Skyview display, rather than coax interference to the SV network... I've found that my single SV display (not EMS or ADAHRS) is creating huge amounts of RF interference which disrupts even my ICOM handheld (tuned to a local ATIS on 131.35) up to 10 feet away! Has no-one else seen this? As a design decision, I can't sacrifice COM for Skyview...!
If anyone here's got any ideas, in terms of possible underlying problems and remedies, I'd be very grateful. I don't want to put my Skyview display in a lead box or leave it on the ground! :-?
thanks
=bill
Bill:
Contact Tech Support - support@dynonavionics.com or 425-402-0433, and have the S/Ns of your SkyView Displays handy (SETUP > LOCAL DISPLAY SETUP > DISPLAY HARDWARE INFORMATION).
billythefish
New Member
Hey there, thanks for the response; I'll call support today or tomorrow. In the interim I replaced my antenna feedlines with RG142 and professionally fitted connectors, which has made little difference. Not surprising given the problems I've had with the handheld ICOM radio near the SV unit!
My serial number is 1183.
Kind regards,
=bill
My serial number is 1183.
Kind regards,
=bill
billythefish
New Member
Dynon support have been kind enough to send me the Skyview EMI kit but that has made little difference. To illustrate the problem I have posted a video on youtube, see:
http://youtu.be/ewbP3V5Av2I
Anyone any further ideas? I can't "go live" like this! Could there be something wrong, internally, with my SV-1000 unit, like a poor internal shielding or connection?
=bill
http://youtu.be/ewbP3V5Av2I
Anyone any further ideas? I can't "go live" like this! Could there be something wrong, internally, with my SV-1000 unit, like a poor internal shielding or connection?
=bill
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There probably isn't anything wrong with your display. EMI can be a bit hard to predict, but here's the full story (the below is a repost from a couple other threads)..Unfortunately, all of the engineers who could possibly weight in with a bit more helpful advice are at Aero Friedrichsafen at the moment. I'll ping them to see if they can offer anything else, but, it will be at least a few days before we'll have an update.
-----
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 of you 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.
We do a lot of work on EMI, and as proved recently, we do pass the certification requirements for avionics. Even though that is true, we're committed to making SkyView work well for everyone, so we'll continue to work on improvements, including hopefully some hints on wiring practices that may help a lot.
Just the same, the good news is that we lab-tested and field-tested filters that are simple plug-in devices on the D37 and D9 connections (for use on early SkyView displays only) that offer a large amount of noise reduction. It performed in the field as well as it worked in the lab, solving any noise issue, and we should be able to offer it shortly. Newer SkyView displays have this filtering built into them already.
-----
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 of you 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.
We do a lot of work on EMI, and as proved recently, we do pass the certification requirements for avionics. Even though that is true, we're committed to making SkyView work well for everyone, so we'll continue to work on improvements, including hopefully some hints on wiring practices that may help a lot.
Just the same, the good news is that we lab-tested and field-tested filters that are simple plug-in devices on the D37 and D9 connections (for use on early SkyView displays only) that offer a large amount of noise reduction. It performed in the field as well as it worked in the lab, solving any noise issue, and we should be able to offer it shortly. Newer SkyView displays have this filtering built into them already.
billythefish
New Member
I took my SV-1000 display unit in to the local avionics dealership in Edinburgh and we could replicate the problem within the store using a handheld radio (SV display only, no network). The unit has now been returned to Dynon HQ (under warranty).
If this RF output problem, caused by the screen, can't be corrected then I will have consider the worst case scenario: starting again with a different avionics package. I do not want to do this.
Debugging this problem - following up on every possible angle for RF Interference, shielding and re-shielding every cable, source, and device susceptible to EMI - has cost me months of effort and a season of flying
If this RF output problem, caused by the screen, can't be corrected then I will have consider the worst case scenario: starting again with a different avionics package. I do not want to do this.
Debugging this problem - following up on every possible angle for RF Interference, shielding and re-shielding every cable, source, and device susceptible to EMI - has cost me months of effort and a season of flying
billythefish
New Member
Just so that you know, I was not able to resolve this. The unit came back marked 'repaired' by Dynon but with no actual change in behaviour.
I am an engineer by trade and I'm struggling to understand this. When I put a handheld (iCom transciever) next to a 'fresh' D1000 unit in my local avionics retailer, connected to a test harness provided by them, it exhibits the same behaviour -- Massive amounts of RF Interference within a radius of about 6 feet from the SV unit when tuned to the local ATIS frequency, 131.35.
I have therefore ruled out a wiring problem, grounding, etc.
I have ruled out that it is my D1000 unit specifically - it occurs when using another (shop-owned) D1000.
I have ruled out that it is my radio, we have tried another portable radio, same problem.
So why is this happening? A design problem with the hardware? In which case why isn't this happening to other owners / installations? I simply don't understand it.
All suggestions very welcome because I'm about to throw my Dynon unit away. Or smash it up very publicly on youtube and associated social media.
I am an engineer by trade and I'm struggling to understand this. When I put a handheld (iCom transciever) next to a 'fresh' D1000 unit in my local avionics retailer, connected to a test harness provided by them, it exhibits the same behaviour -- Massive amounts of RF Interference within a radius of about 6 feet from the SV unit when tuned to the local ATIS frequency, 131.35.
I have therefore ruled out a wiring problem, grounding, etc.
I have ruled out that it is my D1000 unit specifically - it occurs when using another (shop-owned) D1000.
I have ruled out that it is my radio, we have tried another portable radio, same problem.
So why is this happening? A design problem with the hardware? In which case why isn't this happening to other owners / installations? I simply don't understand it.
All suggestions very welcome because I'm about to throw my Dynon unit away. Or smash it up very publicly on youtube and associated social media.
TRCsmith
Member
The whole thing sounds strange to me. I realize you are having a problem, first off you have a several thousand dollar (USD) EFIS system and you choose to use a $150.00 (USD) hand held radio in front of it.
Do you have a panel mounted comm radio? If so have you tried yet to see if the RF is getting to it? Second, what kind of engineer are you, most engineers would want to help find a solution to this rather that destroy it on you tube. If you not happy with it why not just sell it, and get something else?
I’m not trying to pick on you, just wanting to see a fix or a reason for the problem you’re having.
We all want a happy ending to this.
I for one will put my hand held in front on my SV this week and see what happens.
Do you have a panel mounted comm radio? If so have you tried yet to see if the RF is getting to it? Second, what kind of engineer are you, most engineers would want to help find a solution to this rather that destroy it on you tube. If you not happy with it why not just sell it, and get something else?
I’m not trying to pick on you, just wanting to see a fix or a reason for the problem you’re having.
We all want a happy ending to this.
I for one will put my hand held in front on my SV this week and see what happens.
swatson999
Well-Known Member
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Does this only happen on that one frequency? Or are there others?
Can you put your handheld on scan mode, and find *all* of the frequencies where it breaks squelch due to this interference?
Once you have the list of frequencies, does it exhibit the same interference on the panel-mounted radio in your plane?
What brand of handheld(s) and panel-mount(s)? What model numbers?
Others need *all* information available in order to try to replicate the issue and narrow down the possible causes.
Can you put your handheld on scan mode, and find *all* of the frequencies where it breaks squelch due to this interference?
Once you have the list of frequencies, does it exhibit the same interference on the panel-mounted radio in your plane?
What brand of handheld(s) and panel-mount(s)? What model numbers?
Others need *all* information available in order to try to replicate the issue and narrow down the possible causes.
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The SkyView is a powerful computer with a large LCD screen and thus, the SkyView display does give off RF energy. Technically, all electronics to, and so does every object in the universe that is not at absolute zero temperature. Thus, the fact that you are able to make a radio in close proximity break squelch is not a very strong test. It is possible to set the squelch on a radio such that it breaks squelch when you walk into the room since you're warmer than the room on average. It's a binary measurement of a very analog signal.
The TSO's for equipment acknowledge this. They have a threshold for noise, not a requirement that there is none. There are categories of thresholds, and equipment can give off more noise if it's in the cockpit where the antenna is shielded by the plane versus equipment that is installed on the outside of the plane 3 feet away from your COM antenna. There is an assumption that your antenna is many, many feet away from your panel and shielded at least somewhat. The TSO does not actually require that a display in a cockpit not interfere with a handheld radio in the cockpit.
All that being said, we've tested SkyView and it meets the requirements of a device on the outside of the plane with direct line of sight to an antenna. That does still not mean it gives off no RF energy, just that it is manageable in a well engineered installation.
As you mentioned, we have thousands of SkyView units in the real world, and they work and do not interfere with communications. Because these are homebuilt airplanes, every one is unique, and some have greater challenges than others. These are the challenges you would have paid an engineer at Cessna to overcome if you bought a certified plane. We do our best to work with individual customers and help them find the right solution for their plane.
I don't see in your above posts what the primary issue is in a completed airplane. Do you have a fully installed SkyView, and a installed panel radio? What kind of radio is this? What kind of plane? What kind of COM antenna and where located? What are the squelch level differences required with SkyView OFF and ON?
The TSO's for equipment acknowledge this. They have a threshold for noise, not a requirement that there is none. There are categories of thresholds, and equipment can give off more noise if it's in the cockpit where the antenna is shielded by the plane versus equipment that is installed on the outside of the plane 3 feet away from your COM antenna. There is an assumption that your antenna is many, many feet away from your panel and shielded at least somewhat. The TSO does not actually require that a display in a cockpit not interfere with a handheld radio in the cockpit.
All that being said, we've tested SkyView and it meets the requirements of a device on the outside of the plane with direct line of sight to an antenna. That does still not mean it gives off no RF energy, just that it is manageable in a well engineered installation.
As you mentioned, we have thousands of SkyView units in the real world, and they work and do not interfere with communications. Because these are homebuilt airplanes, every one is unique, and some have greater challenges than others. These are the challenges you would have paid an engineer at Cessna to overcome if you bought a certified plane. We do our best to work with individual customers and help them find the right solution for their plane.
I don't see in your above posts what the primary issue is in a completed airplane. Do you have a fully installed SkyView, and a installed panel radio? What kind of radio is this? What kind of plane? What kind of COM antenna and where located? What are the squelch level differences required with SkyView OFF and ON?
TRCsmith
Member
Something else to think about, as I will. I have an extra comm antenna in my other winglet with the connector behind the instrument panel. I'll fabricate a extension coax cable to plug into the hand held just in case I need a backup radio, and assuming RF is a problem in my plane for a hand held.
jakej
Well-Known Member
You're going to trash a good system worth thousands & keep a cheap handheld :-? I'm glad you're not an accountant.
trevpond
New Member
I'm with you there Jake, any handheld within 6 feet of any EFIS is going to be affected.
Money to burn, it must be lovely to be so wealthy being able to destroy gear like that. There must be cheaper ways to make your point, even if you are wrong.
Money to burn, it must be lovely to be so wealthy being able to destroy gear like that. There must be cheaper ways to make your point, even if you are wrong.
billythefish
New Member
Thanks everyone for your responses. Obviously smashing up my equipment is something I want to do when the frustration really kicks in and I'm extremely frustrated by this. :'(
The reason I've been using a handheld is because I see these symptoms on the panel mounted radio and I needed a second data point to test; I borrowed an ICOM handheld to make sure that it wasn't a fault in my panel-mounted radio, e.g. sensitivity to the type of EMI / RF being radiated by the SV unit. The panel mounted radio is a Funkwerk ATR-500 (thanks for asking) which my local avionics reseller tells me is /not/ particularly susceptible to RF interference. The fact is, that I've now tested the SV unit next to the following:
- my panel mounted radio (atr500)
- a handheld icom transciever (IC-A24 I think)
- a handheld provided by my local avionics store (another icom)
That kind of rules out the radio, doesn't it? I've tested the handheld connected to the aircraft's aerial coax, thinking it might be the aerial, no change to the signal. Just to be clear, in all cases the signal received by the radio changes from readability 5 to readability 1: this is no minor squelch adjustment. My equipment is not fit for purpose and I genuinely do not understand how/why no-one else is having this problem - particularly as we replicated the situation in my local avionics store!
As per a previous post you can see this in operation here:
http://youtu.be/ewbP3V5Av2I.
If anyone could shed any light on this then I'd really appreciate it. Right now I'm thinking the only approach here is to move the radio to the back of the airplane. Trig Avionics are about to release a GA radio (TY91) which separates the control head from the transceiver itself and so that may be an option (inverse squared rule). That would be an expensive option too.
I was really excited about the Skyview unit, and an early customer. Fitting it has set back my build by maybe two calendar years (given the amount of time I get to spend on my aircraft) and I can't see an end in sight. :'(
The reason I've been using a handheld is because I see these symptoms on the panel mounted radio and I needed a second data point to test; I borrowed an ICOM handheld to make sure that it wasn't a fault in my panel-mounted radio, e.g. sensitivity to the type of EMI / RF being radiated by the SV unit. The panel mounted radio is a Funkwerk ATR-500 (thanks for asking) which my local avionics reseller tells me is /not/ particularly susceptible to RF interference. The fact is, that I've now tested the SV unit next to the following:
- my panel mounted radio (atr500)
- a handheld icom transciever (IC-A24 I think)
- a handheld provided by my local avionics store (another icom)
That kind of rules out the radio, doesn't it? I've tested the handheld connected to the aircraft's aerial coax, thinking it might be the aerial, no change to the signal. Just to be clear, in all cases the signal received by the radio changes from readability 5 to readability 1: this is no minor squelch adjustment. My equipment is not fit for purpose and I genuinely do not understand how/why no-one else is having this problem - particularly as we replicated the situation in my local avionics store!
As per a previous post you can see this in operation here:
http://youtu.be/ewbP3V5Av2I.
If anyone could shed any light on this then I'd really appreciate it. Right now I'm thinking the only approach here is to move the radio to the back of the airplane. Trig Avionics are about to release a GA radio (TY91) which separates the control head from the transceiver itself and so that may be an option (inverse squared rule). That would be an expensive option too.
I was really excited about the Skyview unit, and an early customer. Fitting it has set back my build by maybe two calendar years (given the amount of time I get to spend on my aircraft) and I can't see an end in sight. :'(
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- 13,226
Bill,
You still haven't told us what kind of plane this is. Metal vs. composite makes a difference.
If a radio is designed well, it makes no difference where the RF part of the radio is, only the antenna. Test this on your handheld: Take the antenna off, and now it doesn't break squelch anymore because the RF doesn't get in to the body of the handheld. Thus, hopefully the ATR500 is well designed and the location of it doesn't matter at all.
Here's the tests we would have a user run in this case (and hopefully would be the tests an avionics shop would know to run on their own):
1) Unplug the antenna from the radio and put a terminator on the antenna port. Now does SkyView break squelch? If it does, then either the radio has awful shielding, or the noise is conducted, not radiated, which is a totally different issue than what you see with your handheld.
2) If #1 doesn't break squelch, plug the coax back in, but at the antenna end, put a terminator on. Now do you have an issue? If so, then your coax is not coax, it's an antenna, and it's not supposed to be. You have either broken wires, or insufficient quality coax.
3) If #1 and #2 pass, put the antenna on, and then power SkyView or the radio with an alternate power supply. If you have the backup battery, pull the breaker for SkyView and hold down button #1 to turn it on. If there is no noise in this case, it's conducted noise.
4) Park another airplane as close as possible to your plane and check it's radio. If SkyView is actually transmitting so much RF power that it means you can't hear other people clearly anymore, then the same will be true of an airplane just a few feet away as well. If that plane is not affected, then it's conducted or coax related.
These are the starting points. Let us know the results and then we can figure out the next steps to a solution once we know more data.
You still haven't told us what kind of plane this is. Metal vs. composite makes a difference.
If a radio is designed well, it makes no difference where the RF part of the radio is, only the antenna. Test this on your handheld: Take the antenna off, and now it doesn't break squelch anymore because the RF doesn't get in to the body of the handheld. Thus, hopefully the ATR500 is well designed and the location of it doesn't matter at all.
Here's the tests we would have a user run in this case (and hopefully would be the tests an avionics shop would know to run on their own):
1) Unplug the antenna from the radio and put a terminator on the antenna port. Now does SkyView break squelch? If it does, then either the radio has awful shielding, or the noise is conducted, not radiated, which is a totally different issue than what you see with your handheld.
2) If #1 doesn't break squelch, plug the coax back in, but at the antenna end, put a terminator on. Now do you have an issue? If so, then your coax is not coax, it's an antenna, and it's not supposed to be. You have either broken wires, or insufficient quality coax.
3) If #1 and #2 pass, put the antenna on, and then power SkyView or the radio with an alternate power supply. If you have the backup battery, pull the breaker for SkyView and hold down button #1 to turn it on. If there is no noise in this case, it's conducted noise.
4) Park another airplane as close as possible to your plane and check it's radio. If SkyView is actually transmitting so much RF power that it means you can't hear other people clearly anymore, then the same will be true of an airplane just a few feet away as well. If that plane is not affected, then it's conducted or coax related.
These are the starting points. Let us know the results and then we can figure out the next steps to a solution once we know more data.
billythefish
New Member
Hi,
thanks for your help.
The aircraft is a (mostly) metal Tecnam Sierra P2002.
I will test the handheld with / without aerial tonight but I think the problem is that neither the handheld nor the panel radio are sufficiently shielded to radiated EMI to co-exist with the skyview unit.
I think I've tested your suggestion #3 before but I'll also try that again this evening.
I've just ordered an RF terminator and I'll try #1 and #2 as soon as it arrives. I'm fairly sure that the coax will be fine as it was RG142 made for me by Bob Nuckolls (Aeroelectric Connection) - a previous attempt to fix this problem, I replaced all coax with professionally terminated cables.
Thanks again.
=bill
thanks for your help.
The aircraft is a (mostly) metal Tecnam Sierra P2002.
I will test the handheld with / without aerial tonight but I think the problem is that neither the handheld nor the panel radio are sufficiently shielded to radiated EMI to co-exist with the skyview unit.
I think I've tested your suggestion #3 before but I'll also try that again this evening.
I've just ordered an RF terminator and I'll try #1 and #2 as soon as it arrives. I'm fairly sure that the coax will be fine as it was RG142 made for me by Bob Nuckolls (Aeroelectric Connection) - a previous attempt to fix this problem, I replaced all coax with professionally terminated cables.
Thanks again.
=bill
TRCsmith
Member
I tested my SV 10 inch last night with my Icom 24 hand held. What I found was RF Interference with the squelch level below 22 was was active, above 23 to 24 all worked normal. I then placed the radio within 4 inches of the screen with the squelch at 24 the squelch went off again. There is no way I could transmit with the Icom that close to the screen in normal operation.
So with my setup everything works great. No RF problems.
Note: I was receiving on 122.7 and atis was 134.75 ATIS was clear.
Aircraft is a Long-EZ
So with my setup everything works great. No RF problems.
Note: I was receiving on 122.7 and atis was 134.75 ATIS was clear.
Aircraft is a Long-EZ