SV-intercom-2s music input

Pilotlight11

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When I plug an external source into the music input jack I indeed hear it in my headset UNTIL rpms exceed 2500 (rotax 914), then input is muted until I throttle back.

I'm hoping this is not as it should be.

Any suggestions?
 

Dynon

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A couple of thoughts: The music will mute if voice squelch is broken (as would normally happen when you talk, but which can also happen if external sound is over the threshold you have set with the intercom squelch knob. Try unplugging the mic side only of your headsets to see if this is the culprit.

Clicking the squelch knob can defeats/enables the auto mute for the music input when intercom conversation breaks squelch, so you can play with that too.

The other things that will mute your music - by design - are outputs from non-muting inputs such as EFIS audio, and radio transmissions. If anything is producing audio on any of those inputs, your music will mute.
 

Pilotlight11

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Dynon:
I'll try unplugging the mic side, but does that not imply that the engine sound is going through the mic that is right up against my lip? Again this ONLY happens when the RPMS are increased past a certain point. Otherwise everything is fine. There are no other variables such as you suggested.
What impact on this issue would the squelch level that is set through the display have? And while were at it, what is a good initial setting for that squelch? Not sure why the engineers made the radio squelch only adjustable by going through the menu. I know I can defeat the squelch on the panel, but that is not adjusting it. Or am I missing something in the design? If you have the comm unit does that override or negate the radio squelch setting on the set up menu?
 

Dynon

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The display squelch setting only impact the carrier level at which the receiver side of the Dynon radio allows audio through when it sees radio energy. If the Dynon radio is RXing (shown on the com panel display and on the top bar on SkyView), that would definitely do it, so look there too. And if that's happening, something is injecting RF noise into the radio to make it break squelch.
 

Pilotlight11

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It will be a while until I can test this again. I have had to deconstruct the front end of the aircraft to get at all the electronics. But I certainly agree that there is a bunch of RF interference being generated. There is definitely something amiss with the 261 and com. So far the only advice I've received is to use RG-400 which was already present. The latest issue is that keying the mic causes the ELT remote display LCD to light up and flash. HOld the mic key and the remote buzzer goes crazy. Disconnecting the ELT antenna stops the behavior. The ELT is located in the same place it always has been, but it is a new ACK E-04 unit. I went to the effort of moving the com antenna as far away from the ELT antenna as physically possible which doubled the distance to about 26" with zero results. If I don't start solving problems faster than they keep coming up I'll just ask for an RMA and switch to Garmin. I thought I was doing the right thing as far as compatibility by switching everything to Dynon. With as many posts as I've read about the 261 the engineers HAVE to know there is an issue. $10,000 worth of new equipment and I'm grounded because no one seems able to diagnose an interference problem.
 

dynonsupport

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Bob,
While we understand your frustration, noise with the transponder is not a common issue. We have sold thousands of transponders and only know of a few cases of noise. Additionally, the transponder is actually the Trig TT22, of which tens of thousands have been sold and are very well regarded. There is no known issue with this transponder that causes more noise than any other transponder. In fact, due to the all digital nature and low power, it's quieter than most. My own personal plane is a composite and I've never heard a peep from the transponder. The internet can be a funny place, where people only report issues they have, but rarely the successes. Of course, one way our competitors solve that is to not have a public forum at all...

We're here to help you out, and if we knew of an obvious problem or solution, we'd tell you. But right now we're as confused as you are since this just isn't something we've seen before. Let us keep helping you out.

The next step in troubleshooting this kind of issue is to find out if it's RF or DC wires. The simplest way to do this is with a dummy load. You can plug this right into the transponder instead of the Coax and see if the noise stops. If it does, then plug it in instead of the antenna. If it comes back, then it's your cable. If it stays away the whole time, then it's the actual radiated RF, which is a bit of an issue to fix because the TSO requires a specific radiated pattern there and every Mode-S transponder is going to do the same thing.
 

Pilotlight11

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I have never heard of a dummy load before, but looking it up my question is does it have to be rated at the 250 watts that the transponder will put out? IF so that is a $500 suggestion. IF not, please suggest one that is sufficient.

AND, this is a dual issue that I'm not sure has been separated in people's minds. I tried at first to separate the discussions.

1) the transponder is associated with the popping noise. I do not need to activate the com to hear the popping. All that is required is to be too close to the antenna.

2)the ELT LED lighting up and jamming of nearby frequencies is connected to the Com. Activating the transmitter CAUSES the ELT LED to light and flash. Again, removing the ELT antenna eliminates the LED issue.

These two issues appear to be independent as one has no effect on the other.

I have ordered ferrite clamps, several new TNC to BNC adapters (why did the engineers do that?) various sizes of shielded cable to see if replacing any non-shielded cables will help. I have refrained from ordering a power filter until these other items are tried.

Most DC issues end up being a bad ground. I have been fully aware of this for over 30 years, thus I am very careful to read and follow instructions in new situations. However, when one relies on others to build harnesses for specific applications it is assumed they know what they are doing (in this case AS). OF course I had to do the connections from the Skyview cable.
 

Lanceturk

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As an update, I have spent several days conducting numerous tests. The tests were intended to determine what is effective and what isn't in terms of a 'fix' to minimize the 'try this and that', which gets expensive and time consuming and may not result in a fix

My opinion is that the high power narrow XPNDR pulses are getting into most of the sensitive avionics I have onboard. BTW I fly a Glasair so don't have the benefit of a 'faraday cage'.
I measured RF generated audio pulses and they are between 50usec to 130usec. Very small. The problem is they can be heard as a pop/tick. Here are a few things I tried and the results:
1. Took intercom out of panel and wired directly to a small 12v battery and to a headphone via a single jack. Walked around airplane with this 'portable' set up. Result: noise present and increased when closer to XPDR antenna and vice versa. Predictable.


2. Took noise cancelling  Bose headset out of aircraft and with noise cancelling on then walked around antenna. Same Result as intercom.

Conclusion: need to move antenna as far aft as practical to hopefully reduce coupling with all the wires/coaxes/boxes/etc. etc. Need to make sure coax is good RG400 and there are no leaks.
NOTE: Heard that Cirrus found this as an effective fix to their 'plastic' airplanes too.

3. The most irritating issue is the music muting when the SV 'hears a 'tick'. As an interim bandaid, I Designed and installed a roll-off circuit which is inserted between my 'radio audio output' and the intercoms 'radio input'. This reduced the 'tick' amplitude enough to stop triggering the intercom 'mute' function (which annoyingly interrupts the music about every two seconds!). Note that this frequency roll-off does make the Navcom sound more muffled/bass but I kind of like it as it also cuts out a lot of static.
I bet DYNON engineers could change the mute trigger circuit slightly to not respond to these very narrow audio pulses. That would at least allow music to continue to play.
I would be very happy to work with them. My guess is this problem will be very chronic as more and more ADS-B installs are made.

BTW - the 250watts is probably Peak Power which means the 'Average Power', i.e., the heating power is much much less. This means the 50 ohm dummy load can be much much smaller!
 

Pilotlight11

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OMG:

I have been trying to solve two issues since October - both resulting in interference in the com radio.  On thread dealt with the transponder producing popping/clicking sounds and this thread which it turns out is related as I suspected.

I have never been so damn angry at one company in my life. Note that my last post in this thread was 21 Nov and LanceTurk made a post on 27 NOV.  Because the DYNON tech people kept telling me that ONLY the cable I was using could possible be an issue (despite the fact that I kept telling them I had RG400 from the get go) I proceeded on NOV 22nd to tear my airplane apart (meaning taking the rivets out).  I rebuilt the wiring harnesses incorporating shielded cables even where they are not normally used.  It is a 60 mile round trip to my plane so now 4 months latter I have it back together with absolutely no improvement.

So now I read LanceTurk's entry confirming EXACTLY what I had been telling DYNON all along.  Lance is obviously much more of an electronics engineer than I am however, we performed some very similar test to isolate the fact that IT IS THE TRANSPONDER NOT THE CABLES that is interfering with both the headsets and the ability of the intercom to play music.

I too figured out that the transponder antenna has to be as far away from the com panel as possible.  BUT, how do you do that in a composite aircraft?  I put a dipole antenna as far back in my fuselage (Searey) as I could reach. It needs no ground plane as is glued to the hull.  That indeed attenuated the clicking but did not eliminate it and as Lance points out the music muting circuit can still hear it and cuts out.

I have given Dynon every opportunity to help me solve this problem, but quite honestly on the phone they act like no one has a brain except them.  DO THEY NOT realize that most of us put in untold hours trying to solve a problem BEFORE we pick up the phone and admit defeat?

I have no idea what a roll-off circuit (as described by Lance ) is, but will try to find out.  In the mean time, this is a notice to DYNON - THIS IS NOW A VERIFIED PROBLEM, help me solve it or take your equipment back.

[content edited for tone 2/13 --Dynon]
 

Dynon

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Bob: We're genuinely sorry that you're not getting the performance you're looking for here. Our experimental fleet of aircraft are similar enough that we don't see issues like this routinely, and yet every aircraft has a different builder, wiring, and other unique variables that can make troubleshooting issues challenging. Because of this, sometimes subtle interactions between components and products can be tricky to figure out - especially in the audio & RF realm.

If you send a PM to our account with your contact information, I'd like to have one of our senior staff follow up with you to see if there is anything else we can have you try. Also, while we understand that you're frustrated, we copy-edited your post to remove some harsh language (something we almost never do here). We expect everyone here to keep a respectful tone.
 

jakej

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It would be really helpful to know what type of aircraft (I'm guessing composite) & the exact location of the ELT/COM/Transponder antennas.  Composites are a completely different horse when it comes to 'interference/RF' issues.
With the other apparent symptoms you are having I'd be a lot less inclined to blame the equipment - avionics troubleshooting ain't easy sometimes especially by remote control (phone or Forums).  What would you do if you replaced what you have with another product & STILL had similar symptoms ? We need to be 100% sure before we lay blame IMO.
Hopefully the resolution & cause of your 'issues' will be published for others to learn from. ;)
 

dynonsupport

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Bob has a Searey Amphibian. Fiberglass, and he can't put an antenna on the bottom.

For others looking to help, he has more details in the other thread he joined:

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1398673660/17#17

An interesting observation of his:

You do not even have to have the headset plugged into its jacks to get the interference just stand near the plane and you'll get the popping.
 

jakej

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Any real reason why a blade type transponder antenna can't be used on the bottom up front, eg Comant CI 105, they are sure sturdy enough ?
 

jakej

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Bob's situation intrigues me as I've done many avionics installations on composite aircraft like Jabirus & Glasairs but never have had the issues described here.
I know the Searey is a very different scenario as the engine is mid mounted pusher & antenna placement options, & access, is extremely limited.
One other factor, when engine is running, is the 'dirty' ripple current from the rotax alternator - to eliminate that I use the PM/OV Filter kit from bandc.aero, part # 504-1.
There most likely will be no magic one stop fix here but just a series of improvements/changes that will finally resolve the issue IMO.
I don't believe it's necessarily the fault of any equipment here, it's just the characteristics of the airframe & engine combination that is the root cause of the problems here ;)
 

Pilotlight11

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I have been in contact with Dynon off the forum. I'm expecting a call today while I am at the plane.  So as not to be mis understood I will cut and paste a note from a Dynon Official, to wit: " Indeed, we have had a few comments from customers reporting that they are experiencing some sort of coupling between the transponder and the intercom. We do not believe there is a widespread issue as we have many, many very successful installations without these symptoms and often the suggestions such as RG400 co-ax do work.

The transponder is a very high power transmitter where if there are any issues with grounding and shielding between the transponder, radio and intercom circuitry it might cause unintentional interference. Composite aircraft are especially tricky when it comes to grounds, shields and ground planes although these issues are not impossible to correct."

My point in passing this on is that while I'm sure this individual is correct in stating that there are many many successful installations, it has taken what I consider to be an inordinate  amount time and effort to get to a point where someone has taken notice that "this" might just not be a typical case.

I have noticed ont eh Dynon web site that many of the employees have composite aircraft so I am hoping today provides some fruitful progress.

JakeJ is correct - I have a Searey Amphibian. Very limited ground plane - the Gap Seal between the wings is the only metal.  I indeed did install a "flat" dipole antenna as far back in the fuselage as possible and while that attenuated the popping, it did not eliminate it.  And yesterday I confirmed that like the popping noise the interruption in the music circuit does indeed go away when the transponder is switched to standby. 

I will apologies for whatever language Dynon thought was inappropriate for this forum, but not for the frustration it has taken to get someone to take me seriously.  Removing the windshield and front deck of my aircraft three times to solve this is not something I'd wish on anyone.

I obviously though (think) the Dynon equipment with the ability to remotely mount the com and xponder units from the panel was both an innovative and more flexible solution than the traditional center stack.  To that extent I completely redesigned and rebuilt the dash with extreme precision so everything would fit. - See attachment

Perhaps it is that this is the first attempt to use this equipment to construct a 2020 ADBS compliant Searey.  So much the better for Dynon if it works out.  I think Jake is probably accurate when he says the characteristics of the aircraft and engine are contributing factors. Special cases always require innovative solutions. But, unfortunately at 69 I don't have the luxury of waiting around at the end of the cue.

Over the years I have come to adopt the attitude that my personal, individual vote does little at the voting booth, so I vote with my dollars.  I did that when I purchased what I think is roughly $10k of equipment and then spend months attempting to get it to operate correctly.

Jake has asked me what I would do if nothing can get it to operate adequately. Would I chase after some other brand just to encounter the same issue?  No, first I would pick up the phone and call Progressive Aerodyne and find out what they are putting in the production SLSA version of the Searey and find out if it is 2020 compliant. In hind sight everyone will probably ask why I did not do that to begin with. The plane had an 8" Dynon - I like it - I thought upgrading was a good way to go.  Or, I'd consider putting the Garmin equipment that I still have back in the aircraft. Though that would negate the 2020 compliance.

I have tried contacting another member of this forum who posted a potential solution for the music circuit - something called a roll-off circuit, but have not received a response and have no idea how to construct such a circuit.  I AM looking for solutions and jakes lasted recommendation of the PM/OV filter will be investigated.  I'm not in a hurry to rip out what I spent months constructing, however everyone reaches a limit at some point and I really would rather be flying.

I've thought about building a Faraday Cage around the antenna so EM radiation only goes out through the side of the hull but I'm guessing that would compromise the effectiveness of the transponder.

I will report here the results of another posting I made - that of not being able to recalibrate the compass. MY FAULT.  While remaking harnesses for all the equipment with shielded wires (even where never called for) I followed the suggestion for making cables as short as possible. The 9 pin subD connector from the ADAHRS unit is on the aft side of the unit. Normally (I would assume) this cable continues aft toward the display. In my case it needed to go forward to a network hub and I ran it right next to the ADAHRS unit. DO NOT DO THIS. In hind sight it is obvious that I put an electrical current right next to the internal magnetometer of the ADAHRS. By running the cable aft to the open 9pin on the display the problem was eliminated.  IF it is my fault I am more than willing to admit it.  I simply want an aircraft that is safe and not a nuisance to fly.

Thanks to all.
Bob Reinhardt
College Station, Texas
 

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Pilotlight11

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I have written this final chapter for some locals who own the same type aircraft as I have that were helping me so I will cut and paste it here to save some time and effort. 

"Since you two have suffered through all my rants about this you should get the first report of the solution.

My gut tells me I should take the time to summarize the whole affair and submit it to the EAA for publication
as it might save others a bit of frustration and it is much more likely to occur in the future with the new
products that split the display unit from the actual “work” unit.  This issue will probably not occur for the traditional set-up
where the “knobs and dials” are part of the transponder unit and/or com radio.  In addition, it might, but is
unlikely to occur in a metal aircraft.  When I asked at the end of my final conversation with the Dynon product manager whether there
was anything in the installation manual or user’s guide that would have prevented the whole thing, he
confirmed that there was not and that they probably need to make some additions to their instructions. As
close as I can remember he said: “we have not paid enough attention to composite aircraft and failed to
remember everyone does not build an RV.”

The line that would have prevented 6 months of headache is this:  “Ground all the avionics cases together.”

As you both know instructions emphasis over and over that all the ground wires from the harnesses need
to go to a separate avionics ground buss.  And, I assume you know I check that over and over as well
as checking every other possible item suggested – cable type, internal cable grounding, .....

Here is a great illustration (see attached) of why this particular issue was so difficult to track down. 
I constructed this cable.  It is clearly overkill as far as wire gauge  but is what I had laying around. #10 leads
soldered to #4 backbone. From left to right they were connected to: com remote unit; Transponder Remote;
Display unit; com panel unit, intercom panel unit, ADSB-out, and a spare.  The backbone runs behind my
buss tray and connect directly to the #4 battery cable at a common terminal on the right.

It is not the fact that the grounding worked that is of real interest here, it is more what occur when I tried to isolate
which of the connections was “the culprit”.   The Dynon rep was putting his money on the transponder remote unit
since it was mounted to a non-metallic surface.

Once I had established that in fact the popping and music channel interruption had been eliminated I started disconnecting
the leads one at a time.  An external speaker (that turned out to be critical in this test) allowed me to hear if the
music circuit was muted – tested that with a hand held.  To my astonishment the music circuit did not revert to its
“problematic stage” even when I had all the leads again disconnected.  Disconnecting the backbone also did nothing.

While puzzling over this I was distracted by a text message on my phone.  Now the phone was connected via an
audio cable to the intercom – feeding it music.  Whether this actually played any roll in the scenario is not known, but
probably unlikely and an empirical question I’m not sure I care about at this point.  In any event while looking at the text
the speaker went haywire with popping and muting.  In this case I was grateful to hear that.

I went back and touched the ground wire from my wire array to the intercom case on the dash unit and sure enough
muting stopped, no popping. HOWEVER, when I removed the wire everything remained good.  Now, the only people
I can think of that would take that in stride have either never run a conditional experiment or have a whole lot more
intuitive knowledge than I do.

So I stood there and waited and it took 3-4 minutes, but eventually the circuit goes bad and the muting/popping starts
again.  AND, it will not clear unless you ground it again.  So, I’m sure Dave has a better understanding of what is
going on, but Dave (Dynon Dave) said something to the effect that the intercom unit is acting like a big capacitor and
once it gets full, the rest is history.

We also worked out why I was able to produce 35 degrees of error in the compass by moving the wires around.  The
ADAHRS unit was the unit “with the best ground” - in this case it sits on an aluminum plate connected to the buss
tray.  While there is not enough current running the ADAHRS unit itself to create an electrical field strong enough to
effect the magnetometer in the unit, when OTHER units try to find the best ground they added their current to the
path going past the ADAHRS unit.  As a matter of fact it turns out this can be used as a nice little diagnostic tool.
With everything grounded as it is now there is no deflection in the compass (heading indicator) no matter where I place wires or which
wires go where – As it should be. So in the build process if one is able to deflect the compass (heading indicator on the Dynon display)  – something is wrong.

I am sitting here looking at the SV-MAG-236 remote magnetometer I purchased to try and solve the compass issue.
It is probably unlikely I need it as I was able to recalibrate the compass yesterday  but at $140 it’s going in the plane!

I am left with one decision – whether to go back to the monopole antenna. I have yet to fly into controlled AS since
the rebuild so I have no positive assurance I’m being seen.  That is easy enough to test. But perhaps the bigger issue
is that while I had the transponder certified back in September I’d guess swapping the antenna is changing a major
component of that system.  The one piece of luck is that I left a spare RG400 cable up in the gap seal area and
reinstalling the monopole is a matter of drilling one hole.  Leaving the dipole and cable as is would be an easy way
to test if antenna location is indeed irrelevant."

That is the end of what I sent to my buddies.

One take-away here seems to be that if a dash panel (in my case there are four separate and non-connected pieces of metal cover with teak veneer) is separated from where the remote units are mounted the ground wires integrated in the harnesses may not be sufficient to insure proper operation.

I am grateful to Dave at Dynon for spending several hours examining photos of my set-up and discussing potential routes to proceed down. Fortunately, he "got it in one."
 

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vlittle

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The problem you faced and the solution is very common in audio systems. Ever wonder why stereo systems have grounding lugs in the back? That was for connecting all of the equipment chassis together to reduce noise and interference.

There are a lot of lessons to be learned in this thread, but the biggest one is to seek professional help when things go sideways. A competent avionics tech should have been able to debug this for a reasonable cost.

Despite the best efforts of avionics providers to make things plug and play, there are way too many variables.

Thanks for the war stories!

Vern
 

jakej

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Totally agree Vern.  Although photos were asked for they were not available to see the now obvious part of the problem.
It is probably useful to mention now that if you have anything other than a totally aluminum airframe it would be wise to ground the case of most avionics & any seperate instrument panels that they are mounted on - Glasairs, Lancairs, Jabiru, Europas, Lightnings, Falcos & many other types come to mind.
IMO one useful tip when troubleshooting audio 'issues' is to remove any cell phones & iPads plus the power adaptors connected to 12volt cigarette light type sockets - that has caught out a few.
There are many sources of info re wiring aircraft & they make good (some say essential) reading. Some good references are FAA AC43, "The AeroElectric Connection" (Bob Nuckolls - approx $20),  considered to be the 'bible for aircraft' by many, & http://verticalpower.com/_documents/_pdf/Top_10_Wiring_Mistakes.pdf by Marc Ausman (he also has another more extensive book (I think) plus there are videos (E.A.A.) etc all over the internet.

Bob - thanks very much for posting the results, I'm sure many others would not have done the same in the same situation but just left their complaint hanging.
Hopefully now you can go & get some real pleasure out of flying soon.  ;)
 

Pilotlight11

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I got back in the air today and am sad to report that while I am not hearing the popping/click sound the music circuit still cuts out at anything above 2000 rpms. At idle there is no problem, circuit cuts out and mutes when another transmission is "heard", but once the throttle is advanced the music circuit is muted - continually - it never comes back. I tried unplugging my headset mic but that did nothing. Since I'm not aware of another microphone I have to assume something else is interrupting the circuit. Any suggestions?
 
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