STATIC ON MY RADIO AFTER INSTALLATION OF A NEW VARIO

[miltonpilot JLH]

10 days ago, I installed an XCVario in my glider (the old Ilec SC7 croaked). I really like the new vario but it causes static on my radio, as if the squelch is turned off on the radio (it's not). At regular volume setting on the radio the static noise is terrible and I can hardly understand any incoming transmissions. What's (semi) interesting is it only happens when the audio on the vario is sounding off (which is most of the time, either going up or going down). If I turn the vario audio down completely, it does not interfere with the radio. Also, it only interferes on certain frequencies, like the two I use most of the time (122.90 and 123.30). If I tune to 126.30 it is not affected. I've tried rewiring things behind the panel, moving power wires away from the radio, away from any antennae as far as practical given the layout of the instruments in the panel. ALSO, I carry a handheld transceiver in the glider. I turned off the radio and turned on the handheld and it got the same static as the radio!

Any ideas what's causing the problem?

[Steve Koerner]

On Sunday, August 13, 2023 at 7:58:46 PM UTC-7, miltonpilot JLH wrote:
> 10 days ago, I installed an XCVario in my glider (the old Ilec SC7 croaked). I really like the new vario but it causes static on my radio, as if the squelch is turned off on the radio (it's not). At regular volume setting on the radio the static noise is terrible and I can hardly understand any incoming transmissions. What's (semi) interesting is it only happens when the audio on the vario is sounding off (which is most of the time, either going up or going down). If I turn the vario audio down completely, it does not interfere with the radio. Also, it only interferes on certain frequencies, like the two I use most of the time (122.90 and 123.30). If I tune to 126.30 it is not affected. I've tried rewiring things behind the panel, moving power wires away from the radio, away from any antennae as far as practical given the layout of the instruments in the panel. ALSO, I carry a handheld transceiver in the glider. I turned off the radio and turned on the handheld and it got the same static as the radio!
>
> Any ideas what's causing the problem?

Here's a couple ideas:
1. Tightly twist wires carrying power with their return as well as the vario speaker wires. Do this for vario and radio alike.
2. Buy several snap on ferrites. Try snapping them on the associated wiring - especially the wires coming and going to the vario. Snap them close to the vario. I would just try the ferrites on all leads including switches for cruise/climb, speaker leads, etc. RFI is clearly leaking out of your vario. Ferrites can work to reduce and contain the interference.
3. As a final thought, if the above hasn't resolved it: Look at how the grounding works on your panel. Ideally, everything is grounded at a single point. I'm sure other people will have more ideas to try. Also try complaining to the vario manufacturer.

[Mark Mahan]

Steve has good ideas and proper grounding is extremely important. Single point grounds are good, but I have found in metal aircraft separating grounds a few inches apart will remove the interference.
How close are the radio and the vario in the panel? Might try MuMetal and wrap it around your vario, available on Amazon. This works well when the instrument is radiating lots of noise. MuMetal is thin and razor shop, be careful. Have cut myself more than once.
Good luck.

[John Sinclair]

Hi Jimmy,
Are you using an SN-10 or Cambridge GPS? Both these units put out loads of RF!
I fought interference for years and found that turning on radio with no squelch on at all, then turn on all other electrical equipment, (one at a time) and the RF each unit is putting out will be heard. My experience showed that the squelch on the radio was ready to break all the time because of these two noise instruments………….your problem may not be with the new vario, at all?
Last resort, try wrapping radio antenna cable with aluminum foil! Also, move the radio antenna cable as far away from other electrical components a you can! The radio is doing what it is supposed to do………….present what it thinks is a transmission from another radio!
Good luck,
JJ

[AS]

I am not an EE nor do I play one on TV but many moons ago, I had an RF leakage problem with the radio that came with my Libelle. I swear this thing was put together by Marconi himself! It had a separate crystal transmitter and the receiver had to be tuned via a BFO (beat frequency oscillator) to the proper frequency. Anyhow, I digress...
The RF leakage was annoying since every time I transmitted, the vario went nuts. I got a sheet of fine Bronze mesh like this here: https://www.mcmaster.com/9228T67-9228T618/
and soldered the edges together to keep it from fraying out. Then I rolled it up to create a tube big enough to slip the radio into and soldered a grounding wire to one end. It virtually eliminated the RF interference problem and the only dip in the vario I still saw was due to the tremendous inrush power draw. Needless to say, I looked for a more contemporary radio soon after.
Wrapping your offending instrument in a Faraday's cage may help, if the RF leaks out of the instrument itself.

Uli
'AS'

[kinsell]

MuMetal is specifically for magnet shielding. After all machining
operations are done, it has to be annealed at high temp in a hydrogen
atmosphere. I don't think it's appropriate here. Using copper foil to
make a faraday cage would be a better choice.

Several people have mentioned single-point grounds, which is good, but
also single-point power distribution should be used. Daisy chaining
power along instruments is bad news.

RFI problems in a modern cockpit are common, but this sounds unusual, in
that it only happens when audio is generated from the vario. Perhaps
they use square waves to generate the tones, and the harmonics are bad
enough to cause the interference. If an external speaker is used, I'd
disconnect the speaker as an experiment and see if the problem goes
away. If so, it may be possible to just shield the speaker wires.

-Dave

[Moshe Braner]

On 8/14/2023 2:03 PM, kinsell wrote:
> ...

>
> RFI problems in a modern cockpit are common, but this sounds unusual, in
> that it only happens when audio is generated from the vario.  Perhaps
> they use square waves to generate the tones, and the harmonics are bad
> enough to cause the interference.  If an external speaker is used, I'd
> disconnect the speaker as an experiment and see if the problem goes
> away.  If so, it may be possible to just shield the speaker wires.
>
> -Dave

The XCvario audio uses a "class D" amplifier so yes it's a square wave.
The speaker is internal, although there is a jack for an external
speaker, can try using that. And the XCvario case is plastic, I
believe, so adding shielding around it may help. Note that the XCvario
has an internal WiFi/Bluetooth antenna, if you fully shield it it would
not be able to communicate wirelessly, e.g., to XCsoar. If you only
need the ability to update its software occasionally, via WiFi, then
make the shielding removable? That said, you probably won't shield the
front of the vario, so there will still be radio waves going through the
front (heading towards the glider's tail), for better or worse. In most
gliders the communications radio antenna is in the tail, so maybe it
will still receive the interference?

Some radios used in gliders have adjustable squelch, so if the
interfering noise is not too strong, it only needs a bit of adjustment
to stop the squelch breaking, while normal communications would still
work. Alas, some other radio models have no squelch adjustment, or the
adjustment is inside the radio's case, difficult to reach.

[miltonpilot JLH]

Steve, Mark, JJ, Uli, Dave and Moshe: Thank you all for your suggestions. I am going to twist the power and return wires. The speaker in the XCVario is internal so I can't do anything about that. The ferrites sound like a good idea also. Power and grounding is already single point and has been since I bought the glider used 6 years ago. All of the instruments have worked perfectly until the Ilec died and I installed the XCVario. I tried complaining to the vario manufacturer and their reply was basically "...we no of no one having this experience ...".

I do not have an SN-10 or Cambridge GPS in my glider. I have already moved wiring around to keep all of it as far away from the radio and the radio antenna as possible.

Wrapping the vario with bronze mesh sounds like a good idea. I don't use XCSoar and, as mentioned, the only other reason I might have for needing the WiFi is for a software update.

My Becker radio has an automatic squelch so there's nothing I can do about that.

Thanks again for the help guys. I'll be back at the gliderport this coming weekend and will hopefully have some good news to share by this time next week.

JLH/H4

[John Sinclair]

You can adjust the automatic squelch threshold on your Becker………the procedure is in the manual. In fact I finally resorted to raising the threshold on my Becker to solve the problem. You won’t get weak signals, but it will stop breaking squelch all the time. Give me a shout if you can’t find the Becker squelch procedure!
Continue having fun,
JJ

[kinsell]

He said the interference is so bad he can hardly understand incoming
transmissions, so tweaking the squelch isn't going to be adequate to fix
this.

[Moshe Braner]

On 8/14/2023 7:14 PM, John Sinclair wrote:
>
> You can adjust the automatic squelch threshold on your Becker………the procedure is in the manual. In fact I finally resorted to raising the threshold on my Becker to solve the problem. You won’t get weak signals, but it will stop breaking squelch all the time. Give me a shout if you can’t find the Becker squelch procedure!
> Continue having fun,
> JJ
>

Depends on which model from Becker. The AR4201 has a squelch level
adjustment in its service mode menu. The AR3201 has a hole in the side
of the case through which you can (presumably with a small screwdriver)
adjust the squelch level.

That said, the original posting said: "At regular volume setting on the

radio the static noise is terrible and I can hardly understand any

incoming transmissions". That sounds like simply adjusting the squelch
level will not solve the problem, the noise signal is strong enough to
do more than "break the squelch".

[Tim Newport-Peace]

From the description, the interference may not come via the antenna
socket (try replacing the antenna plug with a 50-Ohm dummy load).

If it is magnetic interference (possibly from the internal speaker),
plugging in an External Speaker, 'should' isolate the internal speaker,
and see if that affects the problem. The external speaker and wiring
should be well away from the radio.

However, this sort of problem often defeats remote diagnosis!

[Mark628CA]

> However, this sort of problem often defeats remote diagnosis!

Remote diagnosis and opinion dissemination without actual knowledge is what RAS is famous for.

[kinsell]

On 8/15/23 7:12 AM, Tim Newport-Peace wrote:

>
> From the description, the interference may not come via the antenna
> socket (try replacing the antenna plug with a 50-Ohm dummy load).
>

That's good, trying to isolate the problem.

On the ground, I'd suggest taking the handheld to the tail of the ship
and see if the interference is still strong when it's back there. If it
is, then the ship radio is just acting like a radio should, and the
solution has to come from the vario. A trash masher might prove to be
the optimal solution.

-Dave

[John Sinclair]

On Tuesday, August 15, 2023 at 6:23:44 AM UTC-7, Mark628CA wrote:
> > However, this sort of problem often defeats remote diagnosis!
> Remote diagnosis and opinion dissemination without actual knowledge is what RAS is famous for.

The fact that you also get interference on your hand-held radio gives you a great investigation tool. Does it go away when you turn off the vario? ………..GPS?……….Transponder?…………Computer?…………anything else?

You don’t know where it’s coming from, but you know where it’s going………..into your radio! Disconnect the antenna………I’ll bet the interference stops!………..OK, now try the stub antenna on the panel radio!
As I said before, my issue was a very noisy collection of instruments that were ready to break squelch all the time! To make things even more madning, I found it depends where you are.! No problem at home, but squawking like a banshee at AirSailing!

[Tim Newport-Peace]

On 14/08/2023 19:49, Moshe Braner wrote:
> The XCvario audio uses a "class D" amplifier so yes it's a square wave.
>  The speaker is internal, although there is a jack for an external
> speaker, can try using that.

Good point. If using a remote speaker, using twisted cables (not on the
panel, close to pilots ear might be good) resolves your problem, that is
your solution.

On 14/08/2023 03:58, miltonpilot JLH wrote:
> At regular volume setting on the radio the static noise is terrible
and I can hardly understand any incoming transmissions. What's (semi)
interesting is it only happens when the audio on the vario is sounding
off (which is most of the time, either going up or going down). If I
turn the vario audio down completely, it does not interfere with the radio.

Another good point.

So the interference is Vario-Volume related, and if the Vario-Audio
output is a square wave then the speaker coil is either energised, or
not. A high current change is present controlled by the Volume control.

The problem is presumably carried by the voltage supply cables, or is
magnetic interference?

If the vario is put on an completely independent battery is the problem
affected?

Copper mesh might block RF interference, but not magnetic interference.

[miltonpilot JLH]

This past Friday I went to the gliderport to work on the interference problem. There were still some wires running around behind the panel that had accumulated from the previous owners and I decided to "rip" everything out and start from scratch as far as electrical wiring goes. Prior to the failure of my Ilec SC7 vario, I had the vario and the Flarm powered by one battery and the radio and the transponder powered by another battery. I decided to rewire everything the same way as far as what battery powered what instrument. I tightly twisted every plus and minus power pair and attached ferrites to them. I also moved all of the power wiring as far away as possible from the radio and the radio antenna (my radio works great by the way...loud and clear on outgoing and incoming transmissions). It took me 6 hours to rewire everything (I'm not an electrician or electronics guy)...expletive deleted! I flew the glider on Saturday, 8/19/23, and it was a great soaring day here in Northern Nevada. While on tow and then climbing in the first thermal there was no static on the radio and the vario was chirping away loudly...Eureka! FWIW, for the first 10 minutes of the flight the radio was tuned to 122.90 (the frequency we use at Air Sailing) and then changed to 123.30, still no static...UNTIL, 1 1/2 hours into the flight the static started up again on the radio! I switched back to 122.9 and the static went away. I also listen to NORCAL Approach on 126.30 any time I'm near KRNO and there was no static on that frequency either. I just left the radio tuned to 122.90 for the majority of the 3 hour flight but here's the kicker...about 30 minutes before landing at Air Sailing I switched to 123.30 and there was no static!!! Gremlins!!! The only thing I did not do last Friday was to wrap the vario in brass mesh. I will do that again this weekend and hope for the best.

[Richard Livingston]

We've been dealing with a similar problem in our LS6. I finally traced it down to our Oudie. When plugged into the USB connecting it to our S7 vario, the USB line was acting as an antenna. By turning the squelch off and moving wires, turning things ON and OFF, I was able to figure out what was doing what.

I improved the noise considerably (enough that it doesn't break squelch) by wrapping the back of the Oudie with aluminum foil and placing a ferrite bead on the USB cable near the Oudie. I also found that placing the Oudie near the rear fuselage would also couple noise into the radio. Apparently our comm radio antenna cable that runs to the antenna in the tail is "leaky". I tried a ferrite bead on the antenna coax at the comm radio, but that didn't help much. FYI. These RFI problems can be tricky.

Rich L

[miltonpilot JLH]

Rich L: I have an Oudie N IGC that is on a suction cup mount on the side of the canopy. It has its own internal battery and there are no wires (USB or otherwise) connecting it to the instrument cluster. FYI, I have ADS-b Out installed in my glider but it was not causing any interference problems prior to the installation of the new vario. Now that I think of it, I did not put a ferrite on the power wires going to the ADS-b "box" (a Trig TN72). I don't know if that will help but it can't hurt.

JLH/H4

[2G]

I would remove the vario from the glider and set it up on a table far removed from any other electrical device. Hook up a power source (battery) and test it with a handheld radio close by. Document the test with a short video. If the vario breaks squelch send the video to the manufacturer and ask the them to perform the same test and report back. Try the test with and w/o ferrite beads on the power lines.

This vario has probably not passed US FCC certification required of all consumer electronics. Ask the manufacturer for their FCC certification number. If they don't have it or refuse to supply it they are breaking US law. You can quickly determine this yourself by examining the vario for any FCC ID which they are required to put on the product. There are similar requirements in the EU.

Tom 2G

[Mike Carris]

This vario has CE certification. If I am not mistaken, and I don't think I am, CE certification is accepted by the USA.

I am using one and there is no problem what so ever. It is a great little variometer.

Mike

[John DeRosa OHM Ω http://aviation.derosaweb.net]

One thing that can cause interference are USB adapters that we use to
convert 12Vdc to 5Vdc for our mobile devices.

All of them use a switching power supply which is inherently noisy
with RF "hash" - especially so with the cheap ones and especially when
asked to supply its max power to a power hungry device.

Before installing one in your glider test them by bringing a handheld radio nearby.
I just did this last weekend using a good quality ICOM radio. Thee squelch broke
even when set at 10.

I have been told, but have not tested, that the adapter that the OGN group is
suggesting to power their transmitters are said to be good. I will report back.

John (OHM)

[Eric Greenwell]

I have discovered price is not a good indicator of RF noise. A $6 adapter was quiet in my glider, when a $20 unit wasn't; two very similar $10 adapters in my motorhome gave me a totally quiet one and noisy one. Good thing they are cheap enough, mistakes can be accepted.

[miltonpilot JLH]

All of the instruments in my glider that require external power, run on 12V DC and are powered by 12V DC batteries so I don't have any adapters stepping down the voltage. I do have a Nano 3 and an Oudie N IGC in the glider but they run on their own internal power and are not connected to anything.
JLH/H4

[Dan Daly]

If you haven't tried it, you might put your cell phone in airplane mode to see if it is the cause.

[2G]

CE is a broad CLAIM by the manufacturer that the product meets all requisite regulatory requirements; an FCC ID means that the product has actually been CERTIFIED by a testing laboratory and the test results are available for public inspection. Your experiences are not the same as having it tested at a certified laboratory using calibrated test equipment (you may have a less sensitive radio).

Tom 2G

[Mike Carris]

Tom,
I also use a Becker radio.
Really, no CE testing similar to FCC certification?
Just looked-
No FCC ID sticker on the back of my 302 nor on my ClearNav set up.
On my Nano, it only says CE on the back.

Regards,

Mike

[2G]

Mike, there is no database that I could find of CE-certified products - it seems to be all self-certified. This is markedly different from the FCC, which maintains such a database. So, there is no guarantee that the CE mark is genuine. The company's response to miltonpilot's complaint makes me that much more suspicious that this might be the case. They should have offered to replace it under warranty but probably knew that all of their products have the same deficiency.

Tom 2G