Radio Squelch - Electrical Noise Problems

[Maxx Ruff[_2_]]

I'm trying to sort out electrical noise upsetting many of my clubs radios.

I’ve had moderate but inconsistent results with separating radio wiring
and
use of ferrite beads.

Does anyone know of any on-line info / guides to reduce squelch problems?
(Especially with regard to squelch being upset by electrical noise from
chargers, voltage converters, digital instruments and data wiring).

The problem with cockpit devices causing the need for more aggressive
radio squelch setting seems to be getting worse. Winding up the squelch is

easier than minimising the ‘interference’ but I feel it’s like using
earplugs
instead of fixing a noisy wheel bearing.

I’ve seen and used lots of useful suggestions scattered through numerous

topics on RAS and a sprinkling of possible electrical noise fixes on
Google. I
would really appreciate a pointer to good info and any ‘golden rules’.


Max

[Wyll Surf Air]

If there is a specific voltage converter that seems to be spitting out a lot of noise you might try wrapping it in tin foil. That has worked for me in the past.

[Chris Wedgwood[_2_]]

On Tuesday, June 12, 2018 at 5:30:06 AM UTC+1, Maxx Ruff wrote:
> I'm trying to sort out electrical noise upsetting many of my clubs radios..
>
> I’ve had moderate but inconsistent results with separating radio wiring
> and
> use of ferrite beads.
>
> Does anyone know of any on-line info / guides to reduce squelch problems?
> (Especially with regard to squelch being upset by electrical noise from
> chargers, voltage converters, digital instruments and data wiring).
>
> The problem with cockpit devices causing the need for more aggressive
> radio squelch setting seems to be getting worse. Winding up the squelch is
>
> easier than minimising the ‘interference’ but I feel it’s like using
> earplugs
> instead of fixing a noisy wheel bearing.
>
> I’ve seen and used lots of useful suggestions scattered through numerous
>
> topics on RAS and a sprinkling of possible electrical noise fixes on
> Google. I
> would really appreciate a pointer to good info and any ‘golden rules’.
>
>
> Max

It would be helpful to detail what you've done, what equipment is there, etc..

[[email protected]]

If you can identify which device(s) are the primary culprit, installing a capacitor across the power leads to that device may cut the unwanted noise. Google “low pass filter” and you’ll find good info..

[Martin Gregorie[_6_]]

On Mon, 11 Jun 2018 23:28:23 -0700, Wyll Surf Air wrote:

> If there is a specific voltage converter that seems to be spitting out a
> lot of noise you might try wrapping it in tin foil. That has worked for
> me in the past.

A cheap source of efficient 12v -> 5v converters is to buy 'USB cigar
lighter chargers' from Ebay, throw away the plastic case and solder power
leads onto the 12v side of the PCB. However, these often produce RF noise
because they use a high frequency chopper circuit. I use them, of course,
since they are cheap and easy to find but I mount them inside a small
metal, rather than plastic, box and fit ferrite cores to both 12v and 5v
leads close to the box. I have no noise problems if they're used this way.

The only serious interference noise problem I've had was from a
mechanical T&B. Ferrite cores made no difference to it. The cure was to
fit a "12v interference suppression capacitor" across its its power
leads. These are special purpose polyester film capacitors. Mouser, among
others, sell them or a search using the term shown above will find many
sources, including fleabay.


--
Martin | martin at
Gregorie | gregorie dot org

[PAGA]

With the help of a good avionics friend, we recently found that some of the little GPS pucker did interfere with my radio when powered (and connected to a Kobo), while other models (we switched to a dongle) didn’t.

It took a long systematic one by one elimination test, turning on and off one device at a time. One source of static can be your phone(s) obviously, so your testing must include those. Once you find the culprit the solution is probably simple or already explained by some of the pros above who know electronic better.

Good luck,
686

[Dave Nadler]

On Tuesday, June 12, 2018 at 12:28:25 AM UTC-6, Wyll Surf Air wrote:
> you might try wrapping it in tin foil. That has worked for me in the past.

https://tinyurl.com/y7o8rnpy

[[email protected]]

> It would be helpful to detail what you've done, what equipment is there, etc..

Generally I try to modify the wiring to be as close as possible to John DeRosa's excellent presentations. I haven't found much on the topic of radio interference on his or any other website but would be happy to be corrected.

I've checked for voltage drops to the instruments, cleaned and tightened terminal blocks, grounding, fuses and connectors, separated Radio wiring as best I can (both physically and electrically), placed split ferrites on power, spr and mic/ptt leads to radio. Looped (twice) power wiring to the flarm through ferrite rings, clipped split ferrites on data leads to FLARM display and card readers if present.
I find that the first minute after the Master switch has been turned on is the noisiest, I assume things are initializing during this period. The Flarms seem to be the "primary culprits". A handheld radio confirms this.
The noise is stronger on some frequencies than others, 122.7 Mhz is moderately quieter than frequencies above 130 Mhz.
Should I try a ferrite on the Flarm GPS antenna or will this mess up the GPS?
Also, is a ferrite on the radio antenna cable a really, really bad idea?

I have assumed it is better to run both positive and ground wires to an instrument through the same ferrite OR would it be better to have a ferrite for each wire? Would it be better to have no ferrite on the radio ground so that its chassis is 'closer to RF ground'. Sigh.
I haven't tried a "12v interference suppression capacitor" yet, will order some. Will also order some copper foil to wrap around the flarms (or possibly to make a hat :)

[[email protected]]

I have to agree with PAGA.
It took almost a whole day but taking all units off line and adding them back one at a time identified what system was the source. Then it was a couple hours using ferrite devices to kill the noise. It was amazing to me how specific the positioning of the ferrite device on a wire/cable needed to be. Just moving the ferrite an inch back and forth on a wire/cable made a difference. Eventually, all became good in the world again.

[Maxx Ruff[_2_]]

At 10:39 12 June 2018, Chris Wedgwood wrote:

>It would be helpful to detail what you've done, what equipment is
there,
>etc

I generally try to modify wiring to comply with John DeRosa's excellent
presentations. I haven't found much on his or any other website about
radio interference but would be pleased to be corrected.

http://aviation.derosaweb.net/presentations/#wiring

I have checked for poor batteries, undersized cables, loose or voltage
drops on connectors, fuses, circuit breakers, switches, terminal blocks
and earthing.
I've separated (physically and electrically) as best as reasonably
possible, the wiring of the radio from other wiring.
I've placed solid ferrites on power wiring to the radio and each
instrument.
I've put split ferrites on data, display, memory card and radio mic/spr/
ptt cables.
I took the ferrites back off the memory card cables as I seemed to have
more trouble with the cards while the ferrites were present (but this
may have been caused by people corrupting the cards in a mac pc).

The ' primary culprit' often seems to be the Flarm, especially during the
first minute after the master switch is turned on when everything is
initializing. A hand held radio seems to confirm this. The interference
seems to be worse at higher frequencies with 122.7Mhz being a bit
better than above 130Mhz.

I haven't tried "a 12v interference suppression capacitor" across the
radio leads, will order some. Also ordering some copper foil to wrap
around the flarms (or to make a protective hat)

I'm not sure if its a good idea to clip a ferrite onto the flarm GPS
antenna lead or the radio antenna lead, suggestions are welcome.

[[email protected]]

On Tuesday, June 12, 2018 at 11:30:06 AM UTC-4, Maxx Ruff wrote:
> At 10:39 12 June 2018, Chris Wedgwood wrote:
>
> >It would be helpful to detail what you've done, what equipment is
> there,
> >etc
>
> I generally try to modify wiring to comply with John DeRosa's excellent
> presentations. I haven't found much on his or any other website about
> radio interference but would be pleased to be corrected.
>
> http://aviation.derosaweb.net/presentations/#wiring
>
> I have checked for poor batteries, undersized cables, loose or voltage
> drops on connectors, fuses, circuit breakers, switches, terminal blocks
> and earthing.
> I've separated (physically and electrically) as best as reasonably
> possible, the wiring of the radio from other wiring.
> I've placed solid ferrites on power wiring to the radio and each
> instrument.
> I've put split ferrites on data, display, memory card and radio mic/spr/
> ptt cables.
> I took the ferrites back off the memory card cables as I seemed to have
> more trouble with the cards while the ferrites were present (but this
> may have been caused by people corrupting the cards in a mac pc).
>
> The ' primary culprit' often seems to be the Flarm, especially during the
> first minute after the master switch is turned on when everything is
> initializing. A hand held radio seems to confirm this. The interference
> seems to be worse at higher frequencies with 122.7Mhz being a bit
> better than above 130Mhz.
>
> I haven't tried "a 12v interference suppression capacitor" across the
> radio leads, will order some. Also ordering some copper foil to wrap
> around the flarms (or to make a protective hat)
>
> I'm not sure if its a good idea to clip a ferrite onto the flarm GPS
> antenna lead or the radio antenna lead, suggestions are welcome.

Theoretically a ferrite ring around the antenna's coaxial cable should not affect anything. But if it does, that means there is something wrong with the antenna (such as a broken wire inside) that causes radio waves to be radiated from the coaxial cable itself. That is an issue with transmission, e.g., from the radio, or the FLARM's transmission antenna. The GPS only receives. If the "GPS antenna" is actually a complete GPS receiver that sends the processed data through its cable, that's a different situation, and a ferrite ring on that may help.

BTW running a cable through a ferrite ring twice (looped) is four times more effective than once, as far as the impedance it puts in the way of unwanted radio emissions. (And 3 times is 9x as effective.) Easy to do with a split ring that is large enough, if you have slack in the cable.

[JS[_5_]]

A tool can be made, using a single-coil guitar pickup and a headphone amplifier, to detect noise sources. Managed to get a 400A 3-phase 400v analog stage lighting system quiet using one.
If there was an FSG71M handy, suppose it could have been substituted as a minesweeper.
Good luck,
Jim

[Martin Gregorie[_6_]]

On Tue, 12 Jun 2018 07:20:50 -0700, lbraithwaite wrote:

> I haven't tried a "12v interference suppression capacitor" yet, will
> order some. Will also order some copper foil to wrap around the flarms
> (or possibly to make a hat :)
>
I could be wrong, but I think these capacitors are only useful for
dealing with interference generated by a sparking commutator and brushes
in an electric motor. In a glider you'll only find these in mechanical
T&Bs and artificial horizons.


--
Martin | martin at
Gregorie | gregorie dot org

[[email protected]]

On Tuesday, June 12, 2018 at 1:31:40 PM UTC-4, Martin Gregorie wrote:
> On Tue, 12 Jun 2018 07:20:50 -0700, lbraithwaite wrote:
>
> > I haven't tried a "12v interference suppression capacitor" yet, will
> > order some. Will also order some copper foil to wrap around the flarms
> > (or possibly to make a hat :)
> >
> I could be wrong, but I think these capacitors are only useful for
> dealing with interference generated by a sparking commutator and brushes
> in an electric motor. In a glider you'll only find these in mechanical
> T&Bs and artificial horizons.
>
>
> --
> Martin | martin at
> Gregorie | gregorie dot org

Any energy at radio frequencies can be filtered that way. Probably best to combine both a capacitor (across the wires, only on power supply wires, not signal wires) and a ferrite ring in close proximity. Try the ring at either side of the capacitor, but I would expect the best noise reduction with the ring on the side towards the noise-generating device.

[Chris Wedgwood[_2_]]

Many decent suggestions here. All I will ad is make sure the antenna ground plane is not connected to the power supply ground at the antenna end, because if you do that there will be an earth loop.

[WaltWX[_2_]]

I just discovered the source of RF noise source breaking squelch on my Dittel FSG71M radio. Started on 2nd flight of the season... here's what it was..

There is an LXNAV power converter that was shipped with my Nano. It's also used occasionally to power other devices at 5V. Decided to power my Nano, and this clobbered my vhf radio with RF. Turns out it was the USA A to MINI six inch cable. When I swapped out the cable with another one, the RF noise stopped! It was only pulling about 30mA. Tested same power converter with a Nokia 8 (USB A to USB-C) pulling 600 mA... and it had no RF noise.

PAYS TO CHECK USB A CABLES THAT MIGHT NOT HAVE GOOD SHIELDING OR BE OF POOR QUALITY

Walt Rogers WX

[[email protected]]

On Monday, July 2, 2018 at 10:21:36 PM UTC-7, WaltWX wrote:
> I just discovered the source of RF noise source breaking squelch on my Dittel FSG71M radio. Started on 2nd flight of the season... here's what it was.
>
> There is an LXNAV power converter that was shipped with my Nano. It's also used occasionally to power other devices at 5V. Decided to power my Nano, and this clobbered my vhf radio with RF. Turns out it was the USA A to MINI six inch cable. When I swapped out the cable with another one, the RF noise stopped! It was only pulling about 30mA. Tested same power converter with a Nokia 8 (USB A to USB-C) pulling 600 mA... and it had no RF noise.
>
> PAYS TO CHECK USB A CABLES THAT MIGHT NOT HAVE GOOD SHIELDING OR BE OF POOR QUALITY
>
> Walt Rogers WX

Thanks for the info. I assume you mean a USB A to mini cable. I'm running the exact same setup, I'm going to try a new cable too, and then re-adjust the squelch pot on my 71 (again)...