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Radio Squelch - Electrical Noise Problems



 
 
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  #11  
Old June 12th 18, 05:29 PM posted to rec.aviation.soaring
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Default Radio Squelch - Electrical Noise Problems

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.
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  #12  
Old June 12th 18, 05:36 PM posted to rec.aviation.soaring
JS[_5_]
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Posts: 346
Default Radio Squelch - Electrical Noise Problems

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
  #13  
Old June 12th 18, 06:31 PM posted to rec.aviation.soaring
Martin Gregorie[_6_]
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Default Radio Squelch - Electrical Noise Problems

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
  #14  
Old June 12th 18, 06:51 PM posted to rec.aviation.soaring
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Default Radio Squelch - Electrical Noise Problems

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.
  #15  
Old June 13th 18, 09:32 PM posted to rec.aviation.soaring
Chris Wedgwood[_2_]
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Posts: 51
Default Radio Squelch - Electrical Noise Problems

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.
  #16  
Old July 3rd 18, 06:21 AM posted to rec.aviation.soaring
WaltWX[_2_]
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Default Radio Squelch - Electrical Noise Problems

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
  #17  
Old July 3rd 18, 10:13 PM posted to rec.aviation.soaring
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Posts: 87
Default Radio Squelch - Electrical Noise Problems

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)...
 




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