Results 1 to 34 of 34

Thread: Radio noise

  1. #1

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like

    Radio noise

    HELP!!!

    Airplane on ground not running- radio is clear. Airplane on ground engine running- radio is clear. Aircraft in air static starts immediately after take off and and continues to increase the longer I am in the air until the radio is completely unreadable. After touch down- radio is clear. What is going on here?

  2. #2
    Coyote Ugly's Avatar
    Join Date
    Jan 2008
    Location
    Middle of Nevada
    Posts
    536
    Post Thanks / Like
    Radio is obviously afraid of flying... ��
    "Pops Dory"
    They used to say there are no old, bold pilots, Hell, looka here...

  3. #3

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Thanks Pop I will schedule some therapy for it and let you know what happens

  4. #4
    PerryB's Avatar
    Join Date
    Aug 2007
    Location
    Northern Calif.
    Posts
    1,200
    Post Thanks / Like
    From your description it seems like airframe static is building up and interfering with the radio. Could it be that the antenna is mounted to a surface which has become ungrounded? Is this something that just cropped up, or has it been ongoing?
    After Monday and Tuesday, even the calendar says WTF !

  5. #5
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Trouble shoot it. When it acts up, turn off alternator field then turn back on. turn off one mag off and on then other (mag drop test). Turn off the radio. Turn off the intercom. Pull each breaker, one at a time, then push it in. Note any changes and when they occur. Also, fly with another headset. Do all these simple things first. You might be able to fix the problem yourself, if not, your avionics guy will appreciate the info.

    Just the way you describe the issue, I'd guess problems with either the radio or intercom. What models are you using?

    Web

  6. #6
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    8,303
    Post Thanks / Like
    ground connection for engine/airframe is coming loose as engine flexes/changes to flight position.....

  7. #7

    Join Date
    Feb 2008
    Location
    AK
    Posts
    2
    Post Thanks / Like
    We had a problem like this after having a new mgl v6 installed in our cub, and it was really annoying. After adjusting mic and squelch settings, it is fine except when we get near a FM radio tower in the vicinity.

  8. #8

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    It was never perfect, but the last ten hours it has gotten to the point were the radio is unusable in flight

  9. #9
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    8,303
    Post Thanks / Like
    run new ground wire direct from engine to firewall small stud thats welded to tube(there's 3 of them) 8GA works..... too much slop in original engine mounts to be a good ground system over time

  10. #10

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Thanks Mike. Will the size of the wire matte Red? Also I would like to understand what is going on. It makes sense that the airframe is building up a static charge, what I need to know is is that static charge back beating through the ground the power side or both into the radio? If that's the case will a filter on one of those wires also reduce the noise?

  11. #11
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Do your troubleshooting. Until you know the source of the noise you're just 'shotgunning' and hoping something fixes it. Filters are a great example. It just covers up the noise. Find the source and deal with it appropriately. I never install filters when I install avionics. Unless there is an internal issue in a component, proper wiring and routing always eliminates noise. You still haven't told us the model radio and/or intercom you are running. It makes a big difference if you are running something like a NAT intercom with shielded wires or an old Sigtronics with the jacks grounded to the airframe.

    Web

  12. #12
    btracy's Avatar
    Join Date
    Apr 2004
    Location
    Ohio
    Posts
    993
    Post Thanks / Like
    Is it Transmitting when this happens. I had a similar situation this spring. I thought some one in the area had a hot mic. Found out it was me when I noticed my TX light flickering on and off. Ended up finding the rear push to talk switch had a broken wire. But same thing only in the air would it vibrate to make it cause problems.

  13. #13

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    It is a Becker radio and pm1000 intercom. I did a radio check and I seem to transmit fine so it appears to be only on receiving end. I am at the airport now. Installed a new engine to airframe ground and heading up to try this. Will also check alternator while I am up,

  14. #14

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Engine shut down, clear as a bell. Engine running static. Pulled alternator field still static

  15. #15
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Okay, you eliminated your alternator and loose engine ground as cause. Did you shut down the radio and the intercom to see if the noise goes away with one or the other? Did you pull each circuit breaker and check for changes in noise?

    Let me give you an example: You pull the intercom circuit breaker and no change in noise. Reset it and pull the com circuit breaker and the noise goes away. That would tell you that the source of the noise is in that particular com system.

    You will need to narrow this search down to a particular system in order to meaningful repairs as the source of this noise could, literally, be in any electrical system on the aircraft.

    Web

  16. #16

    Join Date
    Sep 2003
    Posts
    5,592
    Post Thanks / Like
    You did adjust the squelch in the Becker? It has a range of 0-200, and we have found that it takes 175 or so to get it to work. I prefer squelch knobs, but the modern way is to pre-program it.

  17. #17

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Yes I did adjust the squelch in the air to no avail. Just pulled the trim off at the antenna and no ground between and antenna and airframe so going to add one. Looking at the wiring diagram it appears they wired a single power source and ground for the PM 1000 and the becker. If I pulled the DB plug off the back of the PM1000 would that isolate the radio? It also shows an optional ground on the side of the case but it is not grounded on the radio, would this make a difference?

  18. #18
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Quote Originally Posted by CuBob View Post
    Yes I did adjust the squelch in the air to no avail. Just pulled the trim off at the antenna and no ground between and antenna and airframe so going to add one. Looking at the wiring diagram it appears they wired a single power source and ground for the PM 1000 and the becker. If I pulled the DB plug off the back of the PM1000 would that isolate the radio? It also shows an optional ground on the side of the case but it is not grounded on the radio, would this make a difference?
    How/where is your antenna mounted? Don't worry about the case ground on the Becker unless some one got 'creative' on the wiring. Are you saying that the Becker and PM 1000 use a single power wire and single ground wire? If so, removing the connector plug from the PM1000 will isolate it but, unless you have emergency jacks wired directly to the com, you will not be able to use your head phones.

    Check you PM messages

    Web

  19. #19

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Yes there are emergency jakes. The antenna is mounted on the wing root trim. No ground from antenna base to air frame. Wondering if vibration of trim would cause problem. Just about finished with this ground and will see if it helps.

  20. #20

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Just finished a run up,but did not fly. Radio clear we will see what happens in flight

  21. #21
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    I'm not a big fan of mounting the antenna on that fairing but there are about four bazillion of them mounted that way with no noise problems. The only way that the fairing being loose would cause a problem is if the shield braid on the coax cable was not connected and the fairing was not making contact with the airframe through, either physical contact or the mounting screws.

    If you fly again, disconnect the intercom and plug into your emergency jacks. This will tell you if the intercom is the source of the noise or something else.

    Web

  22. #22

    Join Date
    Jul 2010
    Location
    Elizabeth, WV
    Posts
    391
    Post Thanks / Like
    A friend has a squeal in his radio. Disconnect the intercom and squeal goes away. There you are......it's the intercom! Have you changed the battery? Don't need a battery........it's wired in. So did you check the battery? I told you it don't need a battery, it's wired into the radio! Just satisfy my curiosity and open it up, please. Well look at that....there is a battery in there. What's hanging on the wires? Is that corrosion? Well, yah, sorta. It's the connector ends off the 9V battery. You mean the battery fell apart? Well, yah. So how old is that battery that wasn't in there? Ugh, it says 1999 on it. So now the long dead battery is out and the squeal is still there from the intercom. I'd guess the ooze and corrosion from the dead battery fubared the intercom. He's gonna try another intercom, maybe. jrh

  23. #23
    www.SkupTech.com mike mcs repair's Avatar
    Join Date
    Aug 2004
    Location
    chugiak AK
    Posts
    8,303
    Post Thanks / Like
    bump, update?

  24. #24

    Join Date
    Mar 2007
    Location
    Northwestern Minnesota
    Posts
    105
    Post Thanks / Like
    Similar problem with new panel installation by self with new Becker, electronic gauges etc etc. First problem (no volume control) a result of my soldering job (and cold solder joint) on the miserably tiny pins supplied with the radio. Resolved by having an Avionics shop build me a new harness and installing myself. Still static and ultimately determined the static was being generated by the new UMA oil temp/pressure gauge and could be eliminated completely by pulling the breaker( by the method suggested above).

    I assumed it was my solder job on that instrument as well and took to my Avionics shop to have them replace in the plane rather than remove all the sending units for the gauge. Wire harness was redone professionally. Static did not go away. The avionics shop called the company (UMA) and they were well aware of the problem. I returned the gauge to them and they warrantied a new power supply and subsequent installation produced a perfectly clear static free radio.

    I am not an avionics expert by any means but have a little experience in electronics in the past as well as present so was not intimidated by doing the install myself. However I found out from my Avionics shop that they throw the solder type terminals away and install crimp type terminals instead of the supplied terminals. The pins with the terminals supplied are 20-22 gauge pins, yet the wires supplied with and specified for some of the circuits are 16-18 gauge. The harness supplied by my Avionics Shop (Park Rapids Avionics) in Park Rapids MN was really impressive. They also manufacture the Hub system which is another slick wiring system for installing and cleaning up an avionics installation.

    Hope my experience offers some help to either you or others.. Good Luck.........Rod

  25. #25
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Most of us that chase wires will use the crimp pins over the solder type any time it's possible. It actually saves the customer money as the harness assembles more quickly than soldering wires. As for 18 gauge wire in a 20 gauge pin, there are a couple of specialty pins out there that adapt the big wire to a small pin.

    I've found that a lot of guys are willing (and able) to install harnesses in the aircraft but want nothing to do with the fabrication of the harness itself. I love it because I can sit at the table and fab the harnesses and let someone else stand on their head for the installation, lol.

    Was the UMA power supply one of the AC types? If so, make sure to never bundle the AC wires with or near any audio lines. They put out a buzzing type noise that just wont go away unless physically separated. Treat them like P-leads.

    Web

  26. #26

    Join Date
    Mar 2007
    Location
    Northwestern Minnesota
    Posts
    105
    Post Thanks / Like
    Web

    The power supply was internal to the gauge. However the light bezels had an independent power supply invertor that required separation from audio lines. I agree it would be better to sit at the kitchen table working on these things than crammed upside down underneath the panel working in tight spots needing 3 hands when you only have two to fix something.

    One thing my avionics guys suggested and I followed through on was to make my I-Pad mini Air Gizmo dock removable with four screws on the front of the panel. It provided a huge access to the back of the panel which greatly simplified removal of the UMA gauge when I needed to return.........Rod

  27. #27
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Great idea with the panel dock. Always need room to work.

    Web

  28. #28

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    Update! Installed a ground wire from the antenna direct to the frame and all noise disappeared. I took it for an hour flight this morning and the radio was clear as a bell. One of the great things about Supercub.org is the experience and knowledge base of the members. Wire Winnie thanks for taking the time to help, Mike thanks for your input. The only problem with the site is the fact I never get to meet the guys that are so much help and thank them in person.

  29. #29

    Join Date
    Sep 2003
    Posts
    5,592
    Post Thanks / Like
    Yeah - these guys have helped me immensely over the years too.

    So tell me - your antenna was grounded to the upper wing-to-fuselage fairing, but now you have a wire to the steel in the fuselage - those sheet metal screws were not enough to ground it? Did I understand it correctly?

  30. #30
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Glad to hear it worked out. You might want to plan on getting a new coax fabricated for the antenna when you have it apart. Something to work in with an annual.

    Web

  31. #31

    Join Date
    Jul 2007
    Posts
    213
    Post Thanks / Like
    That seems to be correct. There are not that many screws on the upper trim strip.

  32. #32

    Join Date
    Jan 2015
    Location
    Fairbanks, AK
    Posts
    5
    Post Thanks / Like
    Since the purchase of my cub this past spring, I too had been having extremely random radio static problems that didn't seem to correlate much with any one constant. Sometimes certain frequencies on my comms would be crystal clear, other days the same ground or tower frequency would be unbearable. Sometimes it would be a steady static noise, other days I would get pulses when the rear rotating (non-LED) beacon would pulse. Some days I could turn the beacon off temporarily and the noise would go away, other days turning that off wouldn't diminish the noise. Some days, I could turn the circuit breaker switch off for the electric turn and bank I have, and for a while that was the most consistent way to squash the noise, but then that seemed to have less of an effect. Didn't seem to be temp based or RPM based. Again, very very random and no constants that I could find to create the problem or solve it consistently. On the ground everything was crystal clear, after start up and flying things would get noisy.

    As everyone says, check the grounds. I began doing that from tail to tip. First cleaning and ensuring the beacon ground was good.. Tracking wires forward. Check grounds and the wire situation under the wing root panels where my light switches are located, under the seat at my battery, grounded the engine block to the firewall stud as few suggest on here, etc.. Further following wires up to and behind the panel. Separated power wires and routed things further away from audio lines if I could. Outside of grounds we ensured that the VHF radio and antennae were working well enough, and that there was not a ground plane issue. The old Narco 810+ that was in my bird failed at the beginning of August (after take off transmit failed to work, but could receive.. a bench test proved transmit circuits were toast) and was replaced by a Icomm A220.. When having that installed I had hoped that perhaps the radio itself had some internal circuitry that was injecting some sort of interference, but no luck. The static was still there.

    I knew it was something with the radio (not in the intercom), the turn and bank, and then one day discovered turning off the engine gauge also made static things silent.. And it turned out turning off the UMA 2 in 1 engine oil pressure and temp sensor gauge seemed to be the ticket. But unlike turning off the turn and bank, not too keen on flying without seeing what the engine oil is doing of course. I had a new connector put on the gauge as the soldering looked like it could have been suspect and also ran the oil temp/psi sender lines through a different hole in the firewall, away from power wires which they had been sharing another hole with. Both didn't solve anything.

    So long story short, I finally called UMA. They asked when the gauge was purchased (jun 2016), and immediately suggested I send it to them so they could install a new or better radio frequency filter within the gauge itself. I paid shipping both ways, they installed the new RF filter at no cost, and sent it back to me the same day they received it. First flight with the new filter, no noise. I didn't want to get too excited here as I had had temporary success in the past. Second flight, no noise!!

    Thanks to badmdcnman's posts above and comments made about the UMA gauge, they turned me towards the idea that the noise could be that gauge. Happy to have found a solution after 5 months. And if anyone else tells me to 'check the grounds' once more...
    Thanks badmdcnman thanked for this post
    Likes WindOnHisNose liked this post

  33. #33
    wireweinie's Avatar
    Join Date
    Aug 2013
    Location
    Palmer, AK
    Posts
    1,513
    Post Thanks / Like
    Thanks for the feedback. Always nice to hear what the exact cause was.

    Web
    Life's tough . . . wear a cup.
    Likes WindOnHisNose liked this post

  34. #34
    hotrod180's Avatar
    Join Date
    May 2008
    Location
    Port Townsend, WA
    Posts
    1,355
    Post Thanks / Like
    Good on UMA for stepping up to the plate.
    Sounds like you didn't even have to badger them!
    Cessna Skywagon-- accept no substitute!

Similar Threads

  1. Radio noise
    By Eddie Foy in forum Cafe Supercub
    Replies: 8
    Last Post: 01-10-2015, 12:55 PM
  2. Radio noise, radio needed
    By teeweed in forum Cafe Supercub
    Replies: 6
    Last Post: 09-06-2005, 09:03 PM

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •