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Thread: Interference on 123.45 MHz From Engine Monitor

  1. #1
    Steve Pierce's Avatar
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    Interference on 123.45 MHz From Engine Monitor

    Been putting some time on my new to me Super Cub and keep noticing what sounds like a stuck mic on 123.45 when flying with my friends. No one else is hearing it. Sunday I did some investigating with the engine off and a handheld radio. The interference is between 123.625 and 123.400. I pick it up on the ship's radio and a handheld radio. Engine was off and I started pulling circuit breakers. The transmission goes away when I pull the Electronics International CGR30P engine monitor circuit breaker and back on when I push it back on. From conversation with Jason, the previous owner, he noticed this after I installed the new engine with a SureFly electronic ignition module with the resistor from Electronics International back in May. I sent an email to EI and got this back. I need to source the cooper tape and proceed with troubleshooting. Curious if anyone else has had an issue and possible fix.

    I do not think that this corresponds with your electronic ignition install. The CGR passes all the FAA's RF testing and falls below all acceptable radio emissions, but there could be particular frequency bands with a concentration of energy - with the wiring coming out from the CGR, this acts as a bundle of antennas which is likely amplifying this concentration for your highly-sensitive radios to pick up. I spoke to engineering and they suggest using copper tape to wrap (or otherwise shield) the wire harness coming out from the CGR-30P. This should help to contain any natural emissions from the instrument and keep them well below the level of radio susceptibility.


    Please let us know if we can help out with anything else. Thanks again!

    Steve Pierce

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  2. #2
    wireweinie's Avatar
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    Is this actually coming in over the radio or could it be coming in on the intercom?

    Any quick way of disconnecting the Surefly and re checking?

    Web
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    Sounds like a good excuse to use a different frequency. It never fails that if you spend enough time on fingers someone, from who knows where, will chime in wondering what your doing and where you’re at. “Jumbo” or “Shotgun” never have anybody else on it
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  4. #4

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    Quote Originally Posted by wireweinie View Post
    Is this actually coming in over the radio or could it be coming in on the intercom?

    Any quick way of disconnecting the Surefly and re checking?

    Web
    Sounds like he heard it over a hand held as well.
    Remember, These are the Good old Days!

  5. #5
    RaisedByWolves's Avatar
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    Interference on 123.45 MHz From Engine Monitor

    Not any help at all but with the trig radio and built in intercom, no noise when I put the site fly on. Did have some noise but it ended up I forgot to hook up the landing light ground, when I took another ground off. Cut a ground wire to the cgr too. FYI without one of the grounds it will read COM on all fields in red. Isn’t it fun working upside down?


    Sent from my iPhone using Tapatalk

  6. #6
    Steve Pierce's Avatar
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    Quote Originally Posted by wireweinie View Post
    Is this actually coming in over the radio or could it be coming in on the intercom?

    Any quick way of disconnecting the Surefly and re checking?

    Web
    Using the built in intercom of the Trig radio. Interference is there with engine on or off. Flipping the SureFly on or off makes no difference. Only way I got rid of it was to change frequencies or turn off the CGR. Same with engine running or off.
    Steve Pierce

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  7. #7
    cubdriver2's Avatar
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    Friend of mine just put a Trig in a C120 and had noise. Installer blamed radio, Trig sent new radio, same problem. Old guys on Beechtalk said check ELT interference you may need a filter on ELT. Problem solved

    Glenn
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  8. #8
    wireweinie's Avatar
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    Try disconnecting the coax. If it goes away it was coming in on the antenna. If it stays it's being picked up on the wiring. How are the CGR wires and the Trig wires routed? Next to each other or bundled together?

    Web
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  9. #9
    Steve Pierce's Avatar
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    Disconnected the radio antenna coax and it went away. The wires cross each other, boxes are mounted beside each other. I could move harnesses around a bit and get it to stop momentarily.
    Steve Pierce

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    Will Rogers
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  10. #10
    wireweinie's Avatar
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    Maybe just reroute the coax? Otherwise separate the wiring as much as possible.

    Web
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  11. #11
    BC12D-4-85's Avatar
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    If it's entering from a nearby source via the coax outside wire shield (called common mode) then four of these fitting the coax tight might help. If it's entering via the antenna then good luck. Test would be to disconnect the coax at the antenna (isolating the antenna) and leave the coax attached to the radio, then see what happens.

    Also: https://palomar-engineers.com/ferrit...-on-combo-pack

    Gary
    Last edited by BC12D-4-85; 02-17-2022 at 07:43 PM.

  12. #12
    frequent_flyer's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Been putting some time on my new to me Super Cub and keep noticing what sounds like a stuck mic on 123.45 when flying with my friends. No one else is hearing it. Sunday I did some investigating with the engine off and a handheld radio. The interference is between 123.625 and 123.400. I pick it up on the ship's radio and a handheld radio. Engine was off and I started pulling circuit breakers. The transmission goes away when I pull the Electronics International CGR30P engine monitor circuit breaker and back on when I push it back on. From conversation with Jason, the previous owner, he noticed this after I installed the new engine with a SureFly electronic ignition module with the resistor from Electronics International back in May. I sent an email to EI and got this back. I need to source the cooper tape and proceed with troubleshooting. Curious if anyone else has had an issue and possible fix.
    Almost any equipment that has an embedded micro-processor will emit some conducted or radiated EMI. If you know exactly where it is coming from you have a better chance of eliminating it. If it can be isolated to one lead on the CGR it may be possible to fix it with ferrite.

    May be worth trying powering the CGI from a separate temporary battery using twisted pair for power and ground. If that reduces the interference then radiation from the power feed may be your problem.

    if I was closer than AZ I'd like to help you with this. I'd use my spectrum analyzer and EMI probes to try to track down the specific source of the spurious signal.
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  13. #13
    BC12D-4-85's Avatar
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    Maybe ferrite the wires coming from the CGR? Make a one or two turn loop of the bundle through the beads. Just a guess. ^^^^ mo better.

    Gary

  14. #14
    wireweinie's Avatar
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    Or just move the wires so that the noise does not get picked up in the first place. This aint a missile system. Separation is the best way of stopping interference from one unit to the other. Things like beads and filters just cover up the noise. Even if you can't hear it at that moment, it's still being generated.

    Keep in mind that if you double the distance between two wires, the interference decreases to one fourth of what it was. NOT by half. That's why a separation of just an inch or two can cure lots of noise issues.

    Simple is better.

    Web
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  15. #15
    BC12D-4-85's Avatar
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    If interested amuse yourself by walking around a home or business with your handheld AM aircraft transceiver on and squelch off. Go near appliances and wall outlets. We live in a radio interference world.

    Same for an aircraft. First source the noise general area with the handheld then remove the antenna to get closer to the source.

    Gary
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    Had a similar situation in my Pitts with a Becker radio.
    I went into programming mode and turned up (turned down?) the squelch.
    Probably just masked the source if interference but worked.

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    I had this happen when using my Stratus, moved the Stratus to the back and it went away.
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    Scooter7779h's Avatar
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    Why are you using 123.45? 122.725 is the air to air frequency, and nobody uses it. I laugh because "fingers' is jammed, and nobody on the set aside air-to-air frequency. There are rules and FCC assigned air to air, maybe EI when designing the CGR-30 didn't check the harmonics with a frequency that is not assigned for use.
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  19. #19
    BC12D-4-85's Avatar
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    I see that CGR-30P uses a panel display unit and outboard engine data convertor. "The EDC-33P (Engine Data Converter, "EDC") converts all of the engine and aircraft system signals into serial data. This data is transmitted to the CGR display via one wire 5V-Serial Bus" So a couple of components and associated wiring (for power-probe-serial data) could be involved in the harmful interference. Wonder where they suggested wrapping the copper tape to suppress interference?

    Pays to read: "they suggest using copper tape to wrap (or otherwise shield) the wire harness coming out from the CGR-30P"

    Gary
    Last edited by BC12D-4-85; 02-17-2022 at 11:47 PM.

  20. #20
    Steve Pierce's Avatar
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    I am going to rearrange some wiring and see what happens. Will post my results.


    Quote Originally Posted by Scooter7779h View Post
    Why are you using 123.45? 122.725 is the air to air frequency, and nobody uses it. I laugh because "fingers' is jammed, and nobody on the set aside air-to-air frequency. There are rules and FCC assigned air to air, maybe EI when designing the CGR-30 didn't check the harmonics with a frequency that is not assigned for use.
    Probably some of the most outlaw I get these days. Thanks for the heads up, I actually thought it was 122.75, hopefully the FCC won't come down to the Brazos River and write us citations.
    Steve Pierce

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    Will Rogers
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    frequent_flyer's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Probably some of the most outlaw I get these days. Thanks for the heads up, I actually thought it was 122.75, hopefully the FCC won't come down to the Brazos River and write us citations.
    "Weekend warriors flying warbirds have been communicating on 123.45 for so long that it has a nickname—“Fingers”—and although officially designated for use in aircraft flight-testing and transoceanic communications, it has become an unofficial air-to-air frequency. Legally, for air-to-air communications between private, fixed-wing aircraft, there is just one authorized frequency: 122.75 MHz. For general aviation helicopters: 123.025 MHz. Gliders and hot air balloons share 123.3 and 123.5 MHz."

    From AOPA article - https://tinyurl.com/2u6jzzcn

    One US gliding club had an FCC fine of, I think, $15,000 for unauthorized use of 123.3 as it was in conflict with the allocation of that frequency to a local flight school or FBO. That was despite the fact that all cross country glider pilots know 123.3 is "allocated" for their use. FCC can get very nasty when they want to.

    122.75 is a very busy frequency in the PHX area as it is used by most North practice area traffic.

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    Quote Originally Posted by Scooter7779h View Post
    Why are you using 123.45? 122.725 is the air to air frequency, and nobody uses it. I laugh because "fingers' is jammed, and nobody on the set aside air-to-air frequency. There are rules and FCC assigned air to air, maybe EI when designing the CGR-30 didn't check the harmonics with a frequency that is not assigned for use.
    I believe 122.75 is the official air-to-air for fixed wing aircraft.
    I thought 122.85 was also, but I just googled it:

    122.75 air to air fixed wing
    123.025 air to air helo's
    123.3 & 123.5 air to air hot air balloons & gliders

    per this page
    Technique: What's the frequency? - AOPA

    123.45 fingers & 127.47 jumbo are popular but not approved.
    Cessna Skywagon-- accept no substitute!

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    Quote Originally Posted by Scooter7779h View Post
    Why are you using 123.45? 122.725 is the air to air frequency, and nobody uses it. I laugh because "fingers' is jammed, and nobody on the set aside air-to-air frequency. There are rules and FCC assigned air to air, maybe EI when designing the CGR-30 didn't check the harmonics with a frequency that is not assigned for use.
    Around me 122.75 is jammed with a major flight school teaching students how to properly meow on frequency.
    Last edited by OLDCROWE; 02-18-2022 at 11:49 AM.
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  24. #24
    FdxLou's Avatar
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    According to the AIM, Section 4-1-9 (b) 122.725 is a CTAF freq at a non towered airport, along with 122.7, 122.8, 122.975, and 123.0. I'm sure Scooter meant 122.75, not 122.725.
    Lou
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  25. #25
    Scooter7779h's Avatar
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    Quote Originally Posted by FdxLou View Post
    According to the AIM, Section 4-1-9 (b) 122.725 is a CTAF freq at a non towered airport, along with 122.7, 122.8, 122.975, and 123.0. I'm sure Scooter meant 122.75, not 122.725.
    Lou
    Yes Lou, 122.750
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