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SSB noise

Discussion in 'Boat Electronics' started by krj, Dec 19, 2006.

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  1. krj

    krj Guest

    I just finished installing an SSB on my boat. When I turn on my freezer
    I get noise on the radio that sounds like morse code. The freezer has a
    Danfoss BD50 compressor with a digital thermostat. Has anyone else had
    this problem. I think I remember Gordon West writing about this problem
    in one of the sailing mags. but can't remember which one or when.
    krj
     
  2. Leanne

    Leanne Guest

     
  3. krj

    krj Guest

    Thanks for the info. I guess I'll go get some copper screen and try it.
    krj
     
  4. This has been discussed on Rparts forum a couple of times. The power unit
    of the BD series of compressors is a variable frequency inverter and is
    notorious for creating RF noise. Danfoss makes an aluminum shielded model
    but they are hard to find and don't help with conducted noise. The digital
    thermostat is not normally a source.

    Some things that will help are ferrite chokes on all wires going to the
    power unit to reduce conducted noise. You may have to experiment with the
    size to cut the frequencies that you need. Also lining the compressor
    locker with metal screening tied to ground reduces radiated noise.

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  5. Larry

    Larry Guest

    I wish you luck with the shielding. I used to sail on an Endeavour 35
    with an Adler-Barbour ice box cold plate that just tore up VHF Channel
    16, of all channels, with a pulsing noise. I'm on an Amel Sharki 41
    ketch and have installed an Icom M802/AT-140 and insulated backstay on
    the main. On this boat the noise source is a Guest dual 10A battery
    charger that makes broadband noise across the HF band very strong.
    Luckily, it is off at sea.

    To shield that fridge unit, you'd need screen box (It doesn't have to be
    copper. Aluminum will work fine.) with proper feedthrough capacitors for
    each individual wires where it feeds through the box. The ferrite
    absorbers, while useful, will not stop the radiation that must be bled
    off INSIDE the box, to the box itself. This, in effect, creates a
    "screen room" we had in every calibration laboratory I ever worked in.
    In the lab, we had to protect the measurements from RF sources outside
    the screen room. The 5KW AM radio station just outside Charleston Naval
    Shipyard had no signal, at all, inside the room with the door closed.
    This is what you are trying to create. Feed through capacitors are a
    straight wire through the center of a low impedance capacitor from that
    wire to the outside case of it that is threaded to connect it to the
    screen box. The signal coming out the wire couples harmlessly through
    the capacitor to the INSIDE of the box. The AC and control signals are
    much lower in frequency so very little of them couples through to the
    screen and they escape the box. An additional ferrite absorber will
    attenuate anything that escapes further.

    Best of luck to you. You'll find more noise sources as time goes along.
    Anything in that boat that has any kind of switching creates it. Your
    NMEA data network to the instruments is also a prime source of HF noise
    because the manufacturers go on-the-cheap and use unbalanced outputs,
    grounding one side of what should be + and - phased signal lines that
    were supposed to balanced out its radiation. Now with even 1 ground on -
    NMEA data lines, it radiates like hell the whole time the NMEA stuff is
    running. Add that to the wires wrapped around screws and all unshielded,
    again on-the-cheap, and it makes it much worse. You'll find NMEA's
    signal all across the HF bands at regular intervals.

    Larry
     
  6. krj

    krj Guest

    I don't think a Danfoss BD-50 compressor uses NEMA anyplace. That's the
    only equipment turned on except for the SSB. The noise is radiated, NOT
    coming through the 12V wiring. Disconnected the antenna from the SSB and
    the noise goes away. Of course, the station being monitored goes away
    alswo with no antenna.
     
  7. krj

    krj Guest

    Glenn,
    You are right. It is not the digital thermostat. I disconnected the
    thermostat leads from the compressor module and put a jumper between the
    terminals to turn on the compressor. The noise is still there. It is
    being radiated. I have clamp on ferrites on all the wires to the
    thermostat, power leads, etc. Any idea where to purchase the shielded
    module. The local marine refrigeration shop didn't seem to know anything
    about it.
    krj
     
  8. There are 4 different electronic modules for the BD series.:
    You probably have the standard 101N0210 single speed with the plastic box.
    The Danfoss part number for the single speed shielded module is 101N0220.
    The 101N0300 is the AEO variable speed with plastic box and the 101N500 is
    AEO with shield.

    The AEO future saves a bunch of amp hours by adjusting compressor speed to
    the load but the single speed models can be hooked to the Frigoboat SSC and
    get the same optimization with a slightly better algorithm. They both work
    on the principle that the system is most efficient when it runs for long
    cycles at the lowest speed but the SSC has an override to run at full speed
    for chill down.

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  9. krj

    krj Guest

    Glenn,
    Yes, I checked the module and it is the 101N0210. I guess the next task
    is to find someone in Ft. Lauderdale who can get the 101N220 module.
    Hope it isn't a BOATbuc to get a shielded moudle. You sure changing the
    module will solve the problem?
    krj
     
  10. There are 4 different electronic modules for the BD series.:
    You probably have the standard 101N0210 single speed with the plastic box.
    The Danfoss part number for the single speed shielded module is 101N0220.
    The 101N0300 is the AEO variable speed with plastic box and the 101N500 is
    AEO with shield.

    The AEO feature saves a bunch of amp hours by adjusting compressor speed to
    the load but the single speed models can be hooked to the Frigoboat SSC and
    get the same optimization with a slightly better algorithm. They both work
    on the principle that the system is most efficient when it runs for long
    cycles at the lowest speed but the SSC has an override to run at full speed
    for chill down.

    --
    Glenn Ashmore

    I'm building a 45' cutter in strip/composite. Watch my progress (or lack
    there of) at: http://www.rutuonline.com
    Shameless Commercial Division: http://www.spade-anchor-us.com
     
  11. krj

    krj Guest

    As I replied earlier, the problem is radiated noise from the Danfoss
    BD50 compressor control module. I have turn every electrical item on the
    boat on and off individually to determine which, if any, generate noise,
    either via the DC wiring or radiated. None cause a problem except the
    compressor module. Glenn Ashmore provided the part numbers of shielded
    control modules. I believe that when I finally find a place to purchase
    one, my problem will be solved.
    krj
     
  12. krj

    krj Guest

    Actually, after several emails and info from Glenn Ashmore, I found that
    Danfoss makes a shielded version of the controller with ferrite isolated
    leads that will eliminate the noise. Gordon West was full of bs in the
    article about the noise eminating from the digital thermostat. I
    disconnected it and put in a manual one, the noise was still there.
    krj
     
  13. You

    You Guest

    I suspect you will find that, Gordie West is fULL of BS, on a lot of
    things.......
     
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