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  1. #1
    Join Date
    May 2017
    Posts
    3

    Default Identifying unknown antenna

    Hi All,

    I picked up a box of various electronics off ebay recently, primarily for the old chart plotter and GPS that were included to use as an alternative to a raspberrypi / openplotter system I've been working on.

    There were quite a few other bits in the box, most of which I've identified, but there is one piece that's puzzling me, an antenna. There is quite a bit of circuitry on it, and the PCB is labelled "sealink antenna". Having searched on google, I can find almost no useful matches for any of the markings on the PCB.

    The majority of the rest of the equipment in the box was 'navman' brand, there are no markings to suggest this component is though.

    See attached photos below... does anyone know what this actually is?






  2. #2
    Join Date
    May 2007
    Posts
    32,704

    Default Re: Identifying unknown antenna

    That looks like a receiver circuit. All those square silver cans are tuning coils for filters.
    Could be anything from Navtex up to UHF.

  3. #3
    Join Date
    May 2017
    Posts
    3

    Default Re: Identifying unknown antenna

    Ah-ha, that helped.... so one of the other components in the bottom of the box was S15-N Silva, which appears to take Navtex in and outputs RS232 serial.

    For some reason I had completely failed to put two and two together with the antenna, as the connectors are cut, and I suppose I wasn't expecting quite so much circuitry on the antenna (based on no experience...).

    Silva S15-N:


  4. #4
    Join Date
    Jan 2011
    Location
    No fixed abode
    Posts
    2,577

    Default Re: Identifying unknown antenna

    Be very carefull! I think that may be the circituity for a light sabre! May the Force be with you.
    Last edited by Hadenough; 31-05-17 at 21:31.

  5. #5
    Join Date
    Mar 2009
    Location
    UK, Hamble
    Posts
    437

  6. #6
    Join Date
    May 2017
    Posts
    3

    Default Re: Identifying unknown antenna

    Bit of a late response, but as a quick update:

    I got the active antenna hooked into the Silva serial adapter and hooked into a raspberry pi via USB Serial.

    With the baud rate settings from the above link (thanks!) I successfully got back some test messages which are generated by the antenna (not the Silva labelled serial adapter):


    Welcome to the Silva S15-N.
    ZCZC AB34
    THIS IS A TEST MESSAGE FOR THE NAVTEX ANTENNA
    NNNN

    ZCZC AB35
    WAIT TO RECEIVE NAVTEX SIGNAL ON 518KHZ...
    NNNN


    I've had the antenna cabled tied sticking out from the balcony overnight, but unfortunately no Navtex messages received on the 518khz setting. That's in central London though... so not the ideal location, and I'm not sure whether it's reasonable to expect to receive them here.

    I'll leave it up a couple more days, then try it sometime in a more coastal location.

    Not a big loss if it doesn't work, but felt the need to at least try and get all the bits from the box off ebay up and running!

  7. #7
    Join Date
    Nov 2013
    Posts
    1,305

    Default Re: Identifying unknown antenna

    I may be wrong, but I'd try 490...

    More frequent transmissions from Niton which may be your best bet. But ultimately - on a house in London - you might be facing the wrong way/have another building blocking you!

  8. #8
    Join Date
    Jun 2018
    Posts
    1

    Default Re: Identifying unknown antenna

    Hi there,
    I have exactly the same antenna, but no rs232 box. Do you have schematics of the circuit inside S15-n box? Is it something like levels converter?
    Thanks!

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