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ICOM-M802 SSB

Discussion in 'Boat Electronics' started by Wet-n-Wild Bill, Apr 16, 2006.

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  1. I'm looking at SSB for my boat the ICOM-M802 has two RF conectors one to
    the Autotuner and the other for DSC Receive.

    If i opt to only use one antenna for thr Autotuner AT-140. Will i be able
    to use the DSC function of my radio? if so with what linitations?

    Bill
     
  2. hmmm wrong track I guess.....

    802 is an HF only device. The reason for the two RF connectors is because
    it's a class E DSC where you have to be able to receive DSC sentences
    *while* transmitting. Therefore it's has to have two antenna's.

    Remeber that even if we "spare-time-sailors" most often use VHF ch 70 for
    DSC, it's quite possible to run DSC on HF.

    /Bjarke
     
  3. Larry

    Larry Guest

    Nope. M802 requires one transmitting antenna through the autotuner and
    another receiving antenna for its separately-scanning DSC receiver. Ours
    on Lionheart is hooked up to the handrail bolt through the toerail. It was
    cheap and dirty as there's no room for another antenna, like a whip, that
    wouldn't be in the way of sailing it. I was going to change it, but it
    works just fine, what little actual HF DSC traffic is ever transmitted for
    it to receive.

    If you don't hook up the 2nd receive antenna, you won't have HF DSC receive
    scanner capability.

    DO NOT TRY TO PUT A COAX T INTO THE TRANSMIT LINE AND BLOW THE HELL OUT OF
    IT! I've seen two stupids, already, who did. It isn't pretty at 150 watts
    into the DSC receiver...
     
  4. Larry

    Larry Guest

    Sue him when you blow the hell out of it. These diplexers are for using
    two radios on WIDELY SPACED-IN-FREQUENCY DIFFERENT BANDS! THEY DO NOT
    DIPLEX WHEN BOTH RECEIVERS ARE ON THE SAME HF BANDS!

    This nonsense will blow the DSC receiver's front end....I guarantee it.

    DO NOT HOOK BOTH COAX CONNECTORS TOGETHER THROUGH ANYTHING!!

    Geez....
     
  5. You

    You Guest


    that could solve Purple_stars delema, but wouldn't solve the OP's
    original problem, or answer his question......

    The answer to the OP's question, is NO, you need the second antenna
    for DSC to function.....
     
  6. Larry

    Larry Guest

    If we are helping the "average boater", who is not an electronics person,
    any response to this thread about diplexers may lead him astray to putting
    a diplexer in his antenna line, as this thread had nothing, whatsoever, to
    do with VHF or AM/FM radio or diplexers.

    I'd just hate to see him try a diplexer to such a nice radio as the M802,
    in spite of the M802's shortcomings of the wide open cabinet with the
    internal cooling fan sucking sea air into the circuits, a really stupid
    design with its chinzy cable connectors, to boot.

    He was looking for "the easy way out", some method of connecting those two
    tempting connectors together to one cable....a path YOU were providing him
    with I pray he ignores...

    I don't even want him to put up a receiving antenna anywhere near the
    transmitter's antenna for fear of taking out the DSC front end, which is
    broad tuned for the whole HF band.
     
  7. Thanks guy for the info! Since the M802 is HF along with the DSC. What coud
    i do for a receiving antenna?

    My boat which is all aluminum makes a great ground plane. On the Xmit/Rec
    side i'm planning on a 23' whip. As for the DSC REC antenna, can i use a
    shorter antenna, what options do i have to run a long wire, can i lay it in
    an insulated surface in a zigzag pattern. Or must it be pulled straight from
    the balun?

    Bill
     
  8. ted

    ted Guest

    agreed
     
  9. Larry

    Larry Guest

    You could use another 23' whip away from the transmitter's whip. The
    receive antenna is not tuned. The 23' whip is naturally resonant around 10
    Mhz, so that would be great for the whole HF band, better around 8-12 where
    most of the receiving is done, anyway. Just ground the shield of the coax
    to the hull and the center conductor to the whip, isolated from the hull.
     
  10. Steve Thomas

    Steve Thomas Guest

    If one didn't care about receiving DSC during transmit, wouldn't it be
    possible to use an antenna relay, or a manual coaxial switch? I have never
    seen the latter, but I am sure they must exist. There is little enough room
    for hf antennas on a sailboat, but I really like your hand rail solution for
    GRP boats.
     
  11. Don't mess around with switches. To much risc. Check if it can be confugured
    for a lower rate DSC (class D) where send/receive takes place on the same
    (primary) antenna.

    Bjarke
     
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