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Thread: Stupid question about DSC connecting to GPS antenna

  1. #1
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    Default Stupid question about DSC connecting to GPS antenna

    I want to get a black box VHF. I bought a Raymarine Dragonfly 7 chartplotter and darn it- the thing doesn't have an output to connect to a VHF with DSC. (So many acronyms!). Can I just buy an antenna like this one https://www.thegpsstore.com/Standard...nna-P5247.aspx and connect it directly to the VHf, or do I need a chartplotter to interpret the signal and route to the VHF? The VHF I want to get is the Icom M400bb.

    Perhaps a dumb question, but at least I am smart enough to ask first. :-)

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    Default Re: Stupid question about DSC connecting to GPS antenna

    The Dragonfly series is," standalone," not, " networkable," as far as I know. ( Do check with the maker).

    Yes, you can simply purchase a GPS antenna like you show and connect it to the radio.( Some say it's better to have dedicated signal for AIS anyway)

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Thanks, Kevin. I wanted to be sure before I purchased one. Yes, the Dragonfly is stand-alone and has no output, which I wish I had found out before buying it. If this works, I like the idea of a separate antenna for the VHF as a backup to the chartplotter anyway.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Malcolm Schweizer View Post
    I like the idea of a separate antenna for the VHF as a backup to the chartplotter anyway.
    They are a different type of antenna so you would want separates anyhow.

  5. #5
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    Default

    Quote Originally Posted by Favorite View Post
    They are a different type of antenna so you would want separates anyhow.


    There's no difference between GPS antenna suppling data to a plotter or to a VHF. In many cases, a splitter is used so that both devices can use the same GPS antenna.

    Kevin


    Sent from my iPhone using Tapatalk Pro
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Breakaway View Post
    There's no difference between GPS antenna suppling data to a plotter or to a VHF. In many cases, a splitter is used so that both devices can use the same GPS antenna.
    You best not talk like that to an antenna fanatic ! They will lecture you til your eyes glaze over.

    Satellites are way high in the sky, vhf is line of sight at Earth level. You (theoretically) want totally different antennas for those different tasks.

    I do want to build a quadri-helical antenna for the vhf some day, because it is polarized in a sphere rather than vertically or horizontally. That'd be even better on a sailboat, because when your antenna is tilted in relation to the horizon, your antenna becomes less effective in relation to other transceivers which are either vertically or horizontally polarized.

    But since I can't even hear the damn vhf unless I turn the engine off, that project is going on a back burner

    (I believe the high-quality gps antennas are a cloverleaf-shaped design which works best with a high-altitude source like a satellite.)

    Go do a little antenna research, it's a trip. I think there's a whole buncha room to make better antennae for boats.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Is there a mix up of terms maybe?
    My AIS works off my VHF aerial and I use a splitter to manage the double up. Rigged as high as possible for the benefit of both. But my GPS antenna is a very different beast entirely. Disk like and faces directly upwards, can be rigged anywhere with a reasonable view of the sky.
    Philip K. Dick 'Reality is that which, when you stop believing in it, doesn't go away'.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    You best not talk like that to an antenna fanatic ! They will lecture you til your eyes glaze over.

    Satellites are way high in the sky, vhf is line of sight at Earth level. You (theoretically) want totally different antennas for those different tasks.

    I do want to build a quadri-helical antenna for the vhf some day, because it is polarized in a sphere rather than vertically or horizontally. That'd be even better on a sailboat, because when your antenna is tilted in relation to the horizon, your antenna becomes less effective in relation to other transceivers which are either vertically or horizontally polarized.

    But since I can't even hear the damn vhf unless I turn the engine off, that project is going on a back burner

    (I believe the high-quality gps antennas are a cloverleaf-shaped design which works best with a high-altitude source like a satellite.)

    Go do a little antenna research, it's a trip. I think there's a whole buncha room to make better antennae for boats.

    DSC--digital selective calling--is a radio feature that utiiizes GPS data to provide position information. DSC is the topic of this thread.


    Is there a mix up of terms maybe?
    My AIS works off my VHF aerial and I use a splitter to manage the double up. Rigged as high as possible for the benefit of both. But my GPS antenna is a very different beast entirely. Disk like and faces directly upwards, can be rigged anywhere with a reasonable view of the sky.
    Apparently. DSC is not AIS and it is not VHF.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Breakaway View Post
    Apparently. DSC is not AIS and it is not VHF.

    Kevin
    Can come out of the VHF radio so VHF antenna must transmit it......
    https://en.wikipedia.org/wiki/Digital_selective_calling
    Philip K. Dick 'Reality is that which, when you stop believing in it, doesn't go away'.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Can come out of the VHF radio so VHF antenna must transmit it......
    Yes. But only another receiver with a GPS and DSC processor can utilize the position data. A non-DSC set will not receive the emergency message, which is activated with one touch of a button.

    DSC works on HF, and other bands, as well. It is not a " VHF feature," but a feature that radios so equipped can utilize.

    Besides safety, DSC allows one to call another DSC set direct--without interference from, or being heard by, other radios. This can prove convenient and provides privacy.

    Finally, since the vessel's position appear on the VHF display ( along with the channel number and power setting as normal), the boater, in effect, gets a backup position display.

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  11. #11
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    Default Re: Stupid question about DSC connecting to GPS antenna

    Right, so you get your Long and Lat on your radio. handy.
    Must be picking it up with some kind of internal GPS antenna, I doubt its the VHF aerial doing it.
    Philip K. Dick 'Reality is that which, when you stop believing in it, doesn't go away'.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Right, so you get your Long and Lat on your radio. handy.
    More importantly, you touch one button and a distress call with your boats name, description and location gets sent out to every DSC radio in range. In an emergency, this frees the skipper up sooner than were she needed to " manually" make a distress call.

    Must be picking it up with some kind of internal GPS antenna, I doubt its the VHF aerial doing it.
    Correct. The VHF aerial is not. Some sets have a built in GPS; others require input from an external antenna. Depending upon the installed location, an external GPS antenna may be required even if the radio has an internal GPS( The GPS needs a view of the sky for best performance).

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Breakaway View Post
    Correct. The VHF aerial is not. Some sets have a built in GPS; others require input from an external antenna. Depending upon the installed location, an external GPS antenna may be required even if the radio has an internal GPS( The GPS needs a view of the sky for best performance).
    Not to be pedantic but ... DSC is a VHF function. It uses a vhf antenna.

    GPS aka chartplotters use satellites and a gps antenna.

    op's statement was

    "I like the idea of a separate antenna for the VHF as a backup to the chartplotter anyway"

    Doesn't work that way. The chartplotter is gps and uses a gps antenna. DSC is a function of the vhf and uses the vhf's antenna. They are quite different. A vhf antenna is not going to be a backup for a gps.
    Last edited by Favorite; 01-07-2019 at 01:33 AM.

  14. #14
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    Default Re: Stupid question about DSC connecting to GPS antenna

    Doesn't work that way. The chartplotter is gps and uses a gps antenna. DSC is a function of the vhf and uses the vhf's antenna. They are quite different. A vhf antenna is not going to be a backup for a gps.
    OP, Having discovered his new GPS had no way to output its signal, asked about a separate GPS antenna.
    His intent was to make DSC work which requires a GPS antenna.

    Here is what he asked, for reference:

    I want to get a black box VHF. I bought a Raymarine Dragonfly 7 chartplotter and darn it- the thing doesn't have an output to connect to a VHF with DSC. (So many acronyms!). Can I just buy an antenna like this one https://www.thegpsstore.com/Standard...nna-P5247.aspx and connect it directly to the VHf, or do I need a chartplotter to interpret the signal and route to the VHF?

    Kevin


    EDIT: the thread title is: "
    Stupid question about DSC connecting to GPS antenna

    At no time was the purchase, installation or use of a VHF antenna brought up for discussion ( except by you)

    Kevin

    Kevin


    .
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Breakaway View Post
    At no time was the purchase, installation or use of a VHF antenna brought up for discussion ( except by you)
    Actually it was and I quoted that but anyway ... there's some misconceptions here.

    DSC is a vhf function. Originally it was just a one-button Mayday. There were no location coordinates involved.

    Then gps became cheap and effective so they funnelled the output of a chart plotter into the vhf to expand the capabilities of dsc. If you are talking dsc then you are talking vhf (unless you are commercial and also broadcast on other bands - which still would be using a radio antenna, not a gps antenna.)

    Now gps is so cheap they can put one in the same box as the vhf to output coordinates for dsc to the vhf radio. That gps can use its own internal antenna or an external one - but it is not used for the vhf function called dsc.

    The statement was (again)

    I like the idea of a separate antenna for the VHF as a backup to the chartplotter anyway.
    That won't work. If what he meant was "I like the idea of a separate gps antenna for the gps built in the same box as my vhf" then that's an entirely different matter. Although he already has that, they all have an internal one.

    People should say what they mean. It causes less confusion.

  16. #16
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    Default Re: Stupid question about DSC connecting to GPS antenna

    Actually it was and I quoted that but anywa
    Please indicate where a request for info about a VHF antenna was posted..or re-post it, please.

    Although he already has that, they all have an internal one
    No. They don't. Again, as stated in the OP, he is purchasing a " black box" VHF, which requires a separate GPS signal input through an NMEA interface. ( ICOM M400)

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Favorite View Post
    Not to be pedantic but ... DSC is a VHF function. It uses a vhf antenna.

    GPS aka chartplotters use satellites and a gps antenna.

    op's statement was

    "I like the idea of a separate antenna for the VHF as a backup to the chartplotter anyway"

    Doesn't work that way. The chartplotter is gps and uses a gps antenna. DSC is a function of the vhf and uses the vhf's antenna. They are quite different. A vhf antenna is not going to be a backup for a gps.

    Good day all- thanks for the replies. To clarify on the above- It is a VHF radio, but it also has a connection for a GPS input, which typically comes from the chartplotter. The VHF is through a VHF antenna, and the GPS through the chartplotter. It takes the GPS and as stated before, it applies the data to the radio- showing it on the screen, and also transmitting it when you make a call or distress.

    the problem is my GPS does not have an output to connect to the DSC enabled VHF. I want to hook a GPS antenna directly to the DSC enabled VHF. Anyway, I went ahead and bought an antenna and am going to make it work- found a video on YouTube where a guy did it with a similar antenna. If it's on YouTube, it must work, ay? (*haha)

    I am actually still building the boat, but wanted to get all the parts planned out so that during the build I can do the install. Sadly, it may be a while before I can reply to you guys how well this worked.

  18. #18
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    Default Re: Stupid question about DSC connecting to GPS antenna

    Quote Originally Posted by Breakaway View Post
    Please indicate where a request for info about a VHF antenna was posted..or re-post it, please.



    No. They don't. Again, as stated in the OP, he is purchasing a " black box" VHF, which requires a separate GPS signal input through an NMEA interface. ( ICOM M400)

    Kevin
    Correct- I have now bought it- an icom M400bb black box radio with a connection for a GPS antenna. They do make a model with built-in antenna, but it is not a black box type, and because it's a small boat, I wanted the black box type where the receiver is "hidden away" and the mic has all the controls. It seems you can make it work by connecting the GPS antenna directly to the unit, as long as you can figure out which wires are which. We shall see. :-)

  19. #19
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    Default Re: Stupid question about DSC connecting to GPS antenna

    Patience and persistence will get it done. Good luck!

    Kevin
    There are two kinds of boaters: those who have run aground, and those who lie about it.

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