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Re: antenna

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  • Jon
    Hi, Just joined the group an I find this discussion regarding AIS antennas very informative. I guess it helps to have a bit of electronics background. I d love
    Message 1 of 12 , Dec 1, 2006
    • 0 Attachment
      Hi,

      Just joined the group an I find this discussion regarding AIS antennas
      very informative.

      I guess it helps to have a bit of electronics background. I'd love to
      be able to make an antenna but your decription of how to make one has
      me a bit at a lost and having more questions before I read the
      excellent idea and suggestion.

      1. What do you exactly mean by a piece of wire.?What kind of wire? A
      strip of copper gauged wire?

      2. What do you exactly mean by cutting it to a bit over 3/4 wave
      length. How long would that be after I know what is the best wire to get ?

      3. What about radials? Can you direct me to some pictures so I have an
      idea of what you mean?

      4.Sweep VSWR and trim a bit off the end. What does that mean to sweep
      VSWR?

      5.

      --- In aismon@yahoogroups.com, "John Christensen" <JCHere2@...> wrote:
      >
      > True, but check VSWR caused losses, you will probably find that they
      are a
      > fraction of a dB. This is similar to the loss caused by adding a
      couple of
      > feet to your coax. If you are that concerned about signal strength,
      change
      > to a lower loss coax or to ladder line. This will have a much greater
      > effect.
      >
      > Solution #2: Make your own antenna. The types we are talking about
      are just
      > a piece of wire. Cut it to a bit over 3/4 wave length, add some
      radials and
      > it will be much higher gain. Sweep VSWR and trim a bit off the end
      until the
      > VSWR is 1.0 at the frequency you want. You now have a free antenna
      that is
      > as good or better than what you can buy.
      >
      >
      >
      > "The man who would be fully employed should procure a ship or a
      woman, for
      > no two things produce more trouble." Platus 254-184 BC
      >
      >
      >
      >
      > ----Original Message Follows----
      > From: "Brian C. Lane" <bcl@...>
      > Reply-To: aismon@yahoogroups.com
      > To: aismon@yahoogroups.com
      > Subject: Re: [aismon] antenna
      > Date: Tue, 28 Nov 2006 05:34:38 -0800
      >
      > -----BEGIN PGP SIGNED MESSAGE-----
      > Hash: SHA1
      >
      > John Christensen wrote:
      > > Any marine VHF antenna will work fine. Just go to a boat parts
      store and
      > > select one you like.
      > > Even a used parts store should have one.
      > > Good luck.
      > >
      >
      > A Marine antenna will work, but not as well as an AIS antenna. Marine
      > antennas are usually cut for around 158MHz, AIS antennas should be cut
      > for 162MHz.
      >
      > Ham antennas (around 148MHz) are even worse.
      >
      > Morad makes a specific AIS antenna, and Arrow will custom make corner
      > reflectors if you are interested in directional antennas.
      >
      > Brian
      >
      > - --
      > - ---[Office 67.3F]--[Outside 24.2F]--[Server 82.6F]--[Coaster 67.8F]---
      > - ---[ SEA FISHER (369643000) @ 47 37.6000 -122 22.9240 ]---
      > Software, Linux, Microcontrollers http://www.brianlane.com
      > AIS Parser SDK http://www.aisparser.com
      > -----BEGIN PGP SIGNATURE-----
      > Version: GnuPG v1.4.2.2 (GNU/Linux)
      > Comment: Remember Lexington Green!
      >
      > iD8DBQFFbDruIftj/pcSws0RAsyFAKCIXIACcPTjReKdwqCfmjAv57CnowCeLxx9
      > 3ZFu7GpGaqWd3ckbQHrJ2WU=
      > =6/HR
      > -----END PGP SIGNATURE-----
      >
    • John Christensen
      Look up Ham Radio in the yellow pages/Google and get a book on making VHF antennas, there are several. It s not too difficult, but I don t have time to write a
      Message 2 of 12 , Dec 1, 2006
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        Look up Ham Radio in the yellow pages/Google and get a book on making VHF
        antennas, there are several. It's not too difficult, but I don't have time
        to write a book here. The books will include formulas, drawings etc. Any of
        them will answer all of your Q's.
        After that if you still have specific Q's, let me know.
        Good luck.



        "The man who would be fully employed should procure a ship or a woman, for
        no two things produce more trouble." Platus 254-184 BC




        ----Original Message Follows----
        From: "Jon" <it2getting@...>
        Reply-To: aismon@yahoogroups.com
        To: aismon@yahoogroups.com
        Subject: [aismon] Re: antenna
        Date: Sat, 02 Dec 2006 04:51:32 -0000

        Hi,

        Just joined the group an I find this discussion regarding AIS antennas
        very informative.

        I guess it helps to have a bit of electronics background. I'd love to
        be able to make an antenna but your decription of how to make one has
        me a bit at a lost and having more questions before I read the
        excellent idea and suggestion.

        1. What do you exactly mean by a piece of wire.?What kind of wire? A
        strip of copper gauged wire?

        2. What do you exactly mean by cutting it to a bit over 3/4 wave
        length. How long would that be after I know what is the best wire to get ?

        3. What about radials? Can you direct me to some pictures so I have an
        idea of what you mean?

        4.Sweep VSWR and trim a bit off the end. What does that mean to sweep
        VSWR?

        5.

        --- In aismon@yahoogroups.com, "John Christensen" <JCHere2@...> wrote:
        >
        > True, but check VSWR caused losses, you will probably find that they
        are a
        > fraction of a dB. This is similar to the loss caused by adding a
        couple of
        > feet to your coax. If you are that concerned about signal strength,
        change
        > to a lower loss coax or to ladder line. This will have a much greater
        > effect.
        >
        > Solution #2: Make your own antenna. The types we are talking about
        are just
        > a piece of wire. Cut it to a bit over 3/4 wave length, add some
        radials and
        > it will be much higher gain. Sweep VSWR and trim a bit off the end
        until the
        > VSWR is 1.0 at the frequency you want. You now have a free antenna
        that is
        > as good or better than what you can buy.
        >
        >
        >
        > "The man who would be fully employed should procure a ship or a
        woman, for
        > no two things produce more trouble." Platus 254-184 BC
        >
        >
        >
        >
        > ----Original Message Follows----
        > From: "Brian C. Lane" <bcl@...>
        > Reply-To: aismon@yahoogroups.com
        > To: aismon@yahoogroups.com
        > Subject: Re: [aismon] antenna
        > Date: Tue, 28 Nov 2006 05:34:38 -0800
        >
        > -----BEGIN PGP SIGNED MESSAGE-----
        > Hash: SHA1
        >
        > John Christensen wrote:
        > > Any marine VHF antenna will work fine. Just go to a boat parts
        store and
        > > select one you like.
        > > Even a used parts store should have one.
        > > Good luck.
        > >
        >
        > A Marine antenna will work, but not as well as an AIS antenna. Marine
        > antennas are usually cut for around 158MHz, AIS antennas should be cut
        > for 162MHz.
        >
        > Ham antennas (around 148MHz) are even worse.
        >
        > Morad makes a specific AIS antenna, and Arrow will custom make corner
        > reflectors if you are interested in directional antennas.
        >
        > Brian
        >
        > - --
        > - ---[Office 67.3F]--[Outside 24.2F]--[Server 82.6F]--[Coaster 67.8F]---
        > - ---[ SEA FISHER (369643000) @ 47 37.6000 -122 22.9240 ]---
        > Software, Linux, Microcontrollers http://www.brianlane.com
        > AIS Parser SDK http://www.aisparser.com
        > -----BEGIN PGP SIGNATURE-----
        > Version: GnuPG v1.4.2.2 (GNU/Linux)
        > Comment: Remember Lexington Green!
        >
        > iD8DBQFFbDruIftj/pcSws0RAsyFAKCIXIACcPTjReKdwqCfmjAv57CnowCeLxx9
        > 3ZFu7GpGaqWd3ckbQHrJ2WU=
        > =6/HR
        > -----END PGP SIGNATURE-----
        >
      • Jon
        Geez, I got to thinking. In your answer you didn t have time to write a book here. I wasn t asking you to write a book. With the time you spent in a reply you
        Message 3 of 12 , Dec 2, 2006
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          Geez,

          I got to thinking. In your answer you didn't have time to write a
          book here. I wasn't asking you to write a book. With the time you
          spent in a reply you could of just recommended a book in constructing
          VHF antennas with a piece of wire.

          IF you didn't have time to write a book then why even bother with
          such a smart alecky reply.

          I guess it was just to impress us with your Plato quotes.

          John Astad


          --- In aismon@yahoogroups.com, "John Christensen" <JCHere2@...> wrote:
          >
          > Look up Ham Radio in the yellow pages/Google and get a book on
          making VHF
          > antennas, there are several. It's not too difficult, but I don't
          have time
          > to write a book here. The books will include formulas, drawings etc.
          Any of
          > them will answer all of your Q's.
          > After that if you still have specific Q's, let me know.
          > Good luck.
          >
          >
          >
          > "The man who would be fully employed should procure a ship or a
          woman, for
          > no two things produce more trouble." Platus 254-184 BC
          >
          >
          >
          >
          > ----Original Message Follows----
          > From: "Jon" <it2getting@...>
          > Reply-To: aismon@yahoogroups.com
          > To: aismon@yahoogroups.com
          > Subject: [aismon] Re: antenna
          > Date: Sat, 02 Dec 2006 04:51:32 -0000
          >
          > Hi,
          >
          > Just joined the group an I find this discussion regarding AIS antennas
          > very informative.
          >
          > I guess it helps to have a bit of electronics background. I'd love to
          > be able to make an antenna but your decription of how to make one has
          > me a bit at a lost and having more questions before I read the
          > excellent idea and suggestion.
          >
          > 1. What do you exactly mean by a piece of wire.?What kind of wire? A
          > strip of copper gauged wire?
          >
          > 2. What do you exactly mean by cutting it to a bit over 3/4 wave
          > length. How long would that be after I know what is the best wire to
          get ?
          >
          > 3. What about radials? Can you direct me to some pictures so I have an
          > idea of what you mean?
          >
          > 4.Sweep VSWR and trim a bit off the end. What does that mean to sweep
          > VSWR?
          >
          > 5.
          >
          > --- In aismon@yahoogroups.com, "John Christensen" <JCHere2@> wrote:
          > >
          > > True, but check VSWR caused losses, you will probably find that they
          > are a
          > > fraction of a dB. This is similar to the loss caused by adding a
          > couple of
          > > feet to your coax. If you are that concerned about signal strength,
          > change
          > > to a lower loss coax or to ladder line. This will have a much greater
          > > effect.
          > >
          > > Solution #2: Make your own antenna. The types we are talking about
          > are just
          > > a piece of wire. Cut it to a bit over 3/4 wave length, add some
          > radials and
          > > it will be much higher gain. Sweep VSWR and trim a bit off the end
          > until the
          > > VSWR is 1.0 at the frequency you want. You now have a free antenna
          > that is
          > > as good or better than what you can buy.
          > >
          > >
          > >
          > > "The man who would be fully employed should procure a ship or a
          > woman, for
          > > no two things produce more trouble." Platus 254-184 BC
          > >
          > >
          > >
          > >
          > > ----Original Message Follows----
          > > From: "Brian C. Lane" <bcl@>
          > > Reply-To: aismon@yahoogroups.com
          > > To: aismon@yahoogroups.com
          > > Subject: Re: [aismon] antenna
          > > Date: Tue, 28 Nov 2006 05:34:38 -0800
          > >
          > > -----BEGIN PGP SIGNED MESSAGE-----
          > > Hash: SHA1
          > >
          > > John Christensen wrote:
          > > > Any marine VHF antenna will work fine. Just go to a boat parts
          > store and
          > > > select one you like.
          > > > Even a used parts store should have one.
          > > > Good luck.
          > > >
          > >
          > > A Marine antenna will work, but not as well as an AIS antenna. Marine
          > > antennas are usually cut for around 158MHz, AIS antennas should
          be cut
          > > for 162MHz.
          > >
          > > Ham antennas (around 148MHz) are even worse.
          > >
          > > Morad makes a specific AIS antenna, and Arrow will custom make corner
          > > reflectors if you are interested in directional antennas.
          > >
          > > Brian
          > >
          > > - --
          > > - ---[Office 67.3F]--[Outside 24.2F]--[Server 82.6F]--[Coaster
          67.8F]---
          > > - ---[ SEA FISHER (369643000) @ 47 37.6000 -122 22.9240
          ]---
          > > Software, Linux, Microcontrollers
          http://www.brianlane.com
          > > AIS Parser SDK
          http://www.aisparser.com
          > > -----BEGIN PGP SIGNATURE-----
          > > Version: GnuPG v1.4.2.2 (GNU/Linux)
          > > Comment: Remember Lexington Green!
          > >
          > > iD8DBQFFbDruIftj/pcSws0RAsyFAKCIXIACcPTjReKdwqCfmjAv57CnowCeLxx9
          > > 3ZFu7GpGaqWd3ckbQHrJ2WU=
          > > =6/HR
          > > -----END PGP SIGNATURE-----
          > >
          >
        • Brian C. Lane
          ... Hash: SHA1 ... The ARRL has more info than you wanted to know: http://www.arrl.org/catalog/?category=Antennas,+Transmission+Lines+%26+Propagation What you
          Message 4 of 12 , Dec 2, 2006
          • 0 Attachment
            -----BEGIN PGP SIGNED MESSAGE-----
            Hash: SHA1

            Jon wrote:
            > Geez,
            >
            > I got to thinking. In your answer you didn't have time to write a
            > book here. I wasn't asking you to write a book. With the time you
            > spent in a reply you could of just recommended a book in constructing
            > VHF antennas with a piece of wire.

            The ARRL has more info than you wanted to know:

            http://www.arrl.org/catalog/?category=Antennas,+Transmission+Lines+%26+Propagation

            What you want is a vertical antenna. There are designs for one type
            called a J-Pole that have good performance. Look for 2m ham radio
            antenna designs and modify them to be resonant at 162MHz -- there should
            be a formula for calculating the length of the antenna, just substitute
            162 for 146 or whatever they use.

            eHam.net has a long list of antenna projects, select antennas from their
            drop-down menu: http://www.eham.net/links/

            I would say that google is your friend, but these days it is becoming
            increasingly difficult to find useful pages with it.

            Brian

            - --
            - ---[Office 65.8F]--[Outside 32.8F]--[Server 82.5F]--[Coaster 66.2F]---
            - ---[ HYAK WSF (366773030) @ 47 35.2171 -122 26.1196 ]---
            Software, Linux, Microcontrollers http://www.brianlane.com
            AIS Parser SDK http://www.aisparser.com
            -----BEGIN PGP SIGNATURE-----
            Version: GnuPG v1.4.2.2 (GNU/Linux)
            Comment: Remember Lexington Green!

            iD8DBQFFcY/KIftj/pcSws0RAoY7AJ9Aeu2CpTg1o6s6wsaPTWFD1v5XTgCeIhXt
            KkJTq1neHic9BN7gSoBTuG4=
            =C+mp
            -----END PGP SIGNATURE-----
          • JensNL
            A good way to find out when the antenna is optimal is to optimize to the WX channels. they send all the time. ... a ... constructing ...
            Message 5 of 12 , Dec 3, 2006
            • 0 Attachment
              A good way to find out when the antenna is optimal is to optimize to
              the WX channels. they send all the time.
              --- In aismon@yahoogroups.com, "Brian C. Lane" <bcl@...> wrote:
              >
              > -----BEGIN PGP SIGNED MESSAGE-----
              > Hash: SHA1
              >
              > Jon wrote:
              > > Geez,
              > >
              > > I got to thinking. In your answer you didn't have time to write
              a
              > > book here. I wasn't asking you to write a book. With the time you
              > > spent in a reply you could of just recommended a book in
              constructing
              > > VHF antennas with a piece of wire.
              >
              > The ARRL has more info than you wanted to know:
              >
              > http://www.arrl.org/catalog/?
              category=Antennas,+Transmission+Lines+%26+Propagation
              >
              > What you want is a vertical antenna. There are designs for one type
              > called a J-Pole that have good performance. Look for 2m ham radio
              > antenna designs and modify them to be resonant at 162MHz -- there
              should
              > be a formula for calculating the length of the antenna, just
              substitute
              > 162 for 146 or whatever they use.
              >
              > eHam.net has a long list of antenna projects, select antennas from
              their
              > drop-down menu: http://www.eham.net/links/
              >
              > I would say that google is your friend, but these days it is
              becoming
              > increasingly difficult to find useful pages with it.
              >
              > Brian
              >
              > - --
              > - ---[Office 65.8F]--[Outside 32.8F]--[Server 82.5F]--[Coaster
              66.2F]---
              > - ---[ HYAK WSF (366773030) @ 47 35.2171 -122
              26.1196 ]---
              > Software, Linux, Microcontrollers
              http://www.brianlane.com
              > AIS Parser SDK
              http://www.aisparser.com
              > -----BEGIN PGP SIGNATURE-----
              > Version: GnuPG v1.4.2.2 (GNU/Linux)
              > Comment: Remember Lexington Green!
              >
              > iD8DBQFFcY/KIftj/pcSws0RAoY7AJ9Aeu2CpTg1o6s6wsaPTWFD1v5XTgCeIhXt
              > KkJTq1neHic9BN7gSoBTuG4=
              > =C+mp
              > -----END PGP SIGNATURE-----
              >
            • Craig
              I see that these questions were posted several weeks ago but I only saw it today and the questions and answers below are timeless so I thought I would jump in
              Message 6 of 12 , Dec 22, 2006
              • 0 Attachment
                I see that these questions were posted several weeks ago but I only
                saw it today and the questions and answers below are timeless so I
                thought I would jump in with my two cents.


                >
                >
                > ----Original Message Follows----
                > From: "Jon" <it2getting@...>
                > Reply-To: aismon@yahoogroups.com
                > To: aismon@yahoogroups.com
                > Subject: [aismon] Re: antenna
                > Date: Sat, 02 Dec 2006 04:51:32 -0000
                >
                > Hi,
                >
                > Just joined the group an I find this discussion regarding AIS
                antennas
                > very informative.
                >
                > I guess it helps to have a bit of electronics background. I'd love
                to
                > be able to make an antenna but your decription of how to make one
                has
                > me a bit at a lost and having more questions before I read the
                > excellent idea and suggestion.
                >
                > 1. What do you exactly mean by a piece of wire.?
                > What kind of wire? A strip of copper gauged wire?

                Antenna wire can be just about anything, a rusty coat hanger, a piece
                of speaker wire scavanged from your stereo system. It could also be
                a nail or a bolt or a steel rod. Empty soda cans also work well.
                Basically the word "wire" when talking about antennas means anything
                that conducts electricity. This includes copper, tin, aluminum, gold,
                silver and steel.

                Then only real strength requirement is for the "wire" to be strong
                enough so that your home made antenna will not crumble under its own
                weight.

                >
                > 2. What do you exactly mean by cutting it to a bit over 3/4 wave
                > length. How long would that be after I know what is the best wire
                to get ?

                In theory, a wavelength is the speed of light divided by the
                frequency of the radio signal. thus a 300 MHz signal has a wavelength
                of 1 meter. A 150 MHz signal has a wavelength of 2 meters.

                Since AIS is at a frequency of 162 MHz, its theoretical wavelength is
                just a little shorter than two meters.

                Radio waves in a wire slow down from the speed of light so the actual
                wavelength of a real antenna is a little bit shorter than its
                theoretical wavelength. It slows down even more if you put the wire
                antenna inside a fiberglass antenna as is done with a typical marine
                VHF antenna.


                >
                > 3. What about radials? Can you direct me to some pictures
                > so I have an idea of what you mean?

                Here are some links to photos of VHF groundplane antennas with
                radials that form a "ground plane":

                http://www.radio-
                electronics.com/info/antennas/quarter_wave_vert/radial_system.gif

                http://www.packetradio.com/images/bcc6mgp.jpg

                http://www.radiowavz.com/ANTENN~1/img080.gif





                >
                > 4.Sweep VSWR and trim a bit off the end. What does
                > that mean to sweep VSWR?

                VSWR means "Voltage Standing Wave Ratio" Its a measure of how much
                energy is being reflected back down the coax from your antenna into
                your radio. You can use VSWR information as you trim your antenna
                wires to see where it is tuned (peaked) at the exact frequency you
                want.


                >
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