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  • radioman712000
    hi all i live in se london and trying to to monitor AIS but dont seem to be able to. I can hear london vts, coastguard and other vhf marine signal but not
    Message 1 of 8 , Mar 1, 2008
      hi all i live in se london and trying to to monitor AIS but dont seem
      to be able to. I can hear london vts, coastguard and other vhf marine
      signal but not AIS. Am i too far off to receive AIS signal? am using
      aor 3000a plus radio with a discone antenna on top of my roof. i dont
      have a discriminator at the moment but using an audio cable to the line
      input of computer.the s/w am using is the shipplotter. Can anyone help?
    • harrybriscoe
      ... Hi, If it is ShipPlotter you are using, then you have no need of the AISMON software as ShipPlotter is able to decode the messages from the audio signal.
      Message 2 of 8 , Mar 1, 2008
        --- In aismon@yahoogroups.com, "radioman712000" <radioman712000@...>
        wrote:
        >
        > hi all i live in se london and trying to to monitor AIS but dont seem
        > to be able to. I can hear london vts, coastguard and other vhf marine
        > signal but not AIS. Am i too far off to receive AIS signal? am using
        > aor 3000a plus radio with a discone antenna on top of my roof. i dont
        > have a discriminator at the moment but using an audio cable to the line
        > input of computer.the s/w am using is the shipplotter. Can anyone help?
        >

        Hi,
        If it is ShipPlotter you are using, then you have no need of the
        AISMON software as ShipPlotter is able to decode the messages from the
        audio signal. AISMON is used where there is a requirement to provide
        standard AIS NMEA sentences (eg !AIVDM...) which can be transferred
        over any communications medium, to be fed into other navigational or
        charting software that cannot handle audio signals. ShipPlotter can
        also do this but it costs more money. There are likely to be members
        of the ShipPlotter forum that are using the same receiver as you and
        could directly advise as of the suitability of that setup and whether
        any hardware modifications are necessary.
        If you are in SE London, then AIS reception from the pleasure craft
        operating around Blackfriars should be strong. My experience is that
        Blackheath (near the 24h tea hut) is a good site for AIS reception but
        Shooter's Hill just two miles away is poor, most likely because of
        receiver de-sensing due to a number of high-power transmitters at that
        site. I am south of Dartford and my path to Central London is blocked
        by the high ground at Shooters Hill but can receive as far as Charlton
        with only an aerial in a low tree. If I take a portable system to
        Upper Belvedere, just a few miles away, I can receive the whole of
        London and normally the Star & Garter base station in Richmond Park.
        Hope this helps,
        Harry.
      • radioman712000
        Hi Harry, thanks for your reply. Yes am using shopplotter software.I live in bromley just after catford. I seem to be able to hear the signal but cant decode
        Message 3 of 8 , Mar 3, 2008
          Hi Harry, thanks for your reply. Yes am using shopplotter software.I
          live in bromley just after catford. I seem to be able to hear the
          signal but cant decode nothing yet. Have contact AOR for the
          discriminator cable and will cost me about 15 quid including postage.
          I cant wait to see how shipplotter works. By the way, what the
          difference b/w shipplotter and AISMON ? sorry to ask and which one is
          better. When i get my cable and connect it up will let you know how
          things are going on from bromley in kent.Roland

          --- In aismon@yahoogroups.com, "harrybriscoe" <harry@...> wrote:
          >
          > --- In aismon@yahoogroups.com, "radioman712000" <radioman712000@>
          > wrote:
          > >
          > > hi all i live in se london and trying to to monitor AIS but dont
          seem
          > > to be able to. I can hear london vts, coastguard and other vhf
          marine
          > > signal but not AIS. Am i too far off to receive AIS signal? am
          using
          > > aor 3000a plus radio with a discone antenna on top of my roof. i
          dont
          > > have a discriminator at the moment but using an audio cable to
          the line
          > > input of computer.the s/w am using is the shipplotter. Can anyone
          help?
          > >
          >
          > Hi,
          > If it is ShipPlotter you are using, then you have no need of the
          > AISMON software as ShipPlotter is able to decode the messages from
          the
          > audio signal. AISMON is used where there is a requirement to provide
          > standard AIS NMEA sentences (eg !AIVDM...) which can be transferred
          > over any communications medium, to be fed into other navigational or
          > charting software that cannot handle audio signals. ShipPlotter can
          > also do this but it costs more money. There are likely to be members
          > of the ShipPlotter forum that are using the same receiver as you and
          > could directly advise as of the suitability of that setup and
          whether
          > any hardware modifications are necessary.
          > If you are in SE London, then AIS reception from the pleasure craft
          > operating around Blackfriars should be strong. My experience is that
          > Blackheath (near the 24h tea hut) is a good site for AIS reception
          but
          > Shooter's Hill just two miles away is poor, most likely because of
          > receiver de-sensing due to a number of high-power transmitters at
          that
          > site. I am south of Dartford and my path to Central London is
          blocked
          > by the high ground at Shooters Hill but can receive as far as
          Charlton
          > with only an aerial in a low tree. If I take a portable system to
          > Upper Belvedere, just a few miles away, I can receive the whole of
          > London and normally the Star & Garter base station in Richmond Park.
          > Hope this helps,
          > Harry.
          >
        • harrybriscoe
          Hi Roland, You cannot say which program is better, ShipPlotter or AISMON, since they are not equivalent in terms of what they do. Until AISMON was developed,
          Message 4 of 8 , Mar 4, 2008
            Hi Roland,
            You cannot say which program is better, ShipPlotter or AISMON, since
            they are not equivalent in terms of what they do. Until AISMON was
            developed, the only way to decode AUDIO AIS signals was via
            ShipPlotter, which is a paid for program. ShipPlotter is not designed
            for use in a navigational environment but suppose that you wished to
            use one of the top-grade professional navigational programs with an
            AUDIO AIS signal, like that which is output from a VHF receiver like
            yours. In that case, you would need to use AISMON to sample the AUDIO
            AIS signal and convert it into a meaningful digital form. The
            meaningful digital form used by charting programs, like ShipPlotter
            and others, is NMEA !AIVDM.... sentences. This is a standard and
            messages in this format can be sent to any computer in the world via
            the Internet. These are not analogue audio signals but complex,
            combinations of computer-generated letters and numbers which convey
            the information in a digital format.

            If you are still not clear on this, write back and I shall try to be a
            bit more specific on any areas that you are not sure about.

            Regards,
            Harry.






            --- In aismon@yahoogroups.com, "radioman712000" <radioman712000@...>
            wrote:
            >
            > Hi Harry, thanks for your reply. Yes am using shopplotter software.I
            > live in bromley just after catford. I seem to be able to hear the
            > signal but cant decode nothing yet. Have contact AOR for the
            > discriminator cable and will cost me about 15 quid including postage.
            > I cant wait to see how shipplotter works. By the way, what the
            > difference b/w shipplotter and AISMON ? sorry to ask and which one is
            > better. When i get my cable and connect it up will let you know how
            > things are going on from bromley in kent.Roland
            >
            > --- In aismon@yahoogroups.com, "harrybriscoe" <harry@> wrote:
            > >
            > > --- In aismon@yahoogroups.com, "radioman712000" <radioman712000@>
            > > wrote:
            > > >
            > > > hi all i live in se london and trying to to monitor AIS but dont
            > seem
            > > > to be able to. I can hear london vts, coastguard and other vhf
            > marine
            > > > signal but not AIS. Am i too far off to receive AIS signal? am
            > using
            > > > aor 3000a plus radio with a discone antenna on top of my roof. i
            > dont
            > > > have a discriminator at the moment but using an audio cable to
            > the line
            > > > input of computer.the s/w am using is the shipplotter. Can anyone
            > help?
            > > >
            > >
            > > Hi,
            > > If it is ShipPlotter you are using, then you have no need of the
            > > AISMON software as ShipPlotter is able to decode the messages from
            > the
            > > audio signal. AISMON is used where there is a requirement to provide
            > > standard AIS NMEA sentences (eg !AIVDM...) which can be transferred
            > > over any communications medium, to be fed into other navigational or
            > > charting software that cannot handle audio signals. ShipPlotter can
            > > also do this but it costs more money. There are likely to be members
            > > of the ShipPlotter forum that are using the same receiver as you and
            > > could directly advise as of the suitability of that setup and
            > whether
            > > any hardware modifications are necessary.
            > > If you are in SE London, then AIS reception from the pleasure craft
            > > operating around Blackfriars should be strong. My experience is that
            > > Blackheath (near the 24h tea hut) is a good site for AIS reception
            > but
            > > Shooter's Hill just two miles away is poor, most likely because of
            > > receiver de-sensing due to a number of high-power transmitters at
            > that
            > > site. I am south of Dartford and my path to Central London is
            > blocked
            > > by the high ground at Shooters Hill but can receive as far as
            > Charlton
            > > with only an aerial in a low tree. If I take a portable system to
            > > Upper Belvedere, just a few miles away, I can receive the whole of
            > > London and normally the Star & Garter base station in Richmond Park.
            > > Hope this helps,
            > > Harry.
            > >
            >
          • Tomek
            Hi, (this is my first post here) ... Well, actually you can easily compare them in their common part - decoding live audio signal. I have just used Shipplotter
            Message 5 of 8 , Apr 7 12:32 AM
              Hi,

              (this is my first post here)

              > You cannot say which program is better, ShipPlotter or AISMON, since
              > they are not equivalent in terms of what they do.

              Well, actually you can easily compare them in their common part - decoding live audio signal.
              I have just used Shipplotter and AisMon simultaniously on the same computer. It seems for me that AisMon is by far better than SP for decoding - it decoded much more messages properly.

              However, I have to perform more tests.

              Tomek
            • Dave Houy
              Tomek, ... That is my experience as well. Your unbiased AISMon author;-) Dave
              Message 6 of 8 , Apr 8 6:32 PM
                Tomek,

                > I have just used Shipplotter and AisMon simultaniously on the same
                > computer. It seems for me that AisMon is by far better than SP for
                > decoding - it decoded much more messages properly.

                That is my experience as well.

                Your unbiased AISMon author;-)

                Dave
              • JensNL
                ... AIS comments For the receiver part I agree they are about the same. But you will find out that the packets they receive aren t 100% the same. First if you
                Message 7 of 8 , Apr 9 8:40 AM
                  --- In aismon@yahoogroups.com, "Dave Houy" <davehouy@...> wrote:
                  >
                  > Tomek,
                  >
                  > > I have just used Shipplotter and AisMon simultaniously on the same
                  > > computer. It seems for me that AisMon is by far better than SP for
                  > > decoding - it decoded much more messages properly.
                  >
                  > That is my experience as well.
                  >
                  > Your unbiased AISMon author;-)
                  >
                  > Dave
                  >
                  AIS comments

                  For the receiver part I agree they are about the same. But you will
                  find out that the packets they receive aren't 100% the same.

                  First if you really want to compare the two receivers you should
                  record a .wav file and let them decode that.
                  This way you can compare on 100% same data and you can repeat them.
                  Try to play with the gain in the file and you will see that different
                  packet come thru. I use GOLDWAVE I think that there is a free demo,
                  to record the file.

                  I have played with my own receiver and compared with the other two.
                  And if I use the .wav file that come with AISMON as data input I get
                  a total of 110 packets (packet type 1 & 3). And AISMON gets only 94.
                  And Shipplotter gets 95 as I remember. (I only had a demo so I can't
                  check it anymore)
                  I have tried just to filter the file, and move the offset. That way I
                  can get AISMON to find 105 packets. (The AVG routine in AISMON is
                  bad).
                  The offsets you want to remove is the one that come because of
                  different TX freq and the RX freq, there are often more than 1000 Hz
                  in differences, the other is because the soundcard is AC coupled so
                  the first part of a packet can start a way from the center level, if
                  the noise before the packet is strong.

                  I have decoded 113 different type (1 & 3) packets in the file but not
                  at the same time.
                  In the file I have found 1 base station type 4 packet coming from San
                  Diego about 100 miles away.

                  Remember that the way you hook up to the radio will have influence.
                  To small a CAP to GND kill the high freq (and change the phase). To
                  small will let too much 900KHz thru.

                  And the soundcard in your PC will have some influence as well. My
                  laptop is fine but I have an old desktop where there is a consistent
                  DC offset.

                  Jens
                • Tomek
                  ... The packets I compared were really the same since I used both programs at the same time. I agree that for a real comparison I should do more tests. ... For
                  Message 8 of 8 , Apr 16 4:53 AM
                    > First if you really want to compare the two receivers you should
                    > record a .wav file and let them decode that.
                    > This way you can compare on 100% same data and you can repeat them.
                    > Try to play with the gain in the file and you will see that different
                    > packet come thru. I use GOLDWAVE I think that there is a free demo,
                    > to record the file.

                    The packets I compared were really the same since I used both programs at the same time. I agree that for a real comparison I should do more tests.


                    > I have tried just to filter the file, and move the offset. That way I
                    > can get AISMON to find 105 packets. (The AVG routine in AISMON is
                    > bad).
                    > The offsets you want to remove is the one that come because of
                    > different TX freq and the RX freq, there are often more than 1000 Hz
                    > in differences, the other is because the soundcard is AC coupled so
                    > the first part of a packet can start a way from the center level, if
                    > the noise before the packet is strong.
                    For now, I have anyway a DC offset from my receiver on the order of 1.5 V. I'll remove it when I install the optocoupler between the radio and the receiver (I can adjust levels there) and I'll check if it helps.


                    > And the soundcard in your PC will have some influence as well. My
                    > laptop is fine but I have an old desktop where there is a consistent
                    > DC offset.
                    Yes, of course. But again - I used the same card for both programs. With the original laptop card I get only few hits, but the external USB SB card works fine. Probably the reason is that I use microphone input on a built-in card since the line-in is damaged and part of the spectrum is removed or distorted.

                    Tomek
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