Article: 51200 of rec.radio.amateur.digital.misc From: "Michael" Subject: Receiving VMS (Vessel Monitoring Signals) from Inmarsat-C Message-ID: Date: Tue, 14 Feb 2006 13:13:15 +0100 I have been playing around with receiving AIS (Automatic Identification System) signals. AIS is used on ships, it is used to send information about your position, etc via VHF to the surrounding ships. But know this started to get a bit boring. So know I wan to try to se if it is possibly to receive the VMS signals from Inmarsat-C. The VMS system is manly used on fishing vessels. On the ship there is a box with a gps and satellite tranciver. The position information is send each hour, to a land earth station, were it is distributed to the different authorities. The first thing is to receive the signals. But also to decrypt the data can be complicated. Any help or advices are welcome. Also if you have some good links to people ho have been dealing with projects like this, could be useful. Cheers Michael From LeadWinger Sun Feb 19 01:11:19 EST 2006 Article: 51201 of rec.radio.amateur.digital.misc From: Dick Newsgroups: rec.radio.amateur.digital.misc Subject: Re: APRS settings for long-distance train trip? Date: Tue, 14 Feb 2006 19:50:41 -0700 Organization: Posted via Supernews, http://www.supernews.com Message-ID: References: <1139283046.421074.162550@g14g2000cwa.googlegroups.com> <2t9gu1psfrmvvqrr2rsbh26hqd46q3k0eo@4ax.com> <6115v1pjcin1ejlb8ig8ieb44rcoe0plf5@4ax.com> X-Newsreader: Forte Agent 1.93/32.576 English (American) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Complaints-To: abuse@supernews.com Lines: 31 Path: news1.isis.unc.edu!arclight.uoregon.edu!canoe.uoregon.edu!newshub.sdsu.edu!newsfeed.news2me.com!newsfeed.icl.net!newsfeed.gamma.ru!Gamma.RU!sn-xt-sjc-02!sn-xt-sjc-06!sn-xt-sjc-01!sn-post-01!supernews.com!corp.supernews.com!not-for-mail Xref: news1.isis.unc.edu rec.radio.amateur.digital.misc:51201 On Wed, 15 Feb 2006 01:32:22 GMT, Tony VE6MVP wrote: >On Mon, 06 Feb 2006 22:03:01 -0700, Dick wrote: > >>t's OK in a city, but when you get out in the sticks you >>need POWER, and the TH-D7 isn't going to give it to you. Sometimes >>even my D700A with external gain antenna won't reach a gateway. I >>have stood in my front yard with my TH-D7, looking directly at the >>mountain where the repeater is located, and been unable to connect >>without moving around to different locations. Give it a try, but you >>may be disappointed. > >The problem in your particular place might be that the mountain top >digipeater is hearing so many systems from so many places that yours >just isn't making it through. Especially if it can see other mountain >top digipeaters. > >That said I would think Greg would be far better off if he could put >mag mount antenna on the top of the train. > >Tony That might be the case, but we are in a pretty remote area. There is no question though, that a power increase takes care of the problem. My experience with the D7 includes a lot of travel in the west (Arizona, Utah, Nevada) The ability to connect with a digipeater was few and far between with the D7. Going to the D700 makes all the difference. Dick Article: 51202 of rec.radio.amateur.digital.misc From: Bob Bob Subject: Re: Can't run TCP/IP through AX.25 using Linux References: <1138719759.587807.123920@g43g2000cwa.googlegroups.com> <1139782596.021967.153510@z14g2000cwz.googlegroups.com> <1140107910.463509.79490@g44g2000cwa.googlegroups.com> Message-ID: Date: Thu, 16 Feb 2006 14:17:31 -0600 That RS232/serial run is in my view way too long if you are running at 115K2, even when shielded. I would suspect that noise is being introduced into the circuit. RS232 isnt a balanced system like RS485 or XBaseT ethernet so you dont gain the benefits of common mode rejection. You may even have earth loops occurring in your computer/mains/ground setup that puts main noise onto the cable shield. The simple test is to reduce the DTE rate from the computer to the radio to the next step down to see if that helps. If the modems offer hardware compression you might lose your peak speed but gain a higher reliability. Generally speaking the slower the bit rate the longer the cable can be. The data rate problem is the same thing that gfilion was fighting on. I understand the Aerocomm fixes the TX/RX ratio at 50% to make PPP work and thus you get the low data rate. You may of course also be suffering >from radio interference. I remember the Cisco Aironet boxes use to keep stats as to their performance. If the Aerocomm boxes do that may be a place to check. One simple thing you can do if you think it is another transmitter is to change to horizontal polarisation in the hope that most other users will be on vertical. I have had a look around for Ethernet radios on 900MHz and they arent real cheap (like USD700/pair etc). The serial offerrings all seem to have the same rate limitations you have encountered and as yet I havent seen a USB connected one (to gain a higher rate than 115K2). They seem to be more for telemetry/SCADA use rather than a FDX internet link. My flippant suggestion to get another Aerocomm pair and connected them for full duplex operation might be cost viable for you. You'll need to play with the hardware a bit but I dont see any problems if you can tell the modems to stay in the right mode. I get the impression that this will then get you 57K6. I am seriously thinking of taking some of my works 2.4GHz RF modules for TX and RX and supplying my own QAM modulation scheme to them. The idea being to run maybe 1MB/sec via the USB port. I can do that as a radio amateur but will need to check whether I can use the ISM band in that manner. I can certainly tune it to the FCC spec but dont know if I have to go through a type approval process. A very long term project I am afraid. In that vein I am also looking for AX25/packet QAM I/Q modems that would do that part for me. Good luck! Cheers Bob Braath Waate wrote: > > Thanks Bob for all of your good suggestions. > Article: 51204 of rec.radio.amateur.digital.misc From: Bob Bob Subject: Re: Can't run TCP/IP through AX.25 using Linux References: <1138719759.587807.123920@g43g2000cwa.googlegroups.com> <1139782596.021967.153510@z14g2000cwz.googlegroups.com> <1140107910.463509.79490@g44g2000cwa.googlegroups.com> <1140137309.132302.86300@g14g2000cwa.googlegroups.com> Message-ID: <3a5hc3-88f.ln1@p400bob.personal.cox.net> Date: Fri, 17 Feb 2006 09:05:06 -0600 Hi Braath The kind of stats I am talking about is more the bit error rate one. ie what percentage of the radio packects are mangled or not getting through. It is common in a radio system to have some percentage of failure. I use to administer two non licensed links, one on 2.4Ghz and the other on 5.7. Towards the end of its useful life the 2.4GHz link had about 90% retries mainly from interferring sources. In that case we got much better reliability limiting it to the 1MB speed (as against 11). The newer less populated 5.7GHz link ran about 20% retries. The fullduplex radio pair configuration I suggested would use separate frequencies and maybe even antenna polarisation/space separation to reduce interference. ie two antennas at each end. Using a diplexor to allow two boxes on the one antenna is probably a bit cost wasteful. The idea is that at one end you force one box into transmit mode and the other to receive. You also have to specify a fixed channel instead of allowing automatic operation. The node names would also have to be paired. Connection to the computer is as you stated but some configuration of the handshaking lines (RTS, CTS, DTR etc) would also be needed. I expect that Connexlink would have already done this with their equipment so there may even be an application note on it available. It would of course be smart to run all lines back to the PC and do the patching there, in case you want to send commands to the unit itself and need both TX/RX lines available. Cheers Bob Braath Waate wrote: -- > I'm sorry I don't understand the radio pair suggestion; wouldn't the > pair of radios just interfere with each other? Is the idea to hook the > tx lead of the serial port to one radio and the rx lead to the other? > How would they hook to the antenna?