Posted: 2/22/2009 5:42:15 PM EDT
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Data Connection... I am looking for some suggestions about a project that I am working on. I wrote a program that sends packets between two computers (mostly UDP, but some TCP). These computers are running XP Pro. It took a long time to get the bugs worked out of the program, but now it works great. Since I was mostly concerned with getting the program to work, I have been using WiFi as the networking connection. Now It is time for the next step. I need to have greater range than WiFi has the ability to give me. I am hoping for a range of between 5-10 miles. One of these computers is onboard a vehicle. I wrote a driver to send commands from its USB port. Those commands are interpereted by a custom circuit (I built it) that runs some moter controllers. This computer basically drives the vehicle. It also controlls an arm, a camera on servos, gps unit, laser rangefinder, headlights, and a host of other important things. The other computer basically acts a a "remote controll". Although many actions of the vehicle are autonamous, the operator has the ability to controll them from his interface as well. I need to have whatever connection I use show up as a regular "internet" network connection on the computers. My program will not run if it needs to send data by any other means. My Idea was to use radios to connect the computers by transmitting the sound from their voice modems (telephone wire plugged into radio's mirophone and speaker jack). This is problamatic because the computer expects to see a dial tone and telephone switch provided normally provided by the phone company. The video feed is currently transmitted on the 70cm band. I was planning to use this band for the data as well. Does anyone have a suggestion for how to set up this data transmition between the computers? Remember that no suggestion will be considered "too out there" as I have already needed to custom build all of the other circuits and programing to make the thing work in the first place. Thanks,  MAX K1GJ |
I thought about that.  There are two problems. First, It would only work where there is cell coverage. Second, I need two cards. That comes to almost $1,500.00 a year! I am sure that I could build something for less than the first year's cost for cell cards. I really just need some ideas for exactly what I should start building. Plus, there is always the satisfaction of doing the whole job yourself! MAX |
| Depending on terrain and what you are able to mount the antennas to 5 to 10 miles is easy with off the shelf gear and some decent antennas. I did a job awhile back for a local city that shot 7.7 miles with two WRT54g routers using ddwrt for the firmware and a couple of parabolic antennas to make the link strong. It works great and only was taken down due to some .gov equipment replacing the link and letting the muni piggyback on their secure data stream. |
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There are high powered 2.4ghz cards and even 900mhz cards. However, both of these solutions are only long range point to point links and will not work well when mobile.
You might look into ax.25. Its a ham radio data protocol. It has tremendous support under linux. I dont know about windows. But you could setup a linux system at each end networked with the windows system to act as a gateway. I've done all of this stuff at one point or another. -Foxxz |
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Linux is not a problem as all of the software is running in fully platform independent JAVA. If there are better solutions available under Linux I will need to check them out. I have only been running XP Pro so far because it is the OS I know best. There is no other reason for it at this point so if this project would be easier to complete using a different OS I'd be alright with changing that. Does ax.25 have the ability to transmit IP packets? If it does this would definitely be worth doing some reading up on. Any other ideas? MAX K1GJ |
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Motorola "Canopy" setup would/could get you what you want...but ......$$$$
Motorola Canopy I haven't looked...but maybe you can find something on eBay. Then there's something I've always wondered about.....packet/data tranmission via a digital HAM radio setup to a distant end radio/computer setup. |
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I do this sort of thing every day. BUT....working in limited bandwidth 25 KHz channels or narrowband 12.5 KHz channels.
What is your bandwidth requirement? If it's fairly low, Midland SD-171 (VHF) or SD-174 (UHF) data radios are a simple way to establish a point to point data link via straight RS232 data. Your biggest problem will be the tradeoff between range and throughput for a given power level. Large bandwidth and long range requires high power and high cost. Here, take a look at some possible answers: http://www.rfwiz.com/Maxon/Maxon_LegacyData.htm CJ |
| Digi makes off-the-shelf gear that will do what you want. http://www.digi.com/products/wireless/xpress.jsp |
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Quoted:
Linux is not a problem as all of the software is running in fully platform independent JAVA. If there are better solutions available under Linux I will need to check them out. I have only been running XP Pro so far because it is the OS I know best. There is no other reason for it at this point so if this project would be easier to complete using a different OS I'd be alright with changing that. Does ax.25 have the ability to transmit IP packets? If it does this would definitely be worth doing some reading up on. Any other ideas? MAX K1GJ Yes! ax.25 will allow you to setup an interface with an IP and send packets over the air. Back in college we used some old pentiums as packet radio gateways and setup 3 different networks. They were able to communicate over the gateways on which we had 2m handhelds hooked into. The handhelds had a cable from the soundcard to their speaker and mic jack. A pin off the joystick port (or serial) from the computer keyed the mic on the radio. I think we only manged 2400 baud 
-Foxxz |
