Slashdot Mirror
Build Your Own 10Mbps Microwave Data Link
Rob writes: "I found this site called The Microwave Data Link Project where a guy is attempting to link 2 LANs (2 miles apart) by a 10Mbps Microwave Data Link. I've seen the plans for these links, but never wanted to learn all that amateur radio stuff, but this guy is going to lead people step by step how to build it, including how to get your FCC License, and more. Should be interesting to follow the progress!"
The cost of me doing it is quite a bit more than his project since I have to relay to get around trees. Microwave has to be line of sight. However if I had line of sight between 2 networks up to 30 miles away I could use:
2 lucent wavelan cards: $150 ea
2 24db grid dish antennas: $150ea
2 40' cables $50ea.
Total $700
I could save money here on the antenna's, get a couple 10dbi antenna's for $70ea, and still get 10 miles.
Figure the time going into making the stuff, and licensing (this is unlicensed stuff I use), the excellent software, stability, etc, not to mention the range and that $200 difference goes away really fast. Not to mention we'll have to see if he make it at $500.
Before everyone gets excited about doing this project, please take the time to understand that Amateur Radio is specifically prohibited from being used to carry commercial communications. Be mindful that what constitutes "commercial" communications is subject to interpretation. Note also, that encryption *may* be prohibited under this regulation (No SSL for you!)
Here's an excerpt of the relevant federal regulation:
(a) No amateur station shall transmit:
(1) Communications specifically prohibited elsewhere in this Part;
(2) Communications for hire or for material compensation, direct or indirect, paid or promised, except as otherwise provided in these rules;
(3) Communications in which the station licensee or control operator has a pecuniary interest, including communications on behalf of an employer. Amateur operators may, however, notify other amateur operators of the availability for sale or trade of apparatus normally used in an amateur station, provided that such activity is not conducted on a regular basis;
(4) Music using a phone emission except as specifically provided elsewhere in this Section; communications intended to facilitate a criminal act; messages in codes or ciphers intended to obscure the meaning thereof, except as otherwise provided herein; obscene or indecent words or language; or false or deceptive messages, signals or identification;
(5) Communications, on a regular basis, which could reasonably be furnished alternatively through other radio services.
The full regulation can be found here.
Chuck Milam, KF9FR
... referenced in the article, at http://www.qsl.net/ke5fx.
/.-worthy. The response came back in about 5 minutes:
:-)
:-)
Amusingly, I submitted the project page to Slashdot myself about a year ago, when I first got the link working. When the submission was rejected, I wrote to one of the well-known admins at Slashdot asking what I needed to do to make it
I just didn't think it was interesting enough.
Sorry.
--
| (admin name omitted) | Just want to be misunderstood,
| (admin name omitted) | I wanna be feared in my neighborhood.
| http://slashdot.org/ | Just want to be a moody man,
| codejockey*gangstero | say things that nobody can understand.
| flove*lovemachine*wr | --Pete Townshend, Misunderstood
Dejected, I was forced to admit that my news-for-nerds quotient just couldn't compete with the guy who built a PC case out of Zebrano wood, or whatever the story-of-the-day was at the time. Consequently, Rob gets major props from me for doing a better job writing up the submission than I did.
Now for the bad news: out of many thousands of hits my site's received over the past year, only one guy, an EE professor at a local university, has successfully duplicated my efforts. In my mind, that somewhat validates the unnamed Slashdot admin's decision not to publicize the project in the first place. People, this is not a project for beginners or casual electronics buffs! In the year since I finished the project, a couple of excellent alternative solutions for RF data links that make good use of off-the-shelf hardware and homemade antennas have come to light. For instance, there's a good page on the topic of modifying Proxim Symphony cards for long-range service at Low-Cost Wireless Network How-To. I would have to say that this is a better approach for 99% of the people who have looked at my microwave link page and thought about building it. Heck, in retrospect this is what I should have done, instead of putting in all that engineering time on a 100%-custom solution.
My own 10-megabit link has been running great since last June with only a couple of hours' downtime for maintenance and tweaks, and it's easily the most 'educational' project I've ever tackled. But I think it's important to temper peoples' expectations. If you are an experienced electronics hacker with access to a very well-equipped RF test bench or a university EE lab, and you just want to spend a lot of time and money building something something cool, then I highly recommend my microwave link project. If not, do yourself a BIG favor and check out the various wireless-Ethernet card tweaks that have been springing up on the Web.
-- John Miles, KE5FX
Dahlmann tightly grips the knife, which he may have no idea how to use, and steps out into the plain.
The driver support under Linux for the WaveLAN card is fantastic, and the driver is even included with Linux-Mandrake 7.1 -- no special configuration required other than to make sure pcmcia inits before network.
The downside? It's not a 10-Mbps connection, it's only 2-Mbps. However, I routinely run X connections over SSH from a dedicated ssh gateway at my business. The link has fantastic uptime, the signal-noise ratio is almost as good as it gets with a 24dB antenna, and I'm completely undisturbed by power outages (UPS here), snow, rain, etc. High winds (60 m.p.h. + gusts outside right now) do take a toll, though. A 1 watt amplifier allows my 24dB antenna to punch right through the walls of my attic and lets me forget about the many trees, houses, and other obstructions between me and my ISP, 3 miles away.
The WaveLAN card with a pair of antennas and amps would be a much easier, more convenient option for most home users trying to set up this type of connection, IMHO. The amps are pretty expensive (a couple hundred dollars) but do wonders to ensure connection integrity.
Here's what my S/N ratio looks like, catting
Matthew P. Barnson
I learn what I think when I read what I write
p.s. Do you have any information where I can get a free counter for my website?
--
Have fun: Join D.N.A. (National Dyslexics Association)
- No profanity
- No music
- Nothing remotely commercial
- No encryption
After all, it's a privilege to generate an electromagnetic field...--Just the place for a snark!