The PCMIA wireless LAN cards are inexpensive. We purchased ours for less than $30 bucks each on the Internet. Most use either "Integral" or "Patch" style antennas and can have range of up to 1,600 feet at 100mw.
In our tests using two laptop computers, we were able to transmit successfully down to the corner about 800 feet away. We set up both laptops to run the Apache http server and the Real Media Basic Server (free for personal use) We then configured the LAN cards to use TCP/IP protocol and simply typed in the IP addresses into web browsers. When the streams were detected, the web browsers would launch the Real Media Players and we were able to have a QSO.
At 28.8 encoding, it was even possible to have two way (Full Duplex) QSO's but at 56K encoding the stream broke often. The Wireless LAN cards had a rated bandwidth of 512K but much of this is taken up by the protocol functions.
One way QSO's at virtually any encoding speed were possible, and high quality video (P5) was exchanged out to our maximum distance.
Please note that these transmissions would have been perfectly legal under Part 15. However, as we plan to add power and high gain antennas, we took the extra step of joining the Special Temporary Authorization of the TAPR. This will allow us to do several things that would otherwise be illegal such as ue a frequency hopping sequence that differs from the FCC's guidelines for amateur use.
Of Interest: Further comments from the packet folks in California reveals that they may have been pushing digital video through their high speed network as early as 3 years ago! They didn't even think it was important! Another update from Dale Heatherington, WA4DSY: "Based on the date I created the CU-SeeMe directory on my hard drive I'd say the experiment took place in December of 1996 at the earliest. I was running an early OS/2 beta of CU-SeeMe which could only receive video and not transmit. Alan Adamson,NE1H, was running a Windows 95 CU-SeeMe program and transmitted some live video over the 56K RF link to me. The 56K link was kept pretty busy during the session. Due the RX only nature of my program we didn't try two way simultanious video. That's my memory of the experiment. If I'd known it was historic I'd kept notes :-)"
For more information about TAPR, visit their web site at: http://www.tapr.org. Looks under "Spread Spectrum" for information about using digital spread spectrum technology on the Amateur bands.
I believe that high speed packet networks are the best route towards Digital ATV on a wide scale, however, we were eager to experiment with digital ATV, and to begin exploring options for networking. These cards are very inexpensive and therefore, we tried the spread spectrum route first.
Some amateurs in the TAPR spread spectrum STA have achieved ranges out to 14 miles using these cards with small power amps and gain antennas. We hope to try some of the "coffee can" ATV antennas soon and see what kind of range we can achieve here.
Any body out there have access to a high speed 56K packet backbone that so we could try this out on packet too?
Sources of Equipment
Here is a very inexpensive source of the IBM Wireless PCMIA cards (model #92G7787) that I had found earlier. I had not ordered from this dealer because at the time we were unsure of how the system might actually work and he could provide no real technical information. (Though his email was fast and very supportive.)
After that, we found some online documentation and figured out that this card should work fine but by then Bob Askew, our project engineer had found them for cheap elsewhere. In any event, here they are for only $30 bucks each! See http://home.eznet.net/~kento/lancard.html The latest system software drivers are here for download too.
Any day of the week you should be able to find these on http://www.ebay.com. Simply type in "Wireless LAN" into the search engine and bid. Right now they have a ton of them going in a dutch auction, meaning almost everyone who bids will win...for $50 bucks.
A quick search on AltaVista turned up numerous sources for PCMCIA adapter cards that will allow us to use the PCMCIA Wireless LAN cards on our desktop computers as well. They seem to sell in the $80-$100 dollar range, so I think for as little as $300 dollars you could have a working 2.4ghz spread spectrum Digital ATV system! (Assuming that you own the computers, etc..) But remember, that if you want to do anything that is beyond Part 15 limits, you'll have to join a STA or apply for your own from the FCC. Currently, the TAPR requires some documentation before granting the STA inclusion and the FCC is requiring some documentation after the fact. Read the TAPR STA carefully, and be sure that you are willing to comply before even asking to be included. (Editor's note: Also use caution - the 2.4 Ghz Part 15 band extends beyond the edge of the Amateur allocation - by adding an amplifier to the device for Amateur use, you could inadvertently operate outside the Amateur band. It may be easier to use 902-928 MHz Part 15 units instead of 2.4 GHz since the Part 15 band edges are the same as the Amateur allocation.)
To search for these units, type in "PCMCIA Desktop" at AltaVista.
We are going to soon try some of the "Coffee Can" antennas that were in this quarters ATVQ with when I get back from vacation. Can't wait to see how that works!
reprinted with permission from ham radio online
