Amateur Radio Packet Over 802.11 Cards

Skuld-Chan writes: "I stumbled across this the other day -- basically discusses modifying common 802.11 boards for amateur radio bands (or Part 97 rules). Under Part 97 there is a 100 watt limit and no gain limit (unlike the 6 db gain limit on Part 15). I thought it was interesting :)." Consult your friendly branch of the FCC :) Note that this is just one of several interesting projects from this site.

Comments

Licence revoked:

[Perdo]

Transmit 100 watts across a city, at 2.4 Ghz, and see how long before your amateur radio license is revoked. Part of their rules are to never use more power to conduct your transmission than is necessary. Since 100mw with a high gain antenna is enough power to transmit to the limits of practical line of sight, using more than 100mw is using more power than is necessary. Also, to transmit, you must listen to the channel you are about to transmit on to insure no one else is using that frequency at that moment. Since 2.4 Ghz devices have become so ubiquitous, it is impossible to transmit without stepping on someone, somewhere.

This story reminds me of the one about the website that teaches people to make an x-ray machine. Nice to know, but definitely not for the irresponsible masses.

Re:Licence revoked:

[Perdo]

The automatic gain control on the low noise amplifier in the receive section of the card would shut down the receive path for any card inside the structure where the 100 watt omni is located. Think of when you yell into a mike and it cuts out to protect itself. So, you could provide strong signal to everyone, unless they were too close to you.

And as the article mentioned, this applies to Packet Radio, which by it's nature has a single source and a single destination. Omni directional antennas are used primarily for point to multipoint communication not point to point as is typically used for packet radio.

Also, remember the inverse square law when designing your network. Putting more power into your transmitter does less to improve communications performance at a distance than a properly designed antenna. High gain omni directional antennas are more efficient at propagating your signal than increasing your power to 100w.

For instance, a 15 dBi High Performance Omni sold here for $209.95 increases the effective radiated power by a factor of 100,000. A factor of 10 for every 3 db of gain. So, your standard 100mw transmitter would transmit less power than the 100w transmitter initially, but would fall off less with distance, surpassing the performance of a 100w transmitter on a standard antenna after the first few feet.

The other route is to use a 2.4 Ghz Klystron like this that costs in the neighborhood of $30,000 which of course can be coupled with an high gain antenna, which will not survive long at its maximum rated load.

This is not a competition of Penis sizes or "My athlon is faster than your Intel boxen" this is a game of finesse where the sharpest mind and the most efficient system dominates through signal quality, not signal quantity.

You get Mary on her 2.4 phone and the Muni Hospital complaining about you ruining ther gossip chat and emergency beeper service and you won't just loose you expensive 'leet 2.4 Ghz gear, you will do prison time for willfully jamming vital communications services, tantamount to a terrorist act, post 911.

Want to be 'leet? Implement a flat panel phased array with electronic beam steering to pinpoint your distant end receiver at gain levels limited only by the precision of the real time clock you use to gate the injection of the 0-180 and 180-360 phases of your waveform.

That would cover as many stations as you wanted, within the limits of line of sight. You could go back to college to learn the RF theory necessary to build such a device for the price of a big dumb klystron and go on to dominate the mobile gigabit bandwidth telecommunications arena. Perhaps your choice is clear.

'cept you have to compete with me, and I'm 11 years ahead of you :)