by Andy Nemec, KB9ALN

Hello everyone. As we enter Spring, the focus on our activities turns to outdoor work, or work that requires decent outdoor conditions.

Right now, Joel, N9BQM reports that they are waiting for site conditions to improve so that the radio going to Larry, WD9ESU can be checked out before sending it to him. Same for the the W9DQA radio. Seems that the site they are using for testing has a little mud problem, and we'll have to wait for things to dry out before this can be done.

However, there is a new node to report - a backbone node on UHF in Fort Atkinson. Right now it has little to talk to, but as we get other nodes back up, this will change.

In other news, I have taken GRBBBS off of the node lists in Northeastern Wisconsin. I have kept the station itself up as a "community mailbox". However, it didn't seem logical to keep advertising it as a BBS when Green Bay has no BBS feed and few users. A few people have checked in looking for BBS messages and there have been none in the past few months. If we ever do get a network connection to another BBS and obtain a feed, then I can and probably will re-activate the node portion and once again put the BBS on the node lists

That's all for this time, until next time, 73 from Andy

Introduction to 802.11 Packet Radio by Andy Nemec, KB9ALN

In our last feature, we talked about one of the new technologies impacting packet radio, Icom's D-Star. I was actually able to lay my hands on a pair of these radios and put them through a non-scientific test. There will be more that I'll write about as we get more experience with these radios. In the meantime, we'll start a short series on 802.11 technologies. You will notice that I've referred to it as "802.11 Packet Radio" - which is accurate. While it's not what we usually think of as packet radio (computer, TNC and radio mix), it is packet radio. It sends information in packets. The main difference between these technologies and existing AX.25 technologies is the type and size of the packets.

What is 802.11?

802.11 is a set of wireless data communications standards developed by the IEEE. It is a general class of wireless data devices the operates under FCC Part 15 rules that regulate unlicensed private communications. 802.11 is also called "wireless ethernet" or "Wi-Fi". Ethernet, as a lot of computer users know, has been a wired network that allows the interconnection of computers. This is the same concept, without wires and with radios.

This technology takes the form of a network card containing the usual ethernet technology, a small radio transceiver, and additional parts and computer firmware that are required for radio operation. The card plugs into an existing slot on the computer, and a little antenna sticks out the back of a card, instead of a coaxial or RJ-45 connector. Installing one is very similar to installing a conventional ethernet card

In addition to the PC-based ethernet card, there are other devices that use this technology to provide a link or network access. These are packet routers and Wireless Access Points, or WAPs. These are analogous to a packet radio network nodes. Some also have the ability to connect a wireless network to a wired network, such as a dial-up, DSL or Cable internet.

There are several different types of 802.11 services - designated a through g. They operate in the GHz frequencies, and each has its own maximum data rate. All operate with spread-spectrum technology, so a larger number of users can be accommodated with reduced interference issues.

Three common variations of 802.11 are currently in use - 802.11a (5 GHz with data rates of 54 Mb/s), 802.11b (2.4 GHz with data rates of 11 Mb/s) and 802.11g (2.4 GHz with a data rate of 54 Mb/s). While these data rates are impressive, they do not actually measure throughput.

One throughput test revealed 802.11a and 802.11g averaging approximately 18 Mb/ s, while 802.11b averaged 4.5 Mb/s. These were under near-ideal conditions - computers were located in the same room with no interference known. In actual-use environments - sharing a given channel with others and dealing with other factors that can affect signal quality - 802.11b may effectively be lowered to 1 Mb/s or less.

Notice the frequency bands used for these devices, 2.4 and 5 GHz. Part of these bands lie within Amateur Service allocations - which means that we can operate them under Part 97 rules and regulations, which is why Hams are finding them appealing.

Two types of 802.11 service are primarily used, and are used not only by hams, but by the general public. These are 802.11b and 802.11g. Radiational output power is strictly limited, as these are intended to be used by the general public with little or no technical knowhow. Most have special antenna connectors to discourage unlicensed users from attaching an antenna that may increase radiational output power beyond Part-15 limits. If an external antenna is used, Part 15 users must decrease the output power of the wireless ethernet card to compensate for antenna gain. Amateurs have no such restriction, but must be mindful of Part 97 regulations that require us to use Automatic Power Control when using spread-spectrum power levels greater than 1 watt. Most of these devices operate at power levels of 100 mW to 350 mw, with the highest legal output (for consumers) at 1 Watt.

Amateurs can operate these devices under our Amateur Part 97 rules. This means we can use increased radiational output power levels, meaning that they can use used effectively over greater distances than unlicensed users legally can. The ARRL has suggested that hams using this technology do so carefully, however, as there is a potential for interference with not only unlicensed users, but other hams operating in the satellite and weak-signal segments of our shared bands. They also recommend using horizontal antenna polarization to help reduce any interference to and from other users of 802.11.

802.11 is channelized. For example, 802.11b uses a total of 14 channels, each 22 MHz wide. Not all are available in the U.S., and only 6 of these channels lie within the Amateur Service allocation. Additionally, channel 1 is suggested to be "off-limits". This channel lies within the weak-signal and satellite sub-band, as suggested by the ARRL bandplan..

However, this still gives us a maximum of five 22 MHz wide channels to enjoy. With the high data throughput they are capable of carrying, a whole host of new possibilities can be realized

Next?

This condensed introduction to 802.11 will progress to exploring network infrastructure possibilities and what uses they can be put to. In accordance with the ARRL's ARES push to use this technology for Emergency Communications purposes, we'll also explore the special situations presented in that environment.

Hope you'll be able to join us for the coming articles exploring 802.11 technologies. Until then, 73 from Andy.