WAPR News April, 2005
by Andy Nemec, KB9ALN
Hello and Welcome to Spring! I promise, it is coming.
There are a few pieces of news to report for this issue, though not a flood.
As I mentioned in February, Al N0GMJ has turned over the WAPR treasurer duties to Joel N9BQM. This is a temporary measure until we can locate someone who wishes to take on the duty. In the meantime, Joel has been working on updating the books, getting deposits taken care of, and the like. For those of you who've sent membership dues checks in, please continue to be patient.
As I mentioned last time, this means that we now have a new address to send our dues to, it appears at the top of the page. Speaking of dues, our dues structure remains the same as the last few years. Without the Badger State Smoke Signals, annual dues are a mere $15.00. If you like to read the BSSS on line, then perhaps you'd like to send us $20.00, and we'll send the extra $5 to the BSSS. If you would like a printed copy of the BSSS, we'll include a subscription for $25.00.
It's no secret that conventional packet radio usage has dramatically fallen in the last few years, and so has WAPR membership. In spite of the drop in packet usage, there are still people and groups that make extensive use of packet radio. Therefore, there is still a need to have an organizing and/or managing entity to help coordinate the use of packet radio, both in its "classic" and "new wave" versions.
WAPR is the best choice to carry on that role - really, pretty much the only choice. I am not aware of any packet radio organization that operates state-wide, owns portions of the network infrastructure and supports packet radio network development the way that WAPR does.
For that reason, I ask that if you care about packet radio, please consider joining WAPR. This applies if you operate the classic packet mode, or newer 802.11-type modes.
Coming E-Mail Change:
I've been threatening to do this for quite a while, and finally the wheels are in motion. The timing could be better, but soon I will be changing internet providers (and getting a healthy DSL speed boost in the process). As a result, my E-Mail address will change. My current account will expire before the next issue of the Badger State Smoke Signals comes out. So there may be a time when some people will not be able to contact me.
I will be mass-mailing everyone I can think of to let them know of the change. I am not shy about passing out my E-Mail address, so I encourage those that receive the notice of my changed address to pass it on. I only ask that if you post it publicly, for example on a web page, you do not make it a "clickable" link. Please disguise it from robot computers that harvest E-Mail for spammers. In the case of my current address, it's as simple as showing it as kb9aln (at) gbonline (dot) com.
I'll also apologize in advance to anyone that should get the new address, but forgot to include on the list.
That's our short news report for this time out. Until next time, 73 from Andy.
Ham Implementation of 802.11 Packet Radio by Andy Nemec, KB9ALN
In our last features, we had a short introduction to 802.11 technology, talked about how a wireless ethernet network is configured, explored antennas and then touched on feedline. This time out, we'll discuss an alternative setup
An Installation Alternative
Up to this point, we've discussed a typical wireless ethernet card that is internally mounted in a P.C. A long run of expensive antenna cable is used in this type of installation, and R.F. signal is wasted through feedline attentuation. There is an alternative to this situation, however.
You may remember from a past article in this series concerning network infrastructure a mention of Wireless Access Points. These are stand-alone boxes that have an 802.11 radio system inside, and function as network routers of sorts. They generally have 4 or more wired network ports, and are usually connected to P.C. wired-type ethernet cards. They are, in a sense, bridges that join a wired and wireless network together.
There is no reason why you can't operate a Wireless Access Point (WAP) for yourself, and there are advantages to doing it that way. One is that these are most often mounted outdoors in a weatherproof box on an antenna mast. This way, there is minimal coaxial loss. The WAP is remotely configured and maintained through any one of the ethernet ports. It can function as a whole-house router.
The usual configuration is to install a WAP inside of a NEMA-approved outdoor weather-sealed box, run and connect the ethernet cables, connect the antenna cable, seal all cable holes, and mount the assembly to the antenna mast. This requires less antenna cabling, resulting in less R.F. loss and better radio performance. A side effect is that there is a less direct path for lightning to follow in the unfortunate event that your antenna is struck. However, there are special needs that do have to be considered if one decides to install the system this way.
Running Hot and Cold
Before you decide to put a WAP outside, you need to know if it will work there. This is very easy to overlook. Thermal stability is essential to best data throughput. Be sure you look at the temperature specifications of the unit you have your eye on before UPS brings it to your door.
Along those lines, try to plan your installation so that the unit is not in direct sunlight, exposed to much wind, and is generally in the most "friendly" place it can be. This is not always possible, but anything done to mitigate the effects of a harsh outdoor conditions will help to insure a more successful installation.
Electricity from the Sky
The Amateur's mortal enemy, lighting is not limited to wreaking havoc with large HF antennas and radios. We all know that anything on a rooftop can be fair game for atmospheric electrical activity, both direct and induced.
For strong direct strikes, the best advice is to disconnect everything, including ethernet cabling. In the case of remote-site WAPs, this may not be possible. For the individual amateur who may not have a need to operate during a thunderstorm, this is the best advice. But what if you are operating a system that has to be available during a thunderstorm?
Then protection is in order, starting with the antenna. Consider a very good lighting arrestor that is capable of operating on your intended frequency. Select the one with the least insertion loss, the proper connector (N is best) and you have the potential to save the WAP from all but the strongest of strikes.
This assumes that you have a properly grounded antenna support structure. A good grounding system is a heck of a lot more complex than driving a ground rod into the earth. This is a topic all unto itself, and if you'd like to learn more, consult the sites mentioned near the end of this article.
Of course, you will want to ground the WAP itself, and provide surge protectors for the ethernet cables connected to it. In fact, two surge protectors per cable should be used - one at the WAP, the other at the network card in the computer (or network device). This is important because long runs of cable are susceptible to magnetic fields generated by nearby lightning strikes.
These cables act as an inductor. Remember your grade-school science? When you pass a magnetic field by an inductor, a voltage is induced in the inductor. A very strong nearby strike creates a strong magnetic field that can induce a very high voltage spike in an ethernet cable. Computers, routers and other network devices need to be protected from these voltage transients.
The problem becomes potentially very damaging when you consider that not only your computer, but likely other computers will be connected together. One computer getting "hit" is one thing, but most people who have more than one computer have them connected together to share files. In this case, they could be sharing lightning-induced damage. Protect or disconnect all computers that are networked.
Of course, you probably already have power line surge protection. If not, what are you waiting for?
The one best piece of advice that can be given regarding these installations is that good RF construction practices do pay off. Yes, you are dealing with the somewhat mysterious world of computers. However, we are still connecting them together with Radio. There are basic rules to follow to make a radio work, and deep down, 802.11 is radio.
The same for basic antenna installation practices. Weather-sealing connections is a must, and it doesn't hurt to spray an anti-oxidant on the connectors before assembly (such as Caig De-Oxit D5). Remember, an intermittent connection on a voice radio is an annoyance. With data, it causes an extreme drop in throughput.
The same with a poor ground connection - it can induce static, pops, clicks and other noises that can make data undecodable. If you're using a combination of Aluminum and other metals, remember that dissimilar metals often create corrosion when joined together. Use No-Al-Ox on connections to Aluminum brackets and ground wires. Don't forget to weather-seal those connections, too.
Here are some of the sources of information I used in preparing this feature, and where you may find additional helpful information:
NEMA information and information about grounding and electrical standards:
http://www.nema.org Information on Lightning and Lightning Safety:
Additional lightning, antenna and antenna support structure grounding in-formation:
Surge protection for ethernet and data cabling:
There are plenty of other sites that have information, these will get you started. Searching for "lightning+protection" (without the quotes) on Google will give you more places to visit than you probably have time for. There is plenty of excellent information available on this topic on the web. Of special note is the PolyPhaser site - they have tons of documents, one that even deals with grounding of Ham Radio stations.
And that's where we'll leave our discussion for this time. Until next time, 73 from Andy.
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