Tuesday, February 17, 2009

Local Area Networks

Above: Some common LAN designs. Cick sketch to enlarge.

So, I found myself doodling around a bit with the pencil and grid pad...

If you're reading this blog, then of course, you computer is connected to the Internet.
And, if you're not using an internal modem or an external modem with a serial cable, then you're using a Local Area Network (LAN.)

A popular format for these networks is the Ethernet (IEEE 802.11) using CAT-5 cable. That is what I'm showing at the top of the sketch in Figure (a). You've got a PC, a modem (cable or DSL for phone) and a small Ethernet hub to connect them together. Sometimes, the hub (or a small IP switch) is built into the DSL or cable modem. From their you go across the cable or phone company until you get onto the Internet.

A more complicated (and cooler because it uses RF) solution let's you access the Internet without running a network cable from the PC to the modem. In these "wi-fi" or wireless networks, a popular format is IEEE 802.11g. Many folks have those small blue Linksys WRT54G boxes and wireless cards installed in their computers. Did you know that these units share spectrum with the 2.4 GHz ham band ? The "wireless access point" (aka wireless router) typically contains antennas (1 or 2) an IP router (more about that later) TX and RX equipment and a few Ethernet ports. Being microwaves, you're mileage may vary, but you can get around 100' of range or so. Compare that with 300 ft. for the CAT-5 cables. Not bad.

Figure 'C' shows a DeLuxe setup. Long story short, you can use hubs and switches to segment your network by location or by task. Note I put in a dedicated AP for the Ham Internet (Hinternet) http://en.wikipedia.org/wiki/High_speed_multimedia

I've been reading up on what can be done with the Hinternet. I mentioned one club's experiments in a previous post. I'll report back with more later.

In the meanwhile, how advanced of a wifi setup do you have now ?
My setup strongly resembles Figure B.
I know a couple Hams that work from home that have setups more like C.
If you're back at Figure A and have questions, please let me know.



Mac said...


I have a hybrid network and do NOT use wireless because I found it unreliable when downloading files such as Ham Radio Deluxe. I'm using my wireless router as a coupling between two cables because my cables weren't long enough and I had the wireless router. My wife's laptop does use the wireless router...it came with wireless built in.

Great article and explanation!


Gene (AE5FT) said...

In the interest of discussion, here is my current set-up:

DSL via our favorite BA phone company with phone cord going to Windstream modem. Output from modem via ethernet cable to wireless router (std blue linksys).

I have a wireless "thumb" on desktop and a laptop with wireless card leftover from AT&T phone days.

It all seems to work very well.

KD5NJR said...


Did your Linux deal with the USB adapter for wifi ?

Because that is one of the features in the newer version of the kernel.

We can try a newer version of Knoppix.

Stan(KE5LEP) said...

I have a Linksys WRT54G on my DSL.
I am in agreement with Mac. Sometimes Wireless is not good for large downloads.
I am currently using Windows XP Pro on my main machine. Using IE Version 7 and sometimes Firefox. My XYL machine is running Windows 98 Second Edition with Firefox and IE. A third machine is running Kubuntu with Firefox brouser and KDE Desktop. I can login using Gnome Desktop. My plans for this machine are to make is boot any one of several Linux releases and also boot from the thumb drive. I will also be using several "live Linux" boot disk. These allow using Linux without installing it on the hard drive.

Brad said...

I probably fit into your diagram (b). Some household computers are wired and some are wireless. I've had no problem with large downloads over wireless.

The Hinternet concept sounds interesting. I have heard of hams in rural areas forming their own "internet service" this way. They find one feed point for the internet (cable, satellite), then transmit wireless to each other from that central feed point. Lots of interesting things you can do with 1500 Watts of wifi, huh?


Gene (AE5FT) said...

"Did your Linux deal with the USB adapter for wifi ? "

Took me a little time to give this a try, Scott. The answer is "Nope".

I'll need to work with this a little more (actually a lot more).