Tuesday, April 28, 2015

An FM pileup

Last night was a big drill night for us on the Heyworth fire department. We have a large gas terminal located in our fire district. A pipeline runs to a tank farm where fuel products are stored and then loaded onto semi-trailers for transportation to other storage areas, gas stations, or private tanks. We had the terminal owners and three other mutual aid departments participating in the drill.

Communications is almost always a problem when you get that many people on scene. Radio communications become clogged as 10 apparatus arrive on scene. "Where do you want us? Send me this....Can you go here?" These message repeat over and over, all the while the firefighters performing work are unable to get back to command. Why is this a problem? Because everyone wants to hear all traffic, we stay on ONE frequency. You've got 10 trucks and 25+ people all trying to talk on one VHF FM analog frequency.

If only more of our members were hams, maybe we wouldn't have to discuss why talking over other transmissions doesn't work. Or why putting 25 people on a single channel is not a good idea if we expect two-way communications between more than 5 of them! Nothing like a good 'ole FM pileup to make you want to smack your head against the wall. If nothing else, maybe the single command officer trying to work the pileup WHILE managing the event would realize that we need to work differently.

Friday, April 24, 2015

AREDN first site on the air

I've installed the first of what I hope are many AREDN (Amateur Radio Emergency Data Network) mesh nodes. This site is located on a large grain elevator in Heyworth, IL. It's at the 150 foot level, with two yagi antennas. One antenna is pointed north towards Bloomington, and the other is pointed northeast.

I'm still going some testing with the antenna configuration - with guidance from the AREDN group, it looks like I need point both antennas in the same direction to take advantage of how 802.11 works. I wanted to try to reach two distant locations with this node...the better way to do that is to have two nodes with directional antennas - at least that's what I'm going to try next.

The node is made up of a Ubiquiti Rocket M900 node, two RP-SMA to N jumpers, and two yagi antennas. The node is fed with a CAT5E cable that provides Power over Ethernet (POE) up to the node, and data in both directions. This arrangement results in very little loss - there's nearly no coax. 

This site also houses a UHF analog repeater and the KD9AKF D-STAR repeater. Using vlan capable switch, I am able to create a connection to the internet from this mesh node. It isn't meant to be a replacement for personal use internet - but having the ability to route to and from the internet means I can access services from either side of the mesh as allowed by amateur Part 97 rules.

What's next? I'm working on two more nodes - one is a portable setup that I'm still experimenting with. I'm going to try a 12 mile link to the top of a parking garage sometime. What's interesting to me is playing in the 900MHz ham allocation. So far, 900MHz for this application behaves much more like microwaves than UHF - it does penetrate some structures and obstructions. 

Friday, April 10, 2015

A getting started guide for AREDN

I'm enjoying experimentation with AREDN. Using off-the-shelf equipment, you can build a mesh IP network running in ham frequency allocations. Getting started is a bit tricky at the moment...I've joined the project team to help with some documentation and to do some release testing. Here's a link to a Getting Started guide I'm working on.

If you're interested in playing with mesh networks, take a look at the guide and let me know what you think!