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400km, 3 degrees lattitude, a million dollars - CMH Communications

  
  
  

One of the first things any CMH Heli-Skier learns is that, as part of CMH Heli-Skiing’s endless quest to make Heli-Skiing as pleasant and safe as possible, each guest is assigned their own radio and is trained in how to use it. From a user’s perspective, it’s easy, but behind the scenes, CMH communications are a marvel of modern technology covering almost three degrees of latitude and costing over a million dollars.

For an insiders view of the CMH Heli-Skiing communication system, I tracked down Bob Lutz, the Manager of Infrastructure at CMH:

ski guide radioTD: How does repeater communication differ from direct radio communication?

BL: Every radio has a receive frequency, Rx, and a transmit frequency, Tx.  When your radio is operating in what we call Direct Mode, the Tx and Rx frequencies are the same so you transmit on the same frequency that everyone’s radio is receiving on.  This works great if you want to talk to someone nearby, like your guide or other members of your group, but the small battery and antenna on a handheld radio can only transmit so far and certainly not through mountains to reach a group in another valley. This is where our VHF repeaters come in.

When you change your radio to Repeater Mode, only the Tx frequency changes so that you can still hear radios sending on direct, but you broadcast on a different frequency that only the repeater is listening for.  The repeaters have a much larger antenna, plus they are positioned up high to be able to cover a much larger area.  The repeater also has four to eight batteries similar to the ones in your car for power so it can re-broadcast your transmission much longer distances on the Rx frequency that everyone’s radios (including yours) are listening for.

This leads to the natural question of, why don’t we set the radio to Repeater Mode all the time?  For most of the communications between you and your guide the direct mode works well and there is the possibility you might be too far or too low to reach the repeater that might be 10km away when your guide is just 200m below you.  Secondly, the repeaters are in low power standby state most of the day but when they kick into gear to re-broadcast someone’s message they use a lot of power to reach as far as possible.  If they were running all the time the batteries would run out faster than our solar panels can recharge them.

Rocky in rime

TD: How do the repeaters support the remote internet at the lodges?

BL: Well, our remote lodges are too far from towns to make running phones lines or fibre optic cables feasible especially when you look at all of the avalanche paths we would have to cross along the way.  So for each lodge we had to find a location in a neighbouring valley where we could get telephone service and an Internet connection fast enough to support a lodge full of guests and staff.  Then we had to find sites with a direct line of sight to the lodge and that site.  The shortest leg is 6km and the longest is 31km.  The Bobbie Burns connects to phone lines and a fibre optic cable that are 73km away by the time you add all three legs together.

The phones and people’s web browsing use the same link, the trick is that there is device at the lodge that converts your voice into data packets to join the flow of Internet traffic, but when they reach civilization we convert the data back into an electric signal that we transmit down the phone line.

TD: What is the value of the complete CMH repeater system?

BL: Hmm... a lot of maintenance and upgrades have occurred over the decades and it would be hard to add all of that up.  If you had to rebuild everything from scratch, it would cost roughly $50K-60K per site so a little over $1,000,000 to manage our safety communications, coordinate the ski program, and let people connect to friends and family when they get back to the lodge at the end of the day.

TD: Where is the southernmost CMH repeater?

BL: CMH K2’s Kuskanax repeater at 50°23'54"N

TD: Where is the northernmost CMH repeater?

BL: McBride’s Mt Halverson Repeater at 53°15'30"N

TD: How much maintenance do they require?

BL: Most repeaters require one inspection visit during the off season but during the winter some of them need to be visited regularly to remove rime (ice) from the solar panels to allow the batteries to recharge.  With the Internet repeaters faster radios are coming out every few years so this summer we also went out to upgrade all of the radios that link the Bobbie Burns and Bugaboos to the Internet at Brisco.

BU   Kain Ridge Phone rptr

TD: How does the power system for the repeaters work?

BL: The VHF and UHF repeaters are all solar powered with several batteries similar to the ones in your car.  The Internet repeaters use solar power over 97% of the time but they also have propane Thermal Electric Generators, TEGs, as a backup in case the panels are covered in ice and for those weeks where it snows a lot during the day and they don’t see any direct sunlight through the clouds.  The TEGs rely on a principal where a small electrical current can be created between two different types of metal if there is enough of a heat difference between the two metals.  One side is heated by the propane flame while the other is exposed to the cool mountain air.  The Bobbie Burns system ran on propane for 961 hours last winter during the dark stormy days of December and January.

TD: When did CMH start using the repeaters for internet as well as radio?

BL: Our first attempts were in the summer of 2006 to try and connect Valemount and later the Cariboos to a farm house that was close enough to the Town of Valemount to get ADSL service from Telus.  Our Valemount lodge is farther than the 4.2km limit for ADSL service from the phone company’s central office in town.  In 2009 we realized that we could no longer find parts for our old telephone repeaters for five of the areas so we spent most of the summer of 2010 combining the phone and Internet repeaters into a single site that brought both services to the lodge much more reliably than our early experiments.

BB Dogtooth Phone and Internet Rptr

TD: Are the internet telephone repeaters and the radio repeaters always in the same locations?

BL: No, we position the radio repeaters to provide good coverage to our ski tenures.  This often means putting them up very high near the middle of the tenure.  The Internet/telephone repeaters are placed wherever we can get a line of sight to the lodge and a location with good Internet and telephone service.  We try to keep the Internet repeater sites as low as possible to reduce the electronics’ exposure to harsh mountain weather.

TD: How many repeaters does each area have?

BL: It varies from one to four.

TD: Anything else you'd like to add?

BL: We have three kinds of repeaters, VHF, UHF, and microwave.  The VHF repeaters are the ones most familiar to our guests that allow the lodge to talk to the guides in the field when they are skiing in the outer reaches of our terrain.  Most of our VHF repeaters have a set of UHF radios to allow one area to connect to a neighbouring lodge’s repeater to share information.  If you activate all of the UHF repeaters together it forms a radio link over 400km long, the guides in the Cariboo Range up north can talk to guides as far south as CMH K2 and the Bugaboos

Up until a few years ago, when we switched to telephone conference calls, this is how the guides in the different CMH Areas exchanged observations made in the field to give everyone as much information as possible about the snowpack.

The microwave repeaters are in separate locations and are used to connect our lodges to phone lines and the Internet at the fastest speeds possible regardless of how hard it is snowing.

CMH Heli-Skiing’s vast communication network is one of the many reasons that 70% of our skiers are return guests. For more information, contact CMH Reservations at 1 (800) 661-0252.

Comments

Great post! We should all be proud of the amazing work that Bob Lutz, Rob Whelan and their team does to allow us to communicate with each other over many kms of mountain ranges. It's no small feat!
Posted @ Thursday, January 03, 2013 8:57 AM by Dave Butler
I've often wondered about repeater technology, cost, how extensive the network and so on. Now I know!  
 
Thanks for doing the research and writing this Topher!
Posted @ Friday, January 04, 2013 12:25 AM by Brad Nichols
Comments have been closed for this article.