Those who are following Karl Meltzer's record attempt for a supported AT thru-hike (http://www.whereskarl.com/) can only be underwhelmed by the performance of the SPOT satellite messenger system he has chosen.
Of the two his team has, both have been confirmed to work as of this post on his blog: "Ok. So see the little Karl icons off the trail time-stamped from last night? That's me. After I got the guys all lined out with dinner last night, I drove down the fire road about 7 miles to a clearing by a lake. I had both the SPOT units we have with me so that I could test them out. I turned them on and spent about 25 minutes out there, sending signals and trying to get in touch with someone on my cell phone who could tell me if they were working. They worked."
The reason for such an entry? It's 10-minute uplink has proven painfully unreliable, and many people have asked if the SPOTs are turned on or working properly. In the first days of his run, where he averaged 12 hours of movement per day, he is only showing up with 2 or 3 locations out of a potential of 70 or more. SPOT may have sponsored Karl, but it seems they are hurting their reputation more than helping it with this publicity.
While it is true that heavy foliage can prevent such transmissions, the only areas in which Karl is showing up is in places with NO cover at all, such as on Mt. Katahdin, the Kennebec River, and road crossings where he is meeting his team. Karl will face comparable tree cover the entire length of his attempt except in the above-timberline country of New Hampshire's White Mountains and the southern balds.
Only time will tell how Karl does, but it seems likely SPOT will NOT make a good showing.