6 Photos - Jul 3, 2014
Photo: Ready to test!
(A fifth box is upstairs, and a sixth box is in Portland awaiting my return for another volcano ski trip later this month).Photo: I set up another beacon on Search about, hmm, well, must be approximately 5.7 meters away!
(Yes, the old Opto 3000 -- still the lightest functional beacon to slip into a rando race suit zippered pocket.)Photo: My Gu sandwich.  The exact configuration varied among my three test beacons, since the packets are very slippery and would keep flaking off in various ways depending on the shape of the test beacon's housing.
Note how the Pulse alerts the user to a send problem, but all beacons were similarly affected (whether or not they displayed a warning).
To paraphrase a certain politician:
"All other beacon signals will be degraded by Gu packets, and so will mine. They won't tell you. I just did."Photo: All three test beacons jumped from ~5.7 to a range of 8.3 (shown here ) to a little over 10.
(And no, this isn't interference from my smartphone getting close to take a picture -- before I took out my phone, I noted the distance and then ensured that taking a picture didn't change anything.)Photo: I then used just one test beacon to set up a long-distance test.
The search beacon was consistently showing ~31m for the test beacon without any Gu.Photo: Now with Gu packets on top of the test beacon: the search beacon was not on the very edge of its receive range, as the display jumped around from ~47m, ~50m, to no received signal at all (as shown in this picture):  Scary!
So is the problem the Gu itself or the wrapper?
I don't think the Gu can be the problem, since if the 457 kHz signal can penetrate dense snow and the 90%-water human body, then Gu should be no problem.
(I'll have a bunch of empty packets though at the end of this month after my final ski trip for the season.)
I tried replicating the problem with some similar packaging:  Odwalla bars with much thinner wrapper, some random chocolate-coated coconut bars also with a thinner wrapper, and large bags of cacao powder and of raspberry extract with a shiny wrapper.  (The latter two sets of items are my wife's -- lots of strange stuff here...)
No degradation from any of them, but the wrappers definitely had a different feel from Gu.
However, a wrapper problem would make sense, since I found the same problem with a double layer of household aluminum foil.
By contrast, a car's toll transponder RF shield bag had no effect!
Turns out that the Gu packaging contains both polyester and aluminum, which explains the signal degradation.