DSP and S1 testing of old F1 Beacons

[Jonathan S.]

None of this is very surprising, but it does confirm some expectations.

- Back in February 2007, I first used a DSP to test a portion of a large (~35) fleet of beacons (avy course loaners), which included many old F1 Focus beacons (i.e., pale blue housing, which are therefore of the 1994-2001 vintage, although I neglected to check inside the battery compartment for date of manufacture). Many had drifted out of spec (i.e., +/- 80).

- In March 2007, I tested the entire fleet, and set aside those to be retired/returned.

- In September 2007, I discovered that the beacons I had set aside had not been retired/returned, so I tested everything again. Same testing results.

- In Sepember 2008, the failed F1 units had been replaced by purchases of new D3 beacons. I tested the remaining old beacons, and although it’s possible some had drifted a bit more from the prior year, none had drifted out of spec.

- In March 2009, I tested the entire fleet again. One F1 was way out of spec (160), another was out of spec (90), and three were right on the edge (80). I am pretty sure that all five of these beacons were still within spec half a year earlier.

- During my March 2009 testing, I also used an S1. The S1 failed all five beacons, including the three that according to the DSP were right on the edge (i.e., 80). Other beacons that had drifted to a lesser extent (i.e., up to 70) were passed by the S1.

- A fellow instructor gave me an individually owned old F1 from a student at a prior course. Apparently this beacon was somewhat of a mystery because some beacons but not others could successfully locate it. DSP said off something like 150, and S1 failed it. Given that the search spec is +/- 100, I didn’t think this was much of a mystery.

- And for the punchline: one student had an F2, which I of course immediately commanded him to retire ASAP, to which he agreed. Oddly enough, he was pretty good at searching, since he practiced regularly, although he found the earpiece to be a big drawback. Plus like the other three or so F2 units I have tested, absolutely no drift.

Conclusions:

- The two testers match up well with each other, although the S1 seems to fail beacons that according to the DSP are right on the edge (i.e., 80).

- The rate of F1 drift is very unpredictable. In other words, even if an old F1 has drifted somewhat over at least a seven-year period, it could drift out of spec over an ensuing half-year period.

- I consider all old F1 Focus beacons to be guilty until proven innocent. I recommend not relying on an old F1 focus unless you have you can test it every couple of months with a DSP or S1.

- I have yet to encounter any other drifted beacon.

To-do list:
- If I have time during an upcoming avy course next week, I will create a spreadsheet for current test results, then track them every half year or so that I have an opportunity. (All the beacons are already numbered.) I will also note the date of manufacture from inside the battery compartment.

[pechelman]

is there an indemnified list of beacons similar to bindings?

cant say ive heard of or ever seen one as its usually more along the lines of replacing helmets
but at least with a helmet anyone can visually inspect it for damage...

sounds like you could start a list

and while its comforting to know both DSP and F1 agree, what confidence do we have in their calibration and accuracy?
today id say its pretty good, but what about after a few years of use?
not really looking for a response here, just to provoke some though that maybe another way to test beacons should be readily available, or at least, for a means to verify calibration of beacons that can measure drift.

[Tye 1on]

Interesting, thanks for doing the legwork.

One of my F1's passed all three on an S1.
One of them passed the freq, but not the second [forget what that is].
My F2 passed the freq, but not the second or third.
I know i should shitcan #'s 2 and 3, but it's tough when they can all pick each other up fine...

[Jonathan S.]

Any dual-frequency beacons should be retired.
Otherwise, if it works, well, it works.

How to know it works? For transmission, the DSP & S1 testers are great. S1also tests Pulse On time and total cycle period -- when testing an F1, you need to put it about 1m away to ensure that the continuous carrier background signal doesn't produce a false negative for the S1's second and third tests.

Steve at beaconreviews.com said the DSP was spot-on compared to fancy lab equipment. Might the testers somehow get out of whack over time? I have no idea.

To test receive range, set up a target beacon, first with its transmit antenna pointing direction at you, then at a 90-degree angle. (Note if using a Tracker as a target, its transmit antenna is diaganol to the central axis of the housing.) Check your results against other published tests. Range test vary widely, but if you’re off by more than 10m, something is probably wrong.

How to quickly test whether both main receive antennas are functioning properly:

1. Set up the target and test beacons so that they are in optimal coupling alignment, i.e., pointing directly at each other. (I often use an M2 as a target, since its long skinny housing makes it easy to line up along its main axis.)

2. Put them far enough apart so that it's outside the pinpointing/fine phase, but well within the initial acquisition range.

3. The center directional indicator on the test beacon should display.

If instead the directional indicator is pointing to the side, then one of the two main receive antennas is broken.

I think the only way though to test the third pinpointing antenna would be to set up a pinpointing excercise, first with a dual-antenna beacon to locate a null or spike point, then ensure that a triple-antenna beacon avoids any nulls or spikes there.

[Tye 1on]

S1also tests Pulse On time and total cycle period -- when testing an F1, you need to put it about 1m away to ensure that the continuous carrier background signal doesn't produce a false negative for the S1's second and third tests.

aHA!!!!!!! Not have them sitting 10cm apart?
thanks!

[Jonathan S.]

http://www.tetongravity.com/forums/s...d.php?t=134862