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Richmond, BC
Canada
2473 Posts |
Posted - 03/06/2012 : 7:40 PM
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quote:
Originally posted by Matt
quote:
Originally posted by sgRant
The transceiver frequency is not on the AM band. Hopefully someone will correct me, but I think 457 is about half of 900 where I found good reception AND no radio station. It makes sense that a harmonic of the source frequency could be sensed by the radio. This should show up at the multiples of 457.
This is correct, and I was going to say something about it earlier. There are a number of ways the distortion could be created in either the avalanche transciever or the AM radio.
So if 457Khz (+- 80Khz) is not an analog Amplitude Modulation (AM) frequency, then what is it?
AM (medium wave)brodcasts, amateur radio, and Avalanche beacons fall within the MF (medium frequency) range of 300 - 3000Khz. It's not FM.
AM radio broadcasting in North America starts above 500Khz so hense picking up the harmonic in the 900 range. I have a small international radio which picks up lower frequencies so I'll try it.
quote:
Mine is digital and displays a number that represents the approximate distance to the victim and I believe it generates its own beep which makes it much harder to tell if it is noise or real.
Could this be a continuous carrier signal? The premise being that some older and newer beacons transmit a weak signal during what should be the silent period between tones? possibly causing minor problems for digital beacons which may interpret this as another beacon in the distance and may report "ghost" beacons? |
Edited by - pmicheals on 03/06/2012 7:55 PM |
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Richmond, BC
Canada
2473 Posts |
Posted - 03/06/2012 : 7:58 PM
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| Sorry Steve I misread your post. You meant the tranceiver is not on "your" Am radio's band? Not meaning AM in general. I'm bad |
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Vancouver
1827 Posts |
Posted - 03/06/2012 : 11:14 PM
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quote:
Originally posted by pmicheals
Sorry Steve I misread your post. You meant the tranceiver is not on "your" Am radio's band? Not meaning AM in general. I'm bad
Call it a draw. I wasn't aware other places have different spectrum for "AM". |
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Langley, BC
Canada
1078 Posts |
Posted - 03/07/2012 : 10:48 PM
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quote:
Originally posted by pmicheals
quote:
Originally posted by Matt
quote:
Originally posted by sgRant
The transceiver frequency is not on the AM band. Hopefully someone will correct me, but I think 457 is about half of 900 where I found good reception AND no radio station. It makes sense that a harmonic of the source frequency could be sensed by the radio. This should show up at the multiples of 457.
This is correct, and I was going to say something about it earlier. There are a number of ways the distortion could be created in either the avalanche transciever or the AM radio.
So if 457Khz (+- 80Khz) is not an analog Amplitude Modulation (AM) frequency, then what is it?
AM (medium wave)brodcasts, amateur radio, and Avalanche beacons fall within the MF (medium frequency) range of 300 - 3000Khz. It's not FM.
When you pass a sinusoidal signal through a circuit that is "non-linear" you get additional sinusoids at frequencies that are multiples of the input frequency. So passing the 457KHz signal through such a circuit could easily create 914KHz, which falls in the commercial AM band. |
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Langley, BC
Canada
1078 Posts |
Posted - 03/07/2012 : 11:03 PM
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Basically just read the manual for your avalanche beacon.
They use crude (no) modulation and operate in a frequency band that is smack in the middle of the noise generated by the switch mode voltage regulators used in your portable electronics. Back when the standard was conceived neither portable electronics nor switch mode voltage regulators were as prevalent as they are now. |
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Vancouver
1827 Posts |
Posted - 03/07/2012 : 11:58 PM
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Just looking at the manual for a newer cell phone, it says to beware of interference in the following cases:
- near medical equipment
- near a pacemaker
- near hearing aids
- near blasting equipment
- near fuel or chemicals
- in aircraft
- near automotive electronics such as stereos and safety equipment
- near radios, pc's, tv's etc. |
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Vancouver
1827 Posts |
Posted - 03/07/2012 : 11:59 PM
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quote:
Originally posted by Matt
Basically just read the manual for your avalanche beacon.
They use crude (no) modulation and operate in a frequency band that is smack in the middle of the noise generated by the switch mode voltage regulators used in your portable electronics. Back when the standard was conceived neither portable electronics nor switch mode voltage regulators were as prevalent as they are now.
A perfect excuse to again make all the existing transceivers obsolete by changing the standard. |
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Burnaby, BC
Canada
1310 Posts |
Posted - 03/08/2012 : 07:42 AM
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| Who knows - if they ever make Recco detectors cheap and light. But higher frequencies also have issues. |
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North Vancouver, BC
Canada
433 Posts |
Posted - 02/11/2013 : 08:36 AM
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I was just checking the track my app recorded from my trip to Brockton Point yesterday when I was surprised to see an anomaly. This was the first time I had my beacon on and it was sitting right next to my cellphone which was tracking my route.
Here's what I got:
 Note the messy uphill track.
Here are some of those sections zoomed in:
  
Now here's that same track recorded by my wife (who also had a beacon on but her cellphone was in her pack):
 Note the clean uphill track.
And another one recorded by me the previous day without the beacon on:
 Note the clean uphill track.
Both my wife and I were using the Tracker 2 beacon.
Scary to see this kind of interference... |
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Vancouver
1827 Posts |
Posted - 02/11/2013 : 11:21 AM
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This can be affected by your setting for frequency of recording waypoints. As we know from when we're stopped, gps positioning never settles hunting around, and this effect can cause the result you saw. If you check your settings against your' wife's gps, it would be interesting to know how they compare. I'm not saying the phone isn't a problem, but we need to be careful about this. Or it could be an issue with some phones and some gps in some modes. Maybe someone who knows about frequencies and signal strengths could comment on whether this is even possible.
I've recorded tracks with two gps apps on my cellphone, and if interference is a problem, that situation is ripe for it. I assumed the minor jinking around was because of the 10m waypoint setting, so I've raised it to 20m.
http://www.clubtread.com/sforum/topic.asp?TOPIC_ID=55962 |
Edited by - sgRant on 02/11/2013 11:23 AM |
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north van, bc
Canada
949 Posts |
Posted - 02/11/2013 : 11:51 AM
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| FYI go pro cameras have also been tested to cause interferance. don't use the chest harness for the go pro with an avi beacon. stick it on your helmet. 1-2' away is ok. |
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North Vancouver, BC
Canada
433 Posts |
Posted - 02/11/2013 : 12:03 PM
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quote:
Originally posted by sgRant
This can be affected by your setting for frequency of recording waypoints. As we know from when we're stopped, gps positioning never settles hunting around, and this effect can cause the result you saw. If you check your settings against your' wife's gps, it would be interesting to know how they compare. I'm not saying the phone isn't a problem, but we need to be careful about this. Or it could be an issue with some phones and some gps in some modes. Maybe someone who knows about frequencies and signal strengths could comment on whether this is even possible.
I've recorded tracks with two gps apps on my cellphone, and if interference is a problem, that situation is ripe for it. I assumed the minor jinking around was because of the 10m waypoint setting, so I've raised it to 20m.
http://www.clubtread.com/sforum/topic.asp?TOPIC_ID=55962
I have it set to > 20 meters and I recorded 322 trips with this app (and used 4 different phones to record stuff). This is the first time I got such huge errors with the GPS coordinates.
I did some more tests at home and my cell phone also triggers the multiple burials alert on the beacon.
The manual does say to keep electronic devices 30cms away... |
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Happy go lucky, plaid wearin, postholin, safeway gaitor sportin, old-school film shootin, giver of many regards
Abbotsford, B.C.
Canada
13598 Posts |
Posted - 02/11/2013 : 12:44 PM
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Wow, going to have to watch what the cell does to my gps tracks.
K |
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Qualicum Beach, BC
Canada
1332 Posts |
Posted - 02/11/2013 : 5:14 PM
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| Some clothing has magnetic "buttons" on pockets. Magnets can sometimes turn on or OFF certain models of avi beacons. We found that Mammut Barryvox, for example, were effected. We also could place two of these beacons face to face, move them around and sometimes make one turn on or off, although I'm not sure why anyone would have two beacons in their pocket. This is not to diss Mammut beacons, as I assume other makes of beacons could be effected in the same way. We just happened to have Mammut's. I guess the word of warning is to isolate your beacon from any possible source of interference. |
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Van, BC
Canada
2841 Posts |
Posted - 02/11/2013 : 5:27 PM
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When I first read about possible GoPro interference with transceivers I played around with mine (Hero2 vs. PIEPS DSP) but couldn't get any interference, even holding both right next to / on top of each other. I'm still going to leave the GoPro on the helmet (and probably off), but it was a relief to see no apparent problems.
-Ryan
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North Vancouver, BC
Canada
1656 Posts |
Posted - 02/11/2013 : 5:31 PM
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quote:
Originally posted by Ryan.in.yaletown
When I first read about possible GoPro interference with transceivers I played around with mine (Hero2 vs. PIEPS DSP) but couldn't get any interference, even holding both right next to / on top of each other. I'm still going to leave the GoPro on the helmet (and probably off), but it was a relief to see no apparent problems.
-Ryan
I suspect it would probably be worst when using a WiFi BacPac on a Hero2 but I haven't played around with this either. |
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Avalanche beacon interference by cell phones
