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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Dan Currie on October 31, 2016, 10:35:09 PM
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I have 68 frequencies to coordinate today and found most of the Shure G band filled with a spread spectrum device. Luckly I only have 16 UHFR's down there. This is the first time I've come across something like this in our 470-698mhz range. Any thoughts as to what it is? It's concerning to me that the device isn't limited to a small 6mhz chunk. The show is in a building at the heart of downtown Detroit, Campus Martius viscinity. I'll be there the next two days and will hopefully have more time to investigate now that the initial setup is done.
Apparently my embedding skills are lacking... :-\ so here's the link...
https://www.youtube.com/watch?v=oEpmiPlZqEg&feature=youtu.be
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I have 68 frequencies to coordinate today and found most of the Shure G band filled with a spread spectrum device. Luckly I only have 16 UHFR's down there. This is the first time I've come across something like this in our 470-698mhz range. Any thoughts as to what it is? It's concerning to me that the device isn't limited to a small 6mhz chunk. The show is in a building at the heart of downtown Detroit, Campus Martius viscinity. I'll be there the next two days and will hopefully have more time to investigate now that the initial setup is done.
Apparently my embedding skills are lacking... :-\ so here's the link...
https://www.youtube.com/watch?v=oEpmiPlZqEg&feature=youtu.be
It is a white space video transmission system. Legally if you register the tv channel you plan to use 30 days in advance that device should automatically shut off. If you are a licnesed user you can register it the same day, I believe.
http://whitespaces.spectrumbridge.com/Main.aspx
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It is a white space video transmission system. Legally if you register the tv channel you plan to use 30 days in advance that device should automatically shut off. If you are a licnesed user you can register it the same day, I believe.
http://whitespaces.spectrumbridge.com/Main.aspx
Dan and Pete,
I saw the exact same thing in Phoenix the day before the 2015 Super Bowl, inside a TVBD prohibited zone, and then again this year at Nissan Stadium during CMA Music Fest in the center of my registered circle, all over BTR ranges 3 and 4. In Phoenix, I notified Karl Voss (NFL head of tech & Freq Coordinator) and no one could identify it. The Dept of Homeland Security and US Secret Service were operating nearby (USSS is always frequency-covert) but that wasn't the case in Nashville.
FWIW, I'm unaware of any FHSS DVBD that are currently type-certified, and the video distribution systems that I've seen TX use 8VSB modulation, which looks just like any other DTV station.
https://en.m.wikipedia.org/wiki/8VSB
Something rotten and disruptive to our work is going on here...
Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.
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Something rotten and disruptive to our work is going on here...
Very strange - could be some illegal, of course, device bought in the interweb.....
if you see it again and still cant locate it, fire up a few ULXD transmitters in the same band and see what doesn't work any more.
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Very strange - could be some illegal, of course, device bought in the interweb.....
if you see it again and still cant locate it, fire up a few ULXD transmitters in the same band and see what doesn't work any more.
Will do, with pleasure. :-D
Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.
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Rehearsals went great today. No issues...but the ghost of Hedy Lamarr came back a few hours after call time. If it's around tomorrow after the show I'll see if I can find her.
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Rehearsals went great today. No issues...but the ghost of Hedy Lamarr came back a few hours after call time. If it's around tomorrow after the show I'll see if I can find her.
Hi Dan,
I love the Hedy Lamar reference! Props!
You're using a BB60C, right? That's also my instrument of choice.
It has me wondering, though, if this might be something actually generated by our hardware. Unfortunately, I can't afford a lab quality instrument that sweeps fast enough to consistently catch these signals.
I can say with confidence, though, that these were not only shown by the measurement readout; my mic receivers' meters were showing momentary hits and the BTR users complained about dropouts while this was going on.
Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.
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Happening right now at Music City Center in Nashville, TN. Within 1000ft. of the center of James Stoffo's BAS-LP registered TVBD-prohibited location for the CMA Awards. Measured by two different instruments, walking around the venue, so these are real signals and not self-generated instrument noise.
Edit: Here's a link that should work for Android users:
https://www.youtube.com/watch?v=Xzhepe4gEvU&feature=youtu.be (https://www.youtube.com/watch?v=Xzhepe4gEvU&feature=youtu.be)
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Happening right now at Music City Center in Nashville, TN. Within 1000ft. of the center of James Stoffo's BAS-LP registered TVBD-prohibited location for the CMA Awards. Measured by two different instruments, walking around the venue, so these are real signals and not self-generated instrument noise.
http://cleanwirelessaudio.com/2016-11-02 11-52-03-897.avi (http://cleanwirelessaudio.com/2016-11-02 11-52-03-897.avi)
Lately I've been making a point of walking around for a few blocks around the venue and looking for TV ENG vans. This doesn't sound like what they usually carry (mainly Lectrosonics IFB's) but it might be worth a look-see. Presumably whatever it is didn't walk in. Good luck!
iz
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Lately I've been making a point of walking around for a few blocks around the venue and looking for TV ENG vans. This doesn't sound like what they usually carry (mainly Lectrosonics IFB's) but it might be worth a look-see. Presumably whatever it is didn't walk in. Good luck!
iz
Indeed, I had to shut down an uncoordinated IFB in an ENG van right outside the arena door yesterday.
This signal is way outside the norm for commercial audio gear, and seems to be a mystery. I tried to sniff out the source this morning and had no luck localizing it to a device.
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https://www.youtube.com/watch?v=Xzhepe4gEvU&feature=youtu.be (https://www.youtube.com/watch?v=Xzhepe4gEvU&feature=youtu.be)
Great video, Jason.
I'm not a frequency hopping algorithm myself but this seems too random for my understanding FHSS. I'd expect a constant step size, constant amplitude, and constant linger time, if not constant than a predicable pattern.
The closest thing I have seen to something like this was a transmitter with a failing oscillator that couldn't maintain it's frequency. Fascinating stuff. I'll be on the look out.
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Great video, Jason.
I'm not a frequency hopping algorithm myself but this seems too random for my understanding FHSS. I'd expect a constant step size, constant amplitude, and constant linger time, if not constant than a predicable pattern.
The closest thing I have seen to something like this was a transmitter with a failing oscillator that couldn't maintain it's frequency. Fascinating stuff. I'll be on the look out.
Hi Cameron,
Your post reminds me that I've seen a bad TR-825 pack show this sort of pattern when keyed on.
Hmm...
Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.
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Jason,
Nice work at capturing that video. Your span is .5mhz wide and the source looks like a FM signal that is being modulated constantly, no spars or change of bandwidth. Obviously it is moving around freakishly. Then again a BTR TX doesn't have the 'fork' look. Trying to spark some synapses... some of the shapes this device makes are reminiscent of an 825 being keyed on.
(http://i118.photobucket.com/albums/o111/dblogproductions/btr%20rx%20spike%20width_zpspldf9edb.png) (http://s118.photobucket.com/user/dblogproductions/media/btr%20rx%20spike%20width_zpspldf9edb.png.html)
Or is that the trace left by the persistence leaving a 'flat top' trail' because it's moving so fast? I can't locate an image right now of an 825 pack keyed on not but modulating or static. By chance is there a TR-825 assigned to 534mhz?
I'm glad you appreciated the Hedy Lamarr reference. There were two more rehearsals today with the show/web stream early afternoon. I also brought in the 1302 to have a peek. Both the BB60C and 1302 showed this noise. I inserted a SAW filter in line which has the gak in its bandpass and it didn't go away. So this isn't some sort of false image. I did find it though.
The signal IS roughly 20mhz of Tempest 900 noise!! The Tempest on the show was spewing nonsense 400mhz--ish lower than what it broadcasts. Hedy has been found. Peak to peak in the 902-928mhz range the tempest is 24mhz wide. The other 4mhz are probably being masked by TV station 21 or is under the noise floor.
If you have been seeing something similar to this and the range of the gak has been higher maybe there was a FHSS on the show in the 1.9 or 2.4ghz range releasing hash lower in the spectrum. Keep us posted on what you find.
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Jason,
Nice work at capturing that video. Your span is .5mhz wide and the source looks like a FM signal that is being modulated constantly, no spars or change of bandwidth. Obviously it is moving around freakishly. Then again a BTR TX doesn't have the 'fork' look. Trying to spark some synapses... some of the shapes this device makes are reminiscent of an 825 being keyed on.
(http://i118.photobucket.com/albums/o111/dblogproductions/btr%20rx%20spike%20width_zpspldf9edb.png) (http://s118.photobucket.com/user/dblogproductions/media/btr%20rx%20spike%20width_zpspldf9edb.png.html)
I did find it though.
The signal IS roughly 20mhz of Tempest 900 noise!! The Tempest on the show was spewing nonsense 400mhz--ish lower than what it broadcasts. Hedy has been found. Peak to peak in the 902-928mhz range the tempest is 24mhz wide. The other 4mhz are probably being masked by TV station 21 or is under the noise floor.
If you have been seeing something similar to this and the range of the gak has been higher maybe there was a FHSS on the show in the 1.9 or 2.4ghz range releasing hash lower in the spectrum. Keep us posted on what you find.
A few comments:
1) That is a cool video, if somewhat alarming. +1 on Dan's comments.
2) Tempest 900: I had one out on the Shania Twain tour last summer. The other gear in the rack (a dog's breakfast of com and RF gear) did not like having the antenna mounted on the base station...definitely induced some noise. I used the remote antenna right on top of the rack and things settled down. I have also seen them put out noise when the base station antenna and the remote antenna were in close proximity to each other.
3) I'm not sure if I have a screen shot of this, but on my most recent show I had some interference that was moving around over time. This was definitely intermods from the com system as I was able to listen to it. There were a number of things with the system that I was not too keen on, like two of the four BTR bases having only single TX outs instead of the split one, and those going through a combiner, so that was likely the culprit.