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Author Topic: Spread Spectrum  (Read 1322 times)

Mark Hannah

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Spread Spectrum
« on: September 23, 2016, 10:32:12 am »

What does one do about spread spectrum interference that pops up out of the blue, just before or during a show? 

The situation:

I support the US Air Force Band in Washington, DC where high level individuals attend that have secret service or other security present.  I have never had a problem until last night.  You could say "your luck finally ran out" as a minute or two before the show all 8 IEMs started taking sever hits.

Take a look at this video https://drive.google.com/open?id=0B10H8698n_C4Z194a0t1MWRHS1k.  It will come into focus the last 18 seconds.  You are looking at four of the eight IEMs and what I believe to be the frequency-hopping spread spectrum inference, most likely connected to the secret service's communications.

The Weeds:

At this point in my post, I'll get into the weeds of what I was able to do so anyone that wants to respond can provide accurate help. 

I started looking up and down the spectrum (Sennheiser B range).  The frequency hopping was happening in the whole block except for what appeared to be ~5 MHz at 630 MHz. Grabbed the monitor engineer's and my pack to re-tune and was able to swap out with the vocals between tunes.  The band wasn't so lucky.

The band was driven out into the performance area in two open-top military trucks for three songs.  Their gear was all running on UPS during transit from out-of-view and then temporarily plugged in (power and audio).  The decision had been made before I came on-board to have everyone on IEMs to reduce the current draw on the UPSs.  I didn't argue because there were so few frequencies to coordinate.

In this situation, what do you do?  All was happy 30 minutes before the show while walking around the parade field.  I doubt the secret service will share any information pre load-in.

Thank for your input.

PS.  First time to post a video link.  Let me know if it doesn't work.
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Henry Cohen

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Re: Spread Spectrum
« Reply #1 on: September 23, 2016, 10:42:49 pm »

What does one do about spread spectrum interference that pops up out of the blue, just before or during a show? 

The situation:

I support the US Air Force Band in Washington, DC where high level individuals attend that have secret service or other security present.  I have never had a problem until last night.  You could say "your luck finally ran out" as a minute or two before the show all 8 IEMs started taking sever hits.

Take a look at this video https://drive.google.com/open?id=0B10H8698n_C4Z194a0t1MWRHS1k.  It will come into focus the last 18 seconds.  You are looking at four of the eight IEMs and what I believe to be the frequency-hopping spread spectrum inference, most likely connected to the secret service's communications.

The Weeds:

At this point in my post, I'll get into the weeds of what I was able to do so anyone that wants to respond can provide accurate help. 

I started looking up and down the spectrum (Sennheiser B range).  The frequency hopping was happening in the whole block except for what appeared to be ~5 MHz at 630 MHz. Grabbed the monitor engineer's and my pack to re-tune and was able to swap out with the vocals between tunes.  The band wasn't so lucky.

The band was driven out into the performance area in two open-top military trucks for three songs.  Their gear was all running on UPS during transit from out-of-view and then temporarily plugged in (power and audio).  The decision had been made before I came on-board to have everyone on IEMs to reduce the current draw on the UPSs.  I didn't argue because there were so few frequencies to coordinate.

In this situation, what do you do?  All was happy 30 minutes before the show while walking around the parade field.  I doubt the secret service will share any information pre load-in.

Thank for your input.

PS.  First time to post a video link.  Let me know if it doesn't work.

Best guess as to source - White space device. Mitigation possibilites are:
- Find device and operator and ask them to shut down;
- Register the TV channels you plan to use in one of the geo-location databases prior to use -
     a) At least 1 hour before spectrum need if your a Part 74 licensee, or
     b) at least 30 days before spectrum need if a Part 15 (unlicensed) user.
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Henry Cohen

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Mark Hannah

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Re: Spread Spectrum
« Reply #2 on: September 23, 2016, 11:37:28 pm »

Best guess as to source - White space device. Mitigation possibilites are:
- Find device and operator and ask them to shut down;
- Register the TV channels you plan to use in one of the geo-location databases prior to use -
     a) At least 1 hour before spectrum need if your a Part 74 licensee, or
     b) at least 30 days before spectrum need if a Part 15 (unlicensed) user.

Henry,

During a SynAudCon course, filing for a Part 74 license was discussed.  It is on my To-Do list.  I understand PWS (and other businesses?) can help an individual navigate through the paperwork.

During the course, I got the impression from the instructors that white space devices were not very prevalent yet.  In addition, I know a former White House Comm (WHCA) employee who agreed it was a good chance it was secret service, but we can't prove it.  Thus my original conclusion.  But knowing your experience level, TVBDs will be presented to my boss and the band.

Thank you.
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ProSoundWeb Community

Re: Spread Spectrum
« Reply #2 on: September 23, 2016, 11:37:28 pm »


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