ALS Woes

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Peter Etheredge

Sophomore
Jan 11, 2011
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St. Charles, IL
tnprod.com
And I'm back with more wireless ALS issues (unrelated to my previous inquest about the Nursery thing).

About a year ago we put in a new system at a church and it included a Listen Technologies ALS system. Now in the past we've used Listen systems with great success and for about 11 months this was no exception - in fact the church ordered more receivers due to the system's popularity and their very large elderly crowd. Everything came in crystal clear - no buzzes, no fuzziness, nothing.

Then about a month ago another nearby church installed a new ALS system on the same frequency and these congregation members began picking up the signal from that church. No problem, we'll just change the frequency. Well when we went to do that all of the channels were now noisy, including the one that it had been on. There was a lot of noise and interference on all channels. Nothing we did could fix it. Even with just the test tone on and the transmitter unplugged from the rest of the system there was noise.

Here's where it gets weird though....

At the same time we installed a brand new sound system at a church 2 miles away and while the ALS there (the same Listen system) was fine when we set it up we soon received a call that it was doing the same thing.

It would seem that MAYBE there is some sort of something broadcasting on that frequency in the area causing all this? It's bizarre though that both systems worked fine from the start and then failed.

Anyone ever expierence anything like this before?
 
Re: ALS Woes

I'm not calling into question your design/installation/integration practices, but it would be helpful to know just how you went about selecting the frequency range(s) that you did for those venues. Did you use the manufacturer's online frequency finder? Did you perform an onsite RF scan to detect what type of environment you were dealing with outside of the "usual" TV stations and in-house interference you already took into account? Have you considered there may be a problem with the grounding of the equipment - maybe someone lifted an AC in one or more places?

Also, you may want to see if there have been any recent changes to broadcasting facilities in those trouble areas. I would hope they would be willing to provide some insight.

Good luck and keep us posted!
 
Re: ALS Woes

Jordan Wolf said:
I'm not calling into question your design/installation/integration practices, but it would be helpful to know just how you went about selecting the frequency range(s) that you did for those venues. Did you use the manufacturer's online frequency finder? Did you perform an onsite RF scan to detect what type of environment you were dealing with outside of the "usual" TV stations and in-house interference you already took into account? Have you considered there may be a problem with the grounding of the equipment - maybe someone lifted an AC in one or more places?

Also, you may want to see if there have been any recent changes to broadcasting facilities in those trouble areas. I would hope they would be willing to provide some insight.
Click to expand...
If these are true ALS systems, which it sounds like they are, then they probably operate in the 72.025-75.950 MHz or 216.0125-216.9875 MHz spectrum. As I understand it, ALS is the primary use of the 216 MHz spectrum and an approved secondary use of the 72-76 MHz spectrum along with R/C models and some wireless industrial controls. Neither range is used by broadcasters so while there could be interfering sources, the situation is a bit different than for wireless microphones and IEMs.
 
Re: ALS Woes

Ah, my ignorance on part of the subject is revealed! Thanks for the info, Brad - I tried to look at systems on the manufacturer's site, but there were too many options to look through.

Could the OP provide a link to the system that he installed? That would be most helpful!
 
Re: ALS Woes

Brad Weber said:
If these are true ALS systems, which it sounds like they are, then they probably operate in the 72.025-75.950 MHz or 216.0125-216.9875 MHz spectrum. As I understand it, ALS is the primary use of the 216 MHz spectrum and an approved secondary use of the 72-76 MHz spectrum along with R/C models and some wireless industrial controls. Neither range is used by broadcasters so while there could be interfering sources, the situation is a bit different than for wireless microphones and IEMs.
Click to expand...

This is exactly the case. It's the 72-75 range. And don't worry - when it comes to wireless microphone/IEM systems we have the manufacture's recommended frequencies with us before we even come on site and then we also give everything a thorough scan. :)

Don't know why I forgot to post it but the transmitter in both cases is this:

http://www.listentech.com/lt-803.html

Again have this same unit in a wide variety of installs with no problems at all. It's just these two and again the one was problem free until that other church got something on the same band.


OH! And I should mention that the first thing I did was the obvious - I contacted Listen, however they really weren't much of a help other than asking us to send the units in, which we are doing.
 
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