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[Ike Zimbel]

When I noticed the noise, it was several hours before the service-maybe 3? people in the building-nothing on other than what was on when I did the setup.  I am curious as to what changed-one of the three mics did the same thing on setup and I changed the squelch on that mic-the other two were fine.  Then a week later the other two had an issue so ?

I just ran the scan with default settings out of box, but it quickly found 3 channels so I didn't worry about it.  We are in a small town of 7000 people - it's the largest town in the county and we are probably the most intense RF user in town other than emergency services on Sunday morning so the RF environment is pretty friendly compared to what I read a lot of you dealing with.

I will change the squelch and see how it goes. (just didn't think about that Sunday morning-I usually have about 15 minutes to run through a quick start up routine then off to drive) The only LED wall on the premises is the church sign outside (perhaps 80 feet from the rx through an 18 brick wall that is not rf friendly-but it was on at setup as well.  No SDI either.

Somewhere, maybe here, maybe on the SynAudCon list, I heard about a church that had switched to LED lighting for their architectural lighting. They, of course, chose some "cost effective" bulbs/fixtures, which turned out to be massive RF noise generators... So, are all the lights on when you're getting set up 3 hours before the service, or do they all get turned on closer to when the folks come in?

[Kent Clasen]

Due to the Shure lack of availability we purchased some Sennheiser EW 100 to replace Line 6 systems that outlived their usefulness.  I let the mics autotune and things have been great-when mics are on and being used.  Yesterday when I powered up the system and started prelude music, I noticed 2 of the new mics had the OL Leds on the SQ7 lit up solid-this was with the transmitters off.  I have never seen this in the Shure systems.  This did not happen when I initially installed the mics-I assume that it is some external interference that I need to address at some point, though so far it has not been an issue.  And as soon as I turned the transmitters on everything appeared normal.

Due to our ministry schedule, I turn the system on 3 hours before the service and another tech comes in around half an hour early and actually turns the mics on and does final checks.  Does overloading an input like this for an extended period of time have the potential to damage the input?  Yesterday I just left the transmitters on-but that is kind of wasteful on batteries.

Could it be a low output TV station that only broadcasts at certain times?

In Wireless Workbench you can put in your zip code and when checking for TV statins uncheck the box ‘only use high power TV stations’- this is checked by default. See if any TV stations are selected in the frequency range of your issues.

[Brian Jojade]

This is one of the complaints I have with the Sennheiser EW systems. Their squelch controls are extremely limited and sometimes can have a pretty negative impact on range because of it.

[Russell Ault]

...unless the squelch is wide open (see previous post, which I was typing as you posted yours, Tim). Leaving the squelch wide open is kind of the equivalent of leaving all of your pre-amp gains at full on the desk...if there's noise there, they will find it.

+1; the factory-default squelch on 100-series RXs is both "Low" (in the menu description) and low (in the sense of being below what is practically useful in almost any real-world scenario).

This is one of the complaints I have with the Sennheiser EW systems. Their squelch controls are extremely limited and sometimes can have a pretty negative impact on range because of it.

That's only true of the 100-series; on the 300-series and above (going back to at least G3) the squelch is adjustable in 2 dB increments (although I almost never see 300-series-or-above RXs in the wild).

-Russ

[Bill Meeks]

Somewhere, maybe here, maybe on the SynAudCon list, I heard about a church that had switched to LED lighting for their architectural lighting. They, of course, chose some "cost effective" bulbs/fixtures, which turned out to be massive RF noise generators... So, are all the lights on when you're getting set up 3 hours before the service, or do they all get turned on closer to when the folks come in?

Hi Ike. That was likely my thread from March 2018 here: https://forums.prosoundweb.com/index.php/topic,166611.0.html. Our issue was caused by Chinese manufactured LED bulbs that had been retrofitted into old incandescent fixtures. Replacing the bulbs with similar models from Cree solved the issue by completely wiping out the broadband RF hash. The problem reared its head when we switched from our old 600 MHz analog Mipro stuff to Shure QLXD in the 470 MHz band. The problem was there with the 600 MHz stuff, but was attenuated enough at that frequency to be less of an issue so we never noticed it.

[Ike Zimbel]

Hi Ike. That was likely my thread from March 2018 here: https://forums.prosoundweb.com/index.php/topic,166611.0.html. Our issue was caused by Chinese manufactured LED bulbs that had been retrofitted into old incandescent fixtures. Replacing the bulbs with similar models from Cree solved the issue by completely wiping out the broadband RF hash. The problem reared its head when we switched from our old 600 MHz analog Mipro stuff to Shure QLXD in the 470 MHz band. The problem was there with the 600 MHz stuff, but was attenuated enough at that frequency to be less of an issue so we never noticed it.

Hi Bill, Yep, that was the exact thread I was thinking of. Thanks for posting it!

[Paul Johnson]

Does nobody do this correctly anymore? In fairness, RF theory isn't the best understood subject, but the manufacturers make it worse by the crazy notion that scanning in this way is the best solution.

Clearly if you only have a few channels on the go, it can be mostly successful - but every manufacturer has spent a  lot of time putting together channel plans that feature the least intermodulation issues possible. Sennheiser have so many now with all the bands being subtly or majorly different that band planning is absolutely critical.

First we need to address the notion that having an LED on can damage the system. The OP was considering leaving a pack turned on to keep a light .... out? All analogue RF systems that use FM have no signal noise. Muting this is a system benefit, because it makes people jump when the noise replaces wanted signal through distance, absorption, battery power etc etc. If you had a knob to do this, at some point the threshold would be sufficient to kill the noise - that's all it does. A signal even a little over this threshold opens the squelch. It won't be noise free at that setting and will sometimes chatter when wanted signal dips below the threshold. Some people like to turn the squelch up reducing this chatter, only letting through stronger signals. This can chop the odd word. Other people, like DJs as an example use a radio system to travel perhaps a meter? You'd think they would just use a cable? For them, they'll turn the squelch to maximum so nothing, even a real mic on the same frequency further away, will open the squelch, even if the real mic is off.

The LED comes on when the squelch is open. It is no different from worrying about the LED being on - on a mixer muted channel. It is an indicator to tell you something.

I never, ever use the built in scan facility. It chooses your channels on a false premise - that they are empty. They might be or the mic on that channel might simply be off, or out of range. As soon as it becomes active - like the venue next door turning theirs on - it has failed. It also lets you select inappropriate channels - where Shure or Sennheiser etc have NOT said it's an intermod free channel.

If you work in busy RF areas, there is only one sensible thing to do. Buy something like an RF Explorer. Turn it on and set it to hold. The venue next door battering up their packs then switching them off again gets displayed on the screen. Leave one on for half an hour while you are doing something else - then you will see that your channels are really empty. It won't stop somebody rocking up and wrecking your system with 5 mins to go, but leaving these on shows band occupancy, live. Interference can be predicted sometimes before it happens. FM means there is capture effect, with two RF sources, the strongest covers the weaker. You only get a fight when they both are around the same level. More usually, your system gets taken into a null, leaving next door's loud and clear.

RF management is not common sense. That is why we pay for an A2, who has the job of monitoring and listening to all the channels so potential problems can be noticed before somebody else shoves up a fader.

Shure and Sennheiser have different squelch characteristics. Sennheiser's tend to mute very quickly when signals approach the cutoff. Shure seem to be a bit more forgiving, but both have risk. Sennheiser cut you off abruptly, Shure's seem to allow really noisy signals before they shut off. The reality is you could turn squelch off and deal with the muting yourself - based on what you hear. I've nursed a few systems like this over the years when you know they are always going to be weak. The decision to call it a day in the hands of the mixer, not the electronics.

If you put together a new rack nowadays, then frequency spectrum displays are hardly uncommon. They help with a trained eye watching them. For unattended operation there is always risk. They're not magic, or special - they need skilled people to work them.

Scanning is a system almost guaranteed to not work. Ask yourself to imagine a venue next door using scan, and doing it while you were battering up. Each pack turned on, tested and turned off again. How many of your channels would next door's system declare as FREE?

[Stephen Swaffer]

Paul,

I realize my method was quick and dirty-as a volunteer dealing with a failure of two older system within a very short time period this hit me at a very busy time.  If you read my posts I don't live in a heavy RF area-the only "venue next door" is literally part of our church as well.  An in depth frequency co-ordination is something I want to get done this fall.

The only time the light was on was when the TX was off.  I would like to assume that any input on a modern board would be capable of handling any output levels a modern receiver is capable of putting out-but I'm old enough to know better than to assume.

So far, when the TX is on, all I get is the signal I want-of course, I lock our TX's on and defeat the mutes because letting talent play with mic settings is too many cooks in the kitchen for me.

[Paul Johnson]

I get it, but it is receiving something - just noise. All that matters is what comes out of the receiver. Watching LEDs flicker on and off can help you work out what is happening, once you know how they operate.

[Kevin Maxwell]

A long time ago (in a place far far away) before I got into or even understood anything about frequency coordination I was doing a musical and everything was working fine, until someone went off stage after their part and even though I had their mic down on the mixer I was getting so much interference on their channel that on the analog console I was using I had such a hot interfering signal that you could hear the crosstalk between channels. I think that show was what made me start to understand and get into doing frequency coordination any time I used wireless. BTW I haven’t seen the crosstalk issue with any digital consoles I have used when one channel has a really hot signal on it, before you get to trim it down.

[ProSoundWeb Community]