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Author Topic: Crazy RF event last night...insight appreciated.  (Read 1349 times)

Loren Miller

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Crazy RF event last night...insight appreciated.
« on: May 05, 2018, 03:09:46 pm »

Gig: Simple Awards Dinner, Darby House - Galloway OH 5/4/18

Equipment: 2 Ch of QLXD H50 band with HH(beta 87a) w/passive antenna combiners and 1/2wave 8ft in air

Context: 3pm load in, I do my normal setup, 4pm Do a RF scan on the receivers and it comes up with ch120 and ch126 (low 540's if I recall), I sync the mics and make sure they are on the highest output (10mW) The event starts at 5pm and everything is going great.

Problem: At 8pm on the dot, while in use during the keynote, 1 mic goes completely dead, my 1st thought was battery, but I could see on receiver that it was full and had 9hr 2min left on the charge, I then noticed that the RF meter was gone and blinked 1 bar occasionally over the few seconds I observed, I then grabbed my other mic and ran up with it to switch it out and tested it while I ran the 20-30ft to the stage (clear line of site to antenna) when I handed it over it worked for 1 second then died, I run back to FOH with the 1st mic and do a ch scan and it jumps me up all the way to 596mhz and it is back to working flawlessly. I do the "Run of Shame" one more time and the rest of the night goes off flawlessly.

2 questions: What happened? How do I go about making sure this does not happen again?

My hypothesis:
1. I was using an active tv channel that was "off" and turned "on" at 8pm?
2. I need to study my local TV channels and not use them even if my receiver chooses them?
3. I need to get an RF sniffer, but don't want to haul/buy more.
4. I should have ponied up for Axient that supposedly can detect interference and switch over to a back up channel automatically?

This is a new one to me so any constructive insight appreciated, Thanks - Loren
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Scott Holtzman

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Re: Crazy RF event last night...insight appreciated.
« Reply #1 on: May 05, 2018, 03:15:28 pm »

Gig: Simple Awards Dinner, Darby House - Galloway OH 5/4/18

Equipment: 2 Ch of QLXD H50 band with HH(beta 87a) w/passive antenna combiners and 1/2wave 8ft in air

Context: 3pm load in, I do my normal setup, 4pm Do a RF scan on the receivers and it comes up with ch120 and ch126 (low 540's if I recall), I sync the mics and make sure they are on the highest output (10mW) The event starts at 5pm and everything is going great.

Problem: At 8pm on the dot, while in use during the keynote, 1 mic goes completely dead, my 1st thought was battery, but I could see on receiver that it was full and had 9hr 2min left on the charge, I then noticed that the RF meter was gone and blinked 1 bar occasionally over the few seconds I observed, I then grabbed my other mic and ran up with it to switch it out and tested it while I ran the 20-30ft to the stage (clear line of site to antenna) when I handed it over it worked for 1 second then died, I run back to FOH with the 1st mic and do a ch scan and it jumps me up all the way to 596mhz and it is back to working flawlessly. I do the "Run of Shame" one more time and the rest of the night goes off flawlessly.

2 questions: What happened? How do I go about making sure this does not happen again?

My hypothesis:
1. I was using an active tv channel that was "off" and turned "on" at 8pm?
2. I need to study my local TV channels and not use them even if my receiver chooses them?
3. I need to get an RF sniffer, but don't want to haul/buy more.
4. I should have ponied up for Axient that supposedly can detect interference and switch over to a back up channel automatically?

This is a new one to me so any constructive insight appreciated, Thanks - Loren

All but number 4!  You didn't mention what gear you have.  Some models of Shure can feed data into WWB for a primitive scan.  I don't trust any type of automation on channel selection. 

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Scott AKA "Skyking" Holtzman
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Loren Miller

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Re: Crazy RF event last night...insight appreciated.
« Reply #2 on: May 05, 2018, 03:17:41 pm »

All but number 4!  You didn't mention what gear you have.  Some models of Shure can feed data into WWB for a primitive scan.  I don't trust any type of automation on channel selection.

"Equipment: 2 Ch of QLXD H50 band with HH(beta 87a) w/passive antenna combiners and 1/2wave 8ft in air"
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Scott Holtzman

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Re: Crazy RF event last night...insight appreciated.
« Reply #3 on: May 05, 2018, 03:19:37 pm »

"Equipment: 2 Ch of QLXD H50 band with HH(beta 87a) w/passive antenna combiners and 1/2wave 8ft in air"

How did I miss that?  Perils of answering on a phone.  QLXD is what we have too (I have G50 in CLE if you need more).  It produces a nice scan with Wireless Workbench from Shure.  Download the free software and see what you think.

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Scott AKA "Skyking" Holtzman
River Delta Audio is now:

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Cleveland OH
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Loren Miller

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Re: Crazy RF event last night...insight appreciated.
« Reply #4 on: May 05, 2018, 03:24:58 pm »

How did I miss that?  Perils of answering on a phone.  QLXD is what we have too (I have G50 in CLE if you need more).  It produces a nice scan with Wireless Workbench from Shure.  Download the free software and see what you think.

I'm on it, I assumed with only 2 ch I didn't need to do that at every gig, it sucks learning the hard way!
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Justin Goodman

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Re: Crazy RF event last night...insight appreciated.
« Reply #5 on: May 06, 2018, 03:34:51 pm »

It's all a balancing act ... did the client want to pay for you to come to the venue and do a 24-48 hour RF slow scan?  My guess is they did not ... so you did [almost -- your #1-3 are good] the best you could with the opportunities available.

The other potential thing you could do in a similar circumstance is:

1) If you're only running 2 channels of wireless, it's easy enough in MOST markets to make sure both are operating on different TV channels -- this would provide you some protection against a random station firing up at a given hour.

2) You could have the 2nd mic on the stage with a note at the podium "if the your mic stops working, here's your backup -->" ... then you see them switch and mute swap at FOH. 
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Samuel Rees

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Crazy RF event last night...insight appreciated.
« Reply #6 on: May 06, 2018, 04:40:30 pm »

I'm on it, I assumed with only 2 ch I didn't need to do that at every gig, it sucks learning the hard way!

For me, I use workbench connected to my units to scan every show, for any number of channels, if not for some emergency. Itís not just TV to think about, there are also local public safety bands which one should both avoid for oneís own RF reliability, and for public safety. Your unitsí auto-scan function doesnít know about any of this.

My company has a mostly ULXD inventory which is more feature rich but uses the same backbone RF technology. We frequently deploy much bigger channel counts in a contentious RF environments and  achieve very good reliability. IMHO, no need to go nuts and buy Axient. Even with Axient, youíll still need to use these coordination methodologies to get good performance (and not trample on public safety).

You really do get used to doing these things every time - I think youíll find itís time well spent.


Sent from my iPhone using Tapatalk
« Last Edit: May 06, 2018, 04:43:53 pm by Samuel Rees »
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Andrew Broughton

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Re: Crazy RF event last night...insight appreciated.
« Reply #7 on: May 06, 2018, 05:09:12 pm »

RF bars went to 0? Not interference then. You had a loss of RF.
I'd say most likely a bad antenna cable.
Did you say "Combiner"? I hope you mean "Distributor"... Combiners are for transmitters, not receivers.
Was it a 2-ch receiver? Why did you need a distributor, the Shures are built in.
Were you using 2 antennas?
« Last Edit: May 06, 2018, 05:14:06 pm by Andrew Broughton »
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Jordan Wolf

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Re: Crazy RF event last night...insight appreciated.
« Reply #8 on: May 06, 2018, 05:48:03 pm »

Was it a 2-ch receiver? Why did you need a distributor, the Shures are built in.
The QLXD units only come as single receivers.
Quote
Were you using 2 antennas?
Also a question I was thinking.

I agree on checking the antenna cable.
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TomBoisseau

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Re: Crazy RF event last night...insight appreciated.
« Reply #9 on: May 06, 2018, 07:34:24 pm »

Gig: Simple Awards Dinner, Darby House - Galloway OH 5/4/18

Equipment: 2 Ch of QLXD H50 band with HH(beta 87a) w/passive antenna combiners and 1/2wave 8ft in air

Context: 3pm load in, I do my normal setup, 4pm Do a RF scan on the receivers and it comes up with ch120 and ch126 (low 540's if I recall), I sync the mics and make sure they are on the highest output (10mW) The event starts at 5pm and everything is going great.

Problem: At 8pm on the dot, while in use during the keynote, 1 mic goes completely dead, my 1st thought was battery, but I could see on receiver that it was full and had 9hr 2min left on the charge, I then noticed that the RF meter was gone and blinked 1 bar occasionally over the few seconds I observed, I then grabbed my other mic and ran up with it to switch it out and tested it while I ran the 20-30ft to the stage (clear line of site to antenna) when I handed it over it worked for 1 second then died, I run back to FOH with the 1st mic and do a ch scan and it jumps me up all the way to 596mhz and it is back to working flawlessly. I do the "Run of Shame" one more time and the rest of the night goes off flawlessly.

2 questions: What happened? How do I go about making sure this does not happen again?

My hypothesis:
1. I was using an active tv channel that was "off" and turned "on" at 8pm?
2. I need to study my local TV channels and not use them even if my receiver chooses them?
3. I need to get an RF sniffer, but don't want to haul/buy more.
4. I should have ponied up for Axient that supposedly can detect interference and switch over to a back up channel automatically?

This is a new one to me so any constructive insight appreciated, Thanks - Loren

I had a similar situation occur a few years back.  It was on the 14th (or top) story of a building in Buckhead / Atlanta.  Mid afternoon all wireless checked out fine.  About 2 hours later, as I began to mic the participants for a video shoot,  ALL 10 of the wireless were taking hits!  I tried to find some clean frequencies, but there was NOTHING that would work.  Bottom line, the shoot was a bust! 

I went home quite discouraged and proceeded to try to find out why.  I searched the FCC data base to see if I could find a clue.  At first, nothing.  After further searching different "lists", I came across an entry for a "low power" TV station that only came on in the evening and was located just a block or two away!  Short of coming in on a previous day and doing a 24hr scan, there was nothing that could have prepared me for this.  And even if I had had done so, this particular "band" of wireless would not have worked, regardless!   

I have a soundman friend who later went back there.  He was aware of my experience choose to use some VHF systems instead.  He had no problem whatsoever.

Tom



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