Wireless lavalier noise

J

Jonathany26

Active member
I have two sets of Sennheiser lavalier mics, before every shoot I reset them and scan for available channels, majority of the time they both say no channels available after scan so I will just pick a frequency for each transmitter, no matter what I do I keep getting bad noises like in this link below, this happens even if it is a sit down interview, I have replaced the lavaliers with new ones but I still get this noise, these are the G2 senheiser models not the G3 models

https://vimeo.com/150257301

password: audio

Thanks in advance for any help
 
Which frequency block are you using? You may be in a location that is too saturated in that part of the spectrum. I have the same issue with G band (Sennheiser G3) in the middle of downtown Memphis.

If the clear scan function doesn't turn up anything, you might - *might* - find a channel by running manually through every frequency, which is tedious and nowhere close to a guarantee.
 
I will look at the frequency block when I get home tonight, I am in Chicago and maybe it's the area that I usually shoot in, because I live about 30 miles outside of Chicago in the Suburbs and when I reset it at home and scan for channels I can get at least 2 channels to pop up.
 
Jonathany26 said:
I have two sets of Sennheiser lavalier mics, before every shoot I reset them and scan for available channels, majority of the time they both say no channels available after scan so I will just pick a frequency for each transmitter, no matter what I do I keep getting bad noises like in this link below, this happens even if it is a sit down interview, I have replaced the lavaliers with new ones but I still get this noise, these are the G2 senheiser models not the G3 models

https://vimeo.com/150257301

password: audio

Thanks in advance for any help
Click to expand...

From my looking at the 'Whitespace' channel availability, it appears that in 'downtown' Chicago, TV channels 28 and 41 have been 'reserved' for wireless mics. That 'reserved'... is sort of ambiguous... but that aside...

The frequencies in MHz would be Ch 28 -- 554-560 MHz, and for Ch 41 -- 632-638 Mhz. The following is listed as available for 'whitespace' devices:

22 518-524 White Space **
42 638-644 White Space **
46 662-668 White Space **
48 674-680 White Space **

But that doesn't mean these channels are 'clear'... at the moment there are few, if any active Whitespace devices anywhere...

As for the 'burbs'... unfortunately the above channel availability may change due to location even 'close' to Chicago 'downtown'...

Since you mention G2 Sennheisers... could the channel selections be in the now 'locked out' range above 700 MHz... That band was auctioned off several years ago, and may now be filled with Cell Phone signals... or whatever.
 
Alex H. said:
Which frequency block are you using? You may be in a location that is too saturated in that part of the spectrum. I have the same issue with G band (Sennheiser G3) in the middle of downtown Memphis.

If the clear scan function doesn't turn up anything, you might - *might* - find a channel by running manually through every frequency, which is tedious and nowhere close to a guarantee.
Click to expand...

Here's the 'whitespace' database output for 'downtown' Memphis... the "Reserved" channels should be 'mic reserved'... for better or worse...

Since I don't have wireless mic equipment at all I can't really check out the local to San Diego area availability in the SD 'reserved' channels to see if they are in fact... empty... or filled with junk so as to make them useless...
----

36 602-608 Reserved **
39 620-626 Reserved **
7 174-180 Available **
9 186-192 Available **
12 204-210 Available **
14 470-476 Available **
16 482-488 Available **
18 494-500 Available **
20 506-512 Available **
2 54-60 White Space **
10 192-198 White Space **
11 198-204 White Space **
19 500-506 White Space **
22 518-524 White Space **
24 530-536 White Space **
27 548-554 White Space **
30 566-572 White Space **
32 578-584 White Space **
34 590-596 White Space **
35 596-602 White Space **
40 626-632 White Space **
42 638-644 White Space **
43 644-650 White Space **
44 650-656 White Space **
47 668-674 White Space **
49 680-686 White Space **
 
Ok the frequencies for both of my sets are Sennheiser G2 range 626-662 I guess I need to understand white space and how to look up what channels and frequencies that are available in certain areas, to avoid that interference what do you call that noise that I am hearing?
 
Jonathany26 said:
Ok the frequencies for both of my sets are Sennheiser G2 range 626-662 I guess I need to understand white space and how to look up what channels and frequencies that are available in certain areas, to avoid that interference what do you call that noise that I am hearing?
Click to expand...
Since I don't have any wireless mics, let alone the Sennheiser model you are using, you will have to check the selection options.

According to the Sennheiser Frequency Finder web widget:

It indicates that only channel 42, 638-644 MHz, is 'vacant' in the 'downtown' area, more exactly ... the 60606 Zipcode area... It also indicates there is a licensed transmitter operating on channel 41, 632-638 MHz, @ 25kW some 6 miles away, and the estimated signal strength at the 60606 Zipcode is -65 dBm, which could possibly interfere...

The only other 'sort of available channel' seems to be Ch. 35, 596-602 MHz, and there is a licensed transmitter some 46 miles away, and the estimated signal strength is -85 dBm.

Most of the other channels are 'filled' with something and could possibly interfere with the wireless mic, depending as most of them have signal strength estimates in the -70-50 dBm range.

The 'whitespace' devices are limited to 40 mWs in this area, so it is 'believed' that they would not interfere with the TV transmitters operating on the same channels at some distance...

But the thing of 'whitespace' is that while the device may be authorized to use that channel, if there is interference from the licensed transmitter, the 'whitespace' user can't complain.

On the other hand if the 'whitespace' device interferes with the licensed transmitter, customers or the station can complain about the whitespace device.

In the case of a wireless mic, that is a different situation. And given the Sennheiser widget indicates there is a licensed transmitter on Ch. 41, which the 'whitespace' database claims is 'reserved' for mics... indicates there may be some discrepancy between the Sennheiser database, the 'whitespace' database and what the FCC has actually licensed...

In any case check the Sennheiser database given above for selecting your Sennheiser G2 frequencies and see how it goes.

The 'confusion' is exacerbated by the fact that there is a process called 'repacking' which the FCC is banking on to be able to 'sell' more of the spectrum in the current TV band which for the UHF band is channels 14 to 51, or 470 to 698 Mhz. It is not clear to me when those TV stations have 'repacked' and so the spectrum is available or not.
 
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Jonathany26 said:
Ok the frequencies for both of my sets are Sennheiser G2 range 626-662 I guess I need to understand white space and how to look up what channels and frequencies that are available in certain areas, to avoid that interference what do you call that noise that I am hearing?
Click to expand...

I call that an "RF hit". Something is likely using the same frequency, or is broadcasting over a range of frequencies that include the one you're trying to use, and overwhelming your signal. Old cell phones and pagers were often blamed for "RF splatter" or leakage, and it sounds a lot like this, but it could be anything from EMS communications gear to fluorescent light (any discharge lamp, even HMI) ballast noise.

I'm assuming you're doing the normal safe radio mic things, like using only fresh alkaline batteries (most rechargeable bats can't deliver full voltage, etc.), not letting the antennas touch skin, powering off (airplane mode) all the RF devices on the set (cell phones, pagers, iPads and the like so they aren't constantly pinging the local cell towers), etc.

So that leaves you to finding a separate clear channel for each mic setup, which will likely require a separate scanner, some time, and some thought.

Or... you could use a wire. Wireless is a last resort, and one of the reasons this is true is exactly what you are experiencing. You'll never get this using a $20 USD XLR cable. The wire sounds better, costs way less, and is orders of magnitude more reliable.

That said, people do run radio mics in Manhattan and LA, both RF Hells of their own, so Chicago shouldn't be impossible.
 
Thank you all for your help and replies, the audio side I am still learning, I did not know about cell phones possibly causing interference, we always have them on set, I will start making sure all are in airplane mode, I also have operated my lavalieres with low batteries so that could also be a possibility, I think I will invest in a separate scanner and if I correct all these things and I am still having trouble I will get the Sony lavalieres in the 500MHZ range. But I also think no matter if I keep these or get new ones (lav sets) I will still have to make sure I have available channels.
 
Jonathany26 said:
I think I will invest in a separate scanner and if I correct all these things and I am still having trouble I will get the Sony lavalieres in the 500MHZ range. But I also think no matter if I keep these or get new ones (lav sets) I will still have to make sure I have available channels.
Click to expand...

Why Sony? Just curious, or was that a typo? I have used the current Sony UWP systems (D11) and was not impressed. Sennheiser is the way to go in this price range. The old UWP-V1 systems were noisy and unreliable. The new UWP-Dxx systems are less noisy.
 
The EK100 portable receiver's scan feature is next to useless in a high RF environment. (pity me in midtown Manhattan.. aka, RF hell) You need a external scanner. Better yet.. pro systems, which has this facility built in... unfortunately neither is low cost.
 
Jonathany26 said:
Thank you all for your help and replies, the audio side I am still learning, I did not know about cell phones possibly causing interference, we always have them on set, I will start making sure all are in airplane mode, I also have operated my lavalieres with low batteries so that could also be a possibility, I think I will invest in a separate scanner and if I correct all these things and I am still having trouble I will get the Sony lavalieres in the 500MHZ range. But I also think no matter if I keep these or get new ones (lav sets) I will still have to make sure I have available channels.
Click to expand...

Quick primer on using wireless from Shure. Maybe Alex H. will build a FAQ for how to use a wireless mic system once you have one; that information seems to be lacking in our stickies.

It's not just cell phones. There's a huge number of wireless devices in use all around you all the time, and most of them are made as cheaply as possible. If they leak RF junk it doesn't necessarily hurt their function. Instead, the leaks interfere with the function of other equipment like your wireless mics. This is why we need an FCC to regulate all this equipment, and some way to enforce the rules.

Instead of the Sonys, you might want to look at the Sennheiser G3s. The G3s use multiple antennas (I'm thinking this isn't for actual spatial diversity, but is instead what's often called xmit/receive diversity which is basically two antennas used together) to reduce drop outs and artifacts. I've used G3s in the heart of Manhattan (aka RF Hell) without problems; if they can handle that...
 
I had noise with G3 system that went away after changing the batteries. Just throwing that out there, cheers good luck getting your issue resolved.
 
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