Sennheiser G2 Wireless fatal flaw?

[Damian Clarke]

Thanks for the replies guys.
Chris, just to confirm I am using the bodypack receivers and transmitters, it says on the box ew112-p camera set.
I'll try to answer some of the questions and suggestions:

I have both receivers placed side by side on my belt, antennas pointing up.
They are both connected via the XLR leads to a Zoom H4 strapped to the opposite side of my belt.
I use Bank 8 for both receivers which contains the licence-free frequencies for my region. I scan with one for a free channel, then while this is still switched on I scan with the other.
I tried 863.100 on one set and 864.300 on the second set at the last wedding, plus I changed the frequency quickly on one set as soon as I noticed some interference. The trouble is as I'm sure you understand, I don't generally have time to go hopping back and forth messing around trying to strike it lucky with a magic frequency. I have also tried some frequencies from the other banks and everything works perfectly at home, through walls to outside etc.
The transmitters are placed on the groom and father of the bride at different points during the day, again pointing upwards and practically always in line of sight never more then 10 meters away and with regards to a recent ceremony, literally 4-5 feet away LOL.
It does seem to be when people start arriving so mobile phones has crossed my mind, but I thought the licence-free frequencies would have been ok since they are reserved for private individual and enthusiast use? From what I've hastily researched the mobile/cell phones have their own big frequency range. Perhaps standing by the entrance with a bucket and confiscating phones is in order, since there is always one dipstick who dosen't turn theirs off.

I know that I can turn the transmitters/recievers upside down, space them apart, wave them in the air, shout at them, eat them etc. but surely little enhancments like this shouldn't be the cause of such drastically dismal performance at such close ranges.
I know the Senns are hardly the most expensive units, but for me they are certainly not cheap and paying this kind of money, I expect things to just work with minimal fuss.

I'm going to look into what you said Ty, about the wrong frequency block and generally try and do some more research on frequencies around the UK, but like I said a channel will come up free and clean for a while, people arrive...some interference...scan and change frequency again...seems clear...moment when it counts, interference...can't do anything about it now as I'm behind the camera sweating my bollards off. Nice.
Sorry for the rant and long post and I really appreciate your suggestions. ;-)

Damian.

[Dan Keaton]

Dear Damian,

Thank you for providing the detailed information necessary to troubleshoot this problem.

At first glance it appears that you are doing everything right.

I feel that the main problem is cell phone interference.

Since you are recording to the Zoom H4, you could place the receivers and the Zoom H4 as close as possible to the transmitters. These could be hidden somewhere.

You could build a little box to hold the receivers and the Zoom H4 so that they would be easy to move.

Do you keep your own cell phone off?

[Ty Ford]

Damian,

I have been in two situations with my AT U 100 where the wireless reception was fine during setup. I walk tested the units and was getting 50 feet solid and didn't even need that.

When the talent showed up and I put the transmitters on them, range plummeted to totally unusable and the receiver was four feet from the transmitter. The bride's worked fine. It was the groom's that was unusable. Fortunately I had a boom ready and I went to boom for him and got it all. The groom was excited, and probably didn't have is cell phone turned off (again.)

The other situation was one guy speaking. Again, during setup I had plenty of range and had worked that room with that right a dozen times before with very few problems. I put the body mic on him and reception went to total shit from 8-10 feet away.

I went hardwired and we did OK. He left, and I was able to use the previously malfunctioning system out the room and 100 feet down the hallway. It had to be him.

Some folks think their cell phones are off when they are really in standby. Mine's either on or off.

Hope this helps.

Regards,

Ty Ford

[Damian Clarke]

Thanks for the info Dan, Ty. Just like you say, the more I think about it cell/mobile phones seem to be the only thing that offers some explanation and all locations have that in common.
I'm not so keen on the little box to hold the receivers and H4 near to the transmitters, I feel it kinda defeats the object of wireless and I wouldn't be able to monitor. Also it dosen't seem to matter how close I am as I've learned!
I keep my own phone in the car so I know it can't be that.
The registrar/minister/priest etc. already tells guests to switch off phones just before the ceremony. It's just a consistently ridiculous situation. (say that five times when your drunk lol)
I think I've got four options:
1. Keep trying with the Sennheisers, investigating what frequencies here might be best or offer the least chance of interference *yawn*
2. Look into the ATW-1800's, I think they offer different frequency ranges here than the E category Sennheisers.
3. Sell the Sennheisers, scrap wireless ideas, buy two Zoom H2's and two lavaliers to connect to them.
4. Set fire to everything wireless, curse technology and become a monk.

[Graham Risdon]

Hi Damian

Is there any chance of uploading a small audio extract that allows us to hear the problem you're getting. I'd be interested to see if they're similar to the odd problems I had with my Sonys.

Cellphones are definitely a problem though - I did a conference recently with my AT kit and one of my team had to confiscate an iphone from one of the presenters! I think it's something to do with the "polling" signal they use. I sometimes get interference on the car radio when my mobile goes. That said, cellphone interference is pretty easy to identify. As Ty says, people think switching it to Silent is OK, but the "polling signal" (if that's what it's called) still happens. the only answer is to switch them off completely during a shoot.

[Dan Keaton]

Dear Damian,

When most people hear, "Turn Off Your Cellphones", then think this means to put them on vibrate or in silient mode.

Surprisingly, some people do not even know how to turn off their cell phones completely.

But we need them to be completely off.

Otherwise, their transmissions may cause interference either with your wireless or even the camera's audio when you are not using wireless.

[Damian Clarke]

Dan, that is a good point. I guess it's just something that is virtually uncontrollable in a wedding environment. It does make me wonder though how a lot of other videographers seem to get away with clean interference-free audio most of the time, or if this is just a pre-conception of mine and interference is a general headache for most, why do we bother using it at all?
I suppose it's fine for the studio set and controlled location shoots but out their in the 'one chance to get it right' wilderness.....

Graham, I have attached a 30 second file which is a particularly bad segment of audio.
I suppose the phones still have to be connected or stay in touch with the network even when in silent mode etc. in order to keep up to date on its status and whether there is anything about to be incoming. Would a correct analogy be 'always connected to the net, even though your not necessarily downloading anything'?

[Dan Keaton]

Dear Damian,

I will defer to others, but your interference sounds like general interference from a high powered transmitter and not cell phone interference.

During this sound bite, was the receiver close to the transmitter?

It sounds like this was at the reception and that their may have been a lot of people between the transmitter and the receiver, but I am just guessing.

Were you monitoring the audio via headphones when this was recorded? If so, did you hear this specific interference?

Recommendations:

1. I would try different frequencies.

2. I would not mount the receivers and Zoom H4 on your belt.

I like to keep the receivers as high as possible. When you have them on your belt and you turn around, then the signal has to go through you, or bounce off another object to get to the receiver.

Your audio clip sounded like there were a lot of people crowded around the transmitter.

[Graham Risdon]

Damian

Doesn't sound like the usual cellphone interference to me - more like general interference. I've had something similar when the Tx or Rx batteries have got low...

I've attached a short clip that demonstrates cellphone interference... It's been boosted substantially from the original track to allow it to be heard clearly!

Sorry I can't be more help

[Damian Clarke]

Dan, your right it was the speeches during the reception. I was about 6 or 7 meters away and although there was some guests in between, I still had quite a good straight line of sight as I tend to stand sideways to my tripod, so the receivers mounted on the left side of my belt where pointing in the right direction.
The clip was taken from the groom who was standing at the top table, a few people to either side of him.
The squelch setting was on low which is why it dosen't just go mute and I get to hear all that glorious noise. What difference does it make though, mute or noisy, both unusable.
I was indeed monitoring the audio (with beads of sweat running down my face I might add) and that was exactly what I could hear. My headphones were plugged into the H4.
I just find it amazing that I spend a decent amount of money on quality gear and yet it proves to be so unreliable in real world use. Yet, DJ Wannabe at the local bar gets great audio every week with some crumby two bit no-brand vhf system.
I'm not sure how much higher I could practically mount the receivers and H4. I did put one receiver on my FX1's shoe at one wedding, but I still got loss of signal so I took it off.

Graham, I've listened to your clip and I recognise that blipping noise that phones cause. So that's not my problem....hmmm. I always have tons of fresh AA batteries and replace them religiously even when there is probably sufficient power in them to last quite a bit longer. So I definitely know it's not that either.

I'll try messing around a bit more but who needs this hassle when your a one-man-band?
I really appreciate the help and suggestions though.
Thank-you.

[Dean Sensui]

Quite a few phones generate this kind of interference. I noticed the Nextel phones are especially bad. So bad, in fact, that I even saw it get picked up by a musician's hard-wired PA system at a restaurant!

Maybe it got inducted by the musician's guitar. This kind of interference would normally be experienced from a badly over-driven, heavily amplified and cheap CB radio.

[Damian Clarke]

Wow, seems like nothing is safe!
Do you mean that a cheap CB radio could cause this interference to my Sennheiser's or that the Sennheisers are in fact no better than a cheap CB radio in that they are susceptible to it? Hope that makes sense...
How on earth does everyone else cope with this, what is the point in having 'backup' audio, when the backup audio is indeed more reliable than the main wireless audio? Why not just have two sets of 'backup' audio?
In my case I am seriously considering just having a lav going into a Zoom H2 which can be placed in a pocket and a table mounted H2 nearby for backup. All for the same price as my Sennheiser setup, but without as many headaches. The only price for this is the loss of monitoring, but to be honest I've never really needed to adjust much anyhow.
Ideally though, I would still love to use the Sennheiser setup, as I have it sitting here and it is so handy and lovely when it works. Plus I hate the thought of being beaten by this. *sigh*

[Ty Ford]

Yes, we are pretty screwed. :)

I've had cell phones and blackberries get into hard-wired mics.

It's a mine field out there. Some of the industrial market (meeting rooms at convention centers, congressional committee meeting rooms, etc.) have just been overhauled to provide more shielding so they can better withstand the problems of cell phones, nextels and blackberries.

I think the wireless market gear was already on top of that.

Regards,

Ty Ford

[Dean Sensui]

Cheap CB radios, especially the ones with amplified power mics that are over-driven, can "splatter" their signal over a wide range of frequencies.

Way back, when my television was getting reception via an antenna, I the picture was being badly distorted every so often. On a hunch, I turned on my own handheld CB radio and found the channel the guy was transmitting on.

His signal was badly distorted. He had a power mic and figured if some volume was good, more was better. So he had it cranked way up, not knowing that he sounded badly distorted. So I politely broke in and let him know he sounded bad. He trimmed it back until he sounded perfectly clear, and at the same time the distortion on the TV went away.

Everybody won.

The interference came from equipment whose operating frequency was nowhere near that of TV.

It's probably similar with cell phones.

I don't know how these cell phones get their FCC approval if they generate RF over such a broad spectrum. The noise gets picked up by other electronic equipment that have nothing to do with radio. Sure sounds like a serious design violation to me!

[Vic Owen]

RFI elimination is a science unto itself, and continues to get more complicated due to the increase in transmitters that everyone seems to now be carrying. In some cases, the transmitter itself is at fault, but in the majority of cases, the RFI results from the receiver reacting to frequencies it is not supposed to. TVs are a good example of this, as are many audio systems.

Turning-off as many of the transmitters as possible will make a significant difference -- it goes a long way toward eliminating, or at least reducing, the intermodulation products and other spurious signals that can occur.