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Old June 4th, 2013, 04:38 AM   #1
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Sennheiser lavaliere interruption

Hi!

We have 2 sets of Sennheiser ew100 G2 wireless lavaliere mics.
When we are filming somewhere outdoors (nature, city etc..) we have constant problems with interruptions.
We cannot film even 30 seconds of talk that sound doesn`t get interrupted one or two times. It is like frequency problem, but we have tried to change frequencies many times and it is always the same problem.

Does anyone else have similar problems? How do you solve that? Are there any other better lavaliers that doesn`t have that problems?

Thanks for help
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Old June 4th, 2013, 10:03 AM   #2
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Re: Sennheiser lavaliere interruption

Assuming the signal is intermittently dropping out, going silent, it might be that you are experiencing a phenomenon known as "reflectance." That is typically caused by the radio signals bouncing off metal objects (reflecting off) in the immediate area where you are shooting. One way to at least partially solve the problem is to use a "true diversity antenna." You can do a search on this forum. Seems I remember a couple of threads. Also can do a general online search using those terms to learn about the phenomenon. I experienced it while on a shoot at a power plant. Then I bought a receiver with a true diversity antenna. Haven't had the problem again, yet.

Another problem is having the signal blocked by an object.

Another possibility is a bad cable somewhere and you lose the signal when the cable is jiggled.

Drop outs with some "static" are often due to interference from other wireless devices, cell phones, blackberries, tablets, walkie-talkies (Nextel, Radio Dispatched Trucks, Hotel or other venue communication systems).

Sometimes, I have to use cabled microphones, with long xlr cables. There's a saying "when you're able, use a cable..."
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Last edited by Roger Van Duyn; June 4th, 2013 at 10:11 AM. Reason: typo
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Old June 4th, 2013, 10:36 AM   #3
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Re: Sennheiser lavaliere interruption

Can you post a short clip so we can possibly ID whether it is an RF or cable/connection/acoustical issue? What kind of distances are you expecting?
Have you tried the receiver's scan feature and /or Sennheiser's on-line 'frequency finder' utility to find 'unused' frequency channels.. (though I don't know it's availability for your area)
Other than that, keep the transmitter and receiver in 'line-of-sight' and do not let the system's antennas touch skin or be in close proximity to devices that spew RF like cell phones and other wireless equipment... in fact, it's recommended to have these devices turned off.
Are there any other better lavaliers that doesn`t have that problems?
- All wireless systems experience problems.. There are 'better' more expensive systems, but without proper due diligence in set-up, improved reliability would be minimal at best.
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Old June 5th, 2013, 06:42 AM   #4
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Re: Sennheiser lavaliere interruption

Some people say it's important to have the transmitter and receiver antennas pointing in the same direction (vertical or horizontal). That worked for me a couple of times when I had breakup like you describe.
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Old June 5th, 2013, 02:57 PM   #5
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Re: Sennheiser lavaliere interruption

There are many different things that could cause "interruptions". As Mr. Reineke suggested, posting an example would help us identify what kind of "interruption" you are hearing.

It is necessary to identify exactly what kind of problem you have before we can offer any suggestions. Else we could offer you 50 different things to try, and only 5 might be relevant to your problem.

it would also be useful to give more complete explanation of how/where you are using your equipment. How far apart are the transmitter and receiver? Do you try to make this distance as short as possible? Are you careful to fully extend both transmit and receive antennas? Do you have this problem only when in a city, or out in the countryside also? Are you setting the frequencies of your two systems to compatible frequency channels so they don't interfere with each other?

it sounds like you think it is an RF (interference, or propagation) problem. But are you sure it isn't an intermittent break in the microphone cable, etc?
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Old June 6th, 2013, 07:37 AM   #6
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Re: Sennheiser lavaliere interruption

Another possibility is a broken mic. cable.

I have often seen people just wind the mic. cable round the transmitter after use - if you don't leave a loose loop at the start you strain the cable as it comes out of the plug and can cause a break in the cable.

This can cause intermittent operation.
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Old June 6th, 2013, 08:24 AM   #7
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Re: Sennheiser lavaliere interruption

I have had a similar problem using my Zoom H2 when it's on the wedding guests dinner table and the symptoms sound a bit like morse code here and there. I'm wondering if it could be down to cell phone interference.
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Old June 6th, 2013, 08:29 AM   #8
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Re: Sennheiser lavaliere interruption

Without a listen, we're guessing. Can we hear the problem?
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Old June 7th, 2013, 09:49 AM   #9
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Re: Sennheiser lavaliere interruption

Thanks for a lot of replies. Here I have cut some examples where you can hear what am I talking about:
https://www.dropbox.com/s/g4u6ioj225...terruption.wav

@Les Wilson, we will try that, normally the lavaliere on speaker is put verticaly and the one on camera is horizontally. Never thought that can be the problem.

@Richard Crowley, mostly we have interruptions outdoors (especially in cities - we didn`t record too much in nature areas so I can`t say much about that). When we shoot in studio we have that problem very rare. Last shooting that we had was stedicam shot with speaker walking 3-6 meters in front of camera. Transmitter is fixed at the back of speaker on the belt (vertically) and receiver is on the camera (horizontally). The antennas on Sennheiser ew100 G2 are fixed and cannot be extended. Regarding frequency channels as I remember there are 8 of them and we always put the transmitter and receiver on the same channel.

The problem is not with the cable because we tested it and tried 3 different new cables.

Currently I don`t have lavaliers with me but next week I will try some of your suggestions.

Appreciate your help
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Old June 7th, 2013, 11:04 AM   #10
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Re: Sennheiser lavaliere interruption

Classic RF dropout. Not a cable fault. My guess is simply the path. There are a few best practice things to do first. Aerials - vertical on both is best, because they should radiate omnidirectionally. One horizontal and the other vertical is the worst setup. On top of this, a horizontal aerial will have it's nulls left and right, so as the unit is turned the received signal can drop down even further.

All that is happening is that the receiver is working on the edge - at one moment there is just enough signal, then a small body reposition, or camera movement, and it drops below the threshold, the squelch shuts and you get the 'phuttt' noise. If the person wearing the transmitter has it under something, so the aerial is up against their body - then the body absorbs a great deal of the output, especially if they are sweaty. At the other end, the receiver can be blocked by anything in the way too - even the metal of the camera.

I'd put the camera receiver vertical, and repostion the transmitter to be clear of the body (if it isn't).

If you separate your receiver and transmitter by around 10 metres, and then wave the receiver around, listening on headphones, you can usually replicate the dropout. horizontal aerial on one pointing towards the other is usually the worst.
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Old June 7th, 2013, 12:06 PM   #11
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Re: Sennheiser lavaliere interruption

I concur with Paul.
Furthermore, if the transmitter's antenna is in contact with the wearer's skin, you will loss about 80% of RF gain.
Also keep the squelch set to the default 'Low' setting. The transmitters audio gain (sensitivity) should also be set optimally.
Heed my previously stated recommendations.
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Old June 7th, 2013, 01:15 PM   #12
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Re: Sennheiser lavaliere interruption

I completely agree with Mr. Johnson.

Radio signals are polarized, just like polarized light. Both antennas must be in the same plane for maximum transfer of energy. When they are cross-polarized (as you have been doing) you can expect a reduction in RF level of up to -20dB. Mind you, that won't reduce the audio level, but it will greatly reduce the working distance before you have dropouts.

Imagine that an antenna's coverage pattern is like a donut, with the antenna wire running through the center of the hole.

If the antenna wires are horizontal, half of the coverage area will be toward earth, which is of no use whatsoever, and there will be dead spots pointed along the axis of the wire, so when the transmit antenna (or the receive antenna) rotates horizontally, you might encounter a big drop in signal.

If the antenna wires are vertical, the coverage "donuts" will be horizontal, which is ideal: either the talent (transmit antenna) or camera (receive antenna) can rotate 360º in a horizontal plane, and there will be no significant change in the coverage area or range.

Always keep both antennas vertical!
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Old June 7th, 2013, 03:13 PM   #13
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Re: Sennheiser lavaliere interruption

.............................. Always keep both antennas vertical

Does anyone know whether this also applies in real world use of the G3 (I note the OP is using the G2).

The G3 receiver brochure states "this diversity receiver uses the ground connection of the line cable as its second antenna to provide improved reception"

and as long ago as April 2009 John Willett posted on this forum in response to "what is adaptive diversity":

It's another name for "antenna diversity".

The camera-mount receiver is too small to be "true" diversity as that needs a second receiver inside (true diversity is two complete receivers feeding a single output stage).

The G3 camera-mount receiver is the same size as the G2 - the second antenna is the output cable. It has a single RF section and a special circuit that monitors the two antennas and uses the one with the strongest signal.

So it's a diversity receiver, but with the two antennas being switched between a single RF stage, rather than two antennas and two RF stages being switched at the output of the RF stage.

It was deemed to be better this way for on-camera use, as it keeps the size of the receiver down.


My thinking is that although normally its pretty easy to ensure that the antenna on the talent is vertical but rather hard to keep it horizontal, the receiver when mounted on cam is going to be horizontal if placed direct in the cold shoe.

Would you recommend using a small ball and socket head to mount the receiver vertically on the cam or is that largely irrelevant when using the adaptive diversity G3? Maybe that would be a good reason for the OP to bite the bullet and upgrade to the newer G3 thereby also sidestepping other potential conflicts due to available frequency changes.

Pete
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Old June 7th, 2013, 04:57 PM   #14
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Re: Sennheiser lavaliere interruption

The diversity feature is a neat idea, but using the output cable as an aerial is a bit of a compromise - however - in diversity systems, with two close spaced aerials, the real problem is that if both aerials are close together, and in the same plane, as most are. If the transmitter or receiver is in a null, and thus low or zero signal, the other receive aerial will probably be exactly the same. it's standard practice in mains powered radio receiver racks to have the aerials in different locations, on the premise that if one path is down or poor, the other to the second aerial may well be in the clear. People also develop little tricks with polarisation. If one aerial is vertical, then some people will have the second receive aerial at an angle. The theory is that if for some reason the polarisation of the signal is not vertical, then as the signal strength drops, an aerial with an alternative polarisation should go up! The G3 system with one aerial up, and the other (the cable) diagonal to the XLR socket should cover that one.

I'm not sure that Sennheiser's system could really be described as "better" - as it shares one RF section, but it's clearly better than a non-switching system. I have a transmitter for a guitar that uses the cable as the aerial, and it's not really that efficient, as the aerial isn't resonant, and has to be tuned electronically - which means the aerial just isn't so good at capturing RF energy. Still better than one aerial though!

I always mount mine on the rear, vertically. There are a few pictures of cameras with receivers mounted on the top with the aerial pointing towards the front. This is the absolute worst position. The deepest null is an extension along the aerial's direction.
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Old June 7th, 2013, 07:38 PM   #15
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Re: Sennheiser lavaliere interruption

A common practice when one has a pair of close~spaced "whip antennas" is to put them into a "V" formation, rather like the old VHF TV "rabbit ears" from the 1950s. The theory being that having two antennas 90 degrees apart in alignment gives the best possible (in such a limited constraint) coverage of radio waves coming in direct or reflected. It sounds goofy and is counter-intuitive when the transmitting antenna is most likely vertical. But the alignment of a monopole transmitting antenna doesn't really affect the "plane" of the transmitted radio waves.
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