A few years ago I had a problem with interference in my Sennheiser EW100 G2 mics. The issue seemed to be with the rechargeable batteries I was using.

However the problem is back, despite using brand new duracells.

I've scanned for empty channels, set squelch to LOW, checked cable routing, and done a bunch of other tests.

I also replaced the antenna in the transmitter.

Basically I can get interference even if I'm only 10 feet away from the person wearing the mic, even in direct line of sight. If the person is behind a wall, etc, it's far worse.

I was wondering if the solder job on the new antenna could be to blame. I'm hoping I don't need to buy a new set of mics ....

Thanks all!

Any chance you could post a sample of the kind of noises that are occurring?

I have gotten intermittent interference from cell phones near the transmitter on these units. Blackberrys seem to be the worst. Just a thought... also, it's possible for multiple transmitters to create interference, consult the manual for frequency selection tips if you are using or in the presence of other similar transmitters. It's also possible that there is a strong competing broadcast or other transmitter near your frequency. Sennheiser has a web site that lets you check the open frequencies in the place you are working. I assume but do not know that it is available for your country, worth a look:

http://www.sennheiserusa.com/FindFrequency/

There are so many possibilities, we can only offer vague guesses by shooting in the dark.
Without more details AND listening to an example of the interference, the best we can offer is sympathy.

Here in Australia the Sennheiser G2's are in a frequency block that has / or will be taken over by Telcos

Never a good idea to use rechargeable batteries with radio mics and they only give 1.2 volts and can cause problems.

The G2 is quite old now and here in the UK only ch70 is not legal for use, it may be that in your country the RF spectrum has changed so I would check that.

Over time radio mics can go off frequency too so it may be they need a service or indeed you need to buy the latest model that will have the correct frequencies as we have had to here in the UK to allow us to use ch38.

It may also be that the replacement antenna is not working correctly.

Thanks for the reply everyone.

Here's a bit more info:

Mics are: Sennheiser G2 B-Block 626-662 MHz

I experience the problems both in rural and urban areas. Cell phone interference doesn't seem to be the issue.

I live in Guatemala but have had the problems pop up while filming in other countries in Latin America (Costa Rica, Nicaragua, etc). The Sennheiser Frequency Finder doesn't offer up info for Central America.

I've attached a compressed .mov file so you can hear what's going on (I tried to upload a .wav file but DVINFO wouldn't let me).

You can hear three "hits" in the first 10 seconds. I was 2 meters away from the talent, direct line of sight. The "hits" seemed to happen when she turned away from me. Transmitter placed on her hip. Cable was out of the way. Transmitter antenna vertical, receiver antenna horizontal (mounted on hot shoe).

I then moved to about 8-10 meters away, still line of sight. You can hear a lot more "hits."

Fresh set of duracells.

As far as I know your frequency range is not within the range of mobile phones, 3g and 4g are in higher ranges.
It doesn't sound like a cable problem.
Only thing I can think of is that the receiver antennas are bad .. or you have a monday morning make.

Your audio sample strongly suggests that you have an intermittent audio/power connection between the body pack transmitter and the microphone head.

I did NOT hear anything that sounded to me like RF problems. (i.e. I didn't hear any multipath hash, or RFI hits, or squelch tails, etc.)

No wireless kits are in the SAME bands as cell phones. (By design.) However cell phones are powerful enough and "wide-band" enough to cause problems to receivers even many MHz away from the operating channel. Furthermore that very sensitive, unbalanced connection between the body pack/transmitter and the microphone head is particularly vulnerable to cell phone transmissions. ESPECIALLY if the subject who is wearing the clip-on lav also has an active cell phone in their pocket (i.e. inches away!)

If a subject is SO IMPORTANT that they must keep their cell phone active while on camera, give the phone to an assistant to monitor from down the hall.

In theory, at least, the polarization of the transmit antenna and the receive antenna should be the same. Either both vertical, or both horizontal. Again, in theory, having them cross-polarized (as you do, with one vertical and one horizontal) can cause a signal strength reduction of 20 dB or so.

Someone will suggest that if you're in a room with a lot of electrically reflective surfaces, the reflections can change polarization to some extent. Be that as it may, the direct signal should be stronger than the reflections. So when using wireless (which I do very rarely) I have always tried to keep both antennas in the same relative polarization.

Incidentally, the same rule applies outside the world of wireless mics. For example, a lot of emergency comm systems use vehicle-mounted antennas, which are vertical. The base station (or repeater) antennas, likewise, are vertically polarized to maximize efficiency and minimize dropouts.

I'm not saying that this will solve your particular problem (I seem to hear a few different things happening), but I still feel it's an important rule of thumb. I feel very safe in saying that if you do this, it certainly won't make your problem any worse, and might improve things significantly.

This is an interesting thread. For a number of years I have had issues with my G-Band G3 wireless set.

When I discovered the Sennheiser Freq Finder site, it made things much easier. I've found that just because the on location scan says that freqs are clear, they may really not be. Using the online site I can clearly find transmitters in a 60 mile radius and see which bands are 100% free of a signal. That's helped a lot.

It turns out, I bought my G-band before realizing that it is a highly polluted range in my location. As such, I've picked up an A-band and a B-band. So theoretically, I figure between those 3 and my backup pocket recorder, ONE of them should be clear! LOL (double mic the minister and double mic the groom at weddings)

The receiver's built-in scanner is totally inadequate for populated RF environments IMO. I use the on-line frequency finder and/or use an external RF scanner when arriving at the location, then manually check the receiver for extraneous RF.
Additionally the transmitter/receiver 'should be' line-of-sight with antennas and out in the open. The transmitter's antenna should not be touching any skin either.

Totally agree on the scan function - pointless, and designed to cause more problems than it cures!

Are you absolutely certain the squelch isn't turned up really high on the receiver? Even close in body masking can reduce the signal briefly below the threshold and you get that quick phut - Richard's comment about a dodgy cable also produces a very similar sound when the power cycles off and on - so well worth checking.

The talent could have jammed the pack in bending the aerial against the metal body - or could have been very close to sweaty skin, again making any of the other problems worse.

It's not interference in the usual sense of interference from other transmitters - that sounds very different, its a lack of signal - either a quick RF dropout or the mic element losing it's power supply.

Both should be easy to replicate - and if, as usual, you find they work perfectly with cable wiggling and waving around, then consider the talent's mic positioning to be possibly the problem.

This kind of problem isn't rare - happens all the time, that's why radios are a pain in the bum,

Thanks guys.

I've tried two different mics on the transmitter. Both produce the same noise. I think that eliminates the mic cable.

Squelch is definitely set to LOW. I set it to HIGH just for fun and the mic went MUTE.

I placed both antenna pointed down. Cable was clear of antenna on transmitter. No cell phone on talent. Interference seems to be intermittent, until I get about 30'+ from talent, when it becomes nearly constant.

Do I get a local radio technician (generally old guys who've repaired TVs and radios for years) to open it up? Maybe try re-soldering the antenna? Or am I opening myself up to a world or problems?

As an aside, I'm thinking about ordering a set of G3s in any case. Good to have a second set, especially as I live in rural Guatemala. What band should I be looking for? I work across Latin America - have read that G Band (high 500s/low 600s) is reasonably reliable.

I still don't think it is any kind of RF problem (including antenna).
My money is still on the audio/power connection.
If two different mics show the same symptoms, then my top suspect is the mic connector on the transmitter.

I just DO NOT HEAR ANY kind of RF symptoms in the sample. AT ALL.

Richard - how would one verify this is indeed the problem? Is it something repairable?

Do the symptoms completely disappear when the transmitter and receiver are close (1m) to each other?
You can construct an experiment that completely eliminates any RF possibilities by simply having the transmitter and receiver very close to each other. THEN you can test for OTHER possibilities.

Do these two different mics work properly on OTHER transmitters? Does the transmitter work with the other receiver? Does the receiver work with the other transmitter?

You say "I also replaced the antenna in the transmitter." When? How? Did you use a proper replacement (length, etc.)? Or just a random piece of wire?

If the problem is an intermittent cable or connector or solder joint, it is easily repairable (at least IMHO).
If the transmitter or receiver has been damaged or failed and has drifted out of calibration, that will probably take a repair person with RF experience.

We will have to disagree Richard. Most of the cuts are very quick and could easily be the capsule losing cd, but there are a couple where the change to silence has a defined hiss-phut, where to me it sounds very much like squelch closing. Sennheisers with a dry joint on the aerial connection pad do this when the path is very short and the talent moves. I do agree it could be the power cutting, but just that little rf phut makes me wonder. Sennheisers that have been accidentally abused do this sometimes where excess pressure is applied to the rubber aerial protection moulding. It's an easy fix. If it's a dodgy mic then wiggling the cable should verify it, if it's the aerial connection, the a line of site test will identify that one.

Well I don't have anyone around whom I can mix and match receivers/transmitters with, however when the transmitter/receiver are very close together they audio transmitted is just fine. But put the transmitter on someone's left hip, then stand on the other side of them, and faint hits begin periodically. Stand on the same side as the mic, 5 feet away, but with nothing in between and all is good.

I did try two different mic cables/heads on the transmitter and it didn't make any difference.

If you have the same problem with two different mics / cables, it seems likely to be an RF problem.

What about some other questions and suggestions that have been posted here?

When you replaced an antenna, give us the details. How did you make the connection? Was it the correct length, etc.? Tell us everything you can.

Locate the antennas as far as possible from anything that will affect RF. You don't have much choice with the transmitter (except to be sure it's the right length, and straight (not coiled or bunched). Try to get the receiver antenna away from metal, tripod, camera body, etc. Also, you should be using both antennas vertical, or both horizontal. Have you tried that? (Although that should not cause so much attenuation that the system fails at a distance of a few meters.)

You may have a transmitter with low output, or a receiver with low sensitivity, or either (or both) might have drifted off frequency. That can be roughly identified by a swap test, but really needs specialized (i.e. expensive) test gear which you will not have.

If it's not a simple antenna problem, and if you can't arrange a swap, then there's not much more you can do. It's probably time for a factory evaluation.

I ordered the antenna from sennheiser. I soldered it myself. I'm no expert but didn't think I could mess things up (sounds like I was very naive). There are no rf experts where I live, nor shops that could do any service so I took it on myself.

Antennas are straight, not kinked. Tried facing them down and same issue. No metal on the person. Receiver mounted on the camera.

I'm not ideally located for having some of these tests done.

Thanks for your help Greg.

As long as you installed a factory antenna, which was designed for the correct frequency range, that's probably OK. The concern raised by another poster was that you might have simply installed some random-length piece of wire, and that would not have worked very well unless it was the correct length.

Electrostatic discharge (static electricity) can damage electronics, so there's a slim chance you blew out a transistor when you performed the soldering. Since the antenna is supposed to hang out of the device, I would hope that that part of the electronics is fairly well protected against ESD.

It seems that you've eliminated the mic as the culprit. It sounds as if the new antenna is probably OK. (By the way, when did this trouble start, in relation to the antenna replacement?) If you're certain that the problem gets worse with increasing distance, that certainly sounds like an RF issue.

Offhand I don't know what other troubleshooting I can suggest. There is no way for us to measure the RF output of your transmitter, or the sensitivity of the receiver, via the internet! Even a good RF shop would need the correct service literature and specs to evaluate your equipment accurately. And if there are no good RF shops near you, then, unfortunately, I think factory service is your next recourse.

Thanks Greg. I'll let you know if I get it sorted.

I'm sure you've tried different frequencies? In addition, some cameras emit RF spray which can compromise reception somewhat as well, so you may want to try it away from other gear to check.
Sennheiser's replacement antennas are for a specific frequency block, so an 'block A' antenna would not be recommended for your 'block B' system.

Problem resolved.

When I soldered the new antennae a bit of solder ended up touching one of the holes for the screws that hold down the chip board. The screw then created a ground.

With the help of a friend we removed this thin stream and re-soldered the antennae and now it's working perfectly.

I feel a bit stupid, but happy to have my mics back!

Thanks for your help all!! I now have a much better understanding of how my mics work.