Why is my Sennheiser EW 100 G3 not working?

Tom Knight

Tom Knight

Active member
This is driving me crazy. I have a Sennheiser EW 100 G3. It works fine at home in my office, and in my basement. I've used it in a hotel for interviews with no problems.

But the last 4 gigs I've tried to use it on contained horrible interference - A realtor showing a house, a wedding, a lecture, and an interview in a hospital. Here's a sample of the interference when I was attempting to mic the realtor. Incidentally, I left my tripod to get fresh batteries, and the camera fell over. If the mic was working fine, I probably wouldn't have left the camera, and it wouldn't have broken.

It just bugs me that I spent the big bucks on this mic for the realty gig, and for weddings, and it's not working for either.

In the case of the realtor, I realized later that he had a cell phone in his pocket. But in the case of the wedding and the lecture, I asked them to turn off the cell phone, but the audio was still awful and unusable.

Should I change the frequency? Call Sennheiser? Help!

 
First, always balance and lock your tripod before you walk away...

As for the mic, just because one frequency works fine in one place, even in the same city, doesn't mean it will work fine everywhere. It's not a "set it up only once" feature. Check with Sennheiser's frequency finder to see where the least-cluttered frequency blocks are. It's also a good idea, at the start of every shoot, to do a channel scan when setting up your wireless. The G3 has a clear scan function that will find available frequencies.

If you get signal interference, find another channel.
 
Hmmm. You mean I might have to read the manual? ? ?

Actually, I find the manual to be really hard to read. But thanks for the frequency finder. And now I will learn how to scan for open frequencies. Any other thoughts?

When I was at the lecture with about 200 people, I had a sense that there were 200 cell phones on all around me. Would that make my mic useless? Or is it possible to get a good signal in a room with 200 cell phones?
 
Cell phones aren't a guarantee of interference, as it really depends on the phone. There are some smart phones that are notorious. 12 years ago, Nextel was the major culprit (in the days before smart phones). Today, iPhone is a known disturbance.

But I've done work with a G2 in a room of 250 people (assume that up to a third of them have iPhones/smart phones) and have had no issues even with a TX>RX distance of over 100'.
 
Another question - Does anyone have any recommended settings in regard to sensitivity, squelch, or whatever? Are the factory settings OK for general video work?
 
Tom Knight said:
Hmmm. You mean I might have to read the manual? ? ?
Click to expand...

Oy. No "might" about it -- you absolutely have to read the manual. Worse, you have to do what the manual says.

I just got back from a trade show gig in mid-town Manhattan. AKA radio frequency hell. I was doing interviews using my G3 unit in a highrise hotel half a block from Times Square. Cell phones, pagers, and two way radios in all six directions. The G3 gave me crystal clear sound with hardly a glitch.

Because before I started I scanned for open frequencies, picked one of the results, and used that open frequency.

That said, cell phones and in particular pagers are not the cleanest of electronic devices. Some of them leak RF like it's free. Everything from cell phone towers to fluorescent lights can leak RF and interfere with radio mics. Perfection isn't possible. But Sennheiser manages to do pretty well -- the G3s represent an excellent value. If you use them as intended of course.
 
The most important is "sensitivity": this is where you set up the "volume" of the transmitter. This has to be set so when you hold the mic on "normal" distance from the mouth (don't eat it, just somewhere the hight of the chest, about 15cm under mouth (yes I live in a metric country :-p).
Then talk with normal voice, you'll see some moving stuff. It has to be somewhere in the middel, (between middle and 3/4th. If you talk with a louder voice and the led of AF peak lights up, it's to much. So you have to lower sensitivity a little bit...

Cable emulation: can be set to minimum here, http://www.youtube.com/watch?v=mM7UtXbGdlo
 
Thanks for the tips guys. I've been playing around with finding the frequencies, and it seems to be working better. But clearly, I need to read the manual in more detail, and understand all the functions.
 
Bruce Watson said:
Oy. No "might" about it -- you absolutely have to read the manual. Worse, you have to do what the manual says.
Click to expand...

Even more worse you should also understand what all those things in the manual actually mean.

About your sample video: why not use a $20 cable instead of radio transmitter for those 20 feet. Guaranteed perfect transmission quality. If the subject is not moving around there is really no point in using a radio system. Reasons you have learned already.
 
A $3000 radio mic is nearly as good as a $10 piece of cable!

Radio wise, so many people just expect them to work, yet successful working with RF of any kind is a mix of knowledge, skill and a bit of magic. Most radio mics are working in frequency bands well away from cellular frequencies, so phones tend to not cause issues by their output interfering with the radio frequency sections of your radio mic, but they do have a habit of getting into the audio circuitry - which is a totally different problem affecting mics, cables, mixers, cameras and anything else you probably have - not just radio mics.

The out of the box settings usually work fine, but you need to get to grips with a bit of theory. One mic is usually trouble free, the issues arise when more than one is used. I've seen many people just change their displays so each frequency in use is a distance apart. However, to do it properly is more complicated. The manufacturers usually produce a band plan for the band you are working in. These frequencies usually work fine with each other. However, the ones one make suggest may be different from another manufacturer's. They all have slightly different technical specs which impact on channels spacing. Very few locations are RF free - radio masts are all over the place, and you can easily get interference from these. Sometimes it's unpredictable. The way it works is that RF on two frequencies can mix together in very strange ways, and harmonics of a working frequency may not be suppressed properly, and all these things mix together additively and even subtractively to produce spurious signals. Here in the UK, our old VHF radio mic channels were pretty close, maths wise, to our UHF ones - so if the working frequency of your UHF equipment was divided by 4, it landed almost on top of a frequency being used by the older kit. So every time somebody with a VHF pack went near the UHF receiver, strange whistles and rumbles would appear from the UHF kit. Nothing wrong with either - they just won't work near each other. Sennheiser tend to load their kit with handy channels, but most people who buy just one, never even change them. Scanning for empty channels is a sensible idea - but if you do it at ten in the morning, and another user doesn't switch on until 2pm, then it hasn't really helped. Some users who have had interference, just go to the other end of the frequency spectrum to get away from the problems, but rarely put them back again, and then at some locations you get an unstable system. Co-channel interference can be heard and you need to train yourself to recognise lack of signal from interference, and impulse interference from poorly screened equipment from co-channel. There is also intermodulation - the phenomena where one frequency impacts on another - this sounds different again. It takes lots of experimentation to get good at working out what is going on.

Squelch - is broadly the same as the squelch found on any two way radio - from CB to marine band. Backed off, you hear white noise - the absence of signal. Turned up to the point the hiss stops means you're just on the point of signal/no signal, so turning on the transmitter will open the squelch on the receiver. However, as signal strength drops, the signal gets progressively hisser, and then the squelch shuts, only to open again as the person moves. If you set it too high then it will not open unless the signal is VERY strong. Only you can decide what is better. A hissy signal, or no signal. I'd rather have the hissy one, rather than none. Other people want good audio or no audio. Some people turn it off completely, so if a transmitter goes off when the battery dies or somebody switches it off, the sound op will certainly know about it - because the loud hiss makes you jump. Again, personal choice.

Mic sensitivity is all to do with the gain structure of the system. The preamp in the radio mic can be overloaded by really loud singing, shouting or yelling, so adding the pads to reduce sensitivity means that no matter if the source is a whisper or a yell, the pack will not distort, and the maximum signal to noise ratio is achieved. If the pad is still switched in when the mic is being spoken quietly into, then you could only be using the bottom 10% of the available dynamic range, so at the camera input or mixer, you need to apply more gain to get the level up. However, you are increasing that 10% to something louder, bringing up all the hiss, hums and noise too. The setting of input and output levels needs great care to optimise the s/n of the entire chain from mic/radio tx/radio rx/preamp/edit input gain/system output level. get any one wrong and the impact isn't too bad, get two or more wrong and you can wreck the entire thing, quality wise. Some radio packs like the Line 6 digital ones don't have a gain control at all - having (they say) a wide enough dynamic range to make it unimportant. Although sceptical, it does seem to work.

So never treat a radio system as just a cable-less link. It's far, far more complex than that, and WILL let you down at some point. Cost does not mean guaranteed magic, because we live in a very busy RF world. It's surprising we ever get them working at all. Think about Broadway and London's West End. Hundreds of radio mics, all very close to each other. It takes an awful lot of effort to make it work. I'm waiting for the London Olympics. everything is very close together and it's going to be pretty chaotic. With one mic system, things should be very straightforward, but time and time again something goes badly wrong. Never trust them. Always monitor them. Start to really listen - that helps you predict what is happening.
 
Thanks Paulears for your detailed explanation. Now I feel unworthy to use the mic. ;)
anyway, it seems like I've been taking it for granted and need to treat it with more respect.

To the other poster who suggested a cable could have worked - I tried that with those guys before. It worked from an audio point of view, but was cumbersome and awkward. We moved through the house and it was a pain to carry the cable. I would love to get the sennheiser working next time they hire me. I'll learn more about it.
 
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