microphones - Channel 70 cut outs / spikes??

[yourdj]

:p

In the last 6 months or so I have found that I am increasingly getting electrical spikes every hour or so. They sound like a loud SHHHHH and come in waves of 3 or 4. I am using AKG mini dual mics on channel 70 and bought these because of the changeover.

Now, I can only see this as external interference from mobiles, because it has happened at many venues that are in the middle of nowhere, but most often do not have a mast for miles (I looked at off comes map). Could it also perhaps be an incorrect power supply or something? This system has been used for years mind you (although i need to double check the adapter), so mobile interference is the most probably cause.

Before I go out and buy a line 6 can anyone offer me any advice on what to check for or do? Off come have officially said that their masts will interfere with channel 70, which if you ask me is taking the mic a bit (excuse the pun). The last thing I need is for this to happen during a wedding ceremony or speeches (it did a bit on Sat, but no one noticed). Furthermore it may also damage my speakers as its pretty harsh.

The first time it happened was late last year and was on a golf course with nothing nearby. i thought it may have something to do with the shipping (it overlooks the docks), but its happened at 2 out of 3 venues this weekend, and logic suggests that it may have something to do with a lot more people owning 4 G phones now???

Does anyone know of a decent dual digital set or a UHF frequency that won't be affected.

this is what I own:

http://www.akg.com/pro/p/wms40duvosetgroup

17205

[Andy P]

I'm having a similar issue with my Kam radio mics

When they are close to the base or each other the signal drops rapidly and I get interruptions.

At karaoke nights I have to warn the customers not to cross the streams

[Excalibur]

Toby, I've googled the issue, and from what I see, it's a known problem. Apparently, Channel 70 is a quite narrow band, and pretty congested.

Solutions are trickier. If I understand correctly, buying a licence for Channel 38 could be the best solution ( although I don't claim to be at all well versed in this field, so don't take my words as Gospel ), or your 2.4GHz option may work. I've heard some good systems using this option, but again, congestion may be a problem.

Sorry, I can't really give you a definitive answer Toby. Perhaps those more in the know will chip in, let's hope so.

[Nakatomi]

If anything, if mobiles are the cause of the interference it's much more likely to happen further away from a tower. That's because a phone has to increase its power output to talk back to the base station. All receivers are built down to a cost, and selectivity - that's basically immunity from nearby signals, is a compromise. An interfering signal doesn't have to be very close to the receiver frequency to have an adverse effect on reception.

A better built receiver system is going to cost more money. If your mic receiver has an external power supply maybe try putting a ferrite ring or clamp on the cable near the plug end. If the casing of the receiver is plastic, maybe try screening it in metal but remember to leave space around the antenna.

[yourdj]

Toby, I've googled the issue, and from what I see, it's a known problem. Apparently, Channel 70 is a quite narrow band, and pretty congested.

Solutions are trickier. If I understand correctly, buying a licence for Channel 38 could be the best solution ( although I don't claim to be at all well versed in this field, so don't take my words as Gospel ), or your 2.4GHz option may work. I've heard some good systems using this option, but again, congestion may be a problem.

Sorry, I can't really give you a definitive answer Toby. Perhaps those more in the know will chip in, let's hope so.

I have thought about channel 38 as I have a senniser lapel that would work with it too, for ceremonies.
Seems a better option to get a dual 38 and still have the use of the lapel too (assuming it goes that low?).
I also think the general rule is - the lower the band the greater the range so would be better in marquees etc.



If anything, if mobiles are the cause of the interference it's much more likely to happen further away from a tower. That's because a phone has to increase its power output to talk back to the base station. .

My thought exactly. It seems to only happen when people are about in the general area.



At karaoke nights I have to warn the customers not to cross the streams

17207

[Excalibur]

If the casing of the receiver is plastic, maybe try screening it in metal .

Oh Dear Lord, we're back to the tinfoil helmets. :Laugh:

[yourdj]

Oh Dear Lord, we're back to the tinfoil helmets. :Laugh:

i dont understand how that would stop any interference?
Surely its coming through the antennas assuming its not a power adapter problem?
Or are you taking the mickey (original poster) :lol:

I will be looking into a second hand channel 38 system if my sensor goes that low, but line 6 do offer a fantastic range and I have not heard one person complain that has one. Might get both for a good range just incase. The licence are not much for that band. :)

[Excalibur]

Or are you taking the mickey (original poster) :lol:


I suspect he's deadly serious, Toby. I wasn't, about the helmets, mind. :) It was a reference to those folk who line their houses with it, to stop the Government snooping on them, and even go as far as the helmets, to safeguard their brainwaves. ;)

[rth_discos]

Is the limitation here that you are on fixed frequencies with those microphones? Would you be better off with a microphone that lets you change frequency within the 863-865Mhz range?

You only need to be in a venue with an aerobics class going on close by with a headset on the same frequency.. (and that happened to me 20 years ago!!!)

[yourdj]

Is the limitation here that you are on fixed frequencies with those microphones? Would you be better off with a microphone that lets you change frequency within the 863-865Mhz range?

You only need to be in a venue with an aerobics class going on close by with a headset on the same frequency.. (and that happened to me 20 years ago!!!)

Its not other microphone users I think its more advanced than that - mobile phones or something?

It's not a matter of chaining the frequency as its a dual set and it spikes on both channels at the same time so unless I moved it up a notch it may still interfere. 864.375 MHz and 864.850 MHz (Channel 70). If I go nearer 863, i fear that it will become worse!

I have just have lost faith in the whole band 70 channel set and feel that it will be affecting a lot more of us in the near future. :)

Do you think it may be the AKG encryption or something? After all they are a very cheap set of microphones, despite being excellent (minus handling noise), although I have used these for years without any problems at all. Then again it may be the power supply? I will have a look tomorrow.

I have seen a Kam set that runs on the full 38 and also 70 spectrum. May just be the ticket. Will work with my old mics as well as the set supplied (assuming i buy a licence to use them of course).

[rth_discos]

Looking further in to this, I think you were right the first time.

It does appear to be mobile phones.

The spectrum just below 863Mhz is used for 4G services.

Now you mention it tends to happen when you're in the middle of nowhere. This would make sense, as mobile phones have to send a stronger signal to be able to reach the mast that is further away - so their power output will be higher.

It's why it's often best to be relatively close to a mobile phone mast - it means your mobile phone is outputting a much lower power level next to your head.

So I think that is what it is.

Not quite sure what the answer is. Has anyone tried the 2.4ghz wireless mics (not forgetting that's also a very congested frequency).

[yourdj]

I work very regularly at a venue that has a mast right net to it at a college and another one down the road on top of one of the hotels.
I must have done 50 events if not 70 last year and nout at all, so thats what believes me to think its mobile phone related as the more reote venues suffer the spikes, but its still very random! The first time it started happening it was every 10 mins. last Sunday and Sat it was every hour.

Perhaps it linked to one sort of phone type or the signal generated by particular models or even the type of phone carrier (O2 etc.). I would be interested to hear if other people are having these problems as a member of another group has said it happens to his AKG microphones too. The Kam set looks quite good actually, so may look into using that. The worst that could happen is its also getting the problem and I sell it with £20 off and get Line 6.

if line 6 did a dual set I would have one sat in front of me right now, but they don't. I like the practicality and moreover the safety of having a dual microphone set (+ another set (on another band)) in the car just in case as i do a lot of all day hosting, ceremony miss and also for wedding speeches / conferences, so a wired one is out of the question.

17208

http://www.djanddiscostuff.com/sound-c16/microphones-c67/wireless-uhf-c69/kwm1960-hh-dual-microphone-system-p287/s287?utm_source=google&utm_medium=cpc&utm_term=kam-kwm1960-hh-microphone-4740-07&utm_campaign=product%2Blisting%2Bads&gclid=CI-D2sCs4MUCFQHJtAodWWwAkg

[DJColsie]

I work very regularly at a venue that has a mast right net to it at a college and another one down the road on top of one of the hotels.
I must have done 50 events if not 70 last year and nout at all, so thats what believes me to think its mobile phone related as the more reote venues suffer the spikes, but its still very random! The first time it started happening it was every 10 mins. last Sunday and Sat it was every hour.

Perhaps it linked to one sort of phone type or the signal generated by particular models or even the type of phone carrier (O2 etc.). I would be interested to hear if other people are having these problems as a member of another group has said it happens to his AKG microphones too. The Kam set looks quite good actually, so may look into using that. The worst that could happen is its also getting the problem and I sell it with £20 off and get Line 6.

if line 6 did a dual set I would have one sat in front of me right now, but they don't. I like the practicality and moreover the safety of having a dual microphone set (+ another set (on another band)) in the car just in case as i do a lot of all day hosting, ceremony miss and also for wedding speeches / conferences, so a wired one is out of the question.

17208

http://www.djanddiscostuff.com/sound-c16/microphones-c67/wireless-uhf-c69/kwm1960-hh-dual-microphone-system-p287/s287?utm_source=google&utm_medium=cpc&utm_term=kam-kwm1960-hh-microphone-4740-07&utm_campaign=product%2Blisting%2Bads&gclid=CI-D2sCs4MUCFQHJtAodWWwAkg

I first bought the AKGs but couldn't put up with the handling noise or the noise from the switch when you turn then on and off.

I sold them and bought the KAM, which in my humble opinion, are much better. Hardly any handling noise, the on/off/mute switch is noise free and both mikes can be run from one Jack output, leaving one mike
input free on the mixer for my beloved Sennheiser wired mike😀.

Never had any interference or funny noises. I do use them with a foam pop shield though which improves the clarity of the sound.

[Excalibur]

Has anyone tried the 2.4ghz wireless mics (not forgetting that's also a very congested frequency).
Which might bring similar problems, so perhaps not ideal.

I have seen some 2.4 GHz systems used/demoed at a meeting, and I was very impressed with them. It would be useful if we got a report from someone regularly using one in remote areas.




The Kam set looks quite good actually, so may look into using that. The worst that could happen is its also getting the problem and I sell it with £20 off and get Line 6.

Toby, I'm not one for badge snobbery, as you ought to know by now, but as Juski said, a lot of the problem is the receiver failing to reject unwanted signals of whatever sort. Bear in mind, it may not simply be a matter of picking a frequency that doesn't clash on paper, as various harmonics can cause problems, which only appear in use.

Thus, I'm going to suggest that you dip your hand deeply into your pocket, and pull out a Shure or Sennheiser kit. The KAM isn't built to the same standard, and may easily suffer the same problems as you're presently having.

[Nakatomi]

In all honesty I'd expect a brand like AKG would be pretty good no matter what. I wasn't quite joking about trying to improve screening around the case of the receiver. If the electronics inside aren't shielded well enough, just about any signal of sufficient magnitude could affect performance.

Have you eliminated your own radio frequency sources Toby? By that I mean your own phone and or data dongle or tablet?

I find my laptop causes hash on my ancient trantec VHF system so I have to be careful where I site the receiver.

Part of the problem here is that to get approvals for sale in the EU radio gear has to pass certain tests. The criteria is generally that if it recovers well from interference, not that it's totally immune, it'll pass.

Another part of the problem is OFCOM, but we can't do politics here ;-)

[rth_discos]

Another part of the problem is OFCOM, but we can't do politics here ;-)

OFCOM aren't political...

[Nakatomi]

OFCOM aren't political...


True, but they're a government sanctioned entity. And a bunch of muppets

[yourdj]

Bit like Produb :p

I am sure that a senniser would be better at shielding the signal.
Having said that i have only just stated to get the spikes.

I would be interesting to see I got a better quality (Sure for example) unit at the same frequency, whether it would still occur?
I could put them side by side and see if they both do it at the same time.

Its not my phone. I have had it next to the box for years, and nowadays put it on airplane mode.
Same with my iPad.

The main reason I chose the AKG's if because of the size of the box. its mini and fits perfectly in my little mixer/wirless sender box.
I would ideally want another dual set of the same size. The line 6 one is a nice size but most are really large.

I am going to keep an eye on things and work out what the problems are?? I will bring some foil and also move the receiver away from the power supply.

[Imagine]

Aha!!!!! It's not just me then :)

I started noticing this a couple of weeks ago on two different systems.

I've got a cheap and nasty Warrior headset I use for kids parties which when out in the sticks, just started dropping for no apparent reason. I started feeling a bit like Norman Collier! Thinking along the lines of you gets what you pays for, I ignored it.

However, this weekend just gone I was out with my AKG's (same ones as Toby). They were OK on Saturday night in a built up area, but at a kids party on Sunday afternoon strange things started happening!

I'd set up my PA etc. and left everything turned on whilst the Princess person was doing her thing for the kids. But I noticed what can only be described as faint radio type music coming over my PA (so I killed it quickly). Looking at the receiver, mic channel 1 was flickering as well (channel 2 wasn't affected by this). So, carried on with just channel 2 for the afternoon and all appeared to be OK.

Maybe it's time to go back to using cabled mics?

[yourdj]

Aha!!!!! It's not just me then :)

I started noticing this a couple of weeks ago on two different systems.

I've got a cheap and nasty Warrior headset I use for kids parties which when out in the sticks, just started dropping for no apparent reason. I started feeling a bit like Norman Collier! Thinking along the lines of you gets what you pays for, I ignored it.

However, this weekend just gone I was out with my AKG's (same ones as Toby). They were OK on Saturday night in a built up area, but at a kids party on Sunday afternoon strange things started happening!

I'd set up my PA etc. and left everything turned on whilst the Princess person was doing her thing for the kids. But I noticed what can only be described as faint radio type music coming over my PA (so I killed it quickly). Looking at the receiver, mic channel 1 was flickering as well (channel 2 wasn't affected by this). So, carried on with just channel 2 for the afternoon and all appeared to be OK.

Maybe it's time to go back to using cabled mics?

This happens with the music system at my local venue. Ver faint and it flickers on the second channel.
I would say that this was another device rather than mobile phones etc.

I think if I do get a better channel 70 unit that at some point that will be a problem too as the 'public' spectrum is very narrow now!
I think I will get the dual Kam unit at channel 38 as its a nice distance away from channel 70.
I work in the middle of nowhere most the time so a multi channel selection should rule out any possible interference.

I will wait until digital gets better and they bring out dual sets, with lapels too :)

[yourdj]

http://www.dvforums.com/forums/wireless-microphone-ch38-or-ch70