Senn G4 Squelch Problem

[fincaman]

Hello, for years I used cheap soundlab radio mics and had a few problems here and there with interference so I bought three Senn G4s, last night I did a show and found that one of the Senns got interference with the mic switched off. I expected Sennheisers to work perfectly in all situations, is this a fault or can it happen

[Simon Lewis]

It is not unusual for a radio system receiver to pick up interference when the transmitter is not on.

Have you tried adjusting the squelch control to help minimise this? Would you normally keep radio mic receiver channels on the desk on or faders up when transmitters are not switched on or in use?

Edited October 26, 2019 by Simon Lewis

[DrV]

Simon's right of course - you shouldn't really rely just on the squelch to mute the channels. However, if you must do that then you should make use of pilot tone too as belt and braces (I assume a G4 has pilot tone)

[sunray]

Simon's right of course - you shouldn't really rely just on the squelch to mute the channels. However, if you must do that then you should make use of pilot tone too as belt and braces (I assume a G4 has pilot tone)

I remember the days when we could rely on the squelch and would regularly leave leave a radio mic open on a PA system for the MC to use it whenever he wished, we also used VOX or the squelch line to mute the music without notable issues.

 

[Simon Lewis]

I remember the days when there were just two analogue TV broadcasts and no mobile networks....

Times - and radio spectrum use - have changed....!

[paulears]

Two years ago, we had a guy run to our theatre in a panic to tell us one of our radio mics was coming out of a large PA system on the seafront - a Bowls championship, with horn speakers down the prom. They left it powered up when they went home and Bobby Ball was loud and very clear down the prom! Could have been worse, Jim Davidson was on the next day, and that would have been, er, more problematic.

[timmeh2]

Hi

 

This may or may not be of any value, but here goes...

 

I suffer the same issue with the G4 systems; after some investigative work involving oscilloscopes and RF analysis (at some cost) it turns out they can be atrociously susceptible to high-powered 2.4Ghz WiFi and 2.6Ghz 4G/LTE emissions; we upgraded from AT3000 series (which never had an issue) to AT3212 which was practically unusable because of drop-out and poor performance; so we swapped for G4s in the hope they'd do better. Sadly not. Even with pilot tone enabled the venue's wifi can easily overwhelm the receivers causing dancing RF meters when the mics are off, to dropout and crap range whilst they are on.

 

The venue in question has Cisco access points that can transmit at a power far in excess of a hand-held microphone (or belt pack) and just love to hop all over the place, so much to the point that a 2.4Ghz wireless mouse and keyboard will pack up when the venue is full of guests, as will just about every 2.4Ghz radio mic that a visiting act has tried to use; I've seen an AKG Tetrad mic go titsup within 6ft of its receiver, and they are supposed to be bombproof. This is further backed up by the fact that when the venue is empty the interference is non-existant.

 

Bottom line is you're probably experiencing Out of Band interference like I am; the solution is to use external bandpass filters tuned to the particular range that your mics work on, although these cost several hundred quid a pop, and the programmable ones even more.

 

If you're not having issues with them on, then my advice would just be to ignore it, although I have to make sure that the desk channels are muted when not in use, for reasons like Paul has explained above.

 

All the best

Timmeh

 

 

 

 

Edited October 27, 2019 by timmeh2

[paulears]

That's a new one on me and I'd thought better of Sennheiser. Not having good enough filtering to reject 2.4GHz, which is a fair way way, is a big design flaw. The kind of thing you expect with less developed designs but Sennheiser should be far more up to speed. We've had some line 6 handhelds for a few years now and they have been 100% solid but kill wifi devices regularly. People running shows with Qlab remotes being the usual victims, plus the lighting and pa folk. On one recent show, my phone revealed 6 show specific wifi access points that aren't normally there. Thats quite a few potential problem waiting to happen.

[TonyMitchell]

I've found, as indeed would be expected, the condition becomes even more apparent when used outdoors with multiple paddle antennae mounted nice and high and well separated.

In practice though, the trick is to lock the TX so users can only mute their mics as opposed to being able to switch them off, to avoid leaving an open RX to pick up whatever is going on within the overcrowded spectrum.

Going back to the OP, the situation was far less likely with the budget kit he was formerly using, as the usable TX-RX distance was no doubt a fraction of what he now enjoys with the professional kit.

[abbotsmike]

Hi

 

This may or may not be of any value, but here goes...

 

I suffer the same issue with the G4 systems; after some investigative work involving oscilloscopes and RF analysis (at some cost) it turns out they can be atrociously susceptible to high-powered 2.4Ghz WiFi and 2.6Ghz 4G/LTE emissions; we upgraded from AT3000 series (which never had an issue) to AT3212 which was practically unusable because of drop-out and poor performance; so we swapped for G4s in the hope they'd do better. Sadly not. Even with pilot tone enabled the venue's wifi can easily overwhelm the receivers causing dancing RF meters when the mics are off, to dropout and crap range whilst they are on.

 

The venue in question has Cisco access points that can transmit at a power far in excess of a hand-held microphone (or belt pack) and just love to hop all over the place, so much to the point that a 2.4Ghz wireless mouse and keyboard will pack up when the venue is full of guests, as will just about every 2.4Ghz radio mic that a visiting act has tried to use; I've seen an AKG Tetrad mic go titsup within 6ft of its receiver, and they are supposed to be bombproof. This is further backed up by the fact that when the venue is empty the interference is non-existant.

 

Bottom line is you're probably experiencing Out of Band interference like I am; the solution is to use external bandpass filters tuned to the particular range that your mics work on, although these cost several hundred quid a pop, and the programmable ones even more.

 

If you're not having issues with them on, then my advice would just be to ignore it, although I have to make sure that the desk channels are muted when not in use, for reasons like Paul has explained above.

 

All the best

Timmeh

 

 

 

 

 

Which frequency band G4's?

 

I've seen, on a few occasions, one of our Ch38 G4s in a rack slammed on the RF meters (Usually only one RX in a rack of 4 or more), with nothing else in the way. Verified with an SDR/Scanner that there wasn't anything in that range too!

[fincaman]

Hello all and thanks for the replies, my mics are e band and I'm using them in Spain, there were two left on but only one was effected it's late now but tomorrow I'll check what frequencies they were on. Can you turn the pilot tone on and of on the G4s ?

 

[abbotsmike]

Hello all and thanks for the replies, my mics are e band and I'm using them in Spain, there were two left on but only one was effected it's late now but tomorrow I'll check what frequencies they were on. Can you turn the pilot tone on and of on the G4s ?

 

 

Yes you can select whether or not pilot tone is used. To save faffing around, I generally prefer to set the RX how I want it, then use the infared sync feature to carry those settings across to the TX

[timmeh2]

Which frequency band G4's?

 

Hi Mike

 

Ch38; we have four of them, that all misbehave. The 2 remaining AT3000 receivers are in the same rack, and are also in the same band, which don't suffer the same problem.

 

All the best

Timmeh

[fincaman]

Thanks again for the help, I have looked at the receivers and found that they were all on low squelch I've put them to medium in the hope that this will reduce or cure the problem Edited October 28, 2019 by fincaman

[ninjadingle]

Hi

 

This may or may not be of any value, but here goes...

 

I suffer the same issue with the G4 systems; after some investigative work involving oscilloscopes and RF analysis (at some cost) it turns out they can be atrociously susceptible to high-powered 2.4Ghz WiFi and 2.6Ghz 4G/LTE emissions; we upgraded from AT3000 series (which never had an issue) to AT3212 which was practically unusable because of drop-out and poor performance; so we swapped for G4s in the hope they'd do better. Sadly not. Even with pilot tone enabled the venue's wifi can easily overwhelm the receivers causing dancing RF meters when the mics are off, to dropout and crap range whilst they are on.

 

The venue in question has Cisco access points that can transmit at a power far in excess of a hand-held microphone (or belt pack) and just love to hop all over the place, so much to the point that a 2.4Ghz wireless mouse and keyboard will pack up when the venue is full of guests, as will just about every 2.4Ghz radio mic that a visiting act has tried to use; I've seen an AKG Tetrad mic go titsup within 6ft of its receiver, and they are supposed to be bombproof. This is further backed up by the fact that when the venue is empty the interference is non-existant.

 

Bottom line is you're probably experiencing Out of Band interference like I am; the solution is to use external bandpass filters tuned to the particular range that your mics work on, although these cost several hundred quid a pop, and the programmable ones even more.

 

If you're not having issues with them on, then my advice would just be to ignore it, although I have to make sure that the desk channels are muted when not in use, for reasons like Paul has explained above.

 

All the best

Timmeh

 

 

 

 

 

This is gold. We've suffered squelch breakthrough in rooms across campus since we started using G4's (due to the design of our lecture spaces we have to leave the channels open and allow lecturers to turn the mics on and off as needed). We've tried everything from replacing HDMI cables in the lecterns (they do cause their own RF interference) to frequency swapping, and now we've ordered 2 more channels worth of frequencies from Ofcom to try and compensate (we operate on Ch28, increased to include 29 and 31). However this info, coupled with the fact that we have a mobile phone relay station on top of one of our buildings, seems like a very plausible culprit.

 

I'm going to pass this nugget onto the team and our contractors, I may be in touch for some more info at a later date regarding your findings if that's ok?