Strange Interference

[andrewg112]

Good Morning All ...

 

Last night at around 7pm this happened (https://drive.google.com/file/d/1l3z5b55H16dApepkOpfhsCqYnmTQqqm5/view?usp=sharing)

 

Never come across this before. At first we thought it could be something local to the theatre transmitting, we even called the harbour master to see if there was anything happening at the local docks. The more that I think about it, I think it now could be a faulty radio mic transmitter. After re-tuning a number of the mics we thought we had solved the issue, but then all of a sudden the interference returned. Soundwise, its like a popping or loud clicking and you can see how quickly it did it from the video.

 

This was affecting all of our channel 38 mics, we have a small bank of other mics on channel 70 which were totally unaffected. We are using 24 radio mics in total for this show so problem solving is tricky.

 

Thoughts !?

1) If it was one of our G2 transmitters that is faulty can it really be such a strong signal

2) Can a G2 transmitter really transmit across such a wide range of frequencies in such a short space of time

3) An afterthought of the night was that there was a company member who had a rogue transmitter a day or so ago which was showing level on the transmitter but the receiver was never received anything. After some playing around with the pilot tone this (from what I remember) fixed itself.

4) Do we think there is anything local that could transmit this sort of signal ? Paulears kindly had a search around (we live in the same town) and there was nothing he could find (so must be a low powered signal).

 

Anyway .... would appreciate any thoughts before we head back for another show tonight ;-)

 

Thanks,

Andrew

[Jon Wiles]

Hi Andrew

We had a similar problem back in the day!

It blatted all over our VHF channels at the time (licenced)......

Cutting a long story short, we phoned the DTI (as I said, back in the day)......they were there next day! Turns out it was a faulty (flashing) fire exit sign in the council offices next door to the theatre and about 4 floors up.

 

Could be something similar?

[Stuart91]

I had something like that happen with a faulty G3 transmitter. (On Channel 38) It would continually cycle through the entire tuning range, and every time it coincided with one of the other systems we would get a loud pop down that channel.

 

We had twelve channels laid out in order, so got a nice sequential light show along the clip indicators.

[andrewg112]

I had something like that happen with a faulty G3 transmitter. (On Channel 38) It would continually cycle through the entire tuning range, and every time it coincided with one of the other systems we would get a loud pop down that channel.

 

We had twelve channels laid out in order, so got a nice sequential light show along the clip indicators.

 

Thats really helpful to know, its exactly what is happening in this situation, the channels on our desk were mostly laid out in order initially which is when the little video clip was filmed. I almost want to be certain its this thats causing it, as its easy to fix (once worked out which one it is) !! I didnt expect a radio mic transmitter to make the channel clip, so thats interesting to know its happened before.

 

Will get straight on to Ofcom if it comes back tonight when we don't have any radio mic equipment turned on.

 

Thanks,

Andrew

[Shez]

We had twelve channels laid out in order, so got a nice sequential light show along the clip indicators.

That does look a bit like what Andrew was seeing. I've occasionally encountered G2 buttons getting stuck which can if you're unlucky, result in the frequency display spinning like a fruit machine. I assumed that a new frequency wouldn't be activated until Set was pressed but it might be worth experimenting.

[andrewg112]

We had twelve channels laid out in order, so got a nice sequential light show along the clip indicators.

That does look a bit like what Andrew was seeing. I've occasionally encountered G2 buttons getting stuck which can if you're unlucky, result in the frequency display spinning like a fruit machine. I assumed that a new frequency wouldn't be activated until Set was pressed but it might be worth experimenting.

 

Now I recall it, the issue I had with the transmitter is that a level was showing when I talked into the headset, but I did not receive any level at all on the receiver even though the frequency was set correctly on both devices. I do wonder where the transmission from the transmitter was actually going !!

[Stuart91]

That does look a bit like what Andrew was seeing. I've occasionally encountered G2 buttons getting stuck which can if you're unlucky, result in the frequency display spinning like a fruit machine. I assumed that a new frequency wouldn't be activated until Set was pressed but it might be worth experimenting.

 

Our problem was caused by a component failure on the PCB, rather than the physical buttons. We could still go through the menu as usual, but no matter what we selected the behaviour remained the same. It was a quick, fuss-free turnaround under warranty.

[cedd]

 

Will get straight on to Ofcom if it comes back tonight when we don't have any radio mic equipment turned on.

 

 

Don't hold your breath! Certainly around here our local "team" has now become a single guy covering the whole of the north east of the country. Sadly pirate radio, mobile phones and blue light services will all take priority. Best thing you can do is buy yourself an RF Explorer and turn detective yourself.

 

If it turns out it's not a rogue transmitter (sounds like it to me though) then you can direction find the source either using a spare paddle antenna (when the signal is strongest, you're pointing at it) or one of the included antennas with the RF explorer (use the null at the end of the aerial, so when the signal you're looking for dips in strength, you're pointing at it).

 

 

 

[Shez]

Story time...

A venue I work at from time to time kept experiencing interference with their radio mic (fixed frequency UHF) although usually only on bank holiday Mondays. I took a scanner and RF Explorer with me one time to play detective. I could see a weak transmission on that same frequency so took a walk around outside. Circling around the venue I could determine which direction it was coming from so headed that way. Signal became stronger and I could listen to it clearly with the scanner. It was TV audio. I tracked it to one of a couple of residential properties and concluded that it was a wireless headphone transmitter. Power level was far greater than necessary (and possibly legal) as I could pick it up a couple of streets away!

Although tempted, I didn't go door knocking. Trying to explain to a pensioner that we could tell what she was watching on TV from a couple of streets away might have been tricky.

[andrewg112]

Story time...

A venue I work at from time to time kept experiencing interference with their radio mic (fixed frequency UHF) although usually only on bank holiday Mondays. I took a scanner and RF Explorer with me one time to play detective. I could see a weak transmission on that same frequency so took a walk around outside. Circling around the venue I could determine which direction it was coming from so headed that way. Signal became stronger and I could listen to it clearly with the scanner. It was TV audio. I tracked it to one of a couple of residential properties and concluded that it was a wireless headphone transmitter. Power level was far greater than necessary (and possibly legal) as I could pick it up a couple of streets away!

Although tempted, I didn't go door knocking. Trying to explain to a pensioner that we could tell what she was watching on TV from a couple of streets away might have been tricky.

 

Interesting story .... its just annoying at times like this. I certainly forget how vulnerable the equipment can be under the wrong conditions.

 

Imagine the nuisance you could cause driving by theatres and leaving a faulty device during a show.

 

Ofcom will be useless over the weekend too I guess .... if its still a problem I will have to find a way of powering our receiver and go for a walk !!

[Stuart91]

Imagine the nuisance you could cause driving by theatres and leaving a faulty device during a show.

 

I'm still surprised that nobody has disrupted a high profile event this way. I don't expect it'd be hard to build a relatively innocuous looking device that would wipe out a large chunk of RF spectrum.

[andrewg112]

Update: powered up as normal and looked at my suspect transmitter from yesterday. Once powered up the interference returned, once removed we are back to normal.

 

Back to the factory next week.

 

Thanks to you all for your help, going to keep this one out the way so its not sent out to any of you on a hire ;-)

[Stuart91]

Here's a link to footage of how my faulty transmitter behaved. The RF Explorer unit is a very worthwhile investment.

[Rob_Beech]

Hi.

 

Guess who is still alive.

 

This is most likely to be sweat (or other moisture) Ingres into the pack. Rogue partial shorts cause component failure and they can go wideband. It’s not massively common, but common enough to be known about. I’m not sure if they do fixed repairs of G2 anymore. If you take it apart you’ll likely find what looks like rust / exploded components near the up and down buttons and / or near the antenna connections. You may even find solder runs in extreme cases.

 

Rob

[andrewg112]

Hi.

 

Guess who is still alive.

 

This is most likely to be sweat (or other moisture) Ingres into the pack. Rogue partial shorts cause component failure and they can go wideband. It's not massively common, but common enough to be known about. I'm not sure if they do fixed repairs of G2 anymore. If you take it apart you'll likely find what looks like rust / exploded components near the up and down buttons and / or near the antenna connections. You may even find solder runs in extreme cases.

 

Rob

 

Hi Rob, thanks for the suggestion, and thinking about it, there is lots of evidence to suggest this was the case. This occurred on the Thursday night, and the previous show when it was used was on Sunday after an intensive week of tech, dress and then 4x shows over the weekend. I suspect as the sweat ridden transmitter dried out over a few days of non-use and a partial short occurred - that is exactly what I think has caused the problem.