VGA over Cat5 causing interference on radio mic

[Posicoln]

Hi,
We have recently had a new projection system fitted, a projector with a mirrored display for the worship leader/preacher to have. The projector works fine, and the monitor has for a while, but the problem I have is the remote Cat5 back into VGA, at the 'stage' end, causes an interference on a radio microphone reciever which is nearby.

The reciever was in a room out the back, but wasn't getting a good enough signal, so we moved it to the front.

I experimented wrapping the box (converter) in tin foil, and leaving just the power cable plugged in to the box, but nothing stopped it.

The only thing that did make a bit of difference was placing tin foil between the two antennae on the reciever, but whether that was just coincidence i dont knnow, as the sound was intermittent.

I have had a few theories, but still unsure:

• Electromagnetic interference from the box is producing at a frequency the reciever picks up,
• As we are UK, the radio microphne signals have been changing as of Jan 1st, and that is something to do with the problem.

When wrapping it with tin foil, I now realise that maybe i should have grounded the tin foil to make a 'faraday cage'.



Another bit of information: when the guys were fitting the projector, the line to the monitor at the front comes from the projector as cat 5, and they were going to just put the amplifier/converter box by the projector and send VGA down, but this caused terrible 'scan' lines on the projected screen, so they moved it to the front, and there are still some scan lines, but only when the box is on, which does imply an electrmagnetic output.


Thanks in advance for any help.

PS not sure if this is in the correct forum, please move it if not.

[daver2]

The foil needs grounding for any induced currents to 'bleed away' - although this should be a last resort measure!

Placing foil between the antennae is probably a red herring.

What type of radio microphone transmitter/receiver are you having problems with (manufacturer and model)?

Have you tried changing the transmitter and receiver frequency you are using to see if that has an effect?

I live in the UK (Worcester) - is that anywhere near you?

Dave

[Posicoln]

I am in Cornwall, so a little way away. I will have to check the manufacturer and model, and will try to change the frequency, although therre are other radio mics in use too, but these have an external reciever to go into the room at the back.

We are trying to get a 'sound' room, but costs money (of which we are short, after buying the house next door) , and the church is relatively cramped as it is.

[Brad Weber]

Originally Posted by Posicoln

We have recently had a new projection system fitted, a projector with a mirrored display for the worship leader/preacher to have. The projector works fine, and the monitor has for a while, but the problem I have is the remote Cat5 back into VGA, at the 'stage' end, causes an interference on a radio microphone reciever which is nearby.

How do you know that is the cause? I won't say that it is impossible but I seriously doubt that the UTP to VGA balun or interface would be causing interference with your wireless microphones. I'd be more ready to believe the projector as the source of any such problem, but even that would be rare during normal use.

Originally Posted by Posicoln

The reciever was in a room out the back, but wasn't getting a good enough signal, so we moved it to the front.

So did that wireless system ever work properly for any period of time?

Originally Posted by Posicoln

Another bit of information: when the guys were fitting the projector, the line to the monitor at the front comes from the projector as cat 5, and they were going to just put the amplifier/converter box by the projector and send VGA down, but this caused terrible 'scan' lines on the projected screen, so they moved it to the front, and there are still some scan lines, but only when the box is on, which does imply an electrmagnetic output.

I'm having trouble following this, can you describe how the whole system is wired, from sources through any switcher or other electronics to the projector and monitor?

[Posicoln]

Originally Posted by Brad Weber

How do you know that is the cause? I won't say that it is impossible but I seriously doubt that the UTP to VGA balun or interface would be causing interference with your wireless microphones. I'd be more ready to believe the projector as the source of any such problem, but even that would be rare during normal use.

Both systems work okay independently, the microhpone works fine when the box to convert Cat5 to VGA has no power running to it.

I couldn't completely rule out the projector as source, as it has to be on to give a signal to the converter, but if the converter has no power running to it (whiulst projector still on) or when it does have power running to it, does the interference occur.

Originally Posted by Brad Weber

So did that wireless system ever work properly for any period of time?

Sort of, we lacked a good enough radio signal when the reciever was in the cupboard, so we moved it to the side of stage, near to where the monitor is, and all of the radio microhpones work.
(hand held to that reciever, and two lapels through an external antennae through to the cupboard)

Originally Posted by Brad Weber

I'm having trouble following this, can you describe how the whole system is wired, from sources through any switcher or other electronics to the projector and monitor?

The system we specified was a projector fixed at the back, with leads for inputs going to the front and back, these include a VGA input for computer, and composite input. We mainly just use a VGA input straight to the projector.
At the projector there is a cat-5 output from the projector which is identical to what is showing on the projector.
This travels along cat5 to the plug at the front: we take a cat5 cable from there into the converter box, and then a VGA into the Monitor.

This box was primairily only intended as a booster for the signal, and only situated at the back, behind the projector, to then send via a VGA lead to the plug in the wall, of which we then attach a monitor.
This did not work, as it caused 'scan lines' on the projected image, (probably the same interference as what is causing radio mic problem), so in the installation, they ran a cat5 wire down instead of a VGA.

So in short, there is one input (or selection only at the projector, but we dont noramlly change input) whatever the projector shows, the monitor shows too.

Hope this makes more sense,
Thanks again,
Peter

[Brad Weber]

Originally Posted by Posicoln

The system we specified was a projector fixed at the back, with leads for inputs going to the front and back, these include a VGA input for computer, and composite input. We mainly just use a VGA input straight to the projector.

So you have VGA and composite video inputs at the front of the room that go direct to the projector and a second set of VGA and composite video inputs at the rear of the room also going direct to the projector. You then use the projector to select any one of those four sources. Is that correct?

Originally Posted by Posicoln

At the projector there is a cat-5 output from the projector which is identical to what is showing on the projector.
This travels along cat5 to the plug at the front: we take a cat5 cable from there into the converter box, and then a VGA into the Monitor.

Do you know the projector model? Many projectors have a network jack for a network control connection and many projectors have video loop though or 'monitor' outputs. However, I am not familiar with any projectors that have an integrated video over UTP/CAT5 converted output of the selected video input.

[Posicoln]

Yes we can select any 4 inputs on the projector.
I will have to check the make and model though.

The monitor output has worked for a while now, but it has only been whilst sorting out the radio mics (they have been dodgy for a long while) that we have come across this problem.