Rod Pro. Posted November 25, 2012 Share Posted November 25, 2012 I recently done a small conference with 3 radio microphones: 1 lapel and two hand held. I placed the antennas at the front of the room towards the corner. I know you should always avoid corners with antennas but when I did a sound check everything was working perfect. The antennas were connected to BNC in the floor panel, which led to the control room about 10 to 15 metres away. 10 mins before the conference I miked up the chairman and when I went to the control room I couldn't hear him at al!! When the conference started as he approached the lectern I could hear him over the headphones but he kept coming in and out and had a hiss. As I had a lectern back up mic so I just pulled the lapel down and used that mic. When it came to Q&A the problem became noticeable as the vocal kept dropping out on the hand helds! When the conference finished I checked the BNC cable and found 2 small cuts in them. In my experience with those types of cable is its either working or not. I know its difficult to pin point a problem with out physically being their and checking stuff but any suggestions on what might of caused it? Mixed in that room before with no problems. I was using a Shure UA845 distribution system. Link to comment Share on other sites More sharing options...
Mr Steve Posted November 25, 2012 Share Posted November 25, 2012 What are your frequencies? Do you have pilot tone set on your system? Were the squelch settings suitable? Has the system worked properly together before? Link to comment Share on other sites More sharing options...
paulears Posted November 25, 2012 Share Posted November 25, 2012 Are you sure the floor BNC sockets were for RF? Video tie-lines are common, RF ones less so. There's a current topic on radios where people are really keen to avoid RG58 (or 59 for video) cabling. RF cable does not work like video or audio where they either work or don't. Moisture ingress can add many dBs to the attenuation figures. When checking radio systems, the important thing is not the best RF level, it's finding the spots where it is worst. Unknown cable, under the floor - it's a risk using it. In the other topic, you'll find many people insisting that receivers go stage end. As for corners? There is no reason NOT to put them in corners, if that location is a good one for the venue. Link to comment Share on other sites More sharing options...
mackerr Posted November 25, 2012 Share Posted November 25, 2012 Are you sure the floor BNC sockets were for RF? Video tie-lines are common, RF ones less so. There's a current topic on radios where people are really keen to avoid RG58 (or 59 for video) cabling. RF cable does not work like video or audio where they either work or don't. Moisture ingress can add many dBs to the attenuation figures. When checking radio systems, the important thing is not the best RF level, it's finding the spots where it is worst. Unknown cable, under the floor - it's a risk using it. In the other topic, you'll find many people insisting that receivers go stage end. As for corners? There is no reason NOT to put them in corners, if that location is a good one for the venue. As Paul pointed out, video tie lines are common, antenna not so much. Also, installed cable often has to follow a circuitous path. The fact that the control room was 15m away does not mean the cable was 15m long. Also, cuts, or tight bends in antenna cable can seriously degrade the performance of the cable, and both are common in installed cable. It is much more fragile than electrical cable or even video cable. Corners have no impact on antenna performance, but steel does. You want to keep your antennas away from large metallic structures like building beams or scaffolding. The antenna interacts with the structure and changes its pattern, and consequently the gain in the direction you want it to have gain in. If you are using whip antennas that have a theoretical gain of 0dB you need a metallic object to be the ground plane. As mentioned in the other thread, get the antennas as close to the performing area as possible, the loss through the air is more than the loss through the cable, unless it is the wrong cable or broken cable. RG58 is pretty terrible cable. RG8U is pretty much the minimum spec for antenna cable, and RG213 (what Sennheiser specs) is much better, and LMR400 is much than that. Silly rule of thumb... If your antenna cable is smaller than 1cm in diameter, it's probably not the right cable. Mac Link to comment Share on other sites More sharing options...
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