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Moving antennas for wireless mics

Discussion in 'Sound, Music, and Intercom' started by chslighttech, May 7, 2006.

  1. chslighttech

    chslighttech Member

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    At our school our wireless recievers are inside our booth and they dont get very good reception. We have two old Shure bros wireless handheld mics. I can get the model number and such monday if I need it. We are thinking about taking each of the anntennas and placing them above the stage in the ceiling. We would run 4 cables. Two cables for each reciever since they are diversity. I have found some RG 58 cable for cheap. But I dont know what wire we should use? http://www.national-tech.com/catalog/rg58cablebulk.htm we found this wire that my dad said would work. But I dont want to buy something and not have it work correctly. I thought I would ask on the forum cause their might be somebody who has done exactly what I want to do. So what type of wire should I use?
     
  2. Foxinabox10

    Foxinabox10 Active Member

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    The type of wire needed depends on the distance of the run.
     
  3. Footer

    Footer Senior Team Senior Team Premium Member

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    instead of running 4 cables to the stage, why not mount your wirless recievers onstage and run two mic runs back?
     
  4. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    Footer's idea is probably the best. If you can get the receivers closer to the stage, do it. Short of that, there are a couple of issues that you should be aware of if you move the antennas to the stage and leave the receivers in the booth. It is possible that you will actually end up with a weaker signal with cabled antennas versus the current setup. This is due to signal attenuation in the cable and signal loss due to improper antenna mounting*. Also, it is possible that your moved antennas will pick up more noise than before due to the higher antenna placement.

    I highly suggest that you skim over Jim Brown's white paper on wireless microphones. http://www.audiosystemsgroup.com/publish.htm

    *Most whip antennas require a ground plane in order to work properly. While the details are complex (there are entire books on this topic), suffice it to say that you can't just slap an antenna on a cable and expect it to work - it will likely deliver poor to extremely bad performance compared to when it is attached directly to the receiver. If you are really interested in learning more, I suggest you get a copy of the ARRL Antenna Handbook - it's about $30-$40 and worth every penny if this is your area of interest.
     
  5. fosstech

    fosstech Active Member

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    That's very true. I'm a licenced amateur radio operator and know more than the average joe about antenna theory. That book is definately a fantastic read if you want to learn about antennas. It mostly covers ham radio HF communications (10 meters/29.7MHz and below), but there are some things in there about VHF and UHF communications. You may not have to buy it...your local library may have it; mine does.

    I would advise against running a long length of cable. Keep it as short as you can, or use preamplifiers if you can't (expensive however). One thing you may want to research is the type of antenna you're using. The little whips on the backs of the receivers aren't the best antenna designs. You probably will have better luck with a properly tuned Yagi beam array. They look like mini TV antennas that are mounted on their side. Yagis receive and transmit in a pattern not unlike a cardioid mic. The more elements the antenna has, the more directional it will be, and therefore the more gain it will give you. Get four of these, they will likely be cheaper than buying two and a distribution amp. Lots of times the mic companies sell their own, but most of the time they are grossly overpriced. Look around. Antennas that have the correct frequency tuning and correct characteristic impedance will most likely work with the correct connector.

    But I still vote for placing the receivers backstage if you need more signal. The only problem with this is that you can't easily troubleshoot them if something goes wrong with them while they're backstage and you're in the booth. But if that's not possible, use the antenna solution I talked about above.
     
  6. Footer

    Footer Senior Team Senior Team Premium Member

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    Most shows put their wirless onstage and run the lines back.... The lights on your wirless are great for troubleshooting but if its pretty lights or good signal and not pretty lights which one would you choose?... by moving the wireless recievers you should have less issues....
     
  7. tenor_singer

    tenor_singer Active Member

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    I've been told, too, that if you hang a broad frequency antenna and run a wire back to the booth, you can lose signal strength over long runs. This will mean some form of signal booster somewhere between your Antanna and the booth.
     
  8. fosstech

    fosstech Active Member

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    The problem with amplifiers is that they boost everything, including that nasty RFI that might be out there. Sometimes putting an amplifier in line with the receivers actually boosts the normally insignificant RFI enough to break the squelch of the receiver, making the noise a big problem. I still vote for higher gain antennas ;)
     
  9. cutlunch

    cutlunch Active Member

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    Before getting to carried away with long runs of cable there is something I would try. That is put an extension on each aerial and place them just outside the booth. The gain you get may be enough that you don't have to do long runs. It could be the booth blocking the signal. This way you get to keep the receivers in a secure location. If you do move them to the stage someone is bound to play with them.
     
  10. chslighttech

    chslighttech Member

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    Thanks for the advice guys. Ill try what cutlunch said and make a small antenna and hang it outside the booth to see if they are any better. If that doesnt work then I will see if we can move the rack backstage, which should work better since it seems like a lot of people do it. Thnaks for the help!
     
  11. MircleWorker

    MircleWorker Member

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    This is the best Idea.
     
  12. Willy Wonka

    Willy Wonka Member

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    The type of wire needed depends on the distance it needs to be ran.
     
  13. audioslavematt

    audioslavematt Active Member

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    Whatever would we have done without that useful piece of information?
     
  14. Footer

    Footer Senior Team Senior Team Premium Member

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    probably spontaniously combust
     
  15. audioslavematt

    audioslavematt Active Member

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    Which would rip a hole in the universe taking all of us with it.
     

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