Mounting Antennas
- Thread starterwolfman005
- Start date
wolfman005
Active Member
I'd be betting it runs both. School went to an all iPad program last year and now we have the fastest internet I've seen in my life.
Either way we will be purchasing new mics so those antennas will probably be removed and put into storage with the old L4 receivers/transmitters.
I'll be in touch Bill.
Either way we will be purchasing new mics so those antennas will probably be removed and put into storage with the old L4 receivers/transmitters.
I'll be in touch Bill.
wolfman005
Active Member
HA! Like our IT dept will let me go disconnecting their thousand dollar routers...
teqniqal
Well-Known Member
Placed close enough to any receiver and the RF spewing from the router, LAN cabling, and WiFi transmitters can overload the RF front-end of the wireless mic receivers - even if they are in widely separated frequency bands. Better wireless systems filter the spectrum they receive before the signal hits the electronics, but cheaper equipment does not and can be very susceptible to this type of problem.
Your wireless mic antennas should be physically separated (space diversity - for VHF as much as 15 feet, less will work for higher frequencies) and orthogonal (90 degrees to each other for phase diversity). For whip antennas (like shown), the mid-point of the whip should be perpendicular to the primary acting area. For directional antennas (paddles), they should point at the primary acting area (and also be splayed +/-45 degrees as viewed from the performance area). Keep them up high so they don't get humans in between the transmitter and the receiver (we are just 'bags of water', and water attenuates RF). If you have to extend the antenna cables, then use larger gauge for the runs (RG8 vs RG58 - 50 Ohm , RG6 vs RG59 - 75 Ohm) as they have less signal loss per unit distance. Keep the antennas away from metal (ceiling tile grids, conduits, wall studs, rebar in concrete, plumbing, fire sprinkler, metal light fixtures, structural beams, etc.).
Another thing that may be causing problems is lack of operating frequency coordination. Get a good frequency planner like the ones from Shure or Sennheiser and use it. Interfering signals must be accounted-for from local schools, sports facilities, churches, courtrooms, radio / TV, and nightclubs. This constantly changes, and the FCC keeps reducing the available operating bands, so it's just going to keep getting more difficult. You can't just assign frequencies willy-nilly - for optimal performance they have to be mathematically calculated so they don't interfere with each-other.
Consider buying devices that operate in the 900 MHz band, that's not so crowded (yet).
Your wireless mic antennas should be physically separated (space diversity - for VHF as much as 15 feet, less will work for higher frequencies) and orthogonal (90 degrees to each other for phase diversity). For whip antennas (like shown), the mid-point of the whip should be perpendicular to the primary acting area. For directional antennas (paddles), they should point at the primary acting area (and also be splayed +/-45 degrees as viewed from the performance area). Keep them up high so they don't get humans in between the transmitter and the receiver (we are just 'bags of water', and water attenuates RF). If you have to extend the antenna cables, then use larger gauge for the runs (RG8 vs RG58 - 50 Ohm , RG6 vs RG59 - 75 Ohm) as they have less signal loss per unit distance. Keep the antennas away from metal (ceiling tile grids, conduits, wall studs, rebar in concrete, plumbing, fire sprinkler, metal light fixtures, structural beams, etc.).
Another thing that may be causing problems is lack of operating frequency coordination. Get a good frequency planner like the ones from Shure or Sennheiser and use it. Interfering signals must be accounted-for from local schools, sports facilities, churches, courtrooms, radio / TV, and nightclubs. This constantly changes, and the FCC keeps reducing the available operating bands, so it's just going to keep getting more difficult. You can't just assign frequencies willy-nilly - for optimal performance they have to be mathematically calculated so they don't interfere with each-other.
Consider buying devices that operate in the 900 MHz band, that's not so crowded (yet).
wolfman005
Active Member
Isn't there is a sticky on 900mhz devices needing licenses? I'll be working with Bill and our school powers to figure out a solution. I have dabbled with the Shure frequency planning software but it's over my head. Whenever they redo the gym sound system they will have a contractor do all of it professionally.
teqniqal
Well-Known Member
- Not currently - look at the Sabine and Sacom products.
- Modern technology requires that we keep upping our game. Study-up.
- Be sure that they do a frequency coordination for all the RF devices on the whole campus, not just the Gym - otherwise it is futile (or as the techno-borg say: "Impedance is futile").
wolfman005
Active Member
Read this:
http://www.controlbooth.com/threads/stay-away-from-900-mhz-wireless-mics.9140/
As far as a contractor, I won't be here next year. I'll pass on that message to the school.
http://www.controlbooth.com/threads/stay-away-from-900-mhz-wireless-mics.9140/
As far as a contractor, I won't be here next year. I'll pass on that message to the school.
teqniqal
Well-Known Member
The referenced post is inaccurate. Pro audio wireless equipment operates in the 902 - 928 MHz band, not the STL band. The 902 - 928 MHz band is not restricted.
Sorry, but you are wrong. The author of the sticky knows his stuff. There was or maybe still is some equipment made for the Part 74 948-952 band. Only licensed radio and TV stations may use that spectrum. Speaking as one of those broadcasters, I would be hopping mad if I had interference from an illegal user, and wouldn't hesitate to involve the FCC. Granted, the equipment for Part 74 seems to be rare, and stuff for the 902-928 band is much more common.
I actually can provide a reference, courtesy of Jim Brown:
http://www.audiosystemsgroup.com/Which_Coax_for_Wireless_Mics.pdf
With respect to the original post, I would try to get the antennas away from the walls there, and spread apart a bit. Just use RG-6 (if you're not comfortable putting connectors on, then just buy some premade ones and get adaptors). You can use a basic 2-way splitter to connect one antenna to two receivers as well, if that makes things easier.
At 200 MHz, line loss won't be too bad until you start using cables 50-75' or longer.
Mike
teqniqal
Well-Known Member
Agreed, there is some special equipment that is sold only for use by broadcasters (Shure X1 band products and Nady makes a version of their UHF4, there may be others), and it is possible, but highly unlikely, that us mere mortals would come across it. The point I was trying to make is that the Original Post (not the one you read today) about not using anything in the 900MHz band (which has since been modified to clarify they meant 944-960 MHz) was overly broad and inadvertently discredited legitimate products that can be useful when trying to get enough open frequencies to use for a production. - Thanks to Webmaster Dave that got this corrected to reduce confusion by the readers.
Also of interest to the readers is the Shure guide "Operation and Selection of Wireless Microphone Systems"
Similar threads
