Wireless Antennas
- Thread starterericnush
- Start date
Sounds like a good plan to me. Before I start, let me ask: are you having reception issues currently?
I wouldn't use an omnidirectional antenna-rather, use something like the Shure PA805SWB (passive Log-Periodic Dipole Array) or the Lectrosonics ALP500 antenna (any passive LPDA antenna by a wireless mic maker will work about equally well, so shop for price).
I don't see a reason why you can't put them horizontally. Theoretically, you might put the transmitters such that their antennas are horizontal as well but realistically it probably won't make a lick of difference.
No, I highly recommend *against* inline amplifiers. The problem with these amps is that they amplify everything, including TV signals that you don't want. They can also cause lots of problems if you overdrive them (and it's very hard to tell if you're overdriving it other than getting poor performance). Use good coax cable.
By the way, the antenna distributors also have amplifiers in them, but they shouldn't cause much in the way of problems (less gain, and the cable will attenuate the signal a bit to help with any overdrive problems).
Not sure which Shure cable you're looking at, but don't use RG-58. I recommend LMR-400 as the best choice, but it'll be expensive. That's a loss of 3.2 dB, which is very good. RG-6 (75 Ohm cable) isn't quite as good (7 dB loss), but not a bad choice for the price. RG-58 has a loss of 12 dB--not good.
No, you pretty much hit everything on the head here. The key will be good coax and directional antennas. If you do that, you should get a very good system.
Also, just as a check, have you done frequency coordination (for intermodulation products) and verified that you aren't on top of any TV transmitters?
This link may be helpful: http://www.shure.com/stellent/group...ents/web_resource/us_pro_antenna_setup_ea.pdf
And this one: Shure - Wireless Mic Remote Antennas Tool
Read throughly and pay attention to the details, especially regarding the placement of a directional antenna and proper use of in-line amplifiers.
Note, the SLX receiver has a 50 ohm impedance, any 75 ohm cable ie; RG-6, RG-59 would be detrimental to the quality of the system.
edit add: However, do not take the 50 / 75 ohm statement to imply that it won't work. You just need to account for the added losses and make sure the connector is correctly and firmly attached. It's been my experience that most 75 ohm cables are designed for a crimp style connector and I've seen a lot of short cuts taken on the definition of "crimped."
And this one: Shure - Wireless Mic Remote Antennas Tool
Read throughly and pay attention to the details, especially regarding the placement of a directional antenna and proper use of in-line amplifiers.
Note, the SLX receiver has a 50 ohm impedance, any 75 ohm cable ie; RG-6, RG-59 would be detrimental to the quality of the system.
edit add: However, do not take the 50 / 75 ohm statement to imply that it won't work. You just need to account for the added losses and make sure the connector is correctly and firmly attached. It's been my experience that most 75 ohm cables are designed for a crimp style connector and I've seen a lot of short cuts taken on the definition of "crimped."
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GreyWyvern
Well-Known Member
It is best to avoid crimp connectors for that very reason among others. Aside from crimp connectors often not being done right, they introduce more loss than other connectors simply because they are crimped, which can crush the dielectric.
The proper type of connector to use is the compression style. They are designed to somewhat protect the dielectric and basically attach by gripping the outer jacket and shield rather than "biting into" it. They are typically a much sturdier connection with less loss.
They are more expensive, as is the compression tool. However, as with many other things, you get what you pay for.
Dave
I agree with you on the connectors--compression style are best. That said, a 50-75 Ohm mismatch will theoretically only cause 0.18 dB of loss, total (regardless of length). Also remember that receivers and antennas are also not 50 Ohms in real life--receivers may get close, but I guarantee you that the antenna won't come close to 50 Ohms. So the reality is that you should pick RF cable that has the loss per foot you need at the price you want.
And just to reiterate, I *highly* discourage the use of inline amplifiers or powered antennas. Put the money into good coax, and save yourself the headaches of tracking down an overdriven RF amp in your antenna chain.
See this link on coax cable and wireless mics:
http://www.audiosystemsgroup.com/Which_Coax_for_Wireless_Mics.pdf
TimmyP1955
Well-Known Member
Before we get too far into coax choices and what not, have you checked whether you get good reception at FOH with the kit you have? Likewise is there an option to mount antennas at FOH - perhaps under the front edge of a balcony?
And do you have the space at FOH for the extra rack?
Once these basics are established, then we can think more about the specifics of implementing it...
And do you have the space at FOH for the extra rack?
Once these basics are established, then we can think more about the specifics of implementing it...
If hanging on the lighting booms, I would be mindful of the proximity to the lighting fixtures. The metal of the light cans, can affect the reception patern of the antenna. If possible, try to have the antenna a couple of feet above or below the boom, that should be adaquate.
May I ask what groups and channels are each of the wireless units? I've experienced much greater and reliable range, with the SLX series, than what you are indicating here. This may be a problem that can be solved by examining the channel plan and making some changes.
Oh, Where is the venue located? City, state?
May I ask what groups and channels are each of the wireless units? I've experienced much greater and reliable range, with the SLX series, than what you are indicating here. This may be a problem that can be solved by examining the channel plan and making some changes.
Oh, Where is the venue located? City, state?
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Agreed--it is extremely important to make the right channel choices when using more than eight systems at once.
firewater88
Active Member
In my house, I used to have an AT setup FOH that had the little whip antennas that were supplied with the units. I was having issues with drop outs and such so i went to 2 passive paddle antennas at the FOH position. My mix is about 60 feet from proscenium and about 100'+ from the back wall, level with the stage. Once I went to the paddles, I had no issues at all on stage. Could even pick up from dressing rooms backstage. I also had one on the top of a mic stand and one on a side arm at 90 degrees just below it. The diversity would pick up both evenly. I did notice that when an actor would be laying down or the pack get close to vertical, the horizontal antenna was favored.
I have now upgraded to AKG DMS700 digital wireless and placed the rack on stage because I can view all the info on my laptop. I now have one antenna up in the corner of the proscenium (barely noticeable) and one and horizontal just off stage on my torm pipe. Reception is great there too.
They recommended passive antennas for my setup because the cable length would be rather short. I know that when we rent Shure mics, they do come with active paddles and they are fine just off in the wings.
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