Wireless Installed sound antenna questions

Mistermon

Member
Hi,

In our gymnasium, we will be replacing 2 OLD wireless microphones which didn’t get the treatment following a recent sound upgrade. The rack containing the mics is inside a concrete block room. Recently, the PA announcer has complained of signal dropout in certain locations of the gym. I don’t doubt him as the mics are pushing 15 years old with bent non-replaceable antennas. Time for new.

We’ll be replacing with Shure ULX-S receivers and transmitters (to match the Auditorium, Pool, Cafeteria, and portable system) and I’d like to get external antennas to help with reception.

I’ve built a similar system for our 14 auditorium microphones and used active antennas with great success, but that was 100’+ distance to the receivers.

Here’s my question:
Can I use passive antennas mounted outside the sound closet. I don’t want the big paddle-style for fear of gym-related incidents, and I can mount the antennas where they are protected from impact.

My proposed equipment list is this (all Shure):
2- UA221 passive Antenna splitter
2- UA8 ½ wave Omnidirectional antenna (in frequency range of the receivers)
2- 25’ UHF coax cable (also from Shure, so low loss)
2- ULXS systems

Am I in the realm of what is possible.

Thanks for any suggestions,
Rob
 

Aaron Becker

Well-Known Member
To answer the question, yes, a passive antenna mounted outside the closet will work, but I'm not sure if it will significantly improve the results (many variables to say when replacing multiple components of the system).

In terms of antenna placement, line of sight is always going to be best. If that can't be achieved, put the least amount of stuff between the transmitter and receiver antennas. If it's possible to mount the antennas outside this concrete room, you might try that. See if your building folks can punch a hole and mount the antennas above the door on the gymnasium side. Typically stuff in gyms has those mesh bounce-protection cages around it. If you can't get the antennas outside, can you temporarily move the antennas outside just for events? Short of that, can the door to said concrete room be left open during an event only to improve reception?

You may find with a newer system (hard to tell without knowing the specs on the old system) the reception issues go away. Are we replacing a UHF or VHF system? Many variables here that will have to be considered to make a full judgement.
 

Chris15

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I would advise against mounting antennas in mesh cages, you may end up with a shielding effect worse than the concrete wall.

Would the Shure UA864 work - it's the sort of form factor that is more likely to survive a gym than a paddle...

Beyond that, I'd say you're on the right sort ff track...
 

Mistermon

Member
The existing wireless systems are UHF- EV I think. My plan IS to place the 2 antennas outside of the cinder block closet and mount them in a protected area (our gym is conducive to that) that will not need a mesh cage. That's also why I'm opting for the thin antenna instead of the paddle. I don't know too much about the UA864. Do you have experience with it? I have a portable wireless (ULX-S) that I will try next week, placing the receiver outside of the closet- just with the standard antennas.

Thank you Chris and Aaron for the insight.
 

Aaron Becker

Well-Known Member
Sounds like you have a good plan. Mounting the antennas within line of sight should significantly improve your reception issues. Good thing is that remote mounting the 1/2 wave antennas (or even 1/4 wave, I forget what comes with the SLX) aren't going to break the bank if they need to be replaced after a basketball smacks into one of them.
 

Chris15

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...remote mounting the 1/2 wave antennas (or even 1/4 wave...

Remote mounting 1/4 wave antennas carries a risk of worsening performance not improving it.
1/4 wave antennas rely on a ground plane to work, provided by the receiver when directly connected. If remoted, they often don't have such a plane and performance is far from ideal...
 

RonHebbard

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Premium Member
Remote mounting 1/4 wave antennas carries a risk of worsening performance not improving it.
1/4 wave antennas rely on a ground plane to work, provided by the receiver when directly connected. If remoted, they often don't have such a plane and performance is far from ideal...
But what if you mount them on a grounded blank rack panel and possibly even in a rack?
Toodleoo!
Ron
 

FMEng

Well-Known Member
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The orientation of the ground plane relative to the antenna also has significant effect. Just the presence of some grounded metal at the base of a 1/4 wave antenna may not improve matters. Ideally, the antenna should be in the middle of a ground plane, not on the edge of one. An aluminum plate could be placed on the ceiling with the antennas pointed down. Is there a drop ceiling to conceal the whole thing?

5/8 wave antennas don't require ground planes, which is why most manufacturers offer them for wall mounting.
 

RonHebbard

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Premium Member
5/8 wave antennas don't require ground planes, which is why most manufacturers offer them for wall mounting.
FM; Would you mind elaborating on why 5/8th wave antennas don't require ground planes?
Also, are you saying they don't benefit whatsoever from the presence of a ground plane?
Toodleoo!
Ron Hebbard.
 

Chris15

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The application initially referenced was for a school gym.
I don't see rack panels or drop ceilings being viable options, I envisage we're talking about antennas mounted to plastic wallplates or the like on mounting blocks on the concrete wall...
 

brin831

Member
Search rf venue diversity fin ... you can buy a pack with powered splitter cables and antenna which will provide u best of both worlds for the cost of the shure ...
 

Chris15

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Search rf venue diversity fin ... you can buy a pack with powered splitter cables and antenna which will provide u best of both worlds for the cost of the shure ...

I'm not sure how this will hold up to ball abuse, part of the objective was to avoid a fin style antenna that can get knocked...
 

JerseyMatt

Member
I would advise against mounting antennas in mesh cages, you may end up with a shielding effect worse than the concrete wall.

Would the Shure UA864 work - it's the sort of form factor that is more likely to survive a gym than a paddle...

Beyond that, I'd say you're on the right sort ff track...

Bounce cages are not "mesh" in the sense that they will act as Faraday cages. The grid is several inches wide, and mounted to the concrete via anchors. The grid size is far too large to interfere with UHF - which depending on the frequency chosen would have a usable fractional wavelength of as little as 6-8mm. But if you're still concerned, they do make bounce cages out of Lexan these days too.
 

Jay Ashworth

Well-Known Member
If the antenna is just a rubber duckie on a mount, just have Facilities grab a bathroom pull-bar and mount it right over the antenna on the wall. A golf-ball might get behind it, but a basketball won't. And I wouldn't think it was trash the pattern *that* bad...
 

EdSavoie

Well-Known Member
$1000?!? Christ, you can just buy a bunch of crappy antennas and replace as needed long before using $1000 bucks.

EDIT: At that price, it better vaporize the balls...
 

Chris15

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The price is one major concern, but that's also a fairly directional antenna and I'm not convinced that's a good thing in this instance.

A grand a pop is not actually that unreasonable compared to the cost of the rack of 5000 series receivers it's intended to connect to ;)
 

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