# Problem with Shure frequency limitations



## CACtechdude21 (Sep 12, 2010)

We have 12 Shure SLX - H5 and J3 frequencies. We are experiencing several dropouts and reported this to Shure. Shure said that FCC band limits the use of our system especially the J3's. Did anyone else experience this problem and how did you resolve it?


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## EmpireEntertainment (Sep 12, 2010)

ive got 8 sets Shure slx24 with a beta 58 mic and no drop outs here


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## Chris15 (Sep 12, 2010)

Can you please confirm how many are in each band split?
Are you using coordinated frequencies?

WWB says I can't get any frequencies in J3 for the ZIP codes for your address, so I'm not surprised you are having issues...


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## CACtechdude21 (Sep 12, 2010)

We have 12 total. 4 units are H5, and 8 are on J3. 
We are located in Ontario California and here are Shures frequency limitations:

Band= H5 (TV Channels 22-25)
Max no. of transmitters: 8
Recommended group: Group: 3
Recommended channels; 1 (518.2), 2 (519.675), 3 (520.8), 4 (522.45), 5 (523.75), 10 (536.575), 11 (539.6), 12 (541.575)

Band J3 (TV Channels 31-34) is not recommended in ONTARIO, California
below is the link to site for (ontario w/ SLX model):
Wireless Frequency Selection Guide

It will cost $3328.00 for 8 units (in exchange fee per shure) to swap receivers and transmitters.

The wireless system is installed in our Church's auditorium.

I have installed the Shure antennae paddles facing on stage where performers.

This has limited drop-outs but not for all mics and certain areas of the stage.

I have noticed that there strong drop out spot on center stage, it appears to be like a certain invisible force field that cuts off the mics.

What ever suggestions you can give will be a big help.


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## Chris15 (Sep 12, 2010)

So SLX band J3 is TV channels 31-34;
On channel 31 is KTLA at 1000 kW, 32 is KDOC at 1000 kW, 33 is KTBN at 1000 kW and 34 is KMEX with a pending application for 500 kW.
An SLX transmitter is 30 mW. So the TV transmitters 29 miles away are 33 million times, or 75 dB more powerful. But apply some free space loss calculations and it looks like it MIGHT be possible to salvage something.

Don't expect an easy fix. We might be able to work something out, but it's going to be complicated and every little bit will be critical down to cable selection, termination, etc. etc.

Let's start with more information. Distance from transmitters to antennas, construction of the building, topography of the site (if you were on the roof could you see the TV transmitters or are there buildings in the way?), cable length and type between paddles and whatever is next - distribution? Handheld or beltpack or a combination?
Photos could be useful. What's around this dead zone as you call it? Anything large and metallic? Large bodies of water? The choir?

If we can start to build a clear picture we might be able to find some relatively simple options, but realise that it may still be at the end of it that if you want reliable performance you need to get them band swapped...


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## CACtechdude21 (Sep 15, 2010)

Thanks Chris15 for the reply.
For the Shure system, I've followed all instructions from Shure such as having 3 antennae distros leading to the Shure paddles that covers the correct freq bands for J3 and H5.
We also have the right size and length of BNC cables that is recommended by Shure, 1-50' and 1-100'.
The paddles are down stage facing the whole stage to cover every area.
There has always been a dead zone center stage, I believe there may be a large re-bar or something above that area.
The drop-outs are not so bad when there are no performers on stage, however when the stage is full, several drop-outs occurs.
So, technically I believe everything has been correct except replacing the SLX systems.
Please give suggestions on ways to prevent drop-outs. Thanks


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## DaveySimps (Sep 15, 2010)

CACtechdude21 said:


> The drop-outs are not so bad when there are no performers on stage, however when the stage is full, several drop-outs occurs.


 
This is a good sign that your problem is with intermodulated frequencies. Essentially, these are the frequencies that appear when you start to combine all of the carrier frequencies your microphones broadcast on. The more carrier frequencies you are using, the more intermods you have. They start to cause the drop outs because your receivers cannot distinguish the carrier it is looking for from a strong intermod near by.

It really looks like your problem is with frequency selection. Just because the frequency set has a maximum of 12 usable frequencies, does not mean you will always have those available in your area. Using Shure's Frequency Finder, it shows right away that the J3 was not a good set to commit to. In this case there is nothing you can really do other than sending the units to Shure to be retuned to another band that works in your area. A frequency scan is always recommended and is usually money well spent when you are looking into purchasing this many units. That would have given you an idea of what is available / being used in your area. 

~Dave


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## Chris15 (Sep 16, 2010)

It well may be that when these were purchased, the J3 band wasn't fully populated as it is now.
But be aware that at this stage you are fighting against the odds.
Active or passive paddles? 1 pair or 3?
Just because Shure say you should use their 50' and 100' RG213 doesn't actually mean that there isn't loss in that cable, there's about 6 dB of loss in the 100' at 600 MHz...

Could you please email me (there should be an email button attached to my profile) your current frequencies / channels? Intermods as Dave mentioned may be a problem that's not helping the situation.
I'm still having trouble visualising the setup, a picture would really be worth a thousand words here...

Do the dropouts still occur as much with only one or two transmitters operating?


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## FMEng (Sep 17, 2010)

It could be an intermod issue, but I doubt it. The system is marginal with TV stations clobbering the receivers. Your problem is a lousy desired/undesired signal ratio. That ratio has to be improved or the problem won't go away. Bigger coaxes will make both desired and undesired signals stronger, but it won't change the ratio. The only way you might make it better (besides getting off active TV channels) is to use log periodic antennas and orient them so that, when pointed at the stage, ALL of the TV towers are 90 degrees to the axis of the antenna. That way the antenna won't pick up much of the TV signals and the ratio will improve. Other types of directional antennas have side lobes and won't reject off axis sources as well as logs do. Avoid active antennas and splitters because they are likely to create more problems under those conditions.

Or do the simple thing and get systems on quiet channels.


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## Chris15 (Sep 17, 2010)

The main reason I suggested better coax was the Shure way to be lesser coax and active paddles. The active paddles will not be helping things in this case I don't think...


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## waynehoskins (Sep 18, 2010)

This probably won't help this problem, but I'll share this experience with you guys.

I'm mixing a show with 22 radios now, 12 of which the theatre borrowed from another local theatre. I was having all kinds of dropout problems most particularly with two radios in that rack, and to a lesser degree the other 10 in that rack. Sennheiser SAS232 splitter, omni vertical antennas, two 25-ft lengths of RG-58. Set up at the back of the theatre. I tried several things to fix it:
- check IM3 calculations in SIFM (all good except for a few 3-Tx IM3s)
- decrease the line losses in the 58 (shorten one, replace one with LMR-400)
- move one remote antenna very close to stage with 100 feet of 400
- check antenna connections on the transmitters involved

No dice. I was fiddling around with RF connections at the rack with one of the problem radios on and happened to watch the RF bars as I pulled the coax out (to put a vertical directly on it). Signal went up nearly full scale with no antenna. Aha!, it's the antenna splitter.

Turns out this splitter has cavity filters in it, and the radios from the rack are in two nonadjacent 12-meg splits, and the splitter outputs were all kinds of cross-wired. I ripped the rack apart and rebuilt it right, correct cavity filter output to correct split of receiver, and everything is rock solid.

The only problem I had was that this also made the TV station that was co-channel with one of the radios also jump up full scale. Switching that pair of link radios to a clear frequency cleared that right up.

So, if you have antenna splitters with filtering in them, make sure you're not trying to plug them into receivers that are out of the splitter passband.


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## 2mojo2 (Sep 18, 2010)

It sounds as though you got some bad advice when purchasing the J3 systems.
At $3300+ to have them re-tuned, you would be better off to sell the units at 300 to 400 per set and buy new SLX sets at around 600 per set.

It's either that, or line the building with copper.

Good luck..


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## Tex (Sep 20, 2010)

2mojo2 said:


> It's either that, or line the building with copper.



The Faraday Theatre. I like it!


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## Chris15 (Sep 20, 2010)

If you think you need to line the building with copper sheet, then you need to do some more research into Faraday cages

As I said from the start you are fighting an uphill battle... Getting the antennas as close as possible to the source and using the lobes as FMEng noted is going to be your best hope. Or just budget to get a couple of transmitters retuned a year, do you use all 12 every week?


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