Serious RF Wireless Issues

[Blah067]

Last night at our second show of six, we had major RF issues.
We run about 15 AT 7000 Series bodypack transmitters.
(as a side note...if anybody has the frequency charting for these things...please send it to me....) They sell this in multiple bands and I cannot find a list of it anywhere...the one in the user manual doesn't specify what band it's for...??? (good on AT).

The problem....
We had audio cut-outs with 3 bars of RF....
We had RF dropouts when the performers were standing center stage...
we have to work with this gear...
I've isolated what Antenna DA's don't work, and have eliminated 8 of our wireless due to bad DA's.


I think the audio is dropping out with full RF due to squelch issues.
HELP ME PLEASE!
Today when I get there I will be setting all squelches back to full counterclockwise and starting over....please please please help me!
I don't know what I can do to get rid of these RF issues.

[mbenonis]

OK, the first step here is to figure out what frequencies these units are running on. Check the manual, page 7. I know you say they sold it in multiple bandsplits, but I don't see that in the manual so perhaps they didn't? Look at the back of the transmitter and/or receivers as the frequency range is often written there. If you don't see anything, let's assume they're all in the same split.

Manual: http://www.audio-technica.com/cms/re...7000ser_om.pdf

Post back here the frequencies that you have the system set to (all 15 channels, and give me channel number and RF frequency).

Now, by Antenna DA do you mean the distribution amplifier (i.e., active antenna splitter)? What exactly doesn't work about it? How were they hooked up, and how are things hooked up now? What kind of antennas are you using? How many? Where are they, and how far from the stage?

Do you have anything on TV channels 57, 58, or 59?

On squelch. The squelch control tells the receiver when to mute the audio output as a function of input signal strength. So basically when the input RF signal strength drops below a threshold, the audio gets muted. I would probably set it somewhere in the middle, maybe cheating it a bit toward CCW.

Once I have this info, I can help you more!

[museav]

Hopefully you have 15 receivers as well rather than 15 transmitters but just one receiver.

I agree with Mike, I see the 100 channels but nothing about bands. They do show suggested Groups, but I believe that is a suggestion on the channels to use together and not limitations on what is available.

You mentioned in another thread that you had VHF mics and were looking to rent some higher quality UHF mics for an event, are the A-T 7000 units discussed here what you rented? Just trying to understand the situation.

[Blah067]

First of all. NO this thread is not related to the renting thread at all...just to clear this up. That was/is for church. This is for school.

Second. The AT 7000 was sold in two bandsplits, although not listed in the manual. AT for whatever reason decided they didn't need to publish this information. Investigation at previous shows indicated some were 7000 series, while some were 7000x. Band "x" (or not X...i can't really remember) is in channels 45-47...or something....and the other set is in the 700 mhz band. I will post frequencies later this week, we have brush up rehearsal Wed.

We have 24 total receivers. 4 of these I don't use, because the distribution unit has an issue with its power supply not working...(I've trouble shooted this perviously). Basically it just cuts the power at random times, and resetting it doesn't work...you just have to wait for it to come back on. I can't take this risk during the show, and don't use these. The next 4 receivers/trans are for handhelds. Two of the systems are dedicated to our "Lecture system"...aka the idiot system.

Now. Four receivers (as I discovered last night, and confirmed this morning) cannot be used due to lack of RF signal from the transmitters) give about 1 bar of RF (and no audio, even with squelch all the way open) when standing DOWNSTAGE CENTER WITH LINE OF SIGHT. They give no rf when in a pocket (even with antenna out).

Our system has 6 active dipole antennas, (Audio-Technica - Microphones, headphones, wireless microphone systems, noise-cancelling headphones & more : ATW-A54P : UHF Powered Dipole Antennas). I know we have six of these, however we also have 1/2 wave passives....and EMI didn't leave any schematics behind...so I don't really know which ones are hooked up or not. In the back of the rack, they have two antenna cables per cascaded AB out. Only one is connected. Whether it is the 1/2 waves or not I don't know.

Every 4 receivers has its own DA and cascaded into groups of 8 receivers per set of diversity antennas.

I'm pretty certain this RF issue has to be something with the DA itself, because the other four receivers on the same set of antennas work fine, and the transmitters work fine when tuned to different receiver channels.

The antennas are located 60 feet from the stage, and are hung from the catwalks (about 2 feet below them, on the back set of cats).

Thanks so much...

PS-today's run went much better...still a few interference issues....but other than that better than Saturday night. Still wanna hear what you guys have to say! Thanks.

[Blah067]

Because AT made this sooo clear to its customers.....
heres the proof and papers on the two bands of the AT 7000(x) series.

A-T Wireless Frequencies

A-T Wireless Frequencies

[Blah067]

And that would be a YES to the 57, 58, 59 question.... as thats the only frequencies one of the bands operates on.....

And I also talked to our district people. They basically said...well if you need new equipment, you can either pay for it yourselves or live on without it....

Our TD also said it isn't at all possible for us to get new wireless, or rent in the future.

[mbenonis]

Great, thanks for the info. More questions and maybe some answers too.

Originally Posted by Blah067

The AT 7000 was sold in two bandsplits, although not listed in the manual. AT for whatever reason decided they didn't need to publish this information. Investigation at previous shows indicated some were 7000 series, while some were 7000x. Band "x" (or not X...i can't really remember) is in channels 45-47...or something....and the other set is in the 700 mhz band. I will post frequencies later this week, we have brush up rehearsal Wed.

Gotta love A-T. Great, re: frequencies. That more than anything will help me help you. For now, do you know who set the frequencies currently in use, and if they were coordinated in any way?

Originally Posted by Blah067

We have 24 total receivers. 4 of these I don't use, because the distribution unit has an issue with its power supply not working...(I've trouble shooted this perviously). Basically it just cuts the power at random times, and resetting it doesn't work...you just have to wait for it to come back on. I can't take this risk during the show, and don't use these.

If you get some time, see if you can narrow this down further. Try swapping the power brick over from another DA and see if that fixes it. I know one of the Vega DA PSU's we have had to be replaced a long time ago.

Originally Posted by Blah067

Now. Four receivers (as I discovered last night, and confirmed this morning) cannot be used due to lack of RF signal from the transmitters) give about 1 bar of RF (and no audio, even with squelch all the way open) when standing DOWNSTAGE CENTER WITH LINE OF SIGHT. They give no rf when in a pocket (even with antenna out).

Are these receivers on the same DA? Is it possible that the DA is bad (if all four are acting up that would be my first guess)? Or, is it possible that the DA is the wrong frequency band? Speaking of which, do you have a model number for the DA's?

Originally Posted by Blah067

Our system has 6 active dipole antennas. I know we have six of these, however we also have 1/2 wave passives....and EMI didn't leave any schematics behind...so I don't really know which ones are hooked up or not. In the back of the rack, they have two antenna cables per cascaded AB out. Only one is connected. Whether it is the 1/2 waves or not I don't know.

You're gonna have to do some digging unfortunately. It would be immensely helpful to know what receivers are wired to what DA's, and what DA's are wired to what other DA's or antennas. Sounds like kinda a mess based on what you've described. Any chance you can take some photos of the front and back of the rack and send them to me/post them?

Originally Posted by Blah067

Every 4 receivers has its own DA and cascaded into groups of 8 receivers per set of diversity antennas.

So let me get this straight - antennas go into one DA, which feeds four mic receivers and another DA, which feeds another four? And you have three of these going on (for a total of 24 receivers?) Let me know if this is right.

Originally Posted by Blah067

I'm pretty certain this RF issue has to be something with the DA itself, because the other four receivers on the same set of antennas work fine, and the transmitters work fine when tuned to different receiver channels.

Sounds reasonable to me.

Originally Posted by Blah067

And that would be a YES to the 57, 58, 59 question.... as thats the only frequencies one of the bands operates on.....

Wait, let me double check. You have local TV stations on one or more of these frequencies, or on the lower split (45-47)? It would be great to know where you are located so I can pull FCC data on that area (you can PM me if you don't want to broadcast this info).

Originally Posted by Blah067

The antennas are located 60 feet from the stage, and are hung from the catwalks (about 2 feet below them, on the back set of cats).

Thanks so much...

PS-today's run went much better...still a few interference issues....but other than that better than Saturday night. Still wanna hear what you guys have to say! Thanks.

Yeah, 60' should not be an issue at all.

Thanks for the links to the frequency charts.

Glad to hear the run went better, and no problem, we're here to help you!

Mike

[mbenonis]

One more thought. How many DA's work OK, and how many receivers work OK? Maybe you can move the bad DA's over to something else (like the handhelds, if you don't need them for the show) and that might help? Also, of the DA"s that are broken, what is the issue? It sounded like at least one had a Power Supply issue, and one has a RF problem. Finally, what model are the DA's?

[Chris15]

Re the excess antennas; are there a pair of 1/2 waves for each pair of Dipoles? As a means of working out which are connected, try this: power up all your antenna connected DAs and look for the power LEDs on the dipoles. They won't power up unless being juiced up by the DA.

Maybe it's just me, but surely it would have been cheaper and easier to have installed a single pair of antennas in the first place and then split off that to the secondary DAs. Anyway, you've got what you've got...

Do these DAs have internal or external PSUs?

I'm tending to think the way Mike is that the DA that's only passing 1 bar of signal might be for the wrong band, and in this case the "antennas" that the receivers are using are actually the coaxes in the rack...

Re Mike's idea of swap and change of DAs - we are yet to confirm bandwidth on these DAs and so swapping them may cause more grief than it solves...

As noted earlier, a list of all 24 frequencies would be useful - from that we ought to be able to work out if coordination was done.

[Blah067]

The system was installed in 2001 with the building, and to my knowledge, the actual operating frequencies have not been changed. EMI, a local company, installed the system, and worked with the current band director (who had a very strong say in the system). I presume they did the coordination, but that was long before the recent wireless issues arroused.

Yes the four "bad receivers" are connected to the same DA, and I do presume the DA is bad. I have never had a problem with these in the past, and I have yet to tackle this issue due to lack of time. It only recently came up. I am very doubtful that the DA is in the wrong frequency range, but I will certainly check tomorrow.

I cannot move the handhelds to the bad DA's for two reason. 1) The DA's have to work for meetings in the school, and are nice to have for other functions as well.
2) The Handhelds are actually in a seperate bandsplit (if I remember right), so I could work around it, but all the packs in the same range as the handhelds are working fine, no reason to change this.

Yes, you have the antennas figured out.

Still waiting to get up tomorrow for frequencies and model numbers of the DA.

Tomorrow I will post a detailed list of frequencies and the wiring, as well as model numbers.