AC Distribution in an Equipment Box

Hmmm... how do you phantom-power a two-conductor jack?
They add DC, through a current limiting resistor, on to the inner conductor of the coax. It's not really "phantom powering" in the normal sense as it's routinely applied to balanced circuits via two matched 6.8 K resistors but the manufacturer, (Sennheiser possibly but I've forgotten who it was) was calling it "phantom". Definitely "phantom", not "T-powering" as commonly used in the film industry.
Toodleoo!
Ron Hebbard.
 
Okay, it looks like ControlBooth has added something called "Viglink" that hot-swaps an intermediate URL in place of the one you are trying to reach (or, a virus has gotten onto CB that did the same thing). The intermediate link identifies ControlBooth as the sender, so CB probably gets some kind of advertising revenue from the folks boosted on the intermediate page. You can "opt out," which I am guessing puts a cookie into your browser, at this page: http://www.viglink.com/opt-out/

I'm not promising it's safe, but I risked it and it worked for me.

This is a new behavior from Viglink that I have not seen before. I do apologize and will investigate the options to opt out of this type monetization. Viglink does typically provide between $60 and $150 per month in passive revenue, so it's a system that works, but this intermediate site is unacceptable. Either they can provide a clean affiliate link, or they can't for a URL, that's all I will allow. I will let you know as soon as I have a resolution.
 
This is a new behavior from Viglink that I have not seen before. I do apologize and will investigate the options to opt out of this type monetization. Viglink does typically provide between $60 and $150 per month in passive revenue, so it's a system that works, but this intermediate site is unacceptable. Either they can provide a clean affiliate link, or they can't for a URL, that's all I will allow. I will let you know as soon as I have a resolution.

Apparently there was a new option that was added recently to VigLink to offer different merchant URL's if the original destination did not offer affiliate sales. I have sent a request to Viglink support to opt-out of this "feature". I will let you know as soon as it's resolved.

We have a bug report thread going about this here: https://www.controlbooth.com/threads/off-site-link-problem.41799/
 
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The DC on these is normally +12Vdc on the centre of the coax referenced to the shell.
The RF is then superimposed, effectively the whole RF is centred on +12V not 0V. When you AC couple the signal, such as with a series capacitor, the offset disappears and you're left with the RF you care about...
 
When I'm doing permanent installs and I want to get power cabling super clean I buy commercial 1 or 2 space rack-mount CCTV power supplies - generally 10x-18x 12VDC outputs via phoenix connector or screw terminal - and a handful of 2.1mm barrel jacks, some bulk 2 wire cable, and build everything myself so there is no excess cabling.

When I build rental shows, I spec Motionlabs RacPac's that have 1 Powercon connector on the outward face, and 8x Edison connectors on the inward face. I use 8" Wall-Wart Extenders to get the wall warts off of the RacPac so I have room for everything to plug in.
 
Heads-up. Looks like you have 1/4-wave antennas on your SLX's right now. If you use an antenna DA, you can reuse those only if you intend on using them on the DA itself. If you try to remote them, you will need to use 1/2-wave, omni, or directional antennas.

Also mind that you can cascade these units. I would assemble the system in this configuration, so you only need one pair of antennas on your UA #1.
  1. UA844+SWB #1
    1. RX#1
    2. RX#2
    3. RX#3
    4. RX#4
    5. UA844+SWB #2
      1. RX#5
      2. RX#6
      3. RX#7
      4. RX#8
      5. SPARE
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The two UA's will do the heavy lifting for internal power distribution in this instance, but in general it's not unusual to see a power strip in the back of a rack. Functionally speaking, a rackmount power distro is just as much "a power strip" as a $15 power strip is, except you paid more $$$ for it and you added more weight to your rack. If it earns you any less grief, it's strictly because it might not stand out as much to an AHJ as the $15 variety. I would try to avoid standard power strips when possible, but in some cases it's hard to justify adding 1U, 10lbs, and $150 to add an outlet distro to a rack.
 
Looks like you have 1/4-wave antennas on your SLX's right now. If you use an antenna DA, you can reuse those only if you intend on using them on the DA itself. If you try to remote them, you will need to use 1/2-wave, omni, or directional antennas.

Why is that? I use a quarter-wave in my attic for my 70cm amateur radio activities, and it works great. Had to add a ground plane, to keep the radiation angle low, but it's close to 1:1 SWR and has the advantage of extra height.
 
Okay, it looks like ControlBooth has added something called "Viglink" that hot-swaps an intermediate URL in place of the one you are trying to reach (or, a virus has gotten onto CB that did the same thing). The intermediate link identifies ControlBooth as the sender, so CB probably gets some kind of advertising revenue from the folks boosted on the intermediate page. You can "opt out," which I am guessing puts a cookie into your browser, at this page: http://www.viglink.com/opt-out/

I'm not promising it's safe, but I risked it and it worked for me.

I use NoScript plugin with FireFox and I block Viglink by default. There are a few sites that require it to use their shopping cart so I enable it only for those sites.

Kind of related - I keep getting a nag to whitelist Controlbooth.com in my advert blocker (which I've done, we need to keep this resource)... a small annoyance.
 
That's precisely it, the lack of a ground plane if you remote the antenna. A 1/4-wave antenna requires one which it derives from the chassis of the DA or the RX, whereas a 1/2-wave doesn't need this. Also, 1/2-waves are pretty inexpensive so there's not much reason to mess around with trying to fab your own ground plane for a 1/4-wave.
 
That's precisely it, the lack of a ground plane if you remote the antenna. A 1/4-wave antenna requires one which it derives from the chassis of the DA or the RX, whereas a 1/2-wave doesn't need this. Also, 1/2-waves are pretty inexpensive so there's not much reason to mess around with trying to fab your own ground plane for a 1/4-wave.
Heh, I make mine out of aluminum wire I have on a big coil. They're pretty easy to put together.

By "half-wave," do you mean a dipole? To be effective, those need a balun. Otherwise, the extra quarter-wave is really just standing in for a proper ground-plane anyway, and not very well. if you mean a half-wave vertical, that calls for some impedance matching (which I assume a commercial product would include).

Option I like best, actually, is a log-periodic. They're also very easy to make, are somewhat directional, and very broad-banded. As it happens, however, one problem we don't have is signal strength. Our receivers tend never to be more than 100' from the transmitters, with clear line of sight (except for all those wires and the box itself). We generally peg the meters (or we would, if meters still had pegs).
 
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Yup, 1/2-wave ~ dipole. Whether you need an in-line amplifier or not to make up for cable loss depends on your transmission distance and quality of cable. From Shure's user guide for antenna setup:

upload_2017-3-27_13-54-35.png



upload_2017-3-27_13-54-15.png


If you're within 100' and have line of sight from your rack to your stage, I'm not sure I would even bother with directional antennas unless you're trying to reject other RF signals in your neighborhood. Around 100' you should be fine either way, but if you get too close between your transmitters and your antennas, you'll overload the RF on your receivers because of the extra gain afforded by the paddles.
 
Thanks, Mike. Those are handy pages to have. Of course, they don't include the gain you get by having those antennas closer to the stage. Roughly, I'd say we would close the distance by 75%, so add +6 dB for that alone. What I'd really like is to put one of each pair of antennas at opposite ends of the stage. Then we're almost closing the distance by 90%, for +10 dB. More than makes up for the loss over 100 feet of RG213.

But we digress.

My initial question, which several have answered quite well, was whether that semi-rat's-nest of wiring was kosher or not. Consensus seems to be that it is, albeit with the understanding that better options exist. What was particularly interesting, though, was the comment that a much lighter enclosure is possible. I'm going to ask my theater company's board to let me research and recommend better cabinets, possibly two of them. We don't need the wirelesses for everything we do, and it would be much easier to move and store things if they were in two separate, lighter boxes.

As that is really a separate topic, I've started a new thread to ask for more guidance.
 
Curious it about the distro weight. I know when I added antenna/power distribution to our stationary rack (20 mics), I pulled out a box of wall warts I could barely lift. I didn't really compare to the rack mounted units I installed, but it seems like it had to save somethings on weight? I suppose there are some out there that aren't really that heavy though.
 
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I've got an SKB rack at the college with 6 ULX-D receivers (I think they are), and 2 (I'm not sure why 2) Shure distros, which power the receivers and split a pair of rubber ducks on the front panels of each distro. The whole apparatus weighs maybe 30 pounds tops, probably less.
 
Powering over coax is not a Shure advertised feature last I checked, though is is supported with Sennheiser.
The original intent was to allow active antennas and/or inline preamps to be powered.
 
Stevens,

This is an 8 channel rig I put together this winter. 8 Sennheiser G2 wireless systems. 2 Sennheiser ASP1 distro systems (for signal and power) (these systems were pulled out of the big rack and replaced with Sennheiser G3, A & G range systems) and 2, two space drawers for storage. Includes an 8 channel XLR patch bay on the back. All in an 8 space rack I had sitting around. Weighs 30ish lbs.

The nice thing about it; 2 AC plugs power the entire box. All antenna feeds come to a pair of panel mounted BNC connectors (I use 2, flat (1/2 wave?) antennas). And with the XLR patch bay, plugging in signal cables is quick and easy. Makes for quick and easy setup/tear down.

IMG_1406.JPG IMG_1408.JPG
 

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