Simple (I hope) question re wireless systems

[Jim Andrada]

By way of background, I've never used a wireless system.

I record orchestras, concert bands, etc in a church. I usually run XLR cables from my mics to a balcony about 80 - 100 feet from the stage and have my SD 702 upstairs. I run another pair of XLR cables out of the 702 and distribute to three cameras in the balcony for sync.

150 feet of cable doesn't sound like much, but it has to run a pretty circuitous route to get upstairs - across aisles (using protectors to keep folks from tripping on the cables,) along walls, up a staircase, etc using lots of gaffer tape. It's a time consuming project to get it all in place as a ladder is needed at a couple of points. In technical terms, it's a time consuming PITA!!!!!

I'm losing my "trained" cable laying team for the next concert so have been wondering if I could replace the long XLR cables with a wireless link of some kind. I'll be bringing the 702 downstairs and setting it up near the mics and would like to take the signal out of the 702 and send sync signal to the balcony. Since it's only for sync using PluralEyes, I think Mono would be OK and quality doesn't have to be the greatest.

Any thoughts/recommendations would be welcomed. I'd like to keep the cost under $500 or so if possible..

[Anthony Lelli]

if you use pluraleyes to sync in post then you don't need to run from the recorder to the cameras. just use the tracks from the cameras (on a shotgun or even the internal mics) to let pluraleyes compare and sync and then delete the tracks of the cameras (that will be needed only to sync)

[Richard Crowley]

$500 is not reasonable for even a system with one transmitter and one receiver. And it will be expensive to assemble a system with one transmitter and three receivers because that is not the "normal" use-case.

Instead of using a cheap wireless system, maybe we don't understand why you even need to run signals into the cameras? Many of us do this same kind of thing with nothing more than the built-in mics on the cameras as a sync source. I typically don't recommend using the on-camera mic for anything. But using it as a sync source is one of the few legitimate uses, IMHO.

[Don Palomaki]

I agree with Richard. $500 is about the entry point for reasonably reliable single channel wireless systems for voice. If you plan for good music it gets higher. The camcorder audio should be sufficient for sync with most NLEs. System like the AT 10 discussed in recent threads are under $500 and might work, but the jury is still out on them, and, especially fed from a mixer/recorder.

Many wireless systems sell receivers only so you could have one xmitter feeding several receivers, although that is not the most common configuration.

If the camcorders are not in audio AGC mode it can often help when using the waveform for sound sync.

[Rick Reineke]

I concur with Richard, your better off using camera mics for sync than a cheap (unreliable) wireless system.( Though the picture, 'may' need to be bumped a frame or two due to the inherent time delay.. (.Approx.1ms per foot <> 1 frame=30 feet )
BTW, AFAIK.. with the new. low cost wireless systems from AT, Rode and Sennheiser, it's not possible to have multiple receivers with just one transmitter, which can be done with conventional VHS and UHF systems.

[Jay Massengill]

A couple of questions:

What is the actual distance you'll need to transmit?

Is it any problem running an additional small audio mixer and cables from the front of the balcony to the cameras to assure line-of-sight from the transmitter to the receiver?

Since it's mainly for sync, I would use a wireless set that I've written about here before. The Wi Digital WI-ALP55 (I actually have the model 35). It has an advertised range of 100 feet line of sight and I've tested mine through multiple walls out to about 75 feet before breakup.

B&H and other online vendors are currently selling this set for $199 and it comes with the additional USB transmitter "free" (and other extras depending on the vendor).

I've used this set several times in highly crowded 2.4Ghz areas with no problems, and if you just need it for a good strong sync track it would be great. The stereo audio quality is very good! It's useful for so many short-range, stereo transmitting and monitoring tasks.

To reduce your cost I would just use one set, then an inexpensive audio mixer and balanced cables to distribute in the balcony to all three cameras.

I've converted two old light stands by substituting a long wood dowel for the top section of aluminum to elevate the transmitter and receiver for better line-of-sight without having metal right at the devices.

The set I have has a latency of 3/4 of one frame, hardly anything to worry about. And the signal will be much stronger and cleaner than using the on-camera mics to get your software to sync up.

I've run them 4 hours with no problem, but you can also power them by USB if you need really long runtime.

If you decide not to use wireless, I would at least rig up a single small-diaphragm condenser mic at the front of the balcony and distribute this signal to all three cameras. You'd have slightly better audio quality and all three cameras would have the exact same delay.

[Greg Miller]

If on-camera mics are used, 80 - 100 feet will introduce a delay of ~ 72 - 90 msec., although if all three cameras are the same distance from the stage that won't matter very much. Additionally, the sound at that distance will be fairly diffuse and heavy with reverberation, which might make it more difficult to sync the tracks "by ear."

How crowded is the FM broadcast band in Tucson? There are online search engines that will help you find the best "empty channels" between area broadcast stations. (Consider that most drive-in movie theatres use the FM broadcast band to distribute their sound track to cars over a radius of many hundred feet.)

For much less than $500 you could find an FM-band transmitter (most are stereo, although stereo reception actually makes coverage worse) and three portable FM broadcast receivers.

Of course, as with any wireless system, if you want to be really confident, you'd want to test this in advance of the actual event. Also, operation of an unlicensed low power transmitter like this is covered under Part 15 of the FCC rules, which includes audio transmitters (including the ones in XM and Sirius radios), and things like baby monitors, cordless phones, remote door locks for cars, and tons of other things. Still, if you have any qualms about legality, you'd have to do your own research.

[Les Wilson]

I run a wireless link between my Boom Pole operator and camera using a Sennheiser G3 Plugon transmitter on his mixer output and a standard battery powered beltpack reciever on my camera which gives me mic level into the camera. You could do the same thing to provide a wireless link to the balcony. If you want that audio into all your cameras, you could then go wired using a distribution amp connected to your receiver. They make AC powered receivers too. I found 100' a stretch for my Senny G1 wireless units. So that line of sight distance on the G3 is an area to research.

[Paul R Johnson]

I have, currently, something like 36 or so channels of radio microphones of all kinds, analogue or digital, and I can safely say that given the choice of using the receivers 80 feet away from the transmitter, or using a long cable, the cable wins EVERY time. Radio mics are exceptional, until they are not, and if you need reliability that can be predicted, then it's cable - the only sensible option.

In fact, theatres where we do most of our work, it is standard practice to have the receivers on stage, as close to the artistes as possible, and then a multi-core cable, or now cat5, gets the receivers back to the rear stalls mixer. Signal strength in a straight line, in a field, can be quite impressive - but in a building, never so easy. We use Sennheiser's mac application that can track and even record signal strength, and if you watch it, it stays most of the time at 'plenty' then suddenly takes a dive into dropout territory. Hopefully, your signal won't drop below the danger level and while you might get a 'thut', it won't die. Move the aerials further apart, and the average level is still usable, but the nulls will cut you out!

Every time you get to the end, on a system with distance in it, you breath a sigh of relief. One little 'phutt' with some of the people I work with, and they tell 1400 people the equipment AND the operator is Crap! (Thanks Mr Davidson) From time to time, people try using multi-element aerials with 10dB or more gain, but they have many side lobes and sometimes, despite all this gain, a member of the audience going to the loo can introduce just enough attenuation to cause a drop out.

With typical video kit, even with diversity types, there really isn't enough separation between the aerials to make the benefits of diversity work for you, and the small aerials at both ends (usually ¼ wave dipoles) often work without a ground plane, so are nowhere near resonant, and therefore inefficient.

The only rule is distance needs to be the shortest you can manage.

Brand wise, I've never noticed any real difference despite their range claims. The important thing is that aerials and feeder cable don't mean they'll be as good as a few pounds of mic cable.

As for a trained cable laying team? Is there something particularly complicated about it. Cable duties in my world fall to the lower end of my teams ability. If they can't lay a cable, then can they do their shoelaces up?

[Don Palomaki]

A thought - If this is a frequent or standing event, just run the cables permanently.

[Jim Andrada]

Thanks for the comments

I only need one channel - I already have a distribution box with the cameras so one input is enough.

There are usually 2 to 4 cameras close to (or on) the stage as well as the three in the balcony.

Cable laying is a royal pain in the A--! The cable has to cross several areas where the audience will be walking around so several lengths of cable protector have to be taped down and the cable has to be taped to the baseboard all along the run to keep a loop from snagging someone's foot since it runs down the side aisle of the church. It then has to go 10 feet up a wall so it can get led/gaffer taped across the top of the entrance doorway (this is where the ladder is needed) and then up the rest of the way to the balcony where it gets taped to the railing for another 20 or 30 feet. I typically don't have much time to get this done although the church will sometimes allow me to get in the night before to run the cable but this doesn't work if there's another event that evening as they don't want the cables in sight if something else is going on. I figure I do this setup maybe 5 to 7 times a year.

Did I say I was a one man band for all of this??? I've had a couple of folks help with the cable laying, but I can't depend on them being there all the time.

Syncing the cameras by eye is also a real time waster as the conductor is anal about the sync of the sound and the image - it usually takes us a few hours to get it "right". I used PluraEyes the last time and it saved hours of time fussing around and having two or three people looking intently at how close the sound was to fingers hitting keys etc.

Cameras are about 80 feet from the mics (line of sight) and 125 - 150 feet as the cable runs

[Greg Miller]

If you need the audio just for sync, you don't need perfect fidelity. If the signal level occasionally drops below full quieting, and you get a little noise, you'll still be able to sync. Even if you have a dropout for a fraction of a second, you will still have plenty of audio for sync.

I still think a low power FM broadcast band (88.1 - 108.1 MHz) link would be perfectly adequate for this. Some "consumer" transmitters are really junk, but there are a few that put out a very respectable signal for under $50.00. Some are made with "Part 15 community radio stations" in mind, and even have an external antenna. In either case, try hard to get line of sight from transmitter to your receivers. If the transmitter has an external antenna, carefully adjust the length to match your frequency.

Believe me, a better transmitter will not be plagued with all the RF absorption issues that you have with a wireless mic's body pack and short antenna hanging against the talent's body.

For redundancy, split the camera's inputs. Mono radio link into one channel, and a camera-mounted mic on the other. As long as the radio link works, you've saved yourself a lot of painful cable running. Even if the radio link fails completely, you still have camera audio (albeit with delay and reverb) so you have something to sync to.

Take a look at this frequency finder:
Vacant Channel Search Results

Get yourself an acceptable portable radio, go to the church in question, and try the indicated frequencies. See if one or more are truly quiet. If so, the odds are in your favor. Even if one has very weak signal in the background, a good local transmitter should capture the channel. I'll be glad to give you more details if you want to pursue this.

[Jim Andrada]

Hi Greg

Interesting idea - never would have thought of that. It's worth a try

Do you know of any good transmitters?

[Greg Miller]

Jim,

Since you need only one channel, use mono receivers, or combine the receiver L+R to get mono, because FM reception is much less susceptible to noise in mono mode.

One brand with a good reputation is Ramsey Electronics Ramsey Electronics®

They have several different models with a variety of features, some with RF output too high to be legal in the US (those are sold "for export only"). One advantage is that they have external whip antennas, so you can adjust the antenna length to correspond to the frequency you choose. Many of their products are kits, but you will also find some sold on eBay pre-assembled. At any rate, you want to be sure that whatever you buy is frequency synthesized so it's easy to tune and won't drift.

If those look too expensive for you, or if you don't want to get involved with assembly, let me know and I can offer some other suggestions. I will be offline for the next two or three days, so don't be put off if I don't reply right away.

[Don Palomaki]

Azden offered a low cost VHF band 2-frequency wireless system (WLX Pro series).
It include a plug-on transmitter as well as body pack transmitters for about $150.
Extra receivers can be bought separately for about $85 each (e.g., from B&H).

I've used this series them for voice applications in the past.

For more money you could get a UHF model with something 92 frequencies, and plug-in transmitter (better for taking output from a mixer).