Senn 100/500 ENG: Bodypack vs. Plug-in for Distance at
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Old February 16th, 2004, 04:19 PM   #1
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Senn 100/500 ENG: Bodypack vs. Plug-in for Distance

Has anyone had any experience using both these?
Do they get about the same distance
before dropouts? Senn seems to imply that the
plug-in's mic must be metal for reception. My question comes up because I'm considering using the plug-in direct into a mixer. Will this affect the transmission range? Or would I be better using a bodypack into the mixer? Or because the mixer is metal, will this act the same as a metal mic
Anyone have an idea what kind of distance can
be had with the 100/500 plug-in transmitter out
of a mixer?
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Old February 16th, 2004, 06:20 PM   #2
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Drop an XLR cable out the back of the mixer and plug the plug-on into it. You will get plenty of distance as the plug-on uses the XLR shielding as the antenna.
Mike Rehmus
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Old February 16th, 2004, 07:09 PM   #3
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That sounds similar to the setup I've got in mind.
I'm going to tape a mic to the head of a tripod, about
8 feet off the ground. Then I'll run an XLR cable down to a preamp which would be on a chair under the tripod and I'd have the plug-in going directly into the preamp. That should give me some real good distance due to the long
XLR cable, right?
Do you think it would help to raise the preamp
up higher, or wouldn't it matter?
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Old February 17th, 2004, 08:21 AM   #4
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Some things to watch out for. If you go with the 500 series that can supply phantom power, most mixers and preamps don't like to have phantom coming back into the output. Usually they will still work, but will exhibit problems with metering and headroom.
Some cheap mixers are also susceptible to the RF coming back into the output. Test ahead of time.
It's usually good practice to not have any metal to metal contact with the mic and its support. It can attenuate the RF that's being broadcast. I suppose if the conditions where just right, it could actually boost the signal, but that never happens.
The stand, or in this case the tripod, can also act as re-radiators of the RF signal coming from the cable. This will set up an interference pattern with dead spots and hot spots. Test ahead of time to make sure you're in a hotspot and then don't move anything. To some degree this is always the case with any setup, that's why you get occasional RF dropouts as the variables change due to movement. If you have something very "antenna shaped" and conductive like aluminum, steel or carbon fiber close to the transmitter or receiver, you're enhancing this phase cancellation problem.
It would probably be good to have all components as high above people height as you can safely do it. Don't risk your preamp or people with a wobbly high stand, but keep it above chair height if possible. The same with the receiver. Avoid placing the receiver on a metal table and avoid placing the receivers very close to each other unless you're using a single set of antennae that's distributed to all boxes.
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Old February 17th, 2004, 12:56 PM   #5
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Those are some very good points, Jay.
A number of them I wouldn't have thought of.
If the receivers must be close to one another,
as far as assigning channels, is it best to
set the channels as far apart as possible?
Or what degree of channel seperation
is safe to avoid bleeding over.
(My plan is to have the receivers
camera mounted as I wander through
a crowd.)
What's that piece of cloth called that
I've seen that hangs down between
a tripod's legs that is for holding
items? Perhaps I could get that
and put the preamp/transmitters
on that to get it elevated.
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Old February 17th, 2004, 02:10 PM   #6
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Having multiple transmitters really gets complicated because you not only have to deal with the frequencies you're actually using, but those frequencies together generate other frequencies. It takes a computer program to accurately predict the numeric value of useable frequencies. Just having channel separation doesn't ensure success, because the result of two wide frequencies may fall right on top of your 3rd unit. Of course most of us just dial around to find a clear spot instead of using a computer, but it's really fascinating to see on a screen how rapidly you can clutter the spectrum with just a few units and the by-products of their interaction. On top of that, the by-products also interact with all the other frequencies too, but fortunately they are significantly weaker by that time. Major manufacturers like Shure and Lectrosonics can enter the values of your existing units and tell you what problem frequencies to avoid for other units you may want to use. Some makers also print guidelines for how many units within a band of frequencies are useable. In other words, don't be surprised when you read the fine print and discover that your 100-channel boxes can only occupy 5 or 6 spots SIMULTANEOUSLY.
Now, if you are using just one transmitter going to multiple camera receivers you're fine. But if you're using multiple transmitters going to independent receivers you not only have to worry about frequencies but also physical separation. That's what I was actually talking about earlier, if the antennae or unsheilded plastic bodies of the receivers are within inches of each other, they can generate interference. If you have yours separated on different cameras that won't cause a problem.
The cloth sling under the tripod sounds like a good idea. If you're having a problem, move either the transmitter or the receiver while listening. Sometimes it only takes a couple of inches to go from perfect to perfectly awful.
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