Multiple wireless mics?

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lasikdenver

Well-known member
I am relatively new to sound, and have a Sennheiser G3 with my Sony F3. When using the system, I have followed all the recommendations and it works great except for rare bursts of static or the squelch at medium suppressing the sound when I would have had static. This usually happens when I change position of the camera or the talent who has the transmitter hidden in the back suddenly moves, or bends. I have scanned for frequencies, etc but this does not always help. Would there be a benefit to getting a second set at a different frequency and having the receiver mounted at a different spot on my rig? Would having just a second receiver (much easier not to double mic) at the same frequency be of any help as an alternative? Currently, the receiver goes into one of two XLR inputs, so I could have a second feed into the other input. Also, I have found that using the Cineroid EVF which is powered remotely by a D-Tap increases the frequency of these static bursts, but even turning it off does not entirely prevent it. I have checked the cables and they are all secure and this has been a problem since the set was new. Any suggestions would be appreciated.
 
Ensure that the antenna on the transmitter (on the talent) is not taped or laying directly against the actor's skin. This, more than anything will reduce range. What band are you using?
 
"A" BAND FREQ 516.0 most recently-- And Thanks -- It might have been touching skin in some cases. It might also be very close to skin, hanging from pants and trapped between a thin shirt and an outer garment. It is always behind the talent, so their body is between the antenna and the receiver.
 
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The receiver does not always have to be close to the audio recorder or camera. Try getting the receiver behind (or above or to the side) and closer to the talent and running a long cable from the receiver to the recorder/camera. This will give the transmitter a more direct line to the receiver.
 
Thanks for the suggestion. I have the receiver behind the camera on a shoulder/tripod rig where it is attached on the side to a Sennheiser holder that is attached to the side of a V-Mount battery plate. There are many cables in close proximity, one to an external recorder (Samurai) one to an EVF, and the one from the receiver to the XLR input on the front opposite site of the camera -- but they are all shielded cables. I could attach the receiver to the shoe mount on top which aims the antenna forward rather than vertical as it sits in the holder. I would rather save the shoe mount for occasional other uses such as an onboard fill light. It seems that the static is most likely when I tip the camera forward during the shoot, when the receiver actually has a better straight shot at the receiver, but of course the angle of the antenna has changed.
 
lasikdenver said:
Thanks for the suggestion. I have the receiver behind the camera on a shoulder/tripod rig where it is attached on the side to a Sennheiser holder that is attached to the side of a V-Mount battery plate.
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OK, but no mention of how FAR it is between the transmitter and the receiver? Not clear, either, WHY the receiver must be mounted on the camera? Or, for that matter why you must use wireless vs. wired at all?


There are many cables in close proximity, one to an external recorder (Samurai) one to an EVF, and the one from the receiver to the XLR input on the front opposite site of the camera -- but they are all shielded cables.
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Shielded makes no difference to the receiver. It is possible that all the cables nearby the receiver antenna are weakening and/or distorting (via multipath reflections) the RF signal. And the treatment of the transmitter antenna could be a significant factor also, as gpforet suggested.

I could attach the receiver to the shoe mount on top which aims the antenna forward rather than vertical as it sits in the holder. I would rather save the shoe mount for occasional other uses such as an onboard fill light. It seems that the static is most likely when I tip the camera forward during the shoot, when the receiver actually has a better straight shot at the receiver, but of course the angle of the antenna has changed.
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But your own experiments appear to show that having the receiver ON the camera is not an optimal location, moving it slightly here and there seems unlikely to make any significant improvement. Using another wireless mic and/or a different frequency also do NOT seem to be likely solutions. You simply have a lousy RF connection between the transmitter and the receiver. We have mentioned a few things that could be causing that, but there are many others.

I would start out with the receiver directly behind the performer and then move it gradually to the camera position to establish what is the limit of reliable operation for your particular kit and setup.

The option of a second receiver is the whole concept of "diversity reception" found in other models of wireless kits.

The worsening of the symptoms with the EVF is another indication of really marginal RF signal strength. Confirm that neither the transmitter nor receiver antennas are broken.
 
Thanks for all of your help, what a great group of people! The transmitter to receiver varies, indoors about 10 ft outdoors at times up to 30 feet. I am mainly doing interviews and do need wireless. Since it is a "one man band" setup, I have a shoulder mounted rig that can be used on a tripod. I have made significant improvements by changing the receiver/antenna positions slightly and watching the signal strength. Also, I will be more careful in the transmitter with no skin contact.
 
If you are doing interviews, I can't imagine you wouldn't be able to use a wired lav instead of a wireless one, dropping the cable down the back then along the ground/floor where the camera won't see it. Lavs can be challenging enough when wired; a host of additional issues are introduced the moment you start using wireless, and if you don't need it, it is better to do without.

If the receiver is too close to the battery, it is possible that an electrical signal between the battery and camera is causing interference in the audio cable between the receiver and the camera. If the receiver can't be moved off-camera, at least try moving it away from the battery and any power cables.
 
Sorry, there is no evidence that proximity of a battery will affect the receiver in any way. Note that most portable (ENG style) wireless receivers have a battery (or two) right inside the case. By its very nature, the "electrical signal between the battery and camera" is quite literally the cleanest and most interference-free of all electrical signals.

However, fde101's suggestion about using wired vs. wireless is spot on. It is impossible for even a $5000 wireless system to be as reliable as a $20 cable. NEVER use a wireless system when you can use a hard-wired solution.
 
lasikdenver said:
Thanks for all of your help, what a great group of people! The transmitter to receiver varies, indoors about 10 ft outdoors at times up to 30 feet. I am mainly doing interviews and do need wireless. Since it is a "one man band" setup, I have a shoulder mounted rig that can be used on a tripod. I have made significant improvements by changing the receiver/antenna positions slightly and watching the signal strength. Also, I will be more careful in the transmitter with no skin contact.
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But speaking of batteries, do you replace the batteries with fresh ones regularly? Many workers will replace batteries at the start of each shooting day and really careful ones replace them again at lunch and dinner breaks.

Another source of transmission interference is the positioning of the cable from the mic capsule to the transmitter viz a viz the transmitter's antenna. Don't allow the cable to cross over or loop around the antenna. Route it away from the transmitter horizontally around the talent's waist for a ways, tucking it into their waist band around to the front of their body before bringing it up to the capsule. The idea is to keep the mic cable as far away from the transmitter antenna as you can. You definitely don't want them touching.
 
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Another trick I learned from doing rc wireless video that i think translates here is that these antennas radiate out in a doughnut shape and have the weakest signal when the antenna is pointed directly at the rx or directly away.
Try keeping them parallel for optimum signal.
 
I replace the batteries very frequently, and have been using Lithium cells which seem to last forever. Great suggestion on the cable, I was not paying attention to body contact nor to the mic cable touching the antenna, but I will from now on. Thanks for the great tip!
 
This certainly rules out placing the transmitter on top of the camera with the antenna aimed at the receiver (like is shown in the instruction manual from Sennheiser). Curiously, I have found that if I bend the receiving antenna in an arc (putting the tip into one of the cheese plate holes on the opposite side of the battery plate) I get the best reception. I do not know if it is the angle of the antenna, or that the metal of the plate it is touching becomes an extended antenna? I have also just yesterday, rotated the output from the receiver (which I understand is the diversity second antenna) so that it does not touch the first antenna and angles about 180 degrees away, and this also seems to help. Prior to doing these two things, just turning on the EVF with the transmitter off, gave constant static, but now there is none, and with the transmitter on I seem to get a much better signal. I really need to do wireless because there is a fair amount of walking and talking besides just interviews.

My original question was that since I have the extra XLR input on the Sony F3 anyway, why not use it for a second receiver, but maybe this is not a good idea.
 
Good question. The G3 is a diversity receiver. Simply put, the receiver actually contains 2 receivers, and uses two antennas. On the G3, the second antenna is the cable connecting from the receiver to the recording device. The incoming RF is monitors and the "diversity" receiver is continuously looking at these two signal paths for the best RF s/n ratio and switching between them as needed.



lasikdenver said:
My original question was that since I have the extra XLR input on the Sony F3 anyway, why not use it for a second receiver, but maybe this is not a good idea.
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The solution was the transmitter antenna was touching the mic cable. Also, I re-oriented the antenna on the receiver and changed the direction of the secondary antenna on the diversity receiver (they were also very close to touching). I now have good consistent signal strength and no more static bursts.
 
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