Can cell phones interfere with wireless mic?

[Richard Crowley]

I had thought this might reduce the impact of warm bodies on the RF signal. Would it not?

Under normal conditions, I would agree. But your tests and symptoms indicate that you are working on the edge of viability.

I identified the system as a Shure with Body Pack T1-W and receiver T4a-W. The transmitter certainly does have an external antenna.
Although he had been wearing it inside his jacket pocket, I learned this morning that for the last several weeks he's had it clipped to his belt, although he doesn't like it there.

OK, but the issue is whether the antenna wire is deployed properly (hanging straight, not bunched up, and not up against the user)

Okay. So as I said, I increased the gain on the transmitter and reduced the squelch on the receiver. I will put a fresh Duracell 9-volt battery into the transmitter for this Sunday's service.

The gain on the transmitter is only the audio signal gain. It has nothing to do with the strength of the radio waves being transmitted. If you adjusted it up too much, you may cause it to clip or distort during normal use. Not recommended.
The squelch on the receiver only sets the threshold of where the receiver decides signal or nothing. It is true that if the squelch setting his drifted too high, the receiver will quit (mute or squelch) while it still has a viable signal available. The normal way of setting squelch is to turn it down until the receiver un-mutes (so you hear static/hiss), and then turn it back up to mute/squelch. You do this with the transmitter OFF, so that the squelch is set to reject the ambient RF noise floor.

Okay, so what are we saying here? What are the things I can reasonably do to make the system less marginal? Or are there any, aside from moving the receiver to the front of the church? Which, as I've repeatedly said, I'm willing to do if there is no other choice.

1) If the transmitter is not putting out the design power, or not operating in the center of the channel, then you can repair the transmitter. But since service information is probably not available, and it takes specialized experience and equipment, this is probably not a viable solution.
2) If the receiver has drifted out of tune, it could also be re-tuned. But again that takes specialized experience and equipment. It may not be beyond the realm of possibility that there is in your congregation (or circle of friends) an old-school ham (amateur radio operator) who still works on circuits and builds and repairs his own transmitting and receiving equipment. A good "home-brewer" type of ham radio operator could possibly examine and test the rig (transmitter and receiver) and might be able to revive it.
3) Since the system (TX - RX) seems to have marginal operational sensitivity, moving the receiver closer to the transmitter would increase the received signal strength. Guaranteed by the laws of physics.
4) Replacing the system with a more modern unit would probably resolve the problems. But is it not a gold-plated guarantee. I certainly wouldn't buy anything that couldn't be returned if it doesn't help. Beware of bargain-basement wireless systems. They may operate no better than what you have now. I would be very suspicious and wary of anything < $400.

Ideally. But he keeps the transmitter body pack in a drawer in his locked office. It's sometimes not easy to get access to it. Which is why he has always been the one who changes the batteries. But we can develop a protocol for that.

Make a little bracket (like a communion cup holder) next to his office door and put a new battery in there every Sunday morning.

 

[paulears]

Isn't the T4 series elderly and VHF with fixed antennae? It's very unlikely cellphones are going to be the cause of problems, but it's quite possible you have high power VHF comms transmitters in the vicinity that can easily desensitise the receiver. That said, however, I'd bet the problem is simply nulls - and the previous analogy of the meandering paths is what is happening. As bodies are mostly water, they're pretty good at blocking RF, and the receiver may well be getting it's main signal via reflections.

On pro systems, RF monitoring and tracking software is now common, and what happens is that in the main, the RF signal is very strong. Then, it takes a sudden dive as the person moves and the RF level drops to zero. Then it's back up again. In pro systems the actual antennas as separated - being cabled to convenient places. Then, if channel A takes a dive, the signal on channel B from the antenna maybe 20-30 ft away will hopefully still be up. With these cheaper systems the antennas are in almost the same place, so if the path is poor to one, it will also be poor to the other. Just how RF systems work. Fill the room with people, and many of the direct and reflected paths will be marginal. The shorter the path, the more headroom you have to cope with the deep nulls. In VHF systems, it's perfectly possible to step into a radio black hole, maybe just a couple of feet wide where there is no direct line of sight, and reflections that can cancel out the alternate paths. Move just a bit and signal strength returns.

Aerials for VHF are also a compromise - 17 or 18" of dangly ¼ wave is hardy practical, so most antenna systems are helically wound to make them shorter, and of course, less efficient. Press them against a sweaty body and it gets even worse.

 

[David W. Richardson]

Today it once again worked flawlessly. The significant changes from last week are:

1. A somewhat smaller congregation today.

2. A new battery in the transmitter, although the one it had before was supposedly 'pretty new'.

3. Moved the receiver to the far right side of the desk, putting it about 8 inches farther away from the LCD video monitor.

4. Turned off the second wireless receiver (only used when someone is using the handheld wireless to sing a solo) and the assisted listening transmitter (since no one required it today.) Lowered and stowed the antennae for both.

5. Elevated the receiver, but only slightly -- only about 1/2 inch higher than it was before.

6. I extended the pole on which the camera is mounted by about 1 foot, so that means the camera was 1 foot higher above the receiver than it had been previously.

Interestingly, I noticed that the preacher kept the wireless lapel mic turned on throughout the rest of the service, though he didn't use it -- I had signal and peak lights on the receiver for the rest of the service.

The receiver has two signal lights -- one if the signal is stronger on the left antenna, the other if it's stronger on the right antenna. During the main sermon (even though he wasn't using the wireless mic) I noticed it seemed to switch from time to time from one light to the other. But there was always one light lit, they never both went dark.

So today was a good day. We'll see how it goes next Sunday.

 

[jamedia.uk]

Has anyone thought that it might be an Act of God? In this case it is a valid option.....
Not unknown to have the kit and the operator blessed.
(Roman Catholics even try exorcisms)

Though it is far more likely to be a technical problem.

One mundane option, is there a mute button on the transmitter? It is possible for these to get moved, less common but possible is the mute switch is intermittent. Worth checking just to rule it out.

 

[David W. Richardson]

Has anyone thought that it might be an Act of God? In this case it is a valid option.....
Not unknown to have the kit and the operator blessed.
(Roman Catholics even try exorcisms)

Though it is far more likely to be a technical problem.

One mundane option, is there a mute button on the transmitter? It is possible for these to get moved, less common but possible is the mute switch is intermittent. Worth checking just to rule it out.

There is a mute button on the transmitter. Not a button, though -- a slide switch that clicks to each position. Typically the preacher has the transmitter muted until he begins the children's service. At that point he un-mutes, does the service, then mutes again.

It requires a pretty solid action to move the switch position, so it's not likely the switch would move by accident. And since we've had situations where the audio from the wireless mic pops in and out, that would seem to eliminate the mute switch as the problem. That and the fact that during my testing I have tapped, pressed on, and switched both the mute and power switches, and found no anomalies.

Thanks for the input!

 

[TRonin81]

Today it once again worked flawlessly. The significant changes from last week are:

1. A somewhat smaller congregation today.

2. A new battery in the transmitter, although the one it had before was supposedly 'pretty new'.

3. Moved the receiver to the far right side of the desk, putting it about 8 inches farther away from the LCD video monitor.

4. Turned off the second wireless receiver (only used when someone is using the handheld wireless to sing a solo) and the assisted listening transmitter (since no one required it today.) Lowered and stowed the antennae for both.

5. Elevated the receiver, but only slightly -- only about 1/2 inch higher than it was before.

6. I extended the pole on which the camera is mounted by about 1 foot, so that means the camera was 1 foot higher above the receiver than it had been previously.

Interestingly, I noticed that the preacher kept the wireless lapel mic turned on throughout the rest of the service, though he didn't use it -- I had signal and peak lights on the receiver for the rest of the service.

The receiver has two signal lights -- one if the signal is stronger on the left antenna, the other if it's stronger on the right antenna. During the main sermon (even though he wasn't using the wireless mic) I noticed it seemed to switch from time to time from one light to the other. But there was always one light lit, they never both went dark.

So today was a good day. We'll see how it goes next Sunday.

Did you ever find the exact cause?