APX bluetooth interference

[q101atfd]

Our department recently switched to MSA G1 SCBAs with integrated bluetooth microphones, and we use APX6000AN radios with current firmware. We've experienced a number of incidents where there have been unintelligible transmissions from people using the bluetooth mic. Some quick testing with the affected radio and SCBA produced a significant amount of interference when the RSM cord is hanging, or bunched up, next to the radio antenna. However, when the cord is moved or stretched away from the antenna, the transmission becomes completely clear - in the same transmission, without breaking PTT. This problem is reproducible, and I'm wondering if anybody else has experienced this problem? Not sure if this comes into play, but are any or all generations of the XE RSM mic cable shielded?

 

[phantom]

Yeah. USB clocking noise from the mic cord. You can really hear it on an analog channel with low RF signal in. The USB clocking interference can be heard overriding the analog carrier.

Radio firmware fixed it for us. Also, if you are using an XE500, there is firmware in them as well.

 

[q101atfd]

Yeah. USB clocking noise from the mic cord. You can really hear it on an analog channel with low RF signal in. The USB clocking interference can be heard overriding the analog carrier.

Radio firmware fixed it for us. Also, if you are using an XE500, there is firmware in them as well.

What firmware fixed that issue for you? We're on 20.61.00...

 

[q101atfd]

An audio snippet from the incident...

 

[sarguy1941]

are you analog, digital, trunking ? I tested my APX on our G1's when we got them and never had major issues. Biggest issue was trying to convince the department to replace the XTS...

 

[q101atfd]

Digital trunked 7/800. In talking to the user, the radio maintained its bluetooth connection the entire time, and the transmissions weren't interrupted from low signal. We've tested on a few different radio/RSM/G1 combinations, with mixed results but none as bad as this. Working on a more structured testing process to try and isolate the cause.

Correction to original post, we're using APX6000XE AN models with XE RSM.

 

[ndp]

@EM36 I think said he's got a bunch of these in service (in the Pie Sale thread if I remember, lol). Maybe he's got some tips and tricks for ya.

 

[EM36]

Only issues we've seen is when there's 5-6 guys in one small area. That and I find that some of the masks have issues. MSA has a procedure for cleaning the spittlevalve but I find a wide disparity in how some guys sound on fireground and I'm blaming alot of it on this because of how they sound. At times I find they sound like a rsm on the outside of the turnout coat all muffled. The vast majority don't sound like this though and the issues we've seen has been minor so far.

For the record all the front line stuff is on 19.15 fw, with the exception for anything sent to depot and have the new crap rammed down your throat.

I've listened to your recording. I would go back to the fire scene and look at rssi to completely rule that out. Any cellphones in their pockets??? All this chit runs on the same frequencies.

 

[EM36]

Where is the radio? Could it be that the radio is transmitting too close to the bt receiver in the G1? Try moving it.

 

[q101atfd]

We'll have to go back to the site to get the RSSI, but there are parts of the building that will bonk you. The radio is used in the front coat pocket, with the XE RSM hanging directly above it. I am not entirely sure where the BT antenna is on the G1, but I'm assuming its on the bottom rear with all the other electronics, though I could be wrong. Going to meet with a G1 tech in a few days and have lots of questions.

It's a known issue that if there is any air flowing, from a bad seal or open bypass, that the same type of interference sound can occur. The microphone is inline with the air supply, and the G1 applies a noise cancellation technique which I'm a little suspicious of too.

 

[RFI-EMI-GUY]

Our department recently switched to MSA G1 SCBAs with integrated bluetooth microphones, and we use APX6000AN radios with current firmware. We've experienced a number of incidents where there have been unintelligible transmissions from people using the bluetooth mic. Some quick testing with the affected radio and SCBA produced a significant amount of interference when the RSM cord is hanging, or bunched up, next to the radio antenna. However, when the cord is moved or stretched away from the antenna, the transmission becomes completely clear - in the same transmission, without breaking PTT. This problem is reproducible, and I'm wondering if anybody else has experienced this problem? Not sure if this comes into play, but are any or all generations of the XE RSM mic cable shielded?

Pretty bizarre audio recording.

Yes. It could be the RSM cord near the radio antenna. I found that if someone simply hangs a set of keys on the antenna of a P25 radio, the transmitted signal will carry with it clicking from the keys sparking together. Oddly the energy radiated is significant enough to corrupt the signal received at the far end. So I would say you are on right track. The trick will be to mandate some placement of the radio so its antenna does not have anything metallic in the field.

 

[EM36]

Poor signal is part of the issue I think. I heard digitization in part of that clip that sounds like a poor signal. I don't think the rest is a facepiece seal. It's much too noisy. A loose facepiece will stutter and come in and out.

 

[sarguy1941]

OK. All our use was on simplex. Our SOP is simplex in all structures so really never tested on trunking.

 

[kmonares]

We run 8000XE’s and came across a similar issue but not as bad as your audio.
All the same thing with radio in chest pocket with RSM and cord dangling next to the radio and antenna. We made it an sop that if you are using a radio strap it must be worn under your coat with the antenna sticking out the bottom.
If radio is in chest pocket the cord must be wrapped up and around the back of the neck with the RSM attached to the opposite side of the chest. Our issue was audio similar to yours when guys had the radio in a chest pocket with RSM mounted the same way, they were laying flat on the ground and on a trunked p25 channel. Issue went away when using analog simplex tac’s. Other than that single issue we have been extremely happy with the performance of our G1’s, XE500’s, and 8000XE’s connectivity with each other.

 

[q101atfd]

I’ll finally get a chance to get my hands on the original equipment setup tomorrow to recreate it and get it on video. However, in 3 other attempts, we were unable to replicate it with the cord wrap on other radios. I’ll have to try a simplex channel too to see if it’s the same. Thanks for the replies so far.

 

[phantom]

The received RF signal needs to be weak, near the squelch threshold for the artifact to really show itself. A strong RF signal will override the weaker interference.

 

[EM36]

I’ll finally get a chance to get my hands on the original equipment setup tomorrow to recreate it and get it on video. However, in 3 other attempts, we were unable to replicate it with the cord wrap on other radios. I’ll have to try a simplex channel too to see if it’s the same. Thanks for the replies so far

Any luck replicating?

 

[q101atfd]

Any luck replicating?

It wasn't quite as bad as the first time we replicated, but there's a noticeable amount of interference that goes away when the RSM cord is stretched away from the radio. I think there's a couple factors all at play here, and this is just one of them. Not sure if anybody has better contacts at Motorola that can tell me if this is a known issue or not. I didn't bother trying a simplex channel because all of our firegrounds are trunked.

 

[EM36]

Just saw this sri. I'm going to assume you were transmitting from that pack via bluetooth?

 

[q101atfd]

Just saw this sri. I'm going to assume you were transmitting from that pack via bluetooth?

Yeah, the RSM PTT is set to wireless mic