jedimark wrote:To comply with FCC regulations, an electronics device has to accept any RF interference regardless of negative impact. Still no device manufacturer wants their device to get frazzled from external signals, so IC's and electronics pathways are generally well designed to avoid disaster.
I'll disagree that "IC's and electronics pathways are generally well designed" in terms of RF interference.
Geez, you gotta love the wording the lowlife bureaucrats, big business, and their indentured servants in Congress create. "Must accept" sounds good until you read the regulations and figure out what they mean.
47 CFR 15 ยง 15.19 (3)
"This device complies with part 15 of the FCC Rules. Operation is subject to the following two conditions: (1) This device may not cause harmful interference, and (2) this device must accept any interference received, including interference that may cause undesired operation."
Translation: "We put this fancy label on it implying it's a good device in terms of radio interference, but the fine print says a radio signal from something else may break it, and you must not complain about it."
jedimark wrote:A 2.4ghz wireless signal at 100mW or so isn't going to do much, even inside the plastic gizzards of a CPAP machine. I doubt an SD wireless device would use anywhere near that transmission power.
Worst that could happen is the device locks up, and the watchdog timer reboots the device.
Far more destructive energy is coming constantly from solar flares and other radiation from space/radio towers/etc, and these little devices keep on chugging. True, distance has a bearing on signal strength, but I've seen plenty of devices have wireless with the antenna crammed right up near the CPU cores, and they keep running fine.
100 mW isn't likely to blow anything up, but it could easily cause errors. It could easily cause the machine to read or write the wrong value for a variable. Then it might change 10 cm pressure to 4 cm or 20, and keep running. Or screw up some other critical parameter and keep the processor running despite a watchdog timer, if such a thing even exists.
The signal strength from a transmitter that's 1/8 inch from the main processor board is going to be a lot stronger than signals from space, radio towers, etc. On the S9, the SD card actually lays on the main circuit board.
Yes, devices often have wireless stuff crammed right next to the CPU. They often fail to work in the prototypes and have to be redesigned several times to eliminate the problems the radio signal causes before they can be sold.
Even if a watchdog timer goes off, the machine is probably going to shut down. That would be a bad thing to happen in the middle of the night.
I'm not saying problems will happen. However, it wouldn't be surprising if problems do happen, including problems that only happen fairly infrequently. If my CPAP pressure dropped 50% in the middle of the night once a month or so, I'd be unhappy.