• tal@lemmy.today
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    3 months ago

    Like, you can add frequency-hopping-spread-spectrum stuff, but that isn’t a magic wand; I means that yeah, maybe the FHSS device is more-resistant to interference on any one frequency, but it also means that it’s edging into more spectrum space.

    And the problem is if the only way you can reliably get a signal through is by ramming the power up, that creates bad incentives.

    I used to have a Logitech gamepad (an F710) that ran using a proprietary 2.4 GHz wireless protocol. Used it happily for years, I can’t comfortably use it now, because, over the past several years, some devices has shown up that eeevery now and then disrupts the connection briefly. And that’s with the receiver’s antenna and the transmitter’s antenna just a few feet away, with a clear line of sight. Bluetooth gamepads still work okay; I believe that the protocol has got more reliability built into it.

    Now, okay, gamepads are maybe a worst-case scenario. They have hard real-time constrants; you really notice it in the middle of a fast-paced video game if your gamepad stops responding. Just delaying and retransmitting is problematic. Something like, say, a baby monitor briefly dropping out doesn’t matter so much.

    But by the same token, they’re also the canary in the coal mine.

    I have wondered if the end game is going to have to be taking the really high bandwidth things, stuff like WiFi, and shifting it to requiring line-of-sight and a mechanically-aimed laser or something like that.

    I try to make sure that the microwaves in the house have good isolation, for safety and communication integrity,

    Hmm. How do you do that? Like, go to a brick-and-mortar-store that has plugged-in microwaves with a some kind of spectrum analyzer? Just keep buying microwaves until you find one that you like?

    I haven’t paid attention to microwaves, but I have been a little concerned about what LED bulb power supplies do; they’re apparently a rather significant and growing source of noise as everyone is replacing their (silent) incandescent bulbs with LED bulbs. I’ve actively tried to find low-RF-emission bulbs, and it’s a pain.

    As I understand it, the basic problem is a combination of the facts that:

    • They are using a hefty amount of juice.

    • The power line is unshielded, and so can act as an antenna as a PWM power supply flips on and off.

    • Lamps designed for incandescent A19 bulbs, were never designed with LEDs in mind, so the LED’s power supply isn’t built into the lamp; instead, you have to put a small, high-power power supply where users are very price-sensitive in a very small space: inside the bulb.

    Even if there were a low-RF-emission rating, which there isn’t, it’s not as if someone can do something about other people using them.

    I suppose that in the long term, this problem will probably slowly solve itself if people just wind up moving in the direction of lamps designed specifically for LEDs (usually with non-removable LEDs); maybe lamp-integrated power supplies will perform better. But even an LED bulb will hopefully last a long time, not to mention a lamp. So that’s not happening any time soon.

    • MystikIncarnate
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      3 months ago

      FHSS is not magic. In some ways it makes things worse for other protocols while avoiding problems for itself.

      Which leads me into The next comments you made about interference sources. With microwaves and LED bulbs and such. While I do have an SDR, I don’t use it for wireless cleanliness. My access points, mainly Cisco aironet 2802i series, have a feature called “clean air” which isn’t new for Cisco, but other vendors are starting to add similar features to their access points. I believe it’s been included in most mid-range aironet access points since wireless N (around the 2600, maybe before)… Anyways, the built in radios will listen for and analyse interference and provide information related to it.

      Clean Air will report pretty much everything that can be interference with decent accuracy. I’ve personally seen the following: radar, Bluetooth, microwave (oven), and “non-wifi” as interference sources. I believe “non-wifi” is the catch-all for something that can’t be identified.

      Clean Air also reports on what channels are impacted by the inference, and I can also get reports on nearby wifi networks, and what channels they’re on, the frequency width that’s set on foreign access points… On top of that, it gives me a report on how busy the channels are for the configured channels on the access points, with classifications for my wifi traffic, others wifi traffic, noise, and inference.

      With microwaves, I mainly watch the clean air report, if I see microwave (oven) interference, I try to reference the time of the interference, and figure out if the microwave was in use during that time. If it lines up consistently, time to replace the microwave.

      In my experience, new microwaves rarely have an isolation problem. The mark quality in the manufacturing of the microwave, is how long before that happens. Some last a long time, others lose their isolation fairly quickly. Pre-testing isn’t very useful since the isolation is usually fine when It’s new.

      To the same point it’ll pick up interference from other sources, like lightbulbs. So if that’s picked up at all, I’ll have to correlate what lights are on and when, to figure out which ones are the problem. To date, the interference is either off-band, or not significant enough to trigger clean air.

      I know CFL’s put off way more RF interference than LED bulbs. The high frequency required for florescent lamps is far worse than the RF put out by most LED bulbs.

      I’ve considered getting an ekahau sidekick to get a better wireless spectrum analysis, but there’s no way I could afford one right now. If I had more of a purpose for it, beyond my curiosity, then maybe. As it stands, no way. It’s in the neighborhood of $2000+. Unless I can use it to help pay the rent, I won’t be picking that up.