31–40 of 59 posts
Of course, on the RPI there is the good ole GPIO4 abuse: https://tutorials-raspberrypi.com/build-raspberry-pi-radio-t... Works a lot better and has been around a long time.
Very nice, could be used for exfiltration with some tuning. The most advanced example of this kind of inadvertent transmission I've seen is Fabrice Bellards DVB-T transmitting with a standard VGA card: https://bellard.org/dvbt/
As someone recently participated in an EMC measurement, I really don't understand how anyone passes these tests without some kind of cheating (using double-shielded, very expensive industrial cables + hacking with functional earthing).
I've spent months and sleepless nights trying to get a product through the EMC certification. It's certainly possible but it's time consuming and expensive. With a shoestring engineering budget and a product that needs to be on the shelves in a month? Not really. I'm sure many devices on the market are not compliant. I follow lists of products removed from market for non-compliance and there are plenty each week. But…
Another classic example is early cellphones that you would pick up on stereo systems etc. - "dat-dara-dat-dara-dat-dara-dat-dara-daaaaaa" going out in full blast.
Would the cable length affect the tuning or is 125MHz specific to just the switching on the silicon?
Earlier quoted context omitted.
I've spent months and sleepless nights trying to get a product through the EMC certification. It's certainly possible but it's time consuming and expensive. With a shoestring engineering budget and a product that needs to be on the shelves in a month? Not really. I'm sure many devices on the market are not compliant. I follow lists of products removed from market for non-compliance and there are plenty each week. But…
Yeah, I remember in the early 2000s we had a wireless RCA audio/video transmitter, bought at a local electronics store, that played absolute havoc with the WiFi in our house as well as several neighbours. Another classic example is early cellphones that you would pick up on stereo systems etc. - "dat-dara-dat-dara-dat-dara-dat-dara-daaaaaa" going out in full blast.
Some years back when I had some small involvement in new EU regulations that case was actually given as an example of how, even after many reviews, some forms of harmful interference can only become apparent after a technology is already widely deployed.
(Note: As coderjames points out this could be dangerous tinkering. There is typically steady-state noise at 125MHz from Ethernet so it's not that we're putting more energy into the spectrum with this, but adding signal in the form of morse code could draw a lot of attention/distraction to pilots and ATC in the area.) FWIW very brief example of 125MHz tone loss when going to 10MHz demonstrated here when my slow intern…
Clever hack, but a lot of people are misinterpreting what’s going on here. These devices emit some very low level of 125MHz energy during normal operation. This software is simply turning that on and off, but not doing anything to increase the amount of emissions. Presumably the 125MHz emissions are within the FCC allowed envelope anyway, so this isn’t doing anything to exceed normal emissions limits. This only works…
That's all sort of besides the point anyway as nav aids use the lower end of the aviation band, 125MHz is used for AM voice where the interference would be, at worst, audible but not strong enough to cause problems unless reception was already extremely marginal.
Or to put it differently, two pilots hitting their PTT at the same time is already causing far more disruption to operations in the 125MHz range than this thing ever would.
Earlier quoted context omitted.
I've spent months and sleepless nights trying to get a product through the EMC certification. It's certainly possible but it's time consuming and expensive. With a shoestring engineering budget and a product that needs to be on the shelves in a month? Not really. I'm sure many devices on the market are not compliant. I follow lists of products removed from market for non-compliance and there are plenty each week. But…
Yeah, I remember in the early 2000s we had a wireless RCA audio/video transmitter, bought at a local electronics store, that played absolute havoc with the WiFi in our house as well as several neighbours. Another classic example is early cellphones that you would pick up on stereo systems etc. - "dat-dara-dat-dara-dat-dara-dat-dara-daaaaaa" going out in full blast.
(Note: As coderjames points out this could be dangerous tinkering. There is typically steady-state noise at 125MHz from Ethernet so it's not that we're putting more energy into the spectrum with this, but adding signal in the form of morse code could draw a lot of attention/distraction to pilots and ATC in the area.) FWIW very brief example of 125MHz tone loss when going to 10MHz demonstrated here when my slow intern…
If your Ethernet emissions can be picked up by pilots or air traffic control, your are doing something wrong on purpose.
Also I'm not talking about 30 miles away...but if a completely intact cable can be detected with a directional antenna from 100m, an intentionally buggered patch cable installed at a client site for this purpose could pose a bigger concern for pilots in the area. (edit: I might be more tuned in to this (har har) because I live in the flight path of a medical helicopter that flies over at ~500' almost daily.)
Ham folks can seem a bit hair-triggered chicken littles with RF hygiene but it's the product of decades of fighting noise from people that aren't aware of the externalities of their actions.