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That's a neat party trick and all but abusing spurious emissions/harmonics to broadcast in licensed spectrum without proper filtering is just plain irresponsibl

That's a neat party trick and all but abusing spurious emissions/harmonics to broadcast in licensed spectrum without proper filtering is just plain irresponsible. At low power, with an unmatched antenna those signals /probably/ won't make it out of your house but it's not good practice to spew harmonics all over the spectrum, especially GSM bands. I also can't believe that they are working on increasing the TX power. Purposefully emitting all over the spectrum is both iresponsible and illegal.

mathgenius 8y ago
That's why the osmo-fl2k page has the following text: "Before transmitting any signals with an FL2000 device, it is strongly suggested that you check the resulting spectrum with a spectrum analyzer, and apply proper filtering to suppress any but the desired transmit frequency. Operating a transmitter with the unfiltered FL2000 DAC output attached to an antenna outside a RF shielding chamber is dangerous. Don't do it!"
- quickthrower2 8y ago
  Dangerous? Are we talking RF burns here?
  - tomfanning 8y ago
    As in potentially disruptive to critical-to-life public safety systems, e.g. air traffic control, emergency services communications, I suppose. Square waves = theoretically infinite harmonics at positive multiples of the fundamental frequency (in practice reducing with order of the harmonic) Then there's in-band spurs / spurious emissions, different from harmonics.
  - ddalex 8y ago
    I think we're talking jail time here.
- apcragg 8y ago
  A radio amature most likely can't construct a bandpass filter with a high enough Q to filter out all of the spurs while still getting a usable signal. Releasing a tool like this and handwaving away interfearence concerns with an abstract refrence to 'proper filtering' is still iresponsible.
_wmd 8y ago
The project page covers all of this, and takes the time to recommend various filtering strategies. It's not like this stuff is much worse than a faulty washing machine or hair dryer doing the same, or that the very same equipment under control of its official driver couldn't spew junk in exactly the same way
- Johnythree 8y ago
  The device generates a comb of the original baseband, repeated all the way up to VHF. There is no way that a simple passive filter will pick out the wanted signal, while blocking all the others. It would take a sophisticated multi-stage active filter to even come close. The "very same equipment under control of its official driver" won't have an amplifier and antenna connected to its output. If it did, it obviously would fail its EMC test approvals process.
  - _wmd 8y ago
    > The "very same equipment under control of its official driver" won't have an amplifier and antenna connected to its output. If it did, it obviously would fail its EMC test approvals process. Forgive me, but this seems quite a blanket statement to make of the tens-hundreds of millions of VGA cable and LCD/CRT designs and design combinations in deployment for the past 30+ years around the world, equipment combinations that never did (and never will) undergo system testing to verify there aren't, in fact, thousands+ of unintentional transmitters deployed already, by people who haven't a clue about their aberrant devices. It's not like you can't buy dirt-cheap $5 unshielded ultra long VGA extender cables by the literal truckload off AliExpress and eBay, and that you don't find such cables strung vertically to 640x480 projectors hanging off the ceiling of just about every conference center, lecture hall, hotel business suite or similar meeting venue known to man. Meanwhile this project is explicitly about creating a transmitter in an environment where it is understood by every user upfront the result could be noisy
woah 8y ago
If there’s a need for spectrum enforcement, then people should be out doing it. There’s definitely enough money made from government granted spectrum monopolies to pay for it! The idea that you’re pushing here, that there should be varying degrees of a radio equipment prohibition is anti-knowledge and only serves to strengthen the spectrum monopoly businesses.
- TaylorAlexander 8y ago
  Here here!
- simcop2387 8y ago
  Spectrum enforcement does happen. It usually takes a while to identify because there's usually not a large noise source or illegal transmitter. Instead it's usually malfunctioning equipment that's doing stuff it shouldn't. Usually how enforcement happens is that someone complains that this one spot never gets a signal, or their phone always cuts out. Then the big players start getting involved to determine the problem and either get the fcc involved if needed or otherwise inform the offender to get I fixed. That's how stories like this happen, https://www.engadget.com/2016/05/25/florida-man-fined-48k-fcc-jamming-cellphones/ https://www.engadget.com/2016/05/25/florida-man-fined-48k-fc... EDIT: to add there's a lot of unintentional interference sources, neon signs are a typical culprit as they age, http://www.signindustry.com/neon/articles/2004-02-16-RadioFrequency-RC-.php3 http://www.signindustry.com/neon/articles/2004-02-16-RadioFr...
  - Something1234 8y ago
    How do I make a complaint about this? There's one spot on my college campus that's completely dead.
    - asclepi 8y ago
      Don't contact the FCC directly. Contact your cellular operator. They can investigate to see if it is a problem on their end. They will also contact the FCC if necessary.

mathgenius 8y ago

That's why the osmo-fl2k page has the following text: "Before transmitting any signals with an FL2000 device, it is strongly suggested that you check the resulting spectrum with a spectrum analyzer, and apply proper filtering to suppress any but the desired transmit frequency. Operating a transmitter with the unfiltered FL2000 DAC output attached to an antenna outside a RF shielding chamber is dangerous. Don't do it!"

quickthrower2 8y ago
Dangerous? Are we talking RF burns here?
- tomfanning 8y ago
  As in potentially disruptive to critical-to-life public safety systems, e.g. air traffic control, emergency services communications, I suppose. Square waves = theoretically infinite harmonics at positive multiples of the fundamental frequency (in practice reducing with order of the harmonic) Then there's in-band spurs / spurious emissions, different from harmonics.
- ddalex 8y ago
  I think we're talking jail time here.
apcragg 8y ago
A radio amature most likely can't construct a bandpass filter with a high enough Q to filter out all of the spurs while still getting a usable signal. Releasing a tool like this and handwaving away interfearence concerns with an abstract refrence to 'proper filtering' is still iresponsible.

_wmd 8y ago

The project page covers all of this, and takes the time to recommend various filtering strategies. It's not like this stuff is much worse than a faulty washing machine or hair dryer doing the same, or that the very same equipment under control of its official driver couldn't spew junk in exactly the same way

Johnythree 8y ago
The device generates a comb of the original baseband, repeated all the way up to VHF. There is no way that a simple passive filter will pick out the wanted signal, while blocking all the others. It would take a sophisticated multi-stage active filter to even come close. The "very same equipment under control of its official driver" won't have an amplifier and antenna connected to its output. If it did, it obviously would fail its EMC test approvals process.
- _wmd 8y ago
  > The "very same equipment under control of its official driver" won't have an amplifier and antenna connected to its output. If it did, it obviously would fail its EMC test approvals process. Forgive me, but this seems quite a blanket statement to make of the tens-hundreds of millions of VGA cable and LCD/CRT designs and design combinations in deployment for the past 30+ years around the world, equipment combinations that never did (and never will) undergo system testing to verify there aren't, in fact, thousands+ of unintentional transmitters deployed already, by people who haven't a clue about their aberrant devices. It's not like you can't buy dirt-cheap $5 unshielded ultra long VGA extender cables by the literal truckload off AliExpress and eBay, and that you don't find such cables strung vertically to 640x480 projectors hanging off the ceiling of just about every conference center, lecture hall, hotel business suite or similar meeting venue known to man. Meanwhile this project is explicitly about creating a transmitter in an environment where it is understood by every user upfront the result could be noisy

woah 8y ago

If there’s a need for spectrum enforcement, then people should be out doing it. There’s definitely enough money made from government granted spectrum monopolies to pay for it! The idea that you’re pushing here, that there should be varying degrees of a radio equipment prohibition is anti-knowledge and only serves to strengthen the spectrum monopoly businesses.

TaylorAlexander 8y ago
Here here!
simcop2387 8y ago
Spectrum enforcement does happen. It usually takes a while to identify because there's usually not a large noise source or illegal transmitter. Instead it's usually malfunctioning equipment that's doing stuff it shouldn't. Usually how enforcement happens is that someone complains that this one spot never gets a signal, or their phone always cuts out. Then the big players start getting involved to determine the problem and either get the fcc involved if needed or otherwise inform the offender to get I fixed. That's how stories like this happen, https://www.engadget.com/2016/05/25/florida-man-fined-48k-fcc-jamming-cellphones/ https://www.engadget.com/2016/05/25/florida-man-fined-48k-fc... EDIT: to add there's a lot of unintentional interference sources, neon signs are a typical culprit as they age, http://www.signindustry.com/neon/articles/2004-02-16-RadioFrequency-RC-.php3 http://www.signindustry.com/neon/articles/2004-02-16-RadioFr...
- Something1234 8y ago
  How do I make a complaint about this? There's one spot on my college campus that's completely dead.
  - asclepi 8y ago
    Don't contact the FCC directly. Contact your cellular operator. They can investigate to see if it is a problem on their end. They will also contact the FCC if necessary.