4 ms·

Basically, the FCC can slap you with an expensive fine when the local HAMs rat you out.

connicpu 4y ago
A 20cm antenna driven by a raspberry pi's current limited GPIOs won't be powerful enough to get picked up by anything more than a few dozen meters away, especially not powerful enough to get in the way of actual signals being transmitted by a more powerful transmitter
- Johnythree 4y ago
  A 20cm antenna will be a 1/4 wave at 375 MHZ (and a half wave at 188Mhz, etc), and thus will be a very efficient radiator at many different frequencies. Even a tiny signal can be enough to block the operation of a nearby police repeater (which is also trying to hear weak signals).
  - simfree 4y ago
    Perhaps public safety shouldn't be entirely beholden to Motorola rebranding old garbage (ancient TDMA networks being sold as new P25 compliant hardware for tens of millions of dollars) that is then sold as new. Modern protocols like 5G New Radio that have better propogation at the fringes of connectivity would serve life critical applications with improved coverage and significantly more intelligible voice quality than what the current public safety networks are capable of doing. If you look at the telephone/power poles in your neighborhood you will see a device with two antennas hooked into power every few blocks. This is a recieve only amplifier that has to be used to amplify these weak signals from handheld public safety radios that use protocols like TDMA with poor interference resistance and no error correction.
    - Johnythree 4y ago
      It has nothing to do with Motoroa, TDMA, or 5G. If the wanted signal is very weak (eg from a distant aircraft using VHF AM), and there is an interfering signal on the same channel, the emergency communications will be distrupted.
      - simfree 4y ago
        Aircraft using the VHF band with amplitude modulation is going to perform much differently than a police repeater and it's local upstream only amplifiers interacting with low wattage fixed handhelds and medium wattage car mounted mobile radios. Pivoting topics is a bad faith conversational tactic FYI, and doesn't follow HN's guidelines. I encourage you to fully read the guidelines linked at the bottom of the page.
        Johnythree 4y ago
        Nevertheless, the threat is to public safety communications. And not all Public safety use TDMA (or whatever). Aircraft communications is probably the most vulnerable, but so are HF/VHF marine operations, military and a host of others. TDMA amplifiers could well be a problem in your country, but the whole point of the discussion is that transmitting a wide band of RF hash will certainly be detrimental to thousands of other radio users, whether or not they are using a TDMA public network.
        simfree 4y ago
        Amplifiers are often protocol agnostic. Whether your amplifying TDMA, Trunked radio, CDMA etc. Aviation needs to modernize, I have zero sympathy for the aviation community getting constant hallpasses on ancient altimeters that lack filters to reject RF from nearby frequencies, leaded avgas, and abysmal working conditions for those stuck in the industry. The FAA dragging their feet in the USA trying to act like they should never have to test how interference affects hardware on planes is insane, they waited till well past when 3.5Ghz went into cellular use to make any effort to performance test altimeters for band conformance. The FCC's timelines are long, the FAA had at least half a decade heads up of when the 3.5Ghz auction would occur, and additional time after the auction before Verizon and AT&T put the spectrum into service. We have waited 25 years past when everyone else stopped using leaded gas to get rid of leaded Avgas[1]. As a Seattleite who grew up with families made up of Boeing Engineers, the problem of vulnerable radio transmissions from aircraft could be resolved with a network of reception sites just like Gogo uses at a much higher frequency allocation. This problem is just not a priority for the Aviation community, they would rather not invest in better equipment and infrastructure. 1 - https://qz.com/leaded-aviation-fuel-is-prompting-bipartisan-outrage-am-1849355733 https://qz.com/leaded-aviation-fuel-is-prompting-bipartisan-... Edit: Trunked, not Truned
esskay 4y ago
I know nothing about how this all works, how do people know who did it / where it came from? I presume its possible to get a rough location but in a built up area I'd imagine its pretty much impossible to find the person that did it unless it's left running right?
- robotnikman 4y ago
  You can use radio triangulation to determine where the signal source is while it is transmitting
  - dylan604 4y ago
    Unless the transmitter is moving. Steal The Air!! -Pump Up The Volume
- Johnythree 4y ago
  If you are blocking an essential services channel (eg Aircraft, Police, Ambulance, military), the authorities can get a triangulation (within meters) on you in just a few minutes.
- tb_technical 4y ago
  If you're interested, Hams do an activity called a "Foxhunt" where they're trying to triangulate the position of a broadcasted signal. It's sort of like wargaming, but for Hams. This, in conjunction with whoever owns the plot of land the offending device happens to live on, determines who is to blame when someone is broadcasting illegally. Here's a link describing the activity, in case you're interested: https://hamradioplanet.com/what-is-a-fox-hunt-in-ham-radio/ https://hamradioplanet.com/what-is-a-fox-hunt-in-ham-radio/

A 20cm antenna driven by a raspberry pi's current limited GPIOs won't be powerful enough to get picked up by anything more than a few dozen meters away, especially not powerful enough to get in the way of actual signals being transmitted by a more powerful transmitter

Johnythree 4y ago
A 20cm antenna will be a 1/4 wave at 375 MHZ (and a half wave at 188Mhz, etc), and thus will be a very efficient radiator at many different frequencies. Even a tiny signal can be enough to block the operation of a nearby police repeater (which is also trying to hear weak signals).
- simfree 4y ago
  Perhaps public safety shouldn't be entirely beholden to Motorola rebranding old garbage (ancient TDMA networks being sold as new P25 compliant hardware for tens of millions of dollars) that is then sold as new. Modern protocols like 5G New Radio that have better propogation at the fringes of connectivity would serve life critical applications with improved coverage and significantly more intelligible voice quality than what the current public safety networks are capable of doing. If you look at the telephone/power poles in your neighborhood you will see a device with two antennas hooked into power every few blocks. This is a recieve only amplifier that has to be used to amplify these weak signals from handheld public safety radios that use protocols like TDMA with poor interference resistance and no error correction.
  - Johnythree 4y ago
    It has nothing to do with Motoroa, TDMA, or 5G. If the wanted signal is very weak (eg from a distant aircraft using VHF AM), and there is an interfering signal on the same channel, the emergency communications will be distrupted.
    - simfree 4y ago
      Aircraft using the VHF band with amplitude modulation is going to perform much differently than a police repeater and it's local upstream only amplifiers interacting with low wattage fixed handhelds and medium wattage car mounted mobile radios. Pivoting topics is a bad faith conversational tactic FYI, and doesn't follow HN's guidelines. I encourage you to fully read the guidelines linked at the bottom of the page.
      - Johnythree 4y ago
        Nevertheless, the threat is to public safety communications. And not all Public safety use TDMA (or whatever). Aircraft communications is probably the most vulnerable, but so are HF/VHF marine operations, military and a host of others. TDMA amplifiers could well be a problem in your country, but the whole point of the discussion is that transmitting a wide band of RF hash will certainly be detrimental to thousands of other radio users, whether or not they are using a TDMA public network.
        simfree 4y ago
        Amplifiers are often protocol agnostic. Whether your amplifying TDMA, Trunked radio, CDMA etc. Aviation needs to modernize, I have zero sympathy for the aviation community getting constant hallpasses on ancient altimeters that lack filters to reject RF from nearby frequencies, leaded avgas, and abysmal working conditions for those stuck in the industry. The FAA dragging their feet in the USA trying to act like they should never have to test how interference affects hardware on planes is insane, they waited till well past when 3.5Ghz went into cellular use to make any effort to performance test altimeters for band conformance. The FCC's timelines are long, the FAA had at least half a decade heads up of when the 3.5Ghz auction would occur, and additional time after the auction before Verizon and AT&T put the spectrum into service. We have waited 25 years past when everyone else stopped using leaded gas to get rid of leaded Avgas[1]. As a Seattleite who grew up with families made up of Boeing Engineers, the problem of vulnerable radio transmissions from aircraft could be resolved with a network of reception sites just like Gogo uses at a much higher frequency allocation. This problem is just not a priority for the Aviation community, they would rather not invest in better equipment and infrastructure. 1 - https://qz.com/leaded-aviation-fuel-is-prompting-bipartisan-outrage-am-1849355733 https://qz.com/leaded-aviation-fuel-is-prompting-bipartisan-... Edit: Trunked, not Truned

esskay 4y ago

I know nothing about how this all works, how do people know who did it / where it came from? I presume its possible to get a rough location but in a built up area I'd imagine its pretty much impossible to find the person that did it unless it's left running right?

robotnikman 4y ago
You can use radio triangulation to determine where the signal source is while it is transmitting
- dylan604 4y ago
  Unless the transmitter is moving. Steal The Air!! -Pump Up The Volume
Johnythree 4y ago
If you are blocking an essential services channel (eg Aircraft, Police, Ambulance, military), the authorities can get a triangulation (within meters) on you in just a few minutes.
tb_technical 4y ago
If you're interested, Hams do an activity called a "Foxhunt" where they're trying to triangulate the position of a broadcasted signal. It's sort of like wargaming, but for Hams. This, in conjunction with whoever owns the plot of land the offending device happens to live on, determines who is to blame when someone is broadcasting illegally. Here's a link describing the activity, in case you're interested: https://hamradioplanet.com/what-is-a-fox-hunt-in-ham-radio/ https://hamradioplanet.com/what-is-a-fox-hunt-in-ham-radio/