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1. Narrow beam antenna (such as satellite antenna) does NOT propagate signal arround it (OMNIdirectional antennas does that). It's almost impossible to detect i

by hansor 6y ago

1. Narrow beam antenna (such as satellite antenna) does NOT propagate signal arround it (OMNIdirectional antennas does that). It's almost impossible to detect it unless you fly directly over the beam. Think about it as laser beam. 2. It is possible to build verious kinds of covert antennas. Radio amateurs do that all the time. Just google the term "stealth ham radio"

owl57 6y ago
1. Is it expensive for TLAs to deploy drones for exactly that if the practice becomes popular? They won't even need many actual detecting drones: if they look the same as regular surveillance drones, which are already up in the sky in times of unrest, people will probably hesitate to use their transmitters.
wongarsu 6y ago
> Think about it as laser beam. But if you shine a powerful laser beam into the sky it is visible from pretty far away. It's highly focused, but also gets scattered a lot by the atmosphere.
- hansor 6y ago
  Think about it as inivisible laser beam in terms of beam width. We are talking here 2mm wave with very directional antennas - its very hard to detect it. That's actually how spies send data back over the satellites: >Unlike with SW signals, a radio signal to a satellite is very difficult to intercept and trace, as the waves are 'beamed' straight up rather than all around. https://www.cryptomuseum.com/spy/rs804/index.htm https://www.cryptomuseum.com/spy/rs804/index.htm
  - ajsnigrutin 6y ago
    What? There's no way to send a 2mm (width) wave. Yes, parabolic antennas have very high gains in one direction, but they're far from '2mm' and far from 'invisible'. A helicopter with the right equipment flying over urban areas would have an easy job finding them and even pointing out the approximate location (eg. a building) where they're located. If the antenna was inside a huge apartment building, it would be hard to find the right apartment, if the transmitter was turned off, but with single family buildings, it would be easy. Ham radio operators hide and then look for hidden transmitters for fun, so it's not that hard, especially with a budget that is given to the police.
    - hansor 6y ago
      >There's no way to send a 2mm (width) wave. You are very wrong sir. https://en.wikipedia.org/wiki/2-millimeter_band https://en.wikipedia.org/wiki/2-millimeter_band >A helicopter with the right equipment flying over urban areas would have an easy job finding them. That is not true. Helicopter would need to fly RIGHT into such directional and tiny beam. Which is nearly impossible to do in huge city. Even when flying 2m next to it, you would likely not detect it. That is the reason why CIA had so much problem with pinpointing Iridium satellite phones back in Colombia in the 90's.
      - ajsnigrutin 6y ago
        2mm is the wavelength, not the effective width (think of a laserbeam) of the wave. and yes, even with a laser (nanometer wavelengths) it's hard to produce a 2mm wide beam at a helicopter distance.

by hansor 6y ago

owl57 6y ago

1. Is it expensive for TLAs to deploy drones for exactly that if the practice becomes popular? They won't even need many actual detecting drones: if they look the same as regular surveillance drones, which are already up in the sky in times of unrest, people will probably hesitate to use their transmitters.

wongarsu 6y ago

> Think about it as laser beam. But if you shine a powerful laser beam into the sky it is visible from pretty far away. It's highly focused, but also gets scattered a lot by the atmosphere.

hansor 6y ago
Think about it as inivisible laser beam in terms of beam width. We are talking here 2mm wave with very directional antennas - its very hard to detect it. That's actually how spies send data back over the satellites: >Unlike with SW signals, a radio signal to a satellite is very difficult to intercept and trace, as the waves are 'beamed' straight up rather than all around. https://www.cryptomuseum.com/spy/rs804/index.htm https://www.cryptomuseum.com/spy/rs804/index.htm
- ajsnigrutin 6y ago
  What? There's no way to send a 2mm (width) wave. Yes, parabolic antennas have very high gains in one direction, but they're far from '2mm' and far from 'invisible'. A helicopter with the right equipment flying over urban areas would have an easy job finding them and even pointing out the approximate location (eg. a building) where they're located. If the antenna was inside a huge apartment building, it would be hard to find the right apartment, if the transmitter was turned off, but with single family buildings, it would be easy. Ham radio operators hide and then look for hidden transmitters for fun, so it's not that hard, especially with a budget that is given to the police.
  - hansor 6y ago
    >There's no way to send a 2mm (width) wave. You are very wrong sir. https://en.wikipedia.org/wiki/2-millimeter_band https://en.wikipedia.org/wiki/2-millimeter_band >A helicopter with the right equipment flying over urban areas would have an easy job finding them. That is not true. Helicopter would need to fly RIGHT into such directional and tiny beam. Which is nearly impossible to do in huge city. Even when flying 2m next to it, you would likely not detect it. That is the reason why CIA had so much problem with pinpointing Iridium satellite phones back in Colombia in the 90's.
    - ajsnigrutin 6y ago
      2mm is the wavelength, not the effective width (think of a laserbeam) of the wave. and yes, even with a laser (nanometer wavelengths) it's hard to produce a 2mm wide beam at a helicopter distance.