4 ms·

We tried to do passive radar for detecting high energy cosmic rays in 2009 (GNU Radio/USRP) that turned into passive-ish when the team brought a 20kW Harris NTS

by prpl 4y ago

We tried to do passive radar for detecting high energy cosmic rays in 2009 (GNU Radio/USRP) that turned into passive-ish when the team brought a 20kW Harris NTSC Ch 2 (52Mhz) transmitter we decommissioned as part of the move to ATSC. We had a hard time with cosmic rays (relativistic doppler is fun), but meteors, planes, and lightning strikes were common sources of unwelcome signal.

dylan604 4y ago
I spent an evening at a star party chatting with someone that spent a bit of time at the big radio facility on the east coast that is famous for having total radio silence in the area surrounding it. (too early in the morning to remember the name.) One of the stories was specific to listening to meteors from well past the horizon from where they were, and then talking to someone that was able to confirm them visually. This same individual was also previously in the military spending time playing with radars. The stories from that time were even more entertaining. Steering the beam to mess with the sheriff's car, and a few other stories that seemed so crazy I'm still not sure he wasn't just seeing what he could get us to believe.
- blamazon 4y ago
  That'd be the Green Bank Observatory[1], located within the US National Radio Quiet Zone [2] where radio emission is tightly managed. In the highest sensitivity zones near observation facilities, only diesel engines are allowed in motor vehicles as the spark plugs found in gas vehicles effectively constitute a spark-gap transmitter. [3][4] [1]: https://en.wikipedia.org/wiki/Green_Bank_Observatory https://en.wikipedia.org/wiki/Green_Bank_Observatory [2]: https://en.wikipedia.org/wiki/United_States_National_Radio_Quiet_Zone https://en.wikipedia.org/wiki/United_States_National_Radio_Q... [3]: https://en.wikipedia.org/wiki/Spark-gap_transmitter https://en.wikipedia.org/wiki/Spark-gap_transmitter [4]: https://raoulpop.com/2012/04/15/chasing-rfi-waves-part-seven/ https://raoulpop.com/2012/04/15/chasing-rfi-waves-part-seven...
  - Gordonjcp 4y ago
    > only diesel engines are allowed in motor vehicles One would assume mechanical diesels at that, since the piezo injectors in common-rail systems require almost as big a bang as a spark plug. Once I rescued a broken-down Citroën CX that had experienced a complete electrical failure, by removing the little brass slug from the injector pump and screwing the valve body back down, and then push starting the car. Pop the clutch in second and - clattaclattaclattaVROOOM, off it went. Cue a hilarious 15 seconds or so where the power steering, suspension, and crucially braking system had absolutely no hydraulic pressure and I was piloting an unguided unbraked 5mph "missile" across the yard...
    - blamazon 4y ago
      Haha, love the story. Always wanted one of those Citroen sedans. It sadly feels like that culture of being able to get out of a jam with one's car with a bit of simple mcgyvering disappears a bit more every day in modern times. And yes, you're right, mechanical diesels only in the most sensitive areas. You can see some delightful photos of those in the blog post at [4] above :)
    - jojobas 4y ago
      Did it have an electric hydraulic pump for these? Surely the steering and brakes still worked, just required 10x the force or something?
  - sitkack 4y ago
    When I was a kid, my motor cycle had resistors in the spark plug wires that aged out and turned to a fine dust, I could not source replacements, either the resistor or the wires, so I replaced them with brass rod. It had a noticeable effect on TV reception over short distances.
    - blamazon 4y ago
      Ha, that unlocked a memory of removing those resistors on my motorcycle to get more power. I did not get more power but when I explained what I did to the local mechanic I did get a valuable lesson in how combustion works.

by prpl 4y ago

dylan604 4y ago

I spent an evening at a star party chatting with someone that spent a bit of time at the big radio facility on the east coast that is famous for having total radio silence in the area surrounding it. (too early in the morning to remember the name.) One of the stories was specific to listening to meteors from well past the horizon from where they were, and then talking to someone that was able to confirm them visually. This same individual was also previously in the military spending time playing with radars. The stories from that time were even more entertaining. Steering the beam to mess with the sheriff's car, and a few other stories that seemed so crazy I'm still not sure he wasn't just seeing what he could get us to believe.

blamazon 4y ago
That'd be the Green Bank Observatory[1], located within the US National Radio Quiet Zone [2] where radio emission is tightly managed. In the highest sensitivity zones near observation facilities, only diesel engines are allowed in motor vehicles as the spark plugs found in gas vehicles effectively constitute a spark-gap transmitter. [3][4] [1]: https://en.wikipedia.org/wiki/Green_Bank_Observatory https://en.wikipedia.org/wiki/Green_Bank_Observatory [2]: https://en.wikipedia.org/wiki/United_States_National_Radio_Quiet_Zone https://en.wikipedia.org/wiki/United_States_National_Radio_Q... [3]: https://en.wikipedia.org/wiki/Spark-gap_transmitter https://en.wikipedia.org/wiki/Spark-gap_transmitter [4]: https://raoulpop.com/2012/04/15/chasing-rfi-waves-part-seven/ https://raoulpop.com/2012/04/15/chasing-rfi-waves-part-seven...
- Gordonjcp 4y ago
  > only diesel engines are allowed in motor vehicles One would assume mechanical diesels at that, since the piezo injectors in common-rail systems require almost as big a bang as a spark plug. Once I rescued a broken-down Citroën CX that had experienced a complete electrical failure, by removing the little brass slug from the injector pump and screwing the valve body back down, and then push starting the car. Pop the clutch in second and - clattaclattaclattaVROOOM, off it went. Cue a hilarious 15 seconds or so where the power steering, suspension, and crucially braking system had absolutely no hydraulic pressure and I was piloting an unguided unbraked 5mph "missile" across the yard...
  - blamazon 4y ago
    Haha, love the story. Always wanted one of those Citroen sedans. It sadly feels like that culture of being able to get out of a jam with one's car with a bit of simple mcgyvering disappears a bit more every day in modern times. And yes, you're right, mechanical diesels only in the most sensitive areas. You can see some delightful photos of those in the blog post at [4] above :)
  - jojobas 4y ago
    Did it have an electric hydraulic pump for these? Surely the steering and brakes still worked, just required 10x the force or something?
- sitkack 4y ago
  When I was a kid, my motor cycle had resistors in the spark plug wires that aged out and turned to a fine dust, I could not source replacements, either the resistor or the wires, so I replaced them with brass rod. It had a noticeable effect on TV reception over short distances.
  - blamazon 4y ago
    Ha, that unlocked a memory of removing those resistors on my motorcycle to get more power. I did not get more power but when I explained what I did to the local mechanic I did get a valuable lesson in how combustion works.