3 ms·

I mean, sure, measuring occlusion like this is possible in VHF, UHF and beyond. And radar is a real thing that exists, and you can even do passive radar, but to

I mean, sure, measuring occlusion like this is possible in VHF, UHF and beyond. And radar is a real thing that exists, and you can even do passive radar, but to my knowledge you cannot do any of this outside the line of sight of the transmitter and receiver with an object that's only 1-4 wavelengths long. I'd love to be proven wrong because that would be wild and the kind of thing that makes me fall in love with radio all over again, but this source is completely bogus.

bmurray7jhu 5y ago
Over-the-horizon radar uses HF to detect distant objects. See https://en.wikipedia.org/wiki/Over-the-horizon_radar https://en.wikipedia.org/wiki/Over-the-horizon_radar
- ellenhp 5y ago
  With a big antenna array for beamforming, sure, you can do that. You absolutely cannot do over the horizon radar on 10 watts with two omnidirectional antennas though.
  - jrockway 5y ago
    Wait, who is doing WSPR at 10 watts? Most people are just using an unamplified IO pin off their Raspberry Pi or something; milliwatt at best. (It makes WSPR itself all the more impressive, however!)
    - ellenhp 5y ago
      If you have an SSB radio that you can hook up to a PC's sound card using VOX to activate the transmitter, you can use WSJT-X or similar software to do lots of digital modes like WSPR, PSK31, FT-8 and whatever's hot these days. I think best practice for WSPR is to keep power low though, so don't go crazy :)
    - wglb 5y ago
      While there are a lot of folks using very low power on WSPR, there are also a lot on HF doing so with 100 watts, and even more in some cases.
- 8bitsrule 5y ago
  The 'Russian woodpecker' and the US' OTH-B systems built decades ago used pulsed signals of 1 Million watts and up, with gigantic antenna arrays. [0] Comparison to WSPR is impossible (esp. given the complete lack of non hand-wavey details in the article). If the method were at all feasible, it'd very likely be commercially available). [0] https://fas.org/nuke/guide/usa/airdef/an-fps-118.htm https://fas.org/nuke/guide/usa/airdef/an-fps-118.htm

bmurray7jhu 5y ago

Over-the-horizon radar uses HF to detect distant objects. See https://en.wikipedia.org/wiki/Over-the-horizon_radar https://en.wikipedia.org/wiki/Over-the-horizon_radar

ellenhp 5y ago
With a big antenna array for beamforming, sure, you can do that. You absolutely cannot do over the horizon radar on 10 watts with two omnidirectional antennas though.
- jrockway 5y ago
  Wait, who is doing WSPR at 10 watts? Most people are just using an unamplified IO pin off their Raspberry Pi or something; milliwatt at best. (It makes WSPR itself all the more impressive, however!)
  - ellenhp 5y ago
    If you have an SSB radio that you can hook up to a PC's sound card using VOX to activate the transmitter, you can use WSJT-X or similar software to do lots of digital modes like WSPR, PSK31, FT-8 and whatever's hot these days. I think best practice for WSPR is to keep power low though, so don't go crazy :)
  - wglb 5y ago
    While there are a lot of folks using very low power on WSPR, there are also a lot on HF doing so with 100 watts, and even more in some cases.
8bitsrule 5y ago
The 'Russian woodpecker' and the US' OTH-B systems built decades ago used pulsed signals of 1 Million watts and up, with gigantic antenna arrays. [0] Comparison to WSPR is impossible (esp. given the complete lack of non hand-wavey details in the article). If the method were at all feasible, it'd very likely be commercially available). [0] https://fas.org/nuke/guide/usa/airdef/an-fps-118.htm https://fas.org/nuke/guide/usa/airdef/an-fps-118.htm