4 ms·

FT-8 is the current "state of the art" in long range QRP[1]. Sadly it's pretty much only for exchanging a signal report + callsign for contesting. You get 75 b

FT-8 is the current "state of the art" in long range QRP[1]. Sadly it's pretty much only for exchanging a signal report + callsign for contesting. You get 75 bits per 15 seconds. The other tricky part is solar conditions change so different bands don't work during the day/night and local RF pollution can make it really difficult to receive anything in a dense metro area. [1] https://en.wikipedia.org/wiki/WSJT_(amateur_radio_software)#FT8 https://en.wikipedia.org/wiki/WSJT_(amateur_radio_software)#...

cbHXBY1D 9y ago
FT-8 is a game changer. I've never seen a mode take off like it as long as I've been a ham.
- vvanders 9y ago
  Yeah, while FT-8 is really well put together nothing about it that is really that esoteric. I really wish things like Forward Error Correction and more complex modulation made it down to the VHF bands. The fact that the standard protocol there is 1200bps without FEC and basically stuck in the 80s is really a shame. (Yes I know DSTAR/DMR/C4FM exist but they're largely locked into specific mfgrs).
owenversteeg 9y ago
That's very interesting. I've gotten a bit into ham radio recently (just have my technician's & two little radios, nothing fancy) and by far the most interesting thing is long-distance communications. Do you know anything about the reliability (e.x. 1000km transmissions between two rural areas are possible 5% of the time/50% of the time/90% of the time), as well as the kind of antenna you'd need for that? It'd be very cool if a portable setup was possible.
- vvanders 9y ago
  1000km may be stretching things but 200-300mi over say 40 meter band(that stays active day/night) is possible with something called an NVIS antenna[1] the downside is you probably still need ~100W to make it effective which makes portable operation pretty tricky. If the portable HF thing is something that interests you there's something called Summits on the Air which involves hauling a radio up to nearby mountain tops and try to make as many contacts as possible. Even with tech license VHF and HF CW are still something you can do. Elecraft's KX line are really common for these(I own a KX3[3]) and really incredible pieces of kit. With a radio, ~30ft wire and a tree/pole you can definitely make 800mi+ contacts. [1] https://en.wikipedia.org/wiki/Near_Vertical_Incidence_Skywave https://en.wikipedia.org/wiki/Near_Vertical_Incidence_Skywav... [2] http://www.sota.org.uk/ http://www.sota.org.uk/ [3] http://www.elecraft.com/KX3/kx3.htm http://www.elecraft.com/KX3/kx3.htm
- topspin 9y ago
  1000km is achieved routinely with modest HF transceivers; 100W mobile units, for example. Band conditions change, however, so given the limited power an amateur license allows you operate on the bands that are working best at the moment; even 1500W won't work when a band is 'closed.' Fortunately amateurs have access to a lot of bands so some frequency will usually serve. You can do a lot of optimization if you're working fixed sites. Directional gain and optimal take off angles for a given path can be targeted with excellent results. HF antennas are large. A simple 40 meter horizontal dipole (good night time antenna) is 20 meters long, and it needs to be raised to some altitude that achieves the 'bounce' you want, usually 20 meters or less. Smaller, much less efficient antennas exist.
- sizzzzlerz 9y ago
  I've had QSOs from my home in California with hams in Hawaii, Japan, Australia, England, and Poland, among others. It depends on a number of things, like the band you're on, the time of day, antenna, power, mode, etc.. I don't have a big antenna farm or 2KW linear amps, just 100 W radio over wire antennas. In fact, I've made long distance contacts in QRP mode, just 10W or less. It's a lot like fishing. You keep throwing your lure into the water until something takes it.
- cjsuk 9y ago
  We’re on a solar cycle minima at the moment which slightly ruins ionospheric propagation on HF which is the least “line of sight” set of bands. However it’s on the up again so in a year or so expect 1000km regularly. I regularly hear East European stations here in London, UK with a random length bit of wire strung off a home made 40m receiver and into a tree though. Noise here is terrible so I have had to use very heavy narrow bandwidth audio and IF filtering. If you want long distance, be prepared to use very narrow bandwidth i.e. learn CW though (its not that hard although I have trouble copying some of the faster stations).
sevensor 9y ago
I had the great fortune to take a class from Dr. Steve Franke. It was a class on radio communication circuits, and a big chunk of the class was devoted to talking about the different modes. I remember he got really animated talking about phase-shift keying. Dr. Franke is the F in FT-8.
- vvanders 9y ago
  That's very cool, PSK or QAM is pretty darn incredible. I highly recommend breaking open say Numpy or Matlab and working backward from quadrature(sin+cos) into basic 2-PSK, 4-PSK and N-QAM RF mixer modulation/demodulation. The math behind it is mostly basic trig and really impressive considering it is the underpinning of all modern RF modulation(wifi is 2/4/16/64/256-QAM modulation per OFDM carrier for instance).
  - brian-armstrong 9y ago
    If you're a software person, reading how liquid DSP does these modes is very insightful https://github.com/jgaeddert/liquid-dsp/tree/master/src/modem/src https://github.com/jgaeddert/liquid-dsp/tree/master/src/mode...
    - vvanders 9y ago
      That looks really cool. Most of work these days is upstream from TNCs/etc but def keep that in mind if I end up playing around at the modulation level.
    - madengr 9y ago
      GNU Radio too.
- mrtnmcc 9y ago
  Go Fighting Illini!
  - therein 9y ago
    Oh wow he went to UIUC. Another reason to be proud myself. :)

cbHXBY1D 9y ago

FT-8 is a game changer. I've never seen a mode take off like it as long as I've been a ham.

vvanders 9y ago
Yeah, while FT-8 is really well put together nothing about it that is really that esoteric. I really wish things like Forward Error Correction and more complex modulation made it down to the VHF bands. The fact that the standard protocol there is 1200bps without FEC and basically stuck in the 80s is really a shame. (Yes I know DSTAR/DMR/C4FM exist but they're largely locked into specific mfgrs).

owenversteeg 9y ago

That's very interesting. I've gotten a bit into ham radio recently (just have my technician's & two little radios, nothing fancy) and by far the most interesting thing is long-distance communications. Do you know anything about the reliability (e.x. 1000km transmissions between two rural areas are possible 5% of the time/50% of the time/90% of the time), as well as the kind of antenna you'd need for that? It'd be very cool if a portable setup was possible.

vvanders 9y ago
1000km may be stretching things but 200-300mi over say 40 meter band(that stays active day/night) is possible with something called an NVIS antenna[1] the downside is you probably still need ~100W to make it effective which makes portable operation pretty tricky. If the portable HF thing is something that interests you there's something called Summits on the Air which involves hauling a radio up to nearby mountain tops and try to make as many contacts as possible. Even with tech license VHF and HF CW are still something you can do. Elecraft's KX line are really common for these(I own a KX3[3]) and really incredible pieces of kit. With a radio, ~30ft wire and a tree/pole you can definitely make 800mi+ contacts. [1] https://en.wikipedia.org/wiki/Near_Vertical_Incidence_Skywave https://en.wikipedia.org/wiki/Near_Vertical_Incidence_Skywav... [2] http://www.sota.org.uk/ http://www.sota.org.uk/ [3] http://www.elecraft.com/KX3/kx3.htm http://www.elecraft.com/KX3/kx3.htm
topspin 9y ago
1000km is achieved routinely with modest HF transceivers; 100W mobile units, for example. Band conditions change, however, so given the limited power an amateur license allows you operate on the bands that are working best at the moment; even 1500W won't work when a band is 'closed.' Fortunately amateurs have access to a lot of bands so some frequency will usually serve. You can do a lot of optimization if you're working fixed sites. Directional gain and optimal take off angles for a given path can be targeted with excellent results. HF antennas are large. A simple 40 meter horizontal dipole (good night time antenna) is 20 meters long, and it needs to be raised to some altitude that achieves the 'bounce' you want, usually 20 meters or less. Smaller, much less efficient antennas exist.
sizzzzlerz 9y ago
I've had QSOs from my home in California with hams in Hawaii, Japan, Australia, England, and Poland, among others. It depends on a number of things, like the band you're on, the time of day, antenna, power, mode, etc.. I don't have a big antenna farm or 2KW linear amps, just 100 W radio over wire antennas. In fact, I've made long distance contacts in QRP mode, just 10W or less. It's a lot like fishing. You keep throwing your lure into the water until something takes it.
cjsuk 9y ago
We’re on a solar cycle minima at the moment which slightly ruins ionospheric propagation on HF which is the least “line of sight” set of bands. However it’s on the up again so in a year or so expect 1000km regularly. I regularly hear East European stations here in London, UK with a random length bit of wire strung off a home made 40m receiver and into a tree though. Noise here is terrible so I have had to use very heavy narrow bandwidth audio and IF filtering. If you want long distance, be prepared to use very narrow bandwidth i.e. learn CW though (its not that hard although I have trouble copying some of the faster stations).

sevensor 9y ago

I had the great fortune to take a class from Dr. Steve Franke. It was a class on radio communication circuits, and a big chunk of the class was devoted to talking about the different modes. I remember he got really animated talking about phase-shift keying. Dr. Franke is the F in FT-8.

vvanders 9y ago
That's very cool, PSK or QAM is pretty darn incredible. I highly recommend breaking open say Numpy or Matlab and working backward from quadrature(sin+cos) into basic 2-PSK, 4-PSK and N-QAM RF mixer modulation/demodulation. The math behind it is mostly basic trig and really impressive considering it is the underpinning of all modern RF modulation(wifi is 2/4/16/64/256-QAM modulation per OFDM carrier for instance).
- brian-armstrong 9y ago
  If you're a software person, reading how liquid DSP does these modes is very insightful https://github.com/jgaeddert/liquid-dsp/tree/master/src/modem/src https://github.com/jgaeddert/liquid-dsp/tree/master/src/mode...
  - vvanders 9y ago
    That looks really cool. Most of work these days is upstream from TNCs/etc but def keep that in mind if I end up playing around at the modulation level.
  - madengr 9y ago
    GNU Radio too.
mrtnmcc 9y ago
Go Fighting Illini!
- therein 9y ago
  Oh wow he went to UIUC. Another reason to be proud myself. :)