3 ms·

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 interestin

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).

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).