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TLDR: With infinite resources but real technology (no satellites, and no other repeaters possible), how would you best connect two ideal sites in the Arctic and Antarctic with an ideal, well-equipped equatorial repeater?

Though I have some modest experience, I'm a recently-qualified ham (2E1OAT), this is a WILD project that I need the community's help with getting right!

Fogo azimuth map (map radius 10,000km)

Background

For my amateur radio-themed scifi podcast, Lost Terminal, I'm currently writing a plot involving connecting a community on the southernmost town in Argentina, Ushuaia, with a community in the Arctic, on Svalbard.

Almost perfectly between these sites (as the crow flies, see the above azimuthal map, generated on NS6T's fantastic site) is the island of Fogo - with one of the highest mountains in the world, outside of the Himalayas, the volcanic peak of Pico do Fogo.

My story involves building a colossal repeater station right on top of the mountain - bridging between an equally-impressive site on Svalbard, and in Ushuaia. Each of these would then manage local traffic in a more normal way on VHF (the Fogo repeater bridges the two networks).

What might the best bands & modes might be for this astonishing project be? Because of the fictional setting practicality is less of a concern, but the SCIENCE I would like to be TIGHT.

I would be so grateful for any thoughts or advice! :-)

Thoughts so far:

  • HF sporadic propagation is entirely acceptable, perhaps with an elaborate cross-band Automatic link Establishment system aggressively pouncing on openings.
  • VLF is possible, the antennas can be as big as the story requires. Extreme low baud rate (I read 300bit/s in ideal conditions) would mean this is not the only mode I need - I'm hoping for 56k baud rate!

Real word facts:

  • There's no landmasses between the two locations, it's entirely over ocean
  • All 3 sites chosen to have clear sight to ocean from their high points
    • The Svalbard "Northern" site is at 78.943399, 17.350798 (1.1km altitude)
    • The Ushuaia "Southern" site is at -54.781544, -69.179702 (2km altitude)
    • The Fogo "Repeater" site is at 14.974544,-24.383002 (2.6km altitude)
  • Svalbard to Fogo is 7,442.33km
  • Fogo to Ushuaia is 8,827.02km

Fictional background:

  • World is post-apocalyptic solarpunk, population less than 1 billion.
    • Solar panels, batteries, and non-fossil fuel engines are all widespread.
  • The tech is near-future, the collapse happened in 2078
    • About a century later, the survivors are picking up the pieces
  • No internet, no satellites, no PSTN etc. Radio is king.
  • Computers are possible, but they're basic, rebuilt using something like CollapseOS
  • Conveniently the Pico do Fogo volcano is dormant in the future my story is set!

Thank you!

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  • $\begingroup$ I have a hard time believing that a disaster that didn't destroy knowledge would destroy the ability to make computers. It might drastically reduce the size of the chips, but there's people making simple chips in their garage today, so... $\endgroup$
    – user10489
    Jan 29 at 12:30
  • $\begingroup$ Oh you're totally right, no new silicon can be made. However, how many ARM chips are lying around, dozens in every ruined home and office, ready for scavenging? There's a SURPLUS of this raw material in my story! You might find this concept as interesting as I: collapseos.org/why.html $\endgroup$ Jan 30 at 11:06

4 Answers 4

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Suggestion to OP (and all hams): Play with VOACAP Online to get a feeling for HF propagation.

For example here is the whole path:
enter image description here
And here is the expected probability of communication on a few ham bands
(3-element yagis at 100 feet, 1500 W transmitter, quiet receive site, today's sunspots)
enter image description here

See how the best frequency changes over the day, and also that at this distance you never get a super-reliable connection, it's always 50% or sometimes 75% probability of working out. Of course more power or a narrower mode helps, it depends how much bnandwidth your story needs.

You can also run this month by month.


Now for your story, for your island... it's perfect for an "HF Repeater" and for the same class of equipment, dramatically improves the chance of communication. In fact with one huge station at the island, where solar power is plentiful, you could get by with much more modest stations at the ends, where it's stormy and snowing. No need to be on top of the mountain for HF. Use bi-directional antennas, or swing them around to retransmit, or have two sets, opposite sides of the island...

Same simulations doing the link one half at a time:

enter image description here enter image description here
and
enter image description here enter image description here

See how you are approaching 100% probability of communication, on each half of the link, at all times. And this is with just amateur-class stations, affordable today by (American) middle-class people.
Even a 100x increase in power doesn't get the same improvement on the whole link. So perhaps if radios and electricity are expensive, but people and time are cheap, it would make sense to put up this massive repeater on the island. Or elsewhere... play around with it.


VOACAP online also generates nice maps of coverage for a particular station, eg on 15 m, UTC 12:00, transmitting from the Fogo island station:
Probability of communication:
enter image description here

Or the power level at the receiver:
enter image description here

Interesting to see the various skip zones, day/night zones, etc.

You can also download VOACAP, wrap some code around it, and generate more general graphs for all years, all sunspot conditions, evaluate which bands you need long term, etc.

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    $\begingroup$ VOACAP looks like a rather nice tool, ty! Looks like one would want that repeater station to be cross-band - the two paths having different REL profiles - and possibly each end would want to operate split mode too in some circumstances. $\endgroup$
    – jmb
    Feb 1 at 11:55
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    $\begingroup$ OMG Tom this is INCREDIBLE! This is it! Thank you so much for your efforts on my part, I'll dive into these tools and tailor the results to my story, you've cracked it! :-) $\endgroup$ Feb 1 at 12:56
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With infinite resources but real technology, how would you best connect two ideal sites in the Arctic and Antarctic with an ideal, well-equipped equatorial repeater?

Skip the repeater, this calls for a high-MEO satellite constellation with at least four satellites on a polar orbit, so that for both stations there's always a satellite in sight, and the satellites can maintain a direct inter-satellite link. You might cheat a bit and get away with only two satellites on a Molynya-style orbit, where you use the high ellipticality of the orbit to make sure that either one satellite is high enough to see both poles, or each satellite sees one pole and the other satellite (but this would require orbital modelling, which probably is a bit besides the point of your question).

Or, you go for a single geosynchronous satellite that both stations can see.

You could of course reduce cost of the constellation considerable by having more, lower orbit, satellites (rocket equation makes it expensive to lift things into high orbits), but in that case the relay station in the middle won't be very useful: either you have enough satellites that can mesh among themselves, so that you don't need the ground station, or you directly go for a MEO orbit that's high enough for the direct-or-one-hop scenario above; you'd avoid placing a satellite in the inner Van-Allen Belt, but that'd be exactly the earth radius height that would make your relay useful at all as intermediate hop.

No matter what orbit you choose, you can still use your island as control center for the satellites, if your storytelling needs it. Do note however that for polar orbits, you typically put the ground station in polar regions. In fact, the probably most important one in existence is in Svalbard. So, honestly, your island in the middle of the ocean: not that helpful.

Good thing about the satellite solution: although your scenario claims there are no more satellites, it's a bit questionable which catastrophe would have taken the satellites from orbit? Your disaster scenario doesn't seem to imply that happened, and if that's the case: the very first, by modern standards very ad-hoc intercontinental comms satellite was re-activated decades after being decommissioned. And, already now, cartels use analog TV satellites, which are really just dumb frequency transverters ("RF bent pipe") as means of talking to people in the Amazon forest (which means that due to the huge area of coverage, police can't know who they're talking to, where).

So chances are, if "the Collapse" didn't happen too long ago, there's a high probability that you'd just use a TV satellite that's still hovering in geo orbit as relay.

Fully agreeing with user…'s answer, a part of that will require to draw a cable to the arctic and the antarctic to get the data from where you have to the up- and downlink stations. But you'll want a cable there, anyways – polar nights and low irradiance during summer make it impossible to survive there on solar power.

But that's not really a problem in your "practically unlimited resources" scenario – a humanity that knows how to build solar cells, and modern batteries for a billion people, can most definitely produce and lay cables, both copper (for power) and fiberoptic (for data); much easier a task, chemically, process-wise. Also, launching rockets to space is probably not a show-stopper: we landed on the moon (much much harder than getting a couple satellites to MEO) long before our semiconductor production technology was good enough (that means: precise, clean, reliable on large scale) to supply a billion people with power (which is, beyond all, a question of a highly integrated, incredibly complex supply chain. Seems like a lot of your mankind's problems have already been solved!).

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    $\begingroup$ Idunno if rockets or trans-oceanic cable is harder. Rockets if not done right tend to explode. (Or, actually, even if they are done right, just more controlled.) Cable isn't hard to make, but the length of the cable requires quite a large scale of production and huge ships to carry it. I don't think even today we could do that run in a single trip. But neither of these make it impossible. But the "unlimited resources" thing should fix both problems. $\endgroup$
    – user10489
    Jan 29 at 12:32
  • $\begingroup$ @user10489 yeah, "unlimited resources" is really a cheatcode. Laying submarine cables these days is hard, because they are long and need to be stable, so to keep them somewhat affordable yet robust, they're things that are essentially assembled from gigantic "rigid" parts on-ship. But if that ship is not a cost problem: nice. If buying enough high-tech coating instead of having to lay concrete pipe is financially feasible: nice! If having an decode, amplify and forward station every 20 km is energy-wise feasible: great! if operating a small fleet of maintenance submarines … you get the idea. $\endgroup$ Jan 29 at 14:25
  • $\begingroup$ I'm so sorry to push back on this very reasonable idea, the reason satellites are not possible is that most have de-orbited in the 100 years since The Collapse. My constraints are at the end of the question, your suggestion about rockets has reminded me to also specify that fossil fuels have effectively run out (one of the reasons for the global conflict c. 100 years before the story is set was this!) You sound very well-informed, I'd love to read a second answer from you with the 'no satellites' constraints - what would you do if only constrained to point-to-point radio? Thank you! $\endgroup$ Jan 30 at 10:59
  • $\begingroup$ @Tris-2E1OAT Satellites in Geo don't de-orbit by themselves; there's no atmosphere to slow them down, unlike low-LEO satellites (like starlink etc). And while fossil fuel-derived RP1 is indeed a popular first-stage propellant, that's for cost reasons (and you have unlimited resources); you do make later stages run on pure hydrogen or other electrically synthesized fuels, anyway. $\endgroup$ Jan 30 at 11:14
  • $\begingroup$ Marcus, I'm sorry to contradict you, but that's not how I read this: en.wikipedia.org/wiki/Geostationary_orbit#Stability Quite right that they require much less stationkeeping, but it's not zero. I really like the point about hydrogen or synthesized fuels - while that's not where my world is at the moment, it's a great point for a future storyline, thank you! :-) $\endgroup$ Jan 31 at 17:42
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You may have prematurely eliminated some of these options, so for the sake of completeness I'm listing everything.

My first thought is that the best solution would be a fiber optic cable. We've been doing undersea cables since 1865. There's plenty of existing books about this, it shouldn't be hard to research.

Next thought would be a high orbit satellite. A "repeater" would have to be in orbit to be high enough to be useful here. (Yes, these exist now.) The whole point of a repeater is to raise the antenna high enough to overcome the curvature of the earth. Likely you would need multiple satellites for a constant connection, or a network that can relay just to get the path length in a reasonably low orbit.

The next option would be you get lucky and space weather conditions are just perfect enough to get grey line propagation. This would be extremely erratic at best. Not so much unreliable as sometimes you can, sometimes you can't. Higher power might help. Seasonal variations move the grey line, so this might only work certain times of the year for a few hours a day at most.

The final option would be to relay the signal through multiple stations. Unless the stations are each less than 100mi apart, propagation conditions would make this erratic as well. Not so much that it couldn't happen as it would be that you might need to rely on a fairly large network of stations and the message would take a random path. Relayed messages could be done by person without a computer, and if you can have a computer do it, it doesn't require much of a computer -- it doesn't necessarily even need an OS. (For example, look up packet radio BBS.) Note that space weather is going to be a factor for any path longer than 100-200 miles, and solar flares can easily completely black out HF communications at the poles and in extreme cases, even VHF.

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  • $\begingroup$ Thank you very much! I'm hoping to explore the limits of a single-repeater option, which would take advantage of any and all HF atmospheric conditions for this huge DX range, are there no options for such range on HF, even sporadically? $\endgroup$ Jan 27 at 17:56
  • $\begingroup$ Added packet radio example. Forgot about that. Single repeater option will rarely work. (Rarely --> when conditions are exactly right.) Yes, sporadic conditions are possible, and even semi-regular. Grey line and space weather related propagation methods are most likely. $\endgroup$
    – user10489
    Jan 27 at 18:27
  • $\begingroup$ Note that space weather conditions are somewhat random but over an 11 year cycle vary from very unlikely to very likely. When they are very likely they also vary on an 11 day cycle. In other words, on an 11 year cycle sunspots vary from 0 to hundreds. When there are sun spots, they go around the sun in about 11 days, but they can also form and dissipate in that time frame. $\endgroup$
    – user10489
    Jan 27 at 18:49
  • $\begingroup$ I like the satellite idea. Because an apocalypse on earth simply doesn't affect satellites in geosync orbit, especially the older, larger ones are still going to be there. Remember that decommissioned analog TV satellites are nowadays known to be used by criminal organizations in South America for communications with members somewhere in the jungle; there's nothing that stops anyone from just transmitting at the uplink frequency. $\endgroup$ Jan 28 at 14:53
  • $\begingroup$ Space weather is an extremely interesting topic that I'd love to go in to in my story. Does full-band access help here, though? After the collapse of nations, there's no governmental band limits, and in my story the global hams self-organise across the spectrum. I'm imagining some kind of incredible frequency-hopping system that monitors p22 propagation from (say) 3kHz - 30MHz and switches automatically to keep the bridge running (albeit at highly variable speeds!) $\endgroup$ Jan 30 at 11:04
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I'm a new ham myself, so I know just enough to be dangerous - but what about Moonbounce or EME? Although it would limit communications to the times each month that the moon is visible over the horizon at both locations, the advantages are you don't have to have man-made satellites or equipment on an island somewhere. You just need to be able to track the moon with an antenna. According to Wikipedia the US used EME in the 1950s for communications between Hawaii and Washington DC, so it doesn't take a lot of technology. Look for "Communication Moon Relay" for more information about the US project.

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