Personal communication device during blackout

Question

Me and my family are expats currently living in Japan where earthquakes are very frequent. It is expected that a big quake is due and it may happen anytime. Recent big occurence was in 2011 and it was followed by a tsunami. But the main impact happened to the communication during such crisis as everybody uses the network and it gets totally jammed or due to the quake the supporting equipment and network was damaged.

Whatever the reason for blackout, i would like to know if there is a 'handy' communication device available in open market that can be used when the next quake strikes, for communicating with my family without any disruption due to the quake.

Since Amateur/HAM people are usually deployed for linking areas which out of reach during times like mentioned above, please suggest any two way communication device pair (sort of walkie-talkie types i imagine) which can be kept with myself at all times and the other with my family. They should be able to communicate in a metropolitan like Tokyo and should have coverage of atleast 30-50 kms radius.

Thanks in advance!

Answer 1

Given your criteria of Handheld transmitters with a 30-50km range, it would be difficult to do so reliably in a city environment. Here's why:

• Lots of buildings are going to obstruct your signal and cause multipath interference to the parts of your signal that do get out, reducing your range
• Rated "range" on things like handheld walkie talkies that you can buy at the store are best-case scenarios (think two people standing on top of mountains or in an open field) which is not the environment you'd be in
• You would need much more power output than a handheld would provide to be able to reliably communicate that far while being in a city environment between tall buildings
• Most HF (3-30MHz) amateur radios with sufficient power, which is what the people deployed for emergency communication use, are not handheld, though you might be able to communicate that distance with a smaller radio that has an internal battery like the Elecraft KX3 with 10 watts, but this gets to my next point that:
• HF band communications use long wavelengths due to their low frequency, and this means to have an efficient antenna to make use of what little power you have, your antenna would have to be pretty long. Think stringing a wire for 5-50+ meters depending on the frequency you use, and hence unwieldy for emergency communications if you need to be on the move.

You may be more reliably able to communicate with less power and a shorter (but still a meter or two long) antenna on HF using CW (continuous wave - morse code) but learning that is another whole topic in itself.

Sorry to be the bringer of bad news, but I think your best bet would be a 2m VHF/70cm UHF dual mode handheld. Though this would probably only work well if you could both get to high elevation places to avoid your signal being trapped between buildings, so try to get on top of a building above average roof height. Using 70cm/UHF would also mean the antenna would only be ~18 cm long which is less awkward to carry around than a ~50cm long 2m/VHF antenna.

Answer 2

Whatever the reason for blackout, i would like to know if there is a 'handy' communication device available in open market that can be used when the next quake strikes, for communicating with my family without any disruption due to the quake.

Sure, satellite phones and pagers!

This is the kind of things they were invented for, enabling communication without infrastructure, as long as you get a sufficient view of the skies.

Will certainly not work great in the cellars of buildings, though. But that can be said for pretty much everything.

For costs, the best thing I could find was https://en.wikipedia.org/wiki/Iridium_Communications#Post-paid_service ; You might want to check with the Iridium folks yourself.

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One could of course think of setting up an infrastructure of repeaters that get automatically activated in case of an emergency (for example, if they're not kept "off" by a regular "alive" signal) and work off batteries. However if you do that, you'd be effectively doing little else than operating a cellular network – and I really think that DoCoMo might be better than you at doing that reliably.

You might argue that in case of an emergency, you (and your family and maybe a few local hams) might be the only one trying to access these ressources, but to be honest, catastrophe services do exactly that first when they enter a region: pull up a relay infrastructure so that scouts and rescuers are able to communicate with mission control; and they do have capable equipment (at least in Germany). So, better talk to the Japanese emergency services – they might actually be happy to help you with making you part of the responders.

Answer 3

I also don't feel that a V/U ht would be practical for more than a few miles on the built in antenna. Maybe much better with a 5/8 wave mobile antenna. In a densely packed area with big buildings you are not as likely to achieve the distances you desire. There is a possibility with low band hf. But with mobile units antenna effiencies may not be helpful. HF NVIS with a buddiepole antenna may achieve your goals. You would have to try it. Every location is different. Your best bet is hf. 3.5 to 7 mhz NVIS. NVIS means that you are using low (10 ft elevation) horizontal 1/2 wave dipoles. Probably SSB. But even then you would have to try it. CW sets can be very small, low power consumption, and can work better for NVIS at hf. Good luck.