-------- Original Message --------
From: Ted Smith <[email protected]>
Apparently from: [email protected]
To: [email protected]
Subject: Re: [Fwd: Multiple Internets]
Date: Wed, 10 Feb 2016 12:02:57 -0500
>I'm a little skeptical of wireless mesh networks as a general solution
to this sort of problem, because they're inherently chatty, and have
very limited reach.
Wireless meshes are usually short range but there is no architectural reason
they can't be linked by LoS or even longer distances connections. One area
familiar to hams in the VHF/UHF bands is troposcatter. Tropo is similar to the
more common HF phenomenon ionospheric reflection ("skip") but instead uses
refraction changes in lower layers of the atmosphere due to temperature/density
differences.
Tropo is shorter range (generally 100-500 km) than skip and less RF efficient
but tends to be more reliable and because it operates using much higher
frequencies can support much higher bandwidth (data rates). All the VHF/UHF ham
bands and several unlicensed bands (900 MHz, U.S. only), 2.4 GHz and 5.7 GHz
can all support tropo though reflection efficiency tends to be greatest at the
lower frequencies.
Until the advent of satellites tropo use was widespread by commercial and
military. Now that anti-satellite tech is becoming more widespread (e.g.,
recent Chinese launches) tropo is again being investigated
http://www.militaryaerospace.com/articles/2013/07/army-troposcatter-communications.html
I'm considering tropo experiments in one of the ham or ISM bands. Please PM if
you might have SDR or RF skills, time and some money to throw toward this.
Speaking of skip, in my PP Hacker Conference slides
http://s000.tinyupload.com/?file_id=03580328025747098705 I discuss a variant,
NVIS (Near Vertical Incident Skywave), first developed by the Germans during WW
II, which allows HF stations operating between 2 - 12 MHz to bounce signals off
the ionosphere for intermediate rage (25-100 km) non-LoS communications.
WW
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