Building a SatNOGS groundstation: Grounding and lightning protection

Dealing with grounding and lightning protection is obligatory when setting up a roof antenna. Bad grounding might cause not only damage to your antenna and equipment but even your complete home electronics or ignite fire.

Lightning is dangerous for two reasons. Direct lightning conduction can cause impulse voltages of higher than 20 Megavolts, whileas induced voltages can also reach up to 10 Kilovolts. Very interesting I found also this quote [1]:

A lightning has  an impulse voltage of > 20 Megavolts and an impulse current above 100.00 Ampere. Multiplying both numbers, the resulting yields a power that would instantaneosly vaporize any conductor. It does not, because the condctor does not actually conduct the energy of the lightning. The a cable with a diameter of 10mm alumium or 8mm copper only lays out a path, through which the surrounding air gets ionized, through which the actual charge surge current flows. This ionized stream will has a diameter of 2-5 cm and will not ignite anything, as the grounding conductor has a resistance <3 ohms.


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Increasing WR703N flash memory with ExtRoot on OpenWRT 14.07 with usb stick(Easy way)

There are one million awesome things you can do with small router and an OpenWRT firmware on it. I have been surprised how mature, easy to use and community driven it has become.  The WR703N is an awsome device and I have probably never seen such a small device (smaller than a smartphone) with so many features, an USB, Ethernet, Wifi and Linux running for just under 25$.

However 4 Mb is very few, even to run OpenWrt, and you quickly run into flash memory limits. But you can easily work around this limitation using ExtRoot, which allows you to include external USB devices or even network mounts. However the collection of instructions on how to setup ExtRoot makes it look more complicated than it is, and it can be (almost) performed completely by LuCi, OpenWRTs GUI interface in the latest stable release (Breaking Barrier 14.07).


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