Pressure-formed Parabolic Mirror from a Mylar Blanket

Parabolic reflectors are pretty handy devices. Whether you’re building a microwave antenna or a long-distance directional microphone, suitable commercial dishes aren’t that hard to come by. But a big, shiny mirror for your solar death-ray needs is another matter, which is where this pressure-formed space blanket mirror might come in handy.

Pressure-forming was a great choice for [NighthawkInLight]’s mirror. We’ve covered pressure-formed plastic domes before, and this process is similar. A sheet of PVC with a recessed air fitting forms the platen. The metallized Mylar space blanket, stretched across a wooden frame to pull out the wrinkles and folds, is applied to a circle of epoxy on the platen. After curing, a few puffs with a bicycle tire pump forms the curve and stretches the film even smoother. [NighthawkInLight]’s first attempt at supporting the film with spray foam insulation was a bust, but the later attempt with fiberglass mesh worked great. A little edge support for the resulting shiny taco shell and the mirror was capable of the required degree of destructive potential.

We doubt this process can be optimized enough to produce astronomy-grade mirrors for visible light, but it still has a lot of potential applications. Maybe a fiberglass radio astronomy dish could be pressure-formed directly with a rig like this?

Ham Radio WiFi

Many Ham Radio operators in the United States participate in Field Day. This is an annual exercise where radio operators are encouraged to set up stations in conditions that might occur after a natural disaster. Usually, this means taking over some park or camp site, bringing generators, portable equipment, and making it all work for the weekend before you tear it back down.

It isn’t much of a Field Day without electricity. That’s why most stations use a generator, solar cells, or even batteries. Today, though, you probably need an Internet-connected computer to do logging and other features. [HamRadioConcepts] has a video (see below) that shows how they grabbed Internet¬†from a distance for their Field Day site.

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FTA dish used to receive L-band amateur radio

[David Prutchi] has an FTA (free-to-air) satellite dish. This means he can tune and watch freely available satellite television feeds. But this sounds much better than it actually is. There isn’t much that’s broadcasted¬†unecrypted from satellites with the exception of a collection of religious channels. But he still uses the dish by using the FTA satellites to calibrate the alignment, then repositioning it to receive L-Band radio transmissions with his own add-on hardware. In the image above it’s the spiral of wire attached to the dish’s collector.

The satellite transmissions are picked up on the KU-band by an aftermarket horn that [David] purchased for this purpose. To add his own helix receiver he cut a square mounting plate that fits around the horn. This plate serves as a reflector and ground plane, and also hosts the helix connector which picks up the L-band transmissions. He had to be creative with routing the first few inches of the helix but it looks like he manages to get some pretty good performance out of the hardware.

[via Hacked Gadgets]

Various Cantenna builds

cantennas(color)

Here is a classic project used to increase wireless signal strength. Cantennas focus using a waveguide very much like a magnifying glass focuses light. [Robert] made a Natural Light beer cantenna, pictured in the upper left. His approach used three beer cans, a paper towel holder, and a shower curtain rod. On the tipline, he noted a signal boost from 11Mbps to 54Mbps. This is certainly something we can hack together if our room lacks adequate signal. Read about parabolic and seeking versions after the break.

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DISH wins $1050 in satellite cracking case

Who doesn’t love a good corporate espionage story? We certainly don’t mind them, especially when they involve hiring a notable hacker to do the company’s dirty work. It seems this is exactly what happened in the case of Dish Networks vs NDS Group. Last month, Christopher Tarnovsky admitted he was paid $20,000 in cash to crack the security protocols used on DISH Network access cards. NDS Group claimed the reverse engineering was simply for comparative reasons while DISH is said it resulted in $900 million in damages.

The trial came to an end this week with the court finding NDS group guilty of cracking 1 card (a fine of $49.69) and liable for an additional $1000 in damages. Not quite the big payoff DISH was hoping for, but both companies have expressed feelings of vindication about the decision. DISH Networks says that the jury ruled in their favor, proving that they were right all along (just not $900 million dollars right). NDS maintains that Tarnovsky’s work was never publicly shared and that they never intended to flood the black market with cracked cards as DISH has implied.