Metalized Mylar “space blankets” are sold as a survivalist’s accessory, primarily due to their propensity for reflecting heat. They’re pretty cheap, and [HamJazz] has performed some experiments on their RF properties. Do they reflect radio waves as well as they reflect heat? As it turns out, yes they do.
Any antenna system that’s more than a simple radiator relies on using conductive components as reflectors. These can either be antenna elements, or the surrounding ground acting as an approximation to a conductor. Radio amateurs will often use wires laid on the ground or buried within it to improve its RF conductivity, and it’s in this function that he’s using the Mylar sheet. Connection to the metalized layer is made with a magnet and some aluminium tape, and the sheet is strung up from a line at an angle. It’s a solution for higher frequencies only due to the restricted size of the thing, but it’s certainly interesting enough to merit further experimentation.
As you can see in the video below, his results are derived in a rough and ready manner with a field strength meter. But they certainly show a much stronger field on one side resulting from the Mylar, and also in an antenna that tunes well. We would be interested to conduct a received signal strength test over a much greater distance rather than a high-level field strength test so close to the antenna, but it’s interesting to have a use for a space blanket that’s more than just keeping the sun away from your tent at a hacker camp. Perhaps it could even form a parabolic antenna.
Thanks [Fl.xy] for the tip!
They make mylar umbrellas as well. Wonder how one of those would perform.. Or if you could tweak it with different springy ribs or positions for the latch so that it better approximates a parabola
Although not RF, I’ve used a cloth umbrella as a directional microphone just for the sake of trying it.
Umbrella antenna
https://hackaday.com/2023/11/16/umbrella-antenna-protects-you-from-rain-but-not-the-way-you-think/
I remember going out side at a certain time announced in the paper about 1960 and seeing Echo 2 moving across the night sky. It was a reflective balloon designed to bounce radio signals off of and over the horizon.
Reminds me of something I saw where they used a transparent tarp filled with water as a lens.
Ah yes, that’s sometimes listed among survival techniques for starting a fire (well a bag more than a tarp, but same principle).
Umbrella antenna
https://dalybulge.blogspot.com/2022/06/my-hrpt-setup.html
The most famous umbrella antenna was woven by old ladies out of gold plated wire and fixed to the moon buggy, it linked with earth. The bumbershoot hygain.
My remembrance of a Mylar space blanket was H-film. This was a Mylar film with Gold on both sides. I first saw this at the OSO facility in Colorado, in the 60’s.
You might take oxidation of the aluminium into consideration!
I use the metalized blankets to keep sun and heat off my roof windows. Simply usung water, a surfactant and a squeegee did the job. Unfortunately some moisture was left trapped, and over time with some oxygen it corroded the aluminium to aluminium oxide. Since Star Trek movie 4 we know this is a transparent material, much to my dismay. Moreover, The AlO bonded to the glas…
The blankets are not more then Aluminium sputtered mylar sheets. The golden side is the mylar, the silver side is the aluminium. Store dry!
The sheets I got where 17 g per square meter and can be glued together with contact glue, preferrably with some extra solvent for minimized glue thickness. Was researching for a hot air ballon where every gram counts.
So at least you could create bigger and more complex shapes, coat a parabolic dish for some sun heat cooking experiments.
But make sure the Al side stays away from corrosion.
I wonder how these are used in space with the agressive monoatomic oxygen. Gold instead of Aluminium?
G’day everyone — huge thanks for sharing my video on the Mylar space blanket antenna!
This whole wild ride started almost by accident. I spent 13 years living in Whistler, BC, doing a lot of backcountry hiking — and like many hikers, I always carried a Mylar blanket for warmth in emergencies.
Then it hit me: what if this thing could also be used to call for help?
I started playing with metal tape on the blanket — thinking maybe it could be both a thermal layer and a basic antenna. Once I saw the insane RF reflection patterns… the obsession began. WOOOOHOOOO!
Thanks again for the share — I’d love to hear your ideas, feedback.
Cheers!
Simon (VA7BIX / @HamJazz)