SkyCube Update 8/9/12 – The First Satellite Launched by You!
by
Tim DeBenedictis
A communication breakthrough today. So far, we’ve been hamstrung by:
- not having the real power board for the CubeSat manufactured yet and
- not having the real ground radio back from repair at AstroDev’s lab in KY.
We’ve substituted with a makeshift setup using a NiMH battery pack and and a cheap $25 USB radio dongle from eBAY.
So far, we’ve only been successful in transmitting data across a room. But Sunday, while Curiosity was screaming to a landing on Mars, one of our sponsors hiked to space radio + battery pack to the top of Long’s peak in Colorado. I’ll spare you details, but we got a signal transmitted 25 miles – a range increase of 5000x over our previous results – and this is with $25 worth of equipment on the Rx end, not the real ground radio.
The real ground radio gets home the same day I do. We are well on our way to demonstrating success detecting signals from space with home brew radio gear.
My talk at the ASP conference went well. George Takei facebook’d us, and doubled our sponsor count in a day.
Images from David Stillman’s hike up Long’s Peak in Colorado:
Here is a panorama taken by David on Sunday, the day the gear was hiked up Long’s peak:
This is the real SkyCube space radio + antenna, a NiHM battery pack that substituted for the CubeSat power board, and an Arduino for the CD&H board. We did not want to risk David hiking the real CD&H up the mountain.
Scott Cuttler, also on our team, programmed the Arduino to send a simple “HELLO WORLD” message out the radio. In Scott’s own words:
Transmit is 915 MHz exactly. The signal is BPSK encoded and mostly consists of header/footer synchronization bytes, with a tiny real payload of “Hello, World” in the middle. However, all that is irrelevant since what we’re really doing is modulating the signal as a whole off and on. Basically, there are two message lengths, about 1 second and about 2 seconds. Those correspond to dit and dah and spell out “**** * *-** *-** —“, or “hello”. The whole thing starts up as soon as it’s plugged in and repeats in maybe 30 seconds. A simple radio tuned to 915 and AM modulation should pick it up just fine, and the dongle makes it pretty obvious as well.
Here is the $25 eBay gizmo we used to receive the signal:
http://www.ebay.com/itm/EzTV666-USB-Stick-SHIPS-FROM-USA-E4000-Tuner-RTL2832-RTL2832U-RTL-SDR-EzTV-666-/160786708241?pt=LH_DefaultDomain_0&hash=item256fa27711#ht_2619wt_1163
We cobbled a 900 Mhz Yagi antenna onto the above USB gizmo in order to achieve the 25-mile communication success in Colorado.
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