I’ve previously modified a small portable satellite dish into a radio telescope. Since I keep finding these little dishes on the used market, I figured I’d try it with another brand. This particular dish is a “Winegard Carryout”.
It appears to have an ARM-based control board with a stepper motor daughterboard. The only interface I’ve been able to use is an obscure RS-485 to RJ25 jack.
I had initially showed this on my Youtube channel, and then shoved it onto the ever-growing “to-do” pile. A viewer commented that they could get a serial console with some cable adapter trickery. A USB-to-RS232 cable goes to a Dtech RS232-RS485 adapter, then to a custom RJ-25 cable (6-conductor phone cord). It looks like this:
I was able to duplicate this and connect to the console port on the antenna’s brain. I modified my Dish Tailgater code to drive the dish and read signal strength. This time, instead of using the onboard Ku-band LNB, I stuck an L-band patch antenna on the dish and used a Software Defined Radio to read the signals.
You can find my half-assed Python code here: https://github.com/saveitforparts/Carryout-Radio-Telescope/
I’m using an RTL-SDR Blog V3. They seem to be out of stock, but you can get the RTL-SDR Blog v4 for the same price! (link goes to my Amazon affiliate page and gives me a commission if you buy one)
Here’s some info on the L-band patch I’m using. These little antennas are $5 at Ax-Man surplus, or you can find them on eBay.
wiki.muc.ccc.de/iridium:antennas
dodgyengineering.com/2016/09/05/active-gps-antenna-modification/
After about two weeks of struggling with the code, feed, motor indexing, and other issues, I finally got a couple images of various L-band satellites. This is what the satellites look like in radio frequencies as they pass over my location.
First up is Inmarsat-4 F3. This is a geostationary satellite, so to me it looks like a fixed point source in the sky:
Next are some navigation satellites. These are in Medium Earth Orbits, so they move slowly enough (from my viewpoint) that the dish caught them multiple times along their orbital tracks. This frequency is used by GPS, European Gallileo, and Chinese Beidou satellites, so I could be seeing a combination of different systems (Russian satellites use a different frequency).
Here’s my attempt to trace each path in MS-Paint for more clarity:
And finally, here’s a Low-Earth-Orbit Iridium satellite. This went over pretty quickly and appears as a long streak on the left. I scanned with a more limited azimuth to try catching this faster, but I still almost missed it.
I also tried looking at Wifi frequencies (using a Ham-It-Down converter to get into the 2.4ghz band). However, this didn’t work as well, either due to my feed or my code.
I have a few more issues to work out, such as the choppy image that seems to alternate clockwise and counterclocksise motions with different signal strengths. This could be due to a number of things, and I never quite figured it out. I’d also like to try other frequency ranges, like more S-band, Wifi, and fainter L-band signals like GOES. Those improvements will probably have to wait for next year!
My video on the project is here: https://youtu.be/4a2HjE11DcQ
Saveitforparts 