3 ms·
We used to do this back in the mid 70s, we built a VHF receiver (and someone outside in the frost with a big antenna listening to the noise floor and tracking)
by Taniwha 6y ago
We used to do this back in the mid 70s, we built a VHF receiver (and someone outside in the frost with a big antenna listening to the noise floor and tracking) - the signal was an analog FSK (you can kind of imagine it as a single light sensor and the satellite spinning, getting 1 scan line per revolution) - we'd feed the signal to a TV in a dark room with a manual vertical sync button, and with a camera pointing at it.
As the signal started someone would press the sync button and someone else would open the camera shutter when the pass was done we'd close the shutter and wind the film on, we'd get 2-3 passes a night,at around midnight we'd develop the film.
There was also a much faster broadcast around midnight from a geostationary satellite - 12 images (4 around the equator and 4 around the poles) with the communist countries carefully blanked out, you had to change the scanning rates and be nimble with the camera.
It was fun and the alternative was a close to $1m fax ground station (this was before faxes were something most people had even seen)
- phreeza 6y ago> (and someone outside in the frost with a big antenna listening to the noise floor and tracking) I've wondered about this, why were consumer satellite dishes so huge back in the day, and now we seem to be able to get away with much smaller ones? Is the transmitter power on to he satellites higher than it used to be? Or is it better receiver electronics? Or better algorithms/codecs?
- madengr 6y agoYes, all three in combination. GaAs PA, low cost GaAs LNA, and Turbo coding are what made it possible in the 90’s. You’ll notice that many dishes are wedged shaped than circular. This is to keep the beam width under the 2 degree spacing of geostationary satellites.
- karmicthreat 6y agoAlso we have increases the frequencies that we use. Back then it was C-Band, now everyone is using Ku or higher.
- Taniwha 6y agoThis was a home built circ polarised yagi (it was VHFish/UHFish, I forget the freq), it was big and a bit unweildy (a bit of 2x4 bolted to an upright) but not giant and not a dish