8 ms·
As always with radio, it's mostly about unobstructed line of sight and the gain in your antenna system. We're still in communication with Voyager 1, which is o
by NovemberWhiskey 5y ago
As always with radio, it's mostly about unobstructed line of sight and the gain in your antenna system.
We're still in communication with Voyager 1, which is operating on a grand total of about 20W of RF power; and is currently about 14.5 billion miles away.
- Sporktacular 5y agoIt's also handy when you only need a low data rate and can make your channel bandwidth was wide as you like without worrying about licensing restrictions.
- KennyBlanken 5y agoThat's...not how that works. The FCC requires power be dropped to compensate for antenna gain. https://afar.net/tutorials/fcc-rules/ https://afar.net/tutorials/fcc-rules/
- Sporktacular 5y agoFor a space probe? I'm saying to get that performance NASA has some operating freedoms the rest of us don't.
- Sporktacular 5y agoBesides, I didn't mention power level. Yes, effective radiated power is regulated.
- dr_orpheus 5y agoAnd gets up to a whopping 1.4 kbps downlink and 16 bps uplink! https://voyager.jpl.nasa.gov/mission/spacecraft/ https://voyager.jpl.nasa.gov/mission/spacecraft/
- mshockwave 5y agothat is amazing for something 14.5 billion miles away
- tomxor 5y agoIt's also amazing considering it's using a computer built over 45 years ago from discrete components with only 70Kb of memory, while operating on a gradually failing thermonuclear power source. Voyager 1 also holds the world record for the longest continual operation of a computer: https://www.guinnessworldrecords.com/world-records/635980-longest-period-of-continual-operation-for-a-computer https://www.guinnessworldrecords.com/world-records/635980-lo...
- dTal 5y agoWow. World record for the longest continual operation of a computer... achieved in a radiation bath.
- tomxor 5y agoPretty much, although I think the RTG is mounted on a limb as far away from the other equipment as possible, but still the computer needs to be able to tolerate a decent amount of radiation. It also has an interesting redundant design where it has double the component count and can either exploit that for extra compute or redundancy in case of component failure.
- anthropodie 5y agoI think parent comment is talking about cosmic radiation and not the one from RTG which most probably is properly shielded.
- tomxor 5y agoPossibly. I wonder which is the more significant source given it's distance from the Sun.
- timbit42 5y agoThe first modems were only 110 bps.
- nonsapreiche 5y agoYou mean bauds
- deleted 5y ago[deleted]
- Dylan16807 5y agoIt's both. 110, 300 and early 1200 were all one bit per symbol.
- 1024core 5y agoReminds me of the early days of dial-up Internet... ;-D
- anaganisk 5y agoWhich somehow is a dream on a few networks.
- agumonkey 5y agodoesn't atmosphere (or the lack thereof) plays a role in power losses too ?
- jupp0r 5y agoYes, radio waves are attenuated in the atmosphere. This is highly frequency dependent - for practical applications the lower the frequency, the less radio waves are attenuated. In comparison with attenuation from obstacles in non-line-of-sight situations, the atmospheric component is not significant. For really long range propagation on earth, reflections on atmospheric layers are the dominant factor (as there is no line of sights due to the curvature of the planetary surface). See https://www.sciencedirect.com/topics/engineering/atmospheric-attenuation https://www.sciencedirect.com/topics/engineering/atmospheric... for some nice graphs.
- BizarroLand 5y agoDoes that mean that there is an electromagnetic frequency that, no matter how much power we can feasibly put into it, it simply will not transmit through earth's atmosphere due to its' instantaneous attenuation outside of a vacuum?
- jupp0r 5y agoYes, in the terahertz band range for example you have very high attenuation of more than 1000 db/km. It's a spectrum (no pun intended), so depending on where you draw the line on "through earth's atmosphere" in terms of how far you want to transmit, you'll have some frequency where this becomes infeasible or you'll need more directed antennas and/or more transmit power.
- Anunayj 5y agoit does, but it is not as significant in normal weather conditions in the frequency ranges we're dealing with here (Likely sub 2.4 Ghz) [1], (General rule of thumb, Atmosphere absorbs everything except visible spectrum and 10 cm - 10 m wavelength), compare this to effect from the inverse square law. :) Now this might be significant enough in directional waves with a huge constant multiplier (like a 'ideal' laser with no divergence). Someone can probably give insight on it here. 1. https://www.researchgate.net/publication/270512069_Propagation_Power_Loss_Analysis_and_Evaluation_under_Variant_Atmospheric_Conditions https://www.researchgate.net/publication/270512069_Propagati...
- gorgoiler 5y agoThanks for sharing those figures. I've always known "it's amazing" and "it's far away", but those numbers really put things into perspective. Is there anything particularly special about the antennae on the spaceship? They must be rigorously aligned to point at Earth, and even a slight knock would spoil everything? Or is it more resilient than that?
- jjeaff 5y agoI would think the biggest part of being able to transmit that far is the perfect vacuum of space. There is almost nothing, not even air particles between us and the probe. If you threw a beach ball from the distance of voyager straight to earth it would eventually make it here.
- lultimouomo 5y agoVacuum is good, but inverse-square law still applies. There is almost perfect vacuum between Earth and every star in the galaxy, and yet they don't appear nearly as bright as the Sun.
- thfuran 5y agoBut you can see the Andromeda galaxy, which is several quintillion miles away.
- josephg 5y agoSure, but the andromeda galaxy doesn’t have a power budget of 20 watts.
- Sporktacular 5y agoSome photons would make it, just not frequently enough to ascertain any information.
- thfuran 5y ago
- MadVikingGod 5y agoSo by the articles calculations voyager 1 is a steal. At $865 million[1] and 14.5B miles that about 0.034 Euros/Km. 1/20 of what he did in 2005. 1: https://voyager.jpl.nasa.gov/frequently-asked-questions/fact-sheet/ https://voyager.jpl.nasa.gov/frequently-asked-questions/fact...
- causi 5y agoAs always with radio, it's mostly about unobstructed line of sight and the gain in your antenna system. Indeed. If you grow up with your most common radio interactions being an FM car radio and a dumbphone, you get the impression it's entirely about range. Then you buy a drone and find out one pine needle shaves 50% off of your signal strength.
- genewitch 5y agothe mavic 2 series of drones by DJI don't have this issue, but the tradeoff is the controller weighs like 40 pounds, because it's a quite powerful wireless access point. Every other drone i've owned that supported video used an android or ios device to connect to the drone via wifi (drone presents as a WAP). iirc the claimed range is around 8km on the one i have, about 5 miles. I have assuredly gone well over 2km with no issues with control or video feed. This was over a straight highway. I routinely fly around a kilometer away, and the only issues i have is if i launch from an extremely dense patch of pine trees, and only at about 800-900 meters, i will lose video (artifacting for a second), but not control. It's never had to RTH. In case you're curious about city usage, i have a friend that has one he launches from a culdesac in Orange County and can fly in nearly any direction for about 8 minutes* before he hits a geofence, the drone still functions normally. If there is any issues, he can just fly higher. The newest newest DJI stuff claims even more ridiculous range, 15km+ over open water, for instance. If i hadn't used it myself, i wouldn't have believed it, it sounds like BS. * this is 5-7km depending on the tailwind
- dbcurtis 5y agoThe "path loss equation" goes something like: At the receiver, you have "minimum detectable signal", MDS, measured in dBm. At the transmitter, you have power out, measured in dBm. Add transmitting antenna gain, in dB, subtract propagation loss through medium(s), add receiving antenna gain, and if that number is greater than MDS, you win! The Really Great Science in Voyager is the added factor of "coding gain" -- sophisticated error correction codes can give you a many dB adder, at the expense of data rate (nobody cheats Claude Shannon).
- _greim_ 5y agoWould this mean it's possible to communicate with someone orbiting another star? Or do the sheer distances become too great?
- totallyabstract 5y agoFor some two-way wireless protocols (like wifi) you have to take into account the guard interval, slot times and interframe spacing which are all values set in time (~1-50us). For long distance transmissions your speed-of-light limited signal propagation time can exceed these values. In terms of size usually guard interval < slot size < inter-frame space. If propagation exceeds guard interval AND have a channel with lots of echo any communication will be difficult. If propagation exceeds slot timing then coordination between more than 2 devices will be different (high retries/low throughput). If propagation exceeds interframe spacing a two-way wifi connection will not be possible as both stations will think every frame timed out waiting for an ACK. More info here: https://en.wikipedia.org/wiki/Guard_interval https://en.wikipedia.org/wiki/Guard_interval https://en.wikipedia.org/wiki/Distributed_coordination_function https://en.wikipedia.org/wiki/Distributed_coordination_funct... https://en.wikipedia.org/wiki/Short_Interframe_Space https://en.wikipedia.org/wiki/Short_Interframe_Space