Radios in space

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dzanis
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Radios in space

Postby dzanis » Fri Jun 05, 2015 12:29 pm

Hi everyone,

I have kind of technical question regarding technology: do small radios work fine as receivers between starships.

Case in point: Some PCs are on their own ship (which obviously can be strong radio signal transmitter), some PCs are on other ship and would like to hide/not announce their presence. They want to communicate (at least one way). Could the hiding PCs receive specific radio signal (specific frequencies?maybe crypted) on small radio receiving devices (like modern radios) from ship, say 10'000 km apart?
ShawnDriscoll
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Re: Radios in space

Postby ShawnDriscoll » Fri Jun 05, 2015 12:31 pm

Sure. If the radios had strong enough signals and there wasn't too much FCC shielding on the two ships. They would agree on what channel to tune into to. Like CB or short-wave radios.

Normally, there'd be an antenna on the outship of the ship that the radios plug into if they want better reception.

Packet radio could be one-way, sort of. The packets would be encrypted. Laser beam communication might be another way. No audio and no way to listen in if not in the beam's path.
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Re: Radios in space

Postby dzanis » Fri Jun 05, 2015 1:17 pm

Thanks for reply
simonh
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Re: Radios in space

Postby simonh » Fri Jun 05, 2015 2:28 pm

If you use spread-spectrum it'll be practically impossible to listen in, though you could still detect the carrier frequency. 10,000 km is a long way for a small radio to transmit to, but then a big reciever at the other end can mittigate that.

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F33D
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Re: Radios in space

Postby F33D » Fri Jun 05, 2015 3:14 pm

Large radio antennas on Earth can pick up and instantly (within 1 second) pinpoint the source of a 20 watt radio transmission out to the asteroid belt.

Without the Earth's atmospheric attenuation and the interference from all the EM generated by the magnetic field and solar radiation interaction with that (Van Allen belts etc.,) they will be detected by any military type listening system in space. Along with their location being known.
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Re: Radios in space

Postby simonh » Fri Jun 05, 2015 3:38 pm

F33D wrote:Large radio antennas on Earth can pick up and instantly (within 1 second) pinpoint the source of a 20 watt radio transmission out to the asteroid belt.

Without the Earth's atmospheric attenuation and the interference from all the EM generated by the magnetic field and solar radiation interaction with that (Van Allen belts etc.,) they will be detected by any military type listening system in space. Along with their location being known.
Could you go into a little more detail on that? An omnidirectional antenna wouldn't be useful because radio noise would drown out a singal that weak and that far away, and anyway of course wouldn't give you a direction anyway. A directional antenna (presumably a radio telescope) solves the ambient noise problem, but then it has to happen to be pointing in the right direction at the right time, and tuned to the right frequency. Do we really have radio telescopes pointing in all directions, tuned to all frequencies all the time?

Maybe I'm missing something. I know there are other types of directional antenna arrays other than the big dish types. How do you see the detection and pinpointing process working?

Simon Hibbs
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hiro

Re: Radios in space

Postby hiro » Fri Jun 05, 2015 3:47 pm

OK, this doesn't answer your question and I am not knowledgeable on the technical side of radios but I was reading recently how the Voyager spacecraft are still talking to us here on Earth. A quick Google search found this http://science.howstuffworks.com/question431.htm which while not the article I read recently does talk about how a low power radio is working just fine from a long long way away...

ETA: Pin pointing is a simple triangulation from two receivers isn't it?
Last edited by hiro on Fri Jun 05, 2015 3:54 pm, edited 2 times in total.
Reynard
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Re: Radios in space

Postby Reynard » Fri Jun 05, 2015 3:51 pm

Oh careful! The asteroid belt is 450, 000, 000, 000 meters away. Light moves at 299, 792, 458 meters per second. That's about 25 minutes. I take it a ship would need one or more of the sensor upgrades from High Guard (page 45) to receive such weak signals.

Voyager transmits at 23 watts out at the edge of the solar system and can be received. Here's an article describing how they get that signal: http://science.howstuffworks.com/question431.htm
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Re: Radios in space

Postby simonh » Fri Jun 05, 2015 4:36 pm

hiro wrote:OK, this doesn't answer your question and I am not knowledgeable on the technical side of radios but I was reading recently how the Voyager spacecraft are still talking to us here on Earth. A quick Google search found this http://science.howstuffworks.com/question431.htm which while not the article I read recently does talk about how a low power radio is working just fine from a long long way away...

ETA: Pin pointing is a simple triangulation from two receivers isn't it?
From the article.
The Voyager spacecraft has an antenna that is 3.7 meters (14 feet) in diameter, and it transmits to a 34 meter (100 feet or so) antenna on Earth. The Voyager antenna and the Earth antenna are pointed right at each other.
So that's using very large, highly directional antennas pointing precisely at each other.

With highly directional antennas, each antenna doing the triangulation would have to already know precisely which direction to point in to recieve the signal. Otherwise, they'd have to do a search sweep to try and pick it up and get a lock-on. The more directional the antenna and weaker the signal, the longer that would take.

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Re: Radios in space

Postby F33D » Fri Jun 05, 2015 5:06 pm

simonh wrote: So that's using very large, highly directional antennas pointing precisely at each other.
I wasn't aware of that example. I was using an example from a friend in the USAF. The antenna NOT pointing directly at it (they weren't trying to detect and, didn't even know about the broadcast ahead of time). Also, the USAF had an antenna on a satellite in high orbit that detected the same signal and was plenty small enough to fit for a 400 ton SBD.

In short, they fire up that omni-directional 20 watt radio and it will almost assuredly be picked up. Unless there is other radio traffic in that direction of course. Then the likelihood is that it won't be noticed.

The problem is: a 20 watt radio source that close (within the system) when compared to background radio signal strength from outerspace is like lighting a bonfire on a plain in the middle of a moonless night. If there is no curvature of horizon, you can see it for hundreds of miles.
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Re: Radios in space

Postby phavoc » Fri Jun 05, 2015 9:16 pm

The NASA Deep Space Network also knows pretty much exactly where the Voyager probe is, what frequency to listen on an everything else that can be known. That it still works is pretty amazing, but it's not necessarily a fair comparison because of all the knowledge they have.

The issue that your players might encounter is that the hull itself is a pretty good shield against RF transmissions (it can withstand micro-meteorite impacts with ease) - at least that is a possible assumption. So your handheld device inside the hull MAY not work very well without some sort of access to the antenna on the outside of the hull.

Since we don't have collapsed matter, crystaliron or any other Traveller hull materials to use to test the theories it's really how you'd like to play it out. It's easy to say yes, no, or anywhere in between.
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Re: Radios in space

Postby F33D » Fri Jun 05, 2015 10:22 pm

phavoc wrote:The NASA Deep Space Network also knows pretty much exactly where the Voyager probe is, what frequency to listen on an everything else that can be known.
I wasn't referring to NASA. :shock:
hiro

Re: Radios in space

Postby hiro » Fri Jun 05, 2015 11:22 pm

F33D wrote:
I wasn't referring to NASA. :shock:
No but I was :roll:
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Re: Radios in space

Postby Condottiere » Sat Jun 06, 2015 5:41 am

So I assume that the radio message would be intercepted, though it gives the players a narrow window to act before someone might query the signal, especially if it's encrypted, or the wording sounds coded.

That leaves trying to find a window facing the right the direction, and a laser whisker or a narrow beam flashing morse code.
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Re: Radios in space

Postby locarno24 » Mon Jun 08, 2015 8:38 am

If you're trying covert communication in space, you can't go far wrong with a whisker beam. If you're trying to be covert, an omni-directional broadcast can never be a good idea. Comm lasers are generally a better plan.
Understand that I'm not advocating violence.
I'm just saying that it's highly effective and I strongly recommend using it.
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Re: Radios in space

Postby F33D » Tue Jun 09, 2015 1:08 am

locarno24 wrote:If you're trying covert communication in space, you can't go far wrong with a whisker beam. If you're trying to be covert, an omni-directional broadcast can never be a good idea. Comm lasers are generally a better plan.
Yep. Lighting off a flare is not the best way to stay unnoticed.
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Re: Radios in space

Postby phavoc » Tue Jun 09, 2015 1:28 am

locarno24 wrote:If you're trying covert communication in space, you can't go far wrong with a whisker beam. If you're trying to be covert, an omni-directional broadcast can never be a good idea. Comm lasers are generally a better plan.
Comm laser wouldn't work in this case if the players are inside the ship and are not tied in with a link to the ships antenna. Unless they are able to plant one on the outside that isn't part of the ships comm system.

They would be better off using the radio signal but embedding a coded message or some other sort of burst-type of info in it. You can't hide the radio transmission itself, but that doesn't mean you can't piggyback on it in some way. Or you could always go OLD school and transmit everything in the clear but have the words/data coded itself. A simply query to a planet, or ship, or even the ship the players are on could hide the message in plain sight.
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Re: Radios in space

Postby Condottiere » Tue Jun 09, 2015 9:21 am

Background noise on a routine message to traffic control, or if it's routed through a communications satellite, it could be received and transmitted through there.
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Re: Radios in space

Postby CosmicGamer » Tue Jun 09, 2015 1:41 pm

Condottiere wrote:Background noise on a routine message
I'm torn between a couple possibilities. Depending on where you are and how busy the radio traffic, it might be like a single person using a cell phone

A) Just one signal amongst the many and unless there is suspicion and one knows what they are looking for - in this case, calls from a specific phone... The signal may be out there and easily enough found if one is looking. Will the average ship have the tech to intercept, decode, and analyze all radio traffic? Planets, maybe specialized "spy" ships may be trying to do such.
B) With the high level of sensors and tech in a ship, being able to intercept all types of signals may be possible and economical. With the high computing power of a ship, looking for anomalies may be possible with the computer reporting issues to the crew in almost real time.

when a signal with high strength is noticed (not your localized "bluetooth") Computer to comms officer and security
"An unidentified signal was just encountered. Trace will be completed in 47 seconds. Estimate decryption in 173 minutes."

or Computer to comms officer and steward
"The Automatic food dispenser just sent an unusual signal that the restocking bot does not recognize."

With B) as a possibility, any strange signal, piggy backed or otherwise, may be noticed and then traced even if it can't be decoded.

Then as already mentioned
phavoc wrote: Or you could always go OLD school and transmit everything in the clear but have the words/data coded itself. A simply query to a planet, or ship, or even the ship the players are on could hide the message in plain sight.
We are back to A) and the average transmission would likely have enough security that someone would have to be specifically snooping to discover anything.

Perhaps one should just determine the difficulty based on the situation and set a task. Let the characters skill in comms or sensors determine if some way is found to secretly send a message instead of the player and GM needing to understand radio signal transmissions and how they are detected in order to figure something out for themselves.

Perhaps the character that doesn't know much about standard comms and sensors is paranoid and does use a portable comm system thinking it will be more secure but it actually is more likely to get them noticed.
Last edited by CosmicGamer on Tue Jun 09, 2015 2:00 pm, edited 1 time in total.
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Re: Radios in space

Postby F33D » Tue Jun 09, 2015 1:53 pm

CosmicGamer wrote:
Condottiere wrote:Background noise on a routine message
I'm torn between a couple possibilities. Depending on where you are and how busy the radio traffic, it might be like a single person using a cell phone

A) Just one signal amongst the many and unless there is suspicion and one knows what they are looking for - in this case, calls from a specific phone... The signal may be out there and easily enough found if one is looking. Will the average ship have the tech to intercept, decode, and analyze all radio traffic? Planets, maybe specialized "spy" ships may be trying to do such.
In a busy system you won't be noticed by civvies. If you are radioing from a uninhabited area of the system, the mil forces (if any) will probably note it. If it is in the clear, as stated above, and sounds routine, you'll probably be fine.

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