# Tag Info

28

It can be seen through this Wikipedia article that all communication with the Apollo missions was done at about 2.2 GHz, which is well above the frequency that reflects on the Ionosphere (No higher than about 30 MHz). FYI, the Gemini radio system also used frequencies in the UHF range, although it included some VHF, and even some HF. The HF/ VHF signals ...

27

It absolutely could happen, but it would require a more precise pointing than New Horizons has. Lasers of some kind are the best for the high data resolution. The spacecraft to most heavily use lasers in communication is the Lunar Reconnaissance Orbiter. It has also long been talked about as a goal for a Mars communication satellite, which would allow for ...

17

Let's try and do some numbers. We will need to make a few assumptions.I'm going to choose ones which make the calculations easy, varying might produce variation of a factor of 10 or 100 in the answer. A near IR laser with a wavelength of $1 \mu m$ NH transmitting using the LORRI telescope with an aperture of about 20cm. We know NH can point accurately ...

13

There are some big differences between GPS and cell phone signals: GPS relies on the exact timing of a signal (1 nanosecond off = 30 cm of position inaccuracy). Cell phones are much more tolerant to variations in signal timing. Basically they don't care as long as the packets arrive quickly enough not to cause a gap in the audio. GPS transmitters are 18,...

8

The "radio frequency" system draws up to 111.7 W (PDF on Voyager design, table 2 on page 10). This is purely the power amplifier, modulation/demodulation is listed separately at another 11 W. Note that this has nothing to do with the dish. Those 23 W is what comes out of the antenna as radio waves. The dish reflects pretty much 100% of this.

6

TL;DR: Based on the below information, and given 4 assumptions, the maximum number of stations one could legibly hear would be 42 or less. Not sure if there is a factual answer to this question. But as the OP has indicated a "Gedankenexperiment" as the basis of the question. We may theorize, how many stations you can receive. Lets concentrate on the FM ...

6

Steve Linton's answer is excellent, although possibly a bit conservative. Information has been transmitted in the lab via laser at a rate of 1 bit per photon. For proposed uses, Error Detection and Correction codes are definitely indicated. Has anyone proposed, or indeed do we (4) already use, laser-style communications in space? Yes to both, although ...

6

There is existing technology for this, termed "{Active,Passive} GPS Repeater". It is composed of both an antenna outside and inside, with optionally active or passive components to forward the signal. My introduction to it was within an ocean-going vessel, and it worked fine. http://www.terrisgps.com/how-do-gps-repeaters-work/ https://www.tri-m.com/index....

5

This is closely related to the concept of Antenna gain, which for radio transmission measures how narrow a beam the antenna can focus. The narrower the beam, the more accurately you need to point it. However, any laser or radio beam will still be divergent - it will spread out the further away it goes. And it will spread out at the same rate, with the beam ...

4

In general, if you need a local indoor navigation system, then you are better off implementing your own. Generally speaking these are called Indoor Positioning Systems. There isn't yet a standard, but there has been some work to making one. It would be MUCH cheaper, more accurate, and overall just better. GPS satellites are expensive, they are all space ...

3

Since most of the answers discuss FM broadcast signals, let's look at AM broadcast signals as well, and discuss propagation throughout the radio spectrum. I am speaking as an Amateur Radio hobbyist, and junior-level Electrical Engineering student. We have to remember that AM and FM are merely methods of modulation. However, these methods of modulation are ...

2

That paper "Anthropogenic Space Weather" runs to 55 pages, but only 5 pages discuss VLF impact on the ionosphere (chapter 8), while 35 pages (chapters 2-7) discuss EMP from high altitude nukes. This is for the simple reason that even a world-class VLF transmitter like Cutler 24kHz transmitter can only emit a few megawatts, while a big nuke emits billions of ...

2

1. Assuming that your application can (or does) use an external GPS antenna, keep in mind that they are not all the same. They are available in different gains. I use them for two lightningmaps.org receivers. One is far more sensitive than the other, and I might be able to get away from using it indoors (though I have never tried to). 2. Many have had ...

2

Ignoring the latency (actually not that bad) and faraday cage problems, the main problem here is the radio link budget. The link budget is a calculation for how much usable bandwidth (data rate) can be maintained for a certain set of parameters. The parameters the receiver can optimize are the Receiver Antenna Gain and Receiver Losses. Let’s assume Receiver ...

2

Not exactly connecting to a regular Wi-Fi network, but shows what is possible using the suitable configuration. Dish antennas were used on both sides. https://en.wikipedia.org/wiki/Long-range_Wi-Fi The longest unamplified Wi-Fi link is a 304 km link achieved by CISAR (Italian Center for Radio Activities). [...] Antenna is 120 cm with handmade ...

2

Antenna design is about more than just size. In fact antenna elements themselves have maximum useful size (order of one wavelength). But the short story is you cant with any size. The long answer is of course there is always a way, but it would start to get very silly. WiFi frequencies and protocols just dont work over those distances.

2

A few issues here: You don't "pull" information with a radio. That just isn't a thing. When transmitting, radio waves follow an inverse square law: when you double the distance, you quarter the power, which means you rapidly approach the noise floor (from cosmic radiation, solar radiation, you name it) so in order to combat noise, you need to send data ...

1

You have a couple of big problems here: 1) GPS simply doesn't have the accuracy you need. In most cases the best it could hope for is to figure out what room you're in and that wouldn't be 100% accurate. 2) The more stuff in the way the more reflections become an issue and the more inaccurate your fix is even if you manage to get one. There are special ...

1

I went ahead and emailed the responsible people at JPL. They confirmed that there is no planned mission for LEO with IRIS on board.

1

"First Theremin Concert for Extraterrestrials" in 2001 https://en.wikipedia.org/wiki/Teen_Age_Message Three theremin performers from the Moscow Theremin Center – Lydia Kavina, Yana Aksenova, and Anton Kerchenko – were invited to perform seven songs selected by students. The program included two Russian folk songs and works by Beethoven, Vivaldi, Saint-...

1

The FM radio band is divided into 101 channels at 200 kHz intervals. In the USA, the FCC recommends that transmitters in the same area have frequencies at least 4 channels apart, leaving room for 25 transmitters in the same area. The next area over shifts this scheme by 1 channel, etc. to minimize interference. In recent years, this has changed to give ...

1

The power of FM transmitters and the sensitivity of FM recivers are optimized for a range of some 10 km for local transmitters and up to 200 km for transmitters on a mountain. But if a wave goes horizontal from a transmitters antenna straight to the ISS in 400 km above the surface it has to travel a very long distance. Using the formula of Pythagoras gives a ...

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