Skip to main content
26 votes
Accepted

How do GPS receivers communicate with satellites?

The first thing to know is the communication is one-way. There's a satellite-to-receiver transmission, nothing going in the opposite direction. So your cell phone doesn't have to find the radio power ...
mjt's user avatar
  • 376
16 votes
Accepted

Can I build a radio telescope out of a parabolic TV satellite dish?

The primary factor to consider is the directivity of the parabolic antenna. It is given as: $$d=\frac{(\pi D)^2}{\lambda^2} \tag 1$$ where D is the diameter of the dish and $\lambda$ is the ...
Glenn W9IQ's user avatar
  • 18.6k
15 votes
Accepted

Why would you need a signal generator to receive early satellite transmissions?

The earliest Soviet satellites, like Sputnik 1, transmitted what amounted to a CW stream -- just pulsed RF at pretty low power (later Sputniks transmitted data by pulse width modulation, still ...
Zeiss Ikon's user avatar
  • 4,147
12 votes
Accepted

Why does Free space have the highest loss compared to other losses like atmospheric loss, feeder loss etc?

Free space loss is the power lost because it doesn't reach the receiving antenna. An example using an analogy is your eye, looking at the light from a light bulb. If you stand 10 metres away from a ...
tomnexus's user avatar
  • 11.5k
12 votes

How do GPS receivers communicate with satellites?

The receiver does not communicate with the satellite; it just receives. Fundamentally, the receiver listens on one or more well-known frequencies. The receiver determines which satellites it can &...
David Hoelzer's user avatar
  • 1,052
11 votes
Accepted

Who funds amateur radio satellites?

Many of the amateur radio satellites are built, owned, and operated by various AMSAT organizations around the world. They typically get their funds from donations and organization membership fees. ...
mrog's user avatar
  • 1,023
11 votes
Accepted

Why not access the AO-91 satellite at night during eclipse?

In all likelihood the batteries on AO-91 are exhausted. So contact during eclipse could POSSIBLY (at this time probably a very small possibility) cause the batteries to short and not allow any ...
n5tti's user avatar
  • 126
10 votes

How do GPS receivers communicate with satellites?

The other answers already provide very detailed explanations, so I decided instead to suggest a resource which answers your question, but should also be very helpful with your further research: GPS - ...
user9123's user avatar
  • 201
9 votes
Accepted

Antenna polarization when dealing with satellite communications

Satellite engineers tend to use circular polarization for two reasons: When a linearly polarized signal travels through the atmosphere there are anomalies, such as Faraday rotation, that alter the ...
Glenn W9IQ's user avatar
  • 18.6k
8 votes
Accepted

Calculating satellite passes without an internet tracker?

The simplest might be to use an app. On Android, Heavens Above, a product of the 25-year-old website of the same name, stores the orbital elements of the satellites of interest, and does the pass ...
tomnexus's user avatar
  • 11.5k
7 votes
Accepted

Are there any active ham satellites orbiting that use the 5cm band?

Yes! SatNOGS is a pretty cool crowdsourced satellite observation / recording system, and they have a database of known satellites. By the way, if you're using GPredict, the ...
Marcus Müller's user avatar
6 votes
Accepted

How to transmit images and video through a hurricane?

In general, the HF bands (1.8 MHz through 30 MHz) do not have sufficient bandwidth to support live transmission of a video signal. In the US, the FCC does not authorize an emission mode for live video ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes
Accepted

Who regulates ham radio satellites?

When all the communications of a satellite qualify as amateur radio satellite communications, then the frequency coordination is carried out by IARU. ITU delegates this function to IARU. The link ...
Juancho's user avatar
  • 1,154
6 votes
Accepted

What is the turn spacing on a Helix Antenna?

During his long career, J.D. Kraus studied, and experimented extensively with, helix antennas. There is a large body of published work in college text books on this subject. The following summarizes ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes
Accepted

Help understanding this tweet about receiving images from satellite behind the Moon

32-50 degrees EL -- all 11 decodes tonight on JT4G very strong , FT991A 17db LNA, 1/4 hardline 24ft ,Gulf Alpha 8 x 11 beam H-POLE. JT4G - digital signal mode, http://physics.princeton.edu/pulsar/...
imabug's user avatar
  • 689
6 votes
Accepted

Has an amateur radio communication ever taken a path outside the Earth-Moon system?

AMSAT-DL has heard their own echoes on an Earth-Venus-Earth path, on the 13cm band, with the help of the 20-meter dish at Bochum Observatory. It falls a little short of "communication", but ...
hobbs - KC2G's user avatar
  • 12.6k
5 votes

What wireless communication technologies can travel long distances with a high bandwidth?

All kinds of digital microwave technologies can do this, including WiFi. It takes a good antenna location high from the ground, and good antenna gain / transmit power. Commercial wireless ISPs do it ...
Phil Frost - W8II's user avatar
5 votes

I would like to listen to a red roadster in space

Good find of all the frequencies and powers, it sounds like you have all the right basic equipment. But sadly for the roadster, you're too late, it's out of range. The video link is designed for a ...
tomnexus's user avatar
  • 11.5k
5 votes
Accepted

cubesat turnstile antenna material selection

As usual, for antennas, the better your material conducts, the higher your antenna efficiency. Hence, go for copper. It has an excellent conductivity per volume (which might or might not be critical ...
Marcus Müller's user avatar
5 votes

Would the antenna described work?

The purpose of a turnstyle antenna for satellite work is to generate a circularly polarized radiation pattern off of its axis. By adjusting the phasing of the feed to the two crossed dipoles, the ...
Glenn W9IQ's user avatar
  • 18.6k
5 votes

Can I build a radio telescope out of a parabolic TV satellite dish?

It's been done before. The University of Groningen astronomy department runs (ran?) a couple of 2.5 m dishes for radio astronomy exercises. IIRC they mainly observe our Sun (strongest radio source). ...
Hobbes's user avatar
  • 151
5 votes
Accepted

How do amateur satellites stay consistently in the amateur-sat bands acoss the globe?

A simple internet search turns up the IARU's Amateur Radio Satellite Frequency Coordination web page. There you will find an Amateur Satellites Short Info Paper that answers your question: ...
Brian K1LI's user avatar
  • 7,878
5 votes
Accepted

2 meter and 70cm OSCAR expected signal attenuation by topocentric elevation angle, chart?

It's close enough to zero at 2m and 70cm that I wouldn't bother computing it. Judging by ITU-R P.676 the attenuation due to the atmosphere is less than 0.01 dB/km for all frequencies below 1 GHz, and ...
hobbs - KC2G's user avatar
  • 12.6k
5 votes
Accepted

Ham Radio and Space Communications

ISS has amateur radios on board. Sometimes they even work. Sometimes they're on. Sometimes when they are on, there is an astronaut talking on it. Details, schedules, frequencies, etc., can be ...
user10489's user avatar
  • 6,533
5 votes
Accepted

Receiving the ISS SSTV: dipole antenna configuration and orientation

reports it as "U: linear, V: linear" Satellites which transmit and receive at the same time frequently do one on VHF (2m) and the other on UHF (70cm), and they frequently have separate ...
hobbs - KC2G's user avatar
  • 12.6k
5 votes
Accepted

what is the baseband for CATV?

Baseband video is the DC to about 6 MHz signal that encodes the brightness channel, and sync. If it includes colour too then it's called Composite video. Brightness and sync are truly baseband, a ...
tomnexus's user avatar
  • 11.5k
5 votes
Accepted

How do phased array antennas work when they produce spot beams?

I'm doing this from a transmit direction, first, I find that easier to explain. You know that antennas work in transmit as in receive, so what you'll (maybe?) learn will work for reception as well. ...
Marcus Müller's user avatar
5 votes

What's the protocol when making a call on the ISS repeater?

Same as any other FM satellite, which... yeah, is hectic. FM satellites only have one "channel" for everyone in the footprint, passes are short, and if you want to work as far as possible, ...
hobbs - KC2G's user avatar
  • 12.6k
4 votes

Could UHF Earth-Satellite-Earth bouncing of signals off of this large metallized foil satellite be feasible?

Given the large physical aperture of the passive reflector, I would say this presents an excellent opportunity for ESE bounces at VHF and UHF frequencies provided they maintain proper orientation of ...
Glenn W9IQ's user avatar
  • 18.6k
4 votes

doppler LEO satellite

The general equation for the change in frequency due to Doppler shift is: where c is the speed of light, fO is the frequency of operation, and Δv is the relative velocity. When applying this formula ...
Glenn W9IQ's user avatar
  • 18.6k

Only top scored, non community-wiki answers of a minimum length are eligible