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Questions tagged [satellites]

Amateur radio satellites refer to any artificial object in Earth orbit that are useful for amateur radio purposes.

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

I have the possibility to buy a very inexpensive 2.4m parabolic satellite dish and I would like to build a radio telescope from it. Originally this dish was designed to be a satellite TV antenna. ...
SP5RFD's user avatar
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12 votes
1 answer
703 views

Who funds amateur radio satellites?

I am currently studying for my Technician Exam and I am amazed at the sheer number of amateur radio satellites in orbit. Knowing how expensive it is to launch something into space, and assuming there ...
Dave G's user avatar
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11 votes
4 answers
6k views

How do GPS receivers communicate with satellites?

I have a Technical Amateur Radio license so I know the basics of wavelengths. What I'm researching is how GPS works. From what I've read, there are frequencies such as L1, L2, and L5 uses in GPS ...
john_ham_radio's user avatar
11 votes
1 answer
2k views

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

I recently watched, on You Tube, a NOVA program about the British school masters and students who were the first to publish the news that the Soviets had started launching satellites from a new launch ...
John Warren's user avatar
11 votes
2 answers
347 views

Why do satellites receive and transmit on different bands?

Most satellites I've found transmit on VHF and receive on UHF or vice versa. Why is this? I would think there's enough space on a single band.
Skyler 440's user avatar
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10 votes
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Calculating Doppler Shift for satellites

If I know how fast a satellite is moving through space, how can I calculate the doppler shift for the pass?
Skyler 440's user avatar
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10 votes
2 answers
3k views

APRS digi path for ISS digipeater?

So when I try to work the ISS digipeater, what should I set the digi path to be? My setup is a 5 W HT with a 2 m yagi connected to my phone with APRSDroid. I've tried the past few nights with ...
JW03's user avatar
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9 votes
2 answers
971 views

Can there be (long range) propagation of HF from satellites?

HF transmissions from the ground can be reflected by the ionosphere leading to very long distance propagation. Satellites in low Earth orbit (160 km to 2,000 km) fly within the ionosphere (60 km to ...
DarcyThomas's user avatar
9 votes
2 answers
3k views

Are satellites Left or Right hand circularly polarized?

I'm thinking of building some helical antennas for satellite work. I want to know which way to wind them. If satellites are spinning randomly, how can we know if they are left hand or right hand ...
Skyler 440's user avatar
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8 votes
2 answers
428 views

Have hams ever used (clusters of) geostationary satellites as passive microwave reflectors?

A number of geostationary satellites are quite large and/or appear in clusters. Moreover, many of them have large reflectors pointing to Earth (e.g. satellite TV sats). Finally, these satellites are ...
on4aa's user avatar
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8 votes
3 answers
901 views

What gain do I need to talk to SO-50 with my HT?

My HT has 5 W of power, a sensitivity of about 0.2 µV, and I would like to talk to the SO-50 with it. How much gain do I need in my antenna to make this work?
PearsonArtPhoto's user avatar
8 votes
2 answers
2k views

cubesat turnstile antenna material selection

My cubesat team is working on our design for rolled whip antennas to deploy in a UHF turnstile configuration based on this design: What I would like advice on is the material for the antennas ...
Kontakt's user avatar
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8 votes
2 answers
241 views

What will I need to receive the ICE/ISEE-3 transmitter?

The ICE/ISEE-3 spacecraft, launched in 1979, is due to pass by the earth in August, 2014. It was commanded to power down completely years ago, but it appears to have failed to do so, and while it ...
Adam Davis's user avatar
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7 votes
1 answer
134 views

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

I see that 5cm is available for satcom in amateur radio. Are there any active satellites for that? If so, what satellites and are their TLE's available?
KJ7NLL's user avatar
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7 votes
1 answer
404 views

How to talk to the ISS

I have a UHF/VHF transceiver capable of transmitting on UHF and receiving on VHF or vice versa on channel mode. I finally got a directional Yagi antenna so reception/transmission shouldn't be a ...
Skyler 440's user avatar
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7 votes
3 answers
1k views

Store-and-forward capable satellites in operation?

The amateur satellite community used to have a small fleet of pacsat satellites (AO-16 and friends), which were capable of store-and-forward message passing: you could upload messages to the LEO ...
oh7lzb's user avatar
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7 votes
2 answers
818 views

Doppler Shift Compensation in Inter Satellite Communication

I am currently doing a project in the area of optical inter-satellite communication (GEO-LEO). I am using a optical carrier of 281 THz, and the Doppler shift corresponding to it is ±7 GHz. I ...
Seetharama's user avatar
6 votes
1 answer
1k views

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

According to amsat-uk.org, the AO 91 satellite should not be accessed during eclipse because it is near EOL. AO-91 (RadFxSat / Fox-1B) Near end of life. If you find it on, do not attempt to access in ...
KJ7LNW's user avatar
  • 723
6 votes
2 answers
237 views

Identifying signals in the satellite exclusive band

I have just started playing with SDR so I downloaded the relevant amateur band plan for my location, the UK. Tuning around I found things like POCSAG/FLEX pagers as expected and amateur radio (e.g. ...
David's user avatar
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6 votes
2 answers
806 views

Weather Imaging with NOAA satellites - legal?

I would like to build an antenna for receiving NOAA weather satellites. They're receivable at around 137.5 Mhz. I'm a total new to amateur radio stuff. I know that it's not legal to communicate as ...
leAthlon's user avatar
  • 225
6 votes
3 answers
265 views

APT/LRPT images geotagging

I want to extend functionality of some open-source programs which decode APT and LRPT images (wxapt and glrpt). More specifically I want to add possibility to overlay geographical data such as land ...
Drobot Viktor's user avatar
6 votes
1 answer
1k views

What is spin fading in satellite signals?

Why do signals from satellites experience "spin fading" as the satellite rotates? What are the effects that spin fading has on a radio signal? From test question: T8B09
JC Hulce's user avatar
  • 901
6 votes
1 answer
217 views

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

As a bit of curiosity, I was wondering what the longest path ever used by amateur radio operators has been. Of course the opposite side of the Earth is no problem with a good HF station. And you can ...
Phil Frost - W8II's user avatar
6 votes
2 answers
3k views

doppler LEO satellite

I am trying to model Doppler shift of LEO satellite, From my research so far I have come across the following formula: \begin{equation} \frac{f_r}{f_s}=\frac{1-\frac{u}{c}cos\theta}{\sqrt{1-\frac{u^2}...
Rizias's user avatar
  • 161
5 votes
2 answers
314 views

Calculating satellite passes without an internet tracker?

Situation: You want to know when a satellite will pass in order to receive an image transmission or to work an amateur satellite. However, you cannot access internet for whatever reason, and ...
Galaxy's user avatar
  • 199
5 votes
2 answers
2k views

How to transmit images and video through a hurricane?

Background You're in the path of a hurricane, and the eye just passed over your head. There is no electricity (apart from your own generator or battery), there is no mobile network and there is ...
not2qubit's user avatar
  • 378
5 votes
2 answers
340 views

How far from earth do FCC regulations apply?

So, I know people in the space station need a HAM radio license for operation. How Far exactly from earth do you have to be to transmit any RF wave you want without a license?
Skyler 440's user avatar
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5 votes
2 answers
2k views

Receiving the ISS SSTV: dipole antenna configuration and orientation

In short I am trying to receive SSTV Images from the ISS (145.8Mhz) and I all have is a simple "bunny ears" dipole antenna. In what configuration (straight, vee shaped, upside down vee, ...) ...
Steven's user avatar
  • 205
5 votes
2 answers
195 views

I would like to listen to a red roadster in space

I have been listening for signals (any) of the Space-X Falcon Heavy. Just out of curiosity. And I am wondering if anyone has received any. According to the Falcon-9 User Guide table 4.6 looks like ...
Edwin van Mierlo's user avatar
5 votes
1 answer
834 views

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

I have mostly only used non-crowded 2 meter repeaters, but recently I tuned my radio to the downlink frequency: 437.8 mhz while the ISS was passing overhead - just to listen. What I heard was people ...
scm's user avatar
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5 votes
2 answers
81 views

Website for Sat details

I used to use the Amsat website for finding out the status of Sats and other info, like operating frequency etc. It was proving useful, and I like the pass predictor also. Seems nowadays though there'...
user avatar
5 votes
1 answer
296 views

What are the legal requirements for an amateur radio satellite?

Lets say I can throw a satellite into orbit (I've got a good arm). I'm amateur radio qualified so can I just set it up to transmit on an amateur band and start having fun? Is there anyone I have to ...
FraserOfSmeg's user avatar
5 votes
2 answers
558 views

Doppler shift compensation without using predictive modelling

Doppler shift mitigation has been studied extensively in the literature. In my implementations of satellite receivers (using GNU Radio), I use predicted Doppler shift from a software (GPredict) to ...
Moses Browne Mwakyanjala's user avatar
4 votes
1 answer
798 views

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

In a communication Satellite system, there are losses that occur when the signal is received at the antenna and then passed through a communication link to the output stage which could be the receiver....
Signal's user avatar
  • 43
4 votes
3 answers
150 views

Why do satellite tracking programs have to be updated?

So I've heard every once and a while you have to update your satellite tracking software because of the fact that the satellites are falling towards Earth. Why can't the program automatically ...
Skyler 440's user avatar
  • 7,600
4 votes
2 answers
198 views

Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?

Is there some simple utility, or published set of charts, or suite of formulae, where one can approach the situation by inputting a space weather summary, (sunspots, various indexes, etc), the receive ...
always_learning's user avatar
4 votes
2 answers
2k views

How do I listen to the amateur radio satellites?

I'm new to amateur radio, and I would like to listen to those satellites in the orbit. Where do I start? What types of amateur radio satellites exist?
Sumithran's user avatar
  • 573
4 votes
1 answer
357 views

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

The July 14, 2017 NASA Spaceflight article Soyuz 2-1A launches with Kanopus-V-IK and over 70 satellites says: Mayak is a three-unit CubeSat which was built by Tvoii Sektor Kosmosa – or “Your Sector ...
uhoh's user avatar
  • 543
4 votes
1 answer
659 views

What determines the optimum frequency range for the transmission of signals?

What determines the optimum frequency range for the transmission of signals in a system that's transmitting electromagnetic signals between an antenna on the surface of the earth and an orbiting ...
Max's user avatar
  • 123
4 votes
1 answer
2k views

Max El vs Max El Azimuth

I don't have much experience with amateur satellites and I went to the AMSAT website to track a few passes. Two of the terms are "Maximum Elevation" and "Max El Azimuth" I go to look up the terms, ...
Skyler 440's user avatar
  • 7,600
4 votes
1 answer
2k views

Command-line satellite tracking software

Is there any software similar to Gpredict but which can be used without a GUI and can control rotor Az/EL and radio doppler shift? I'm using Linux in particular, especially Ubuntu 14.04. Currently, I ...
user80551's user avatar
  • 201
4 votes
2 answers
612 views

Are there any satellites with 435 MHz uplink?

I have a transceiver working in the 435 MHz ham band. I want to test my uplink capability by communicating with satellites operating in this band. Are there any digital satellites which I can use for ...
Ashish kulkarni's user avatar
4 votes
1 answer
399 views

For Linear Transponder satellites, do I transmit on USB or LSB?

I'm in charge of our Field Day satellite communication, and I'm going to try and do this via SSB on one of the SSB satellites. I know they invert the signal, but is the convention to transmit on USB ...
PearsonArtPhoto's user avatar
4 votes
1 answer
177 views

What value goes in the AX.25 PID field if the Layer 3 protocol is not defined in the standard?

I am working on space-ground networking for a Cube Satellite, and one of our candidate Layer 2 protocols is AX.25. We haven't settled on a physical layer, but it's likely to be some form of quadrature-...
VE9PEG's user avatar
  • 41
4 votes
1 answer
1k views

How to bypass LNA for TX in UHF Antenna?

I want to work with amateur, low power, and/or pico satellites. I would like to use an Eggbeater or Turnstile antenna with my UHF 433 MHz radio, since those antennas are very cheap and easy to build ...
vz0's user avatar
  • 141
4 votes
1 answer
249 views

Warbler vs SoundModem

I'm trying to decode a BPSK 1200 (with no success). In this endeavor I tried both SoundModem and Warbler. The scenario here is the following: Ettus receiver + HDSDR with speaker plugged into mic via ...
KcFnMi's user avatar
  • 353
4 votes
0 answers
60 views

Optimizing Half-Duplex Sequencing: Consolidating RF and Power Connections with Bias-T and VOX

I've successfully implemented a half-duplex sequencing mechanism, which I've illustrated below. The outdoor components are represented in green. In my current setup, I utilize a PLC to control both an ...
Moses Browne Mwakyanjala's user avatar
3 votes
2 answers
3k views

Antenna polarization when dealing with satellite communications

It's easy to understand, conceptually anyway, the difference between a horizontally polarized antenna and a vertically polarized one, when referenced to ground. However, when they are pointed nearly ...
mike65535's user avatar
  • 1,035
3 votes
2 answers
1k views

What is Circular Polarization?

So I just learned that a satellite does not send out a circularly polarized signal, it just switches orientation slowly when it topples through space. I thought that because they were spinning, the ...
Skyler 440's user avatar
  • 7,600
3 votes
4 answers
254 views

Who regulates ham radio satellites?

I have doubts regarding the control authority of the amateur radio satellites, because recently we have drastic changes to Internet control by FCC as the next major decentralized communication system ...
Sampath Madala's user avatar