#radio transmissions

[hateliers]

everyone on this site loves talking abt divorce so i wanna see something

[thethingost]

man i love nope (2022)

[mainblag]

Hey, science side of tumblr: legitimate question of scientific and technological curiosity here!

What would it take to convert a radio telescope into a radar telescope?

For context: I’m writing, and what I’m writing involves radio telescopes. I had assumed, perhaps incorrectly, that most radio telescopes could be used as both receivers and transmitters, believing due to the parabolic-dish nature of many of both such devices, there’d be a relative ease of conversion. But thinking about it, the circuits required to transmit and receive radio waves are quite different from one another. So that nixes my initial thoughts.

However, I just found out about the Goldstone Deep Space Communications Complex, aka the Goldstone Observatory, which not only uses parabolic radio antennae as radio telescopes, but also (and mainly) as a communications array for NASA to keep in touch and transfer data to/from its satellites and deep-space probes. Structurally, the Goldstone radio antennae look not so different from those at, say, the Green Bank Observatory, but I know there’s some sort of equipment that sets them apart.

What I’d like to know is, what equipment is it that sets these dual-function dishes apart, exactly, and what would it take to convert a radio telescope for that function?

Thanks!

( @nasa longshot tag but- )

[virusfriendly]

SDR Research

Tools

GQRX - Spectrum Analyzer

RFanalyzer - Spectrum Analyzer for Android

Universal Radio Hacker - Investigate Wireless Protocols like a boss

ooktools - On-off keying is used extensively in IoT projects

fldigi - I'm not a big fan of fldigi, but its there for when you need to demodulate a common signal

Tools for more specialty purposes

Salamandra is a tool to find spy microphones

rpitx is a RF transmitter for Raspberry PI

Tactics

You don't need to learn DSP, or get your Ham license to explore radio signals. I didn't. You could even explore interesting signals such as vehicle key fobs without learning either, but learning these things will increase your understanding of signals and aid in your ability to go beyond the limitations of your tools.

Digital Signal Processing

The Scientist and Engineer's Guide to DSP was my introduction to DSP and I highly recommend it. Its free online and can be purchased in physical form.

Think DSP in Python is on my todo list. Also free online can can be purchased in physical form.

HAM Radio

Though I haven't taken the test yet. Covid was a major interruption in my plans, and I also plan to pass all 3 tests in one day. Using my personal test taking process, I would first start by reading No-Nonsense Study Guides.

Then take a pretest. Its important that you read all of the material before you take a pre-test as the goal is to retain knowledge, not just memorize a test. Most of the study should be reading/practicing the material, with few pre-tests as self assessments.

There are plenty of apps on Android (and I imagine IOS) that you can use. You need to get 74% to pass the exam, but I always shoot for 90%. If you get 90% on the pre-test, then move on to taking the actual exam.

If you didn't get 90% on the pre-test. The pre-test should be able to break down your score across various sections. Note the sections you're weakest in. From here, I would recommend switching over to the ARRL study guide as they are more detailed and only study the sections you're weakest end. When you complete all those sections, then take another pre-test and repeat until you're ready to take the exam.

Techniques

Accuracy

Radio is a science, but the tools that we can afford as hobbyists are not accurate. The three issues I face is drift, noise, and clock.

Drift occurs typically from your SDR getting hot and is a problem that grows across the session. To counter drift, you'll need to recalibrate your SDR to a Nation Weather Radio station. Find the frequency used in your area and tune to that frequency. You'll notice that you're probably a little off, this is the fault of your SDR not the National Weather Radio station. Set the offset of your SDR until your frequency of the station matches the one advertised. You'll then want to bookmark this frequency and check back to it every hour to insure that your SDR hasn't drifted.

Noise can interfere with interpreting weak signals (either distant, low powered, or both). To reduce noise and improve your signal collection, I'd suggest these guides for reducing on-site noise sources and external noise sources.

Signal Identification

Most signals are standardized or frequently used that dont require extensive analysis, but just identification.

The Signal Identification Wiki is a great place to start, and if that doesn't work, check out the sub-reddit r/signalidentification

This is an archived site that has a collection of digital signals that you could test your demodulation tools with.

Signal Analysis

Signal analysis is for those proprietary signals. As always, remember your ABC's.

Radio signals are fleeting. If you don't capture them, they may not repeat themselves. Don't worry about demodulating them at first. Capture the signals, and you can demodulate them at any time later.

Even if you're not able to record IQ data, for example you're listening to someone else's remote radio (there are a lot around the world on the internet), recording the audio which can be analyzed by tools such as fldigi.

I should add a lot more stuff here in the future.

The Signal Identification Wiki is a great place to start, and if that doesn't work, check out the sub-reddit r/signalidentification

This is an archived site that has a collection of digital signals that you could test your demodulation tools with.

Other Techniques

Using ooktools

NCC's RF testing Methodology

Wireless DoorBell Ringer and another Doorbell hack

Learn Morse Code

Project Ideas

Passive Radar with SDR

TDOA Transmitter Localization with RTL-SDRs

Other Links

No SDR, no problem! Use other people's radios with GlobalTuners.

[divorce-quartet]

going to be reblogging art about tfc for now. Expect possibly some spam. I'll most likely make a piece myself as well.

Miss you, TFC.

[theinterstellarbus]

This is UES Safe Travels, Captain speaking. Unknown vessel, we seem to have gotten a bit off course. Mind giving us a hand? Even just regional starcharts would be appreciated.

Hello UES Safe Travels, this is the Interstellar Bus. I don't have any star charts, but if you'd like direction to the nearest bus stop I can provide that. Will that be suitable? And, if I might ask, what brings you so far out here?

[chairforbackpain]

Blue Torch Radio Is a Big Fat Scam!

Yes, I’m going to go straight out there and say it, Blue Torch Radio is a scam. Completely, totally and unmistakably.

You saw a radio station asking for music and you dropped your link! (You should stop doing that by the way). Only a short time later hit with an alert from the poster to send your music to an email to an address. This account that has asked you to do this is most likely fake. Go ahead and check it. The next step is very important. DO NOT SEND THEM AN EMAIL.

The email address might be their main one or it could be of an individual but always it will be a Gmail address. What’s wrong with Gmail I hear you ask? Well, nothing, but this is supposed to be a radio station that can reach thousands of fans. It’s all, well a bit fishy.

Of course, I send my music to smaller radio stations all the time, but they never charge and they never claim to get my music out there to thousands of fans.

Once you have sent your email to them they will then try and get you to buy their ‘Services.’ Please don’t. Please don’t send money to get played on any radio. Not only is this considered ‘Payola’ but it’s just a terrible idea. They also try to get you to donate or buy them coffee playlist promotional services which I have covered before. Again another scam. They don’t even include Spotify or streaming links. So what exactly does this playlist even do? I have no clue. Don’t assume because you haven’t given them money think that you are 100% safe because they are sure to bombard your inbox with tons of spam emails.

Who is behind this?

I have no clue for certain who is behind this. I have no idea if it is one person who has multiple fake profiles, or multiple working as a team. I do know that this scam is appearing in a lot of Facebook music groups and it seems that a lot of musicians are unaware.

This little ruse has been attempted before under the name ‘College underground radio FM.’ I believe it is the same person or team behind that. My reason for believing that is because it’s the same method being used as before — fake Facebook accounts posting asking for music and giving out the same replies but also for another reason. When trawling through my inbox and the spam emails they sent me, I managed to find this interesting line from both emails.

Music submissions — “Get on the playlist”

For them, both to have the same tone and also includes the same sentence word for word shows the proof. College underground radio FM looks like it doesn’t exist for the most part now. Not that it ever really existed. Not that it ever had 2.4 million website visitors. I do believe that it has morphed into the new scam that is Blue Torch Radio.

What can we do to protect ourselves?

I personally still message a lot of small radio stations with my music. I like to support them and I like what they offer.

When messaging radios most of the time I use a separate email just in case they flood my inbox. I would never ever pay to get on the radio and if they were offering something too good to be true I would stay away from them.

Smaller radios are going to have a tiny reach. There’s nothing wrong with that. You’ve just got to accept that and move on. If you’re on a bunch of smaller stations eventually you’re audience will increase. Things take time; nothing is easy.

Stay safe out there, especially on social media.

[if-you-fan-a-fire]

“INTERIOR OF U.S. NAVY STATION, ARLINGTON, VA.” Toronto Star. April 18, 1922. Page 24. ---- The islands of amateurs all over the continent and in Europe, and hundreds of shops on the high seas, listen in to Arlington every night of the year. The above picture is an interior view of this famous station. Watches and clocks beyond number are set right, or checked, by Arlington’s time signals. To many ocean liners Arlington’s broadcasting service is next in importance to the compass. Call-sign NAA, wave-length 2,500 metres, transmitting by continental code.

[masterofsmoke]

[ithacanradio]

incredible how liberals when confronted with how the Chinese communist revolution doubled life expectancy will default to "actually is it even that important to live twenty years more?" and "i bet their condition was worse even if they lived longer" worstie do you think that a population who dies at 40 had a good life. look me in the eyes.

[notbecauseofvictories]

I finally listened to the latest episode of the silt verses ("latest" meaning "it came out in january, I've just been really busy") and I don't want to be negative but I liked faulkner better when he was unhinged. No more pseudo-therapy or painfully honest conversations for these characters, they need to march to their doom being lonely, unfulfilled, and tragic.

[hateliers]

WERE SO FUCKING BACK

[thethingost]

loud battle of the apocalypse

thanks @foxfireartz for the idea :)

[alivehouse]

oobh i could do this.......

[sirmanmister]

You guys know how the BoS radio signal in Cambridge starts with “to any unit in transmission range” right?

I just realized that they weren’t just yelling into the void hoping for the best, they were trying to contact PALADIN BRANDIS AND RECON SQUAD ARTEMIS in a last ditch effort :(

[divorce-quartet]

I definitely didn't absolutely accidentally reblog stuff onto this blog instead of my main nope not at all (lie)