Wide-Band WebSDR – Shortwave Radio on the Internet | Hacker News Reader

Wide-Band WebSDR – Shortwave Radio on the Internet

websdr.ewi.utwente.nl

201 pointssndean59 comments

There are many more of these: http://websdr.org/

Be sure to check several. Receive capability is not the same across stations or between frequency bands on the same SDR.

it's a shame the author doesn't seem to be interested in opening up their source code:

http://www.websdr.org/faq.html

edit: previous HN discussion regarding PA3FWM's closed source stance:

https://news.ycombinator.com/item?id=18571139

For a very similar, but open source project have a look at https://github.com/jketterl/openwebrx

Yeah, it's sometimes even a bummer to filter by desired frequency band and realize just how limited the options can be. Building a shack at home is a fun project though, and you can target any bands you like.

This is absolutely lovely. I used to mess around with a short-wave radio when I was a kid, and there was a sense of mystery and discovery that was magic. And for me at least it's still there. Just now I happened to find a Romanian radio station, and discovered that about 70% of the time it sounds like Spanish to me, with 30% incomprehensible.

And I love the lovely sounds one gets from trying various modulations and tunings. It makes me think that whoever designed R2-D2's sounds must have been a shortwave fan.

I found some intriguing music at 9700.00 AM.

Turkish I guess? But could be from anywhere from Eastern Europe to Arabia.

That is indeed the Voice of Turkey: https://www.short-wave.info/index.php?freq=9700

I didn't know folks put their radios on the internet like this. Pretty neat discovery. I found some folks by looking at the waterfall spectrograph talking about toilet paper for $2.50 a roll on their CB near Orlando, FL.

http://w4qed.hamshack.info:8073/

Does anyone know if one of these radios can tune into satellite transmissions or if there are any satellites that can be used as a relay?

The most popular satellite transmission receivable with that box is probably the ISS when it passes over. When it comes to using satellites as relays i can tell you that it's a popular practice to pirate unused US navy transponders.

This is probably the one you were thinking of regarding the relays: https://www.wired.com/2009/04/fleetcom/

There are all kinds of amateur radio satellites, and it kind of depends on what you want to do. Hams talk through them all the time, chasing grids for awards or just seeing who's out there.

Getting outside of amateur radio, I understand that Brazilians have made creative use of some kind of US Navy satellite but I don't recall the details...

You can get weather images from NOAA satellites with common SDR receivers: https://www.rtl-sdr.com/rtl-sdr-tutorial-receiving-noaa-weat...

The web ones probably can’t do it because they probably don’t have the right antenna, but SDR dongles are inexpensive so if the web ones intrigue you it’s cheap to get into your own to do more.

It all depends on the antenna the owner has. I’m kinda doubtful any of them are set up so they track satellites overhead full time.

The SDR’s are fully capable of receiving from satellites though. In fact you can even get the older weather satellites up there with nothing more than the rabbit ears that come out of the box in the cheap RTL-SDR kits on amazon. You just have to point them the right way and have the correct polarization and you’ll literally hear the image data they transmit as they pass overhead. Pipe the audio into decoding software and you have yourself an image.

Many other locations exist: http://www.websdr.org

Another directory of receivers, all based on the KiwiSDR Wide-band SDR + GPS cape for the BeagleBone Black, is

http://rx.linkfanel.net/ (map version)

http://kiwisdr.com/public/ (list version)

My kiwi is public and on the list.. its a fun device and has been super useful to me over the years (I record shortwave radio shows, listen in on the ham bands without having to go to my ham shack, etc)

Every time I see a post like this I get the urge to get myself a ham licence, then always realise that realistically I'm never going to join a club in order to do so. I wonder if the authorities might consider, in these interesting times, letting people sit a foundation test online. Seems like it might be a prudent idea.

Are you in the US? There is no requirement to join a club to take the test or study for one. There’s an excellent iOS training app (written by Patrick J Maloney), and after using that for two weeks (e.g., during commute) you’d likely pass with no issue.

Interesting, but no, I'm in the UK. We can sit a theory test online I believe, but there's a practical test you have to pass first, which it seems can only be done through clubs.

I would check with the club. Most tests in the US are administered by clubs, but you don't hav to join them to take it.

You can get the foundation with 2x 1hr visits to a local club. They absolutely don’t want you to do this, they really want you to join but it’s possible.

I got my foundation in 2015, 10watts even in a solar minimum Like just now is plenty.

I have a wire fan dipole strung up around inside my loft and i can do everything i want to on 40m band or above.

I’ve had untold hours of fun with gnu radio and a hackrf.

> You can get the foundation with 2x 1hr visits to a local club. They absolutely don’t want you to do this, they really want you to join but it’s possible.

I know it's silly but it's exactly the prospect of this awkward situation which is stopping me doing it. I can't bring myself to be saying to some old timer: I'm interested in this hobby, you're clearly interested, very knowledgeable and keen to share, but actually I just want to do the test and do my own thing thanks.

Not to mention I suspect every single member of my nearest club is about to be subject to an over 70s isolation policy.

I joined a university club to do the test even though I'm not a student. It might be worth seeing if a local university has a club that would be happy to help you?

As a ham who got licensed at 12 here in the states, I'd encourage you to fight the social element and give it a go... I had mixed feelings about it but it ended up being interesting to learn everything in a classroom style setting.

The hobby itself is huge, from talking locally, digital modes that are available under the signal to noise ratio (basically talking to people under the static around the world) and being in the UK, you could use the geostationary satellite and talk to anyone from UK to south africa, brazil and the middle east with very little effort. (https://eshail.batc.org.uk/nb/)

Check out https://www.essexham.co.uk/ they're pretty 'modern' as I understand it and could point you in the direction of a more local test session.

I've actually been tempted to spend a few weeks visiting a friend there and take the UK foundation course just to get my UK license for the added challenge ;) I used my US license over in Amsterdam when I was there over the summer.

The MiniWhip antenna this thing uses is interesting all on its own, see:

http://www.pa3fwm.nl/technotes/tn07.html

I see they are widely available to buy.

I recently learned that it is possible to buy shortwave airtime on reasonably strong stations for around 30€/hour. I don't have a concrete project yet, but I think there could be some fun projects to be done with this.

Here is an overview of stations that sell airtime:

https://www.reddit.com/r/shortwave/comments/5mocm7/sw_statio...

That seems very cheap. Like it wouldn't even pay for electricity...

I would set up a numberstation just to mystify people.

These can be fascinating. If you tune in at the right times on some American receivers, you can hear the truckers communicate via shortwave. They chat on a few different channels from hundreds of miles apart. It's like typical office chatter, but when they say they're locations it'll be a driver in Louisiana chatting with a driver in Ohio.

Then you can find the number stations (using http://priyom.org/ to find their schedules), screaming fundamentalist preachers, pirate music stations, ham radio (conversations can get very weird), cults, etc.

It's a whole different world, and it's especially fun to browse through at 2 or 3 in the morning.

You can occasionally hear truckers with ham radio licenses, too. :-)

If you're in the US there's a reasonable chance of finding the Cuban numbers station on any given day. I pick it up from my back yard in CA all the time. In fact, a bit more elusive and exciting to me are some of the trickier stations like Radio New Zealand or NHK. Even North Korea is in many cases an easier pull than those...

By the way, anybody interested in an easy and inexpensive on-ramp to listening from your own radio, check out the Radiwow R-108 and XHDATA D-328. These are less fiddly than SDRs, which can be a nice advantage for learning or portability. The Eton Elite Mini is another one that's been really surprisingly good in a small package.

How would one know the parameters to listen for example to maritime radio ("VHF" for me) LSB, USB, IQ ? What are those? I could only listen to local "MW Broadcast" that I gess is AM radio.

Also: Any way to decode CW from a recorded mp3 or similar from this websites?

There are software auto CW decoders.

For instance:

https://www.pa3fwm.nl/software/rscw/

Yes. Learn Morse Code (as I did) and decode it in your head. That's what people did for 100 years and it works great.

Can you describe what is in this frequecy? http://62.14.208.25:7500/?f=7020.00lsbz6

I've been interested in CW forever but never got past theory

You can use a phone app to decode CW. There are many that will do it.

LSB and USB are lower and upper sidebands. On the amateur radio bands it is a convention to use LSB below 10Mhz and USB above. You can find the bandplan for your country by duckduckgoing for 'bandplan usa' or wherever you live.

If you want to learn it in a little more detail, and join in, take your basic amateur radio license. In the UK it is only a weekend course. I rarely operate, but taking the first two amateur licenses was one of the most interesting things I have ever done

What sideband to use on 10Mhz?

"In contrast to other web-controlled receivers, this receiver can be tuned by multiple users simultaneously, thanks to the use of Software-Defined Radio."

Could someone please explain how this is possible?

Are there multiple SDR's present, with each user being allocated their own SDR (which I would understand with no further explanation necessary), or is a single SDR being used to accomplish this, in which case, I would love to understand how that works...

If the latter method (a single SDR) is being used... would someone kindly explain how that magic works?

It's a single SDR hardware with enough bandwidth to receive entire bands at the same time. The captured signal is then processed in software (I assume for each user independently)

EG: https://www.ettus.com/

Sure.

The hardware side of an SDR is a pair of incredibly fast analog to digital converters, capable of tens of millions of samples per second. If you can sample at 40 million pairs of samples per second, you've sampled every radio signal in 20 megahertz of bandwidth, and moved it into a form where you can computer.

There are then techniques that are used to recover individual signals. I'm not really an expert in this, so forgive/correct me if I get this wrong, but my understanding is that multiplying two signals at frequencies A and B is the same thing as adding together a signal with frequency (A+B) and a signal with frequency (A-B).

So for AM radio, if A is the carrier and B is the message, we can multiply (A+B) from the original signal with a copy of A' we generate in the computer. That yields (A+B)-A', which is just B - the signal we want to listen to. (Plus high frequency signals that can be filtered out.)

The thing is, this last step can be done multiple times - as many times as the computer can compute, since it's all done by the process. So that's how it can listen to multiple signals at once.

> There are then techniques that are used to recover individual signals. I'm not really an expert in this, so forgive/correct me if I get this wrong, but my understanding is that multiplying two signals at frequencies A and B is the same thing as adding together a signal with frequency (A+B) and a signal with frequency (A-B).

Yah, this is the gist of how a heterodyne receiver works, along with filters before the mixing to reject the unwanted frequencies.

In practice, in software, you do quadrature. That is, (rf * sin x + rf * cos x) and (rf * sin x - rf * cos x) will each get you just the sum and difference frequencies; this way you avoid any prefiltering.

Fascinating!

"The hardware side of an SDR is a pair of incredibly fast analog to digital converters, capable of tens of millions of samples per second. If you can sample at 40 million pairs of samples per second, you've sampled every radio signal in 20 megahertz of bandwidth"

Yes, that makes a lot of sense!

Never thought about that until now; you (and the other posters who have posted virtually the same thought/thing) have expanded my mind as to what I previously thought possible (but then, I'm a software guy who dabbles in electronics -- not the other way around)...

But anyway, thank you! (and the other posters too!)

Off topic: I am looking for SDR project ideas for a signal processing class (something to do during lockdown I suppose). Right now I'm thinking of doing a pretty rudimentary auto-radio-remix project (ie sample multiple radio stations simultaneously, trigger samples to form a song) or some augmented reality plane flight vector visualization project (ie movement tracking using some kind of sensor fusion between smartphone gps + smartphone camera + radio ads-b data). Any more ideas appreciated!

The second project is already part of flight radar 24.

One I tried to do a while back but didn’t have enough DSP chops for was a SSB tuning correction plug-in. If you mistune SSB (LSB/USB), the voices will be off and have a robotic chipmunk sound to them.

You can find the correct tuning by looking at the frequency relationship of the fundamental and first two or three harmonics in the voice. But it’s pretty tricky because teaching that while someone is talking is a handful. Limited interested audience for that one though.

A mobile TEMPEST attack app would make some waves. A mobile DECT scanner would also be interesting but a bunch of work.

Do the inverse of the posted project: transmit an entire band, for example all ~110 channels of the AM broadcast band. Use an old AM radio to tune to around, and hey every station is playing songs you like :-) It would be nice if this was a UNIX command with paths to ~110 folders of MP3s or something like that.

What is the limit for something like this? I mean with a given DAC of N bits, what resolution do you get with M channels without overflowing?

I've done ten channels of broadcast FM with GNU Radio. The limiting factor is processing power. Here's a spectrum with all channels sending the same audio.

http://www.w6rz.net/fm10.png

It's a constant mystery to me why 90%of webSDRs have such terrible UIs.

Has nobody considered creating one which looks like, oh i don't know a digital shortwave receiver?

I'd love this, but it seems like these days people are against skeuomorphism.

This is an especially fun tool to play around with when SkyKing messages are being broadcast!

https://mt-milcom.blogspot.com/p/what-is-emergency-action-me...

This is so interesting. I just found a bunch of guys talking on a random frequency in Russia. Spent about 10 minutes learning controls, tweaking and adjusting and finally able to hear what they're saying clearly.

Another one https://airspy.com/directory/ But you need to download windows app Sdr#

I love this service. I am really interested in learning how to do this myself. And like others, it would be nice for all the code to be open source.

BBC on 882 KHz.. also on 198 KHz (no long wave in the US) it's interesting what you get on AM broadcast from the Netherlands..

Bloody useless, because there is absolutely nothing to listen to. In olden times every country has their own shortwave radio. And in many languages too, you could heard Finnish from BBC, Radio Moscow, Soviet Estonia, Soviet Karelia, Sweden and Voice of America. Sources were conflicting hugely, like with "minor gas leak" from Chernobyl and "hooligans causing disturbances" in Czechoslovakia.

While there are less public broadcasts on shortwave then there once were, there is still plenty of utility stations, radio amateurs, and various other uses. By no means "bloody useless"

Mobile version doesn’t seem to work on mobile Safari, or I don’t know what I’m doing.

Is the number of users in from statistics at the bottom in thousand? Around 394.34 now.

This is pretty cool please keep it running

Warning, autoplays noise.

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