Wanting to play with SDR

[Red Squirrel]

I want to setup a RPI (will the 1st gen work?) as a SDR server, basically something like these:

http://websdr.org/

I imagine there's all sorts of software that can be used to create that interface, open to suggestions.  I like the idea of it being web based.  I may or may not open it to the public.  I do have the bandwidth for it but there is also the privacy issue I need to investigate. (ex: if someone somehow manages to snoop on any kind of private info that is generating wireless waves either intentionally or not...I doubt it... just something I need to evaluate)

As for the hardware, is this pretty much what I need:

Tuner:
https://www.amazon.ca/gp/product/B01HA642SW/ref=ox_sc_act_title_5?smid=A2ODZQFKJKWN4I&psc=1

Optional board that allows more frequency ranges (I'm curious how exactly that works if anyone wants to explain, and if there's any disadvantage)
https://www.amazon.ca/gp/product/B009LQT3G6/ref=ox_sc_act_title_4?smid=A2ODZQFKJKWN4I&psc=1

Balun for if I want to make a long wire antenna or experiment with other types:
https://www.amazon.ca/gp/product/B00R09WHT6/ref=ox_sc_act_title_3?smid=A2ODZQFKJKWN4I&psc=1

Cable to connect the parts together:
https://www.amazon.ca/gp/product/B00SUVVXIY/ref=ox_sc_act_title_2?smid=AQMXZMVD5PL9J&psc=1

Is there anything else I might be missing?

Also if I want to play around with APRS at some point, would this work for that?  (receive only)

[awallin]

The Dutch websdr software is not available publicly. You may or may not get it from the original author by asking.

openwebrx is available under an open license: http://sdr.hu/openwebrx
The user-interface doesn't have as many features as websdr.

I believe there is a fork of openwebrx made specifically for the kiwiSDR
https://github.com/jks-prv/Beagle_SDR_GPS
it has much better zooming and a spectrum-view and other features not (yet?) in the original openwebrx.

let us know if you find some other open and freely available solutions for web-SDRs!
In the long-term a sub-project of gnu-radio for web-enabled GUI widgets would be awesome...

[Red Squirrel]

I ended up ordering the stuff I linked to, did not really get a chance to play with it though.   I guess there arn't all that many programs out there then?  I kinda figured there would be a flood of them.  I'll check out OpenWebRX.

As a side note I picked up a shortwave radio in the same order, never played with one before.  Actually picking up some stuff from the states, pretty neat.  10Mhz is rather interesting.   Skip propagation is a fun thing.

[Lord of nothing]

do you ever play with an SDR?
How many people live in you area?
Does Cable TV available in your Area?

[james_s]

I've been using those RTL dongles for years, they're awesome for the price. I use mostly SDR# in Windows. I have one on a Raspberry Pi too that runs Dump1090 to receive ADSB transponders, and there's RTL433 that picks up various wireless thermometers, weather stations and light switches.

[Lord of nothing]

maybe you look into: http://forums.radioreference.com/
It is an US forum for sdr and radio stuff.

[Codebird]

A good starting point is an RTL-SDR - for they are cheap as dirt. Obviously SNR, sensitivity, etc won't be as good as a higher-end device, and they can't tune low enough for the HF bands (VHF works easily, though), but they are a good way to become familiar with the software and technology so you will be better informed when you decide what to spend the big money on. Plus they are really easy to make network-accessible.

[BigBoss]

For who wants to play the SDRs.
https://myriadrf.org/

[retrolefty]

I tried some SDR but found the UI of the software just not as satisfying as rotating knobs and flipping switches on a real hardware receivers. But then again I'm old.   

[Codebird]

and they can't tune low enough for the HF bands (VHF works easily, though)

I must make a correction: I have purchased a second rtl-sdr for myself, this time with the direct sampling mod, and can personally confirm that it does indeed tune the HF bands. I hear long-wave radio from Europe, barely, even with a really tiny stick-antenna. Once I stick a proper dipole on this thing it should work better. Picks up a ton of noise though from it's own local oscillator, even though that component has no purpose in direct sampling mode.

[Red Squirrel]

I did not get a chance to play with mine yet but I also got a "hamitup" which is suppose to allow for very low frequencies.  It just plugs into the SDR via coax and then you plug the antenna in it.  How does this work, from a technical standpoint?  Like if the SDR is only capable of handling certain frequencies how does putting a device between it and the antenna change that?  And will the OS/software know?  Or does it do it kinda virtually by upconverting the signal to frequencies the SDR can understand and I have to make that distinction in software?  So say, 100Mhz is actually 100Khz's data being "rebroadcast" on 100Mhz.  That's the only way I see it could be doing it, but I'm kind of new to this stuff so learning.

[Codebird]

"Or does it do it kinda virtually by upconverting the signal to frequencies the SDR can understand and I have to make that distinction in software?  So say, 100Mhz is actually 100Khz's data being "rebroadcast" on 100Mhz."

You got it. Yes, that's how it works, and there's a setting somewhere in the software to tell it you are using an upconverter.

The other way to get the low frequencies on SDR is to use a direct sampling receiver - either one designed for the purpose (ie, pricy) or an RTL-SDR with the appropriate bodge-wire fitted (You can get these pre-made).

[technix]

You can start with the RTL-SDR stack (a $10 USB dongle and you can start listening.) Invest in a SA612 mixer module if you want to hear the lower end of the band (converting the 0-50MHz band up to somewhere RTL-SDR can tune into, like the 200-250MHz band.)

Here are some interesting bands you can hear with straight RTL-SDR:

* FM broadcast
* Airports and airplanes (can be interesting, can be devastating. I had a lot fun listening to Shanghai Hongqiao Int'l Airport Tower which I live very close to.)
* Marine radio
* CB radio
* Some walkie-talkies

With the SA612 mixer you gains access to:

* AM broadcast
* Shortwave broadcast

Since RTL-SDR (including the SA612 add-on) functions as a scanner (wide-band radio receiver) it is very likely you can operate it unlicensed. Going from there you will want to get a HAM license since you will be speaking into the radio spectrum.

Since SDR operation depends on the efficiency of FFT (receiving) and iFFT (sending,) you may want to invest in a moderately powerful GPU (like nVidia GTX 1060 or AMD Radeon RX 470) and make sure OpenCL works on the card so your computer can handle the encoding and decoding of baseband RF signals in real time. I have an R9 380 on my machine (and 16 CPU cores in another) to make SSTV over RTL-SDR work in real time.

[Codebird]

Here are some interesting bands you can hear with straight RTL-SDR:

Amateur radio 2m and 70cm bands. Hang with the hams.

Also a great many 'mystery signals' that must serve some purpose, even if it's very hard to figure out what exactly they are.

[w2aew]

I did not get a chance to play with mine yet but I also got a "hamitup" which is suppose to allow for very low frequencies.  It just plugs into the SDR via coax and then you plug the antenna in it.  How does this work, from a technical standpoint?  Like if the SDR is only capable of handling certain frequencies how does putting a device between it and the antenna change that?  And will the OS/software know?  Or does it do it kinda virtually by upconverting the signal to frequencies the SDR can understand and I have to make that distinction in software?  So say, 100Mhz is actually 100Khz's data being "rebroadcast" on 100Mhz.  That's the only way I see it could be doing it, but I'm kind of new to this stuff so learning.

Yes, it does a frequency up-conversion.  You might find these video explanations helpful:





And for some more background on mixers and frequency conversion:

[HoracioDos]

Hi

Get this book. It shows a lot of interesting areas to explore with SDR. Many projects and software available.
https://www.amazon.com/Hobbyists-Guide-RTL-SDR-Software-Defined-ebook/dp/B00KCDF1QI/ref=sr_1_1?ie=UTF8&qid=1495197858&sr=8-1&keywords=THE+HOBBYIST’S+GUIDE+TO+RTL-SDR

I started to play with unitrunk this year and switched later to trunk-recorder to listen trunked radio systems
https://github.com/robotastic/trunk-recorder

PS:
If you want to learn GNU radio and some basics. Get these too.
https://www.amazon.com/Field-Expedient-SDR-Introduction-Software-ebook/dp/B01M15DO0S/ref=pd_sim_351_5?_encoding=UTF8&psc=1&refRID=HGMB6C0HZE9ERPK29ZWB
https://www.amazon.com/Field-Expedient-SDR-Basic-Analog-ebook/dp/B01LXKJRSA/ref=asap_bc?ie=UTF8

[Lord of nothing]

is there anythink between the Cheap SDR and the very expensive Wideband SDR?

[james_s]

Sure, there's the HackRF, and there's another SDR that is more midrange, something like $130, I forget what it's called.

Nothing comes close to the cheapness of the RTL dongles though, they were a revolution in SDR, dropping the price of entry by orders of magnitude almost overnight.

[Red Squirrel]

Thanks everyone for links and videos, will check those out when I get the chance.     Looks of cool stuff that can be done with it.

[james_s]

Found a page listing a bunch of options.

http://www.rtl-sdr.com/roundup-software-defined-radios/


The SDRPlay is the one I was thinking of earlier but there are some others here that I wasn't familiar with. Still, the cheap RTL dongle is enough to do a lot of really cool stuff.

[Lord of nothing]

Sure, there's the HackRF, and there's another SDR that is more midrange, something like $130, I forget what it's called.

a German Dealer want:
HackRF One Platine    329.00 € + 11€ Shipping. 
That isnt cheap in my eyes.

http://www.rtl-sdr.com/roundup-software-defined-radios/

a lot of SDR with the Same boring Chip: R820T2 

[Codebird]

a lot of SDR with the Same boring Chip: R820T2

It's cheap. It works well enough. And it's cheap. Eight bit capture is hardly ideal, but... it is cheap.

If you want high-end SDR, you can get that too. Just be prepared to pay.

[Lord of nothing]

the company offer the sdr for 1XX$ but the are never available for the price.
I call it scam!

[borjam]

HackRF is interesting only if you intend to transmit with it.

For reception, the good mid range options are (in my opinion):

Only for HF: Cross Country Wireless SDR-4+. There is a very interesting dual diversity version as well. If you order from them, be patient. It's a one man show and it can take time to have your order shipped. But the receiver is really good. Only 192 KHz of bandwidth however.

Broadband: SDRPlay and AirSpy. Both are quite a step above the typical RTL.  AirSpy doesn't cover HF without an up converter, though.

[Lord of nothing]

http://www.sdrplay.com/docs/161115%20RSP2%20flyerV3a.pdf
cost ~200€ with shipping. 
it goes just to 2 GHz
just "Up to" 10 MHz visible bandwidth

AIRSPY-R2    Airspy R2 SDR    232.00 €
AIRSPY-MINI    Airspy Mini SDR    138.00 €
+ 11€ shipping

the arent any cheaper.
In my case I run 2x ADSB + 2 ACARS and for the future I will run 20 more. 
So 10 or 15 AIRSPY-R2 will cost up to 3500€.