Moved thread to Homemade Projects because of included up-converter circuit project added below
Got this little gadget for my birthday for $13 on Amazon and have been having a lot of fun with it since..
This device was originally intended to be used as a TV receiver for European broadcasts but people found out that it can also function as a decent quality SDR radio because of the chips used inside (RTL2832U and R820T). Obviously using it for TV viewing in the US will not work.
The remote it comes with is useless though I suppose it could be used if enough hacking was done with keymaps and linux IR. Software it comes with is completely useless for SDR purposes.
Comes with a dinky 5" magnet mount antenna which if my calculations are right is resonant around 560MHz. Obviously pretty useless for wide band reception so I snipped the antenna and soldered a female F connector on the mini RG-174 coax it comes with and plan to use a discone or other good scanner antenna. The connector on the dongle itself is an MCX type which is kind of a rare connector in my experience and looks a bit fragile.
This dongle can tune anywhere from 24.0MHz to 1.766GHz in AM, NFM, WFM (plus stereo decoding), SSB, and CW. Using a simple up-converter it can be used to listen to DC to HF, and with a down-converter can tune beyond UHF. With most software you can easily change the bandwidth from very narrow 0.5k to barn door wide 500k. Obviously this allows for everything from CW to wide band FM stereo including the digital sidebands used on some FM stereo broadcasts.
I use Linux exclusively on my computers so there is a wide selection of software out there for me to choose from. Windows users can find a good selection also. The most popular being SDR Sharp (SDR#) and GQRX. I decided to go with GQRX v2.2 since it worked flawless on my setup and needed very little tweaking to get the dongle playing nice.
There are many tutorials on the web showing how to compile and install GNU Radio and rtl-sdr and other packages needed, or simply use a package install for your distro if one exist for ease. Sadly for my setup running Linux Mint 13 which is an Ubuntu fork I had to compile GNU Radio from source which took about 3 hours. Then I had to download the source for GQRX and use qtcreator to build that into a binary. This was a pain in the ass as you can imagine but it worked and now it is optimized for my hardware and linux distro. Most people shouldn't have to go through that with other Linux distributions and if all else fails there is always Kali Linux which has support right out of the box for these dongles. Like with most crazy issues, persistence pays off.
Here is a picture of GQRX picking up a regular FM broadcast station:
One issue with these cheap dongles is that the reference crystal in them are sometimes off by a tiny amount but this is easily compensated for in SDR software. For example in GQRX I simply changed the Freq. Correction until a known station was exactly on frequency. Once set this will correct everything across the entire tuning range so no further correction is required and the dongle will be spot on frequency. For mine it was 65ppm (correction.. 67) and I used a weather station on 162MHz NFM as a reference...
LNA gain is another feature that should be setup. It is a simple gain control. Set it too high and you will overload the SDR dongle if connected to a good antenna, set it too low and it won`t be very sensitive. I had no antenna connected at the time of taking the pic so I set it fairly high to show a radio station in the above pic.
These SDR radios are surprisingly sensitive. In fact I was able to dig out ham radio operators on 2 meters that I could hardly hear on my Baofeng UV-5R ham radio and it had no problem breaking GQRXs squelch control! Even was able to listen into CBers on 27MHz with no problems and good sensitivity. When connected to an indoor dipole cut for FM I was able to pick up stations that most of my other radios could hardly hear. Stereo is always on when selected so that even when the pilot signal of an FM broadcast is deep in the static it will still forcefully decode it into stereo unlike most radios which shut off stereo reception when the signal gets weak.
In the near future I plan on putting the dongle into a shielded metal box and running a USB extension cable to it. Put a simple snap on RF choke over the USB cable and have the F antenna connector screwed to the box housing so that the box and jack are RF shielded and separate from the USB grounding. This should reduce most if not all of interference from the computer from being picked up. I will post an update here when I get around to doing that.
These are exciting toys and so much can be done with them. With the 2MHz spectrum view it can be used as a basic spectrum analyzer. There is scanner software out there for both linux and windows along with a heap of other tools that will work with these. If you route the audio using Jack or some other software you can use digital decoding software for everything from RTTY to P25 voice. With GNU Radio the possibilities are endless if you have the software that takes use of GNU Radios features.
There seems to be two versions of these, the R820T that I got and the E4000. The R820 is said to be more sensitive and less problematic, but the E4000 can tune a bit higher.
Here is a really good subreddit forum thing with a lot of people discussing these SDR USB radios.. www.reddit.com/r/rtlsdr/
Already broke the MCX connector. Was a bit drunk and ended up tripping over the cord. Lucky me the dongle was safe but the MCX coax with its jack is now hitting the junk box.
I am not angry over it considering I was going to replace that stupid tiny MCX jack anyways. I knew the thing was flimsy but damn, I barely tapped the thing with my foot and goodbye. The dongle itself is still in once piece like it didn't even get a dent.
Currently working on a simple up-converter using a LA1185 chip. The circuit is so simple it is funny. All the RF is done inside the chip and easily converts HF to VHF using nothing more than a crystal which is completely up to me what IF frequency I use.
I am building it around this circuit here...
There are a few errors in the authors schematic but I figured out what was wrong and will write up my own schematic soon.
The circuit is so damn simple, all it consist of is nothing more than a double balanced mixer IC chip, you provide the low frequency input and it multiplies it by a crystal reference oscillator to a higher frequency that the dongle can decode while rejecting the input and HI frequency because it is a double balanced mixer design. Being that the dongle I have goes down to 24MHz I am opting for a 27.000MHz crystal. This will let me cover 25KHz or so to 26MHz. This easily covers the range on HF that the dongle itself can not provide (24-1750MHz with some coverage but lacking in sensitivity on the band ends is what it covers as-is out of the box w/o a converter).
What amazes me is how much the Nooelec and other brand up-converters cost. All these things are is double balanced mixer circuits. Nothing more or less. There are so many IC chips out there that simply take in a low and combine it with a high to get an IF output. I just picked a chip I scrapped from an old CB radio and it works great.
Now that I already screwed the MPX connector, it is time to solder direct an RF connector that doesn't suck. Encase the unit and converter. What is the worst I can do? Waste $13 on a USB dongle device? LOL I mean c'mon! This is amazing we can buy stuff like this now!
Few pictures of my SDR dongle picking up shortwave stations using the homemade upconverter that is still on breadboard and not yet soldered together...
IF is at 27.005MHz using my upconverter crystal. This could be any value depending on IF value of the crystal. I just happened to use a 27MHz crystal as it works best in the circuit and tunes around 27.005.
CHU Canada...
Can`t wait to transfer the circuit to perfboard and enclose it in a metal box. Works so damn good it kind of freaks me out that it is pulling in some stations that even my DX398 has a hard time with!
I got one a couple months ago and am using SDR# on my laptop.
Cheers!
Are you using SDR# under linux? If so was it hard to setup? I am considering giving that software a try and comparing it to GQRX in hopes that both software don't conflict with one another.
Update: Got the upconverter built on perf and you can see in the picture that there are two blue relays that power on with the switch which flips the antenna jack from passive to active with the converter. With the simple flip of a switch it goes from being a regular RTL2832U dongle to 10kHz to 45MHz upconverted to 50MHz. I decided on using 50MHz as the local oscillator LO frequency, which should give coverage at half that 10kHz-25MHz, with coverage up to 30 or 40MHz with some images of lower frequencies as a side effect, but that is the price paid for using these things in the first place! This means that as is the dongle covers from 24MHz to 1.7GHz give and take, and with the flip of a switch and software low conversion it covers HF from 10kHz to 24MHz. Actually more like 45MHz but lots of mixed images appear at the LO frequency / 2 as I found out the hard way.
So this is now a full coverage receiver from 10kHz to 1.7GHz! I am having so much fun with this I feel like I am cheating on my other radios. Just got to get this beast into a metal box now, add RF gain control and post up a schematic. The circuit is quite simple but theoretically should work as good as most of the others floating around on the internet.
You can see the bent MPX connector I tripped over lol. Will replace that soon enough
BTW can not wait to listen to pirates on this new toy! It will be so fun to tune in on an active night. The sensitivity of this upconverter+dongle is almost equal to my DX398 which means I should have no trouble tuning in SW pirates. Best of all is the ability to select any bandwidth I want. My DX398 starts filtering around 4KHz so it sounds like high quality telephone at best. With SDR you pick the bandwidth. With pirates like XFM using wide band audio I can not wait to catch a show! Even MW broadcasts sound amazing on this when opening the flood gates. Some stations restrict their audio but there are a few that let the barn doors open for audio and you can really hear it with this. It is equal to Mono FM quality. Now time to figure out how to decode C-QUAM and DRM with software
I got one a couple months ago and am using SDR# on my laptop.
Cheers!
Are you using SDR# under linux? If so was it hard to setup? I am considering giving that software a try and comparing it to GQRX in hopes that both software don't conflict with one another.
Vista
I do have a keychain boot for Ubuntu for the lappy, but not enough RAM to do much without installing (not my laptop).
My main box, Debian Lenny, is too old to run GQRX.
Converter is now completed and in a neat translucent box. This ended up looking and working way better than I could have ever imagined..
Schematic..
Put the converter circuit into its own metal tin which was an altoids mint box that I sanded down. Grounding the circuit to the tin in a few places really reduced outside noise down to nothing and helps shield the SDR sitting above it. USB cable ground shield is NOT connected to the shield of the box. This seems to help digital interference from picking up from the computer and prevents a ground loop. SDR dongle is sitting on the tin using a velcro strip for easy removal if I ever need to.
Relays were scrapped from an old 56k modem. They are quite common and only draw about 40ma in operation so with the SDR going on the same port the current draw is within USB specifications.
Cool thing about using a translucent plastic box besides looks is that you can see the SDRs blue light to know when it is plugged in and working. This should also allow the remote control sensor to work if I ever need it for god knows what in the future.
My SDR does have a ESD protection diode in it but I added two more to the F connector to protect the converter IC just in case. Always better safe than sorry!
When the box is set to HI the circuit is not powered or the relays causing the antenna input to feed directly to the SDR for coverage from 25MHz to 1766MHz. When set to LO the circuit becomes powered along with the relays switching the antenna input to the converter circuit and then the converter circuit to the SDR for coverage from 5kHz to 25MHz.
I have tested the converter down to 5kHz using a frequency generator and it does pick up down there! Sensitivity drops very fast <5kHz because it gets very close to the conversion frequency. Above 25MHz sensitivity drops dramatically and the converter should be set to HI to cover above 25MHz properly.
Xtal should be double of maximum conversion frequency for best results. 50MHz yields an upper frequency up to 25MHz. I have not tested higher oscillator frequencies since my SDR dongle covers 24~ on up quite well by itself.
Almost a year now but I want to remind you all how much has changed with SDR radio using these dongles and software. GQRX is now up to version 2.3 and compiles perfectly using the latest gnuradio on Linux. I am still using v2.2 however there is now many debian releases that did not exist a year ago.
When I first got this dongle I spent the whole day compiling gnuradio and the GQRX software. I went through hell and back trying to get this stuff working with my distro (Linux Mint 13 LTS), however now there are a ton of sites with precompiled binaries for Mint, Ubuntu, Debian, RH, Arch, and many others.
It is quite amazing how much stuff can change in a year. Literally a year ago these TV dongles were unheard of, now they are commonplace for VHF/UHF enthusiast along with HF listeners using converters. The software has gone from non-existent to being supported on most distributions of linux, Mac OS, and even Windows.
There really is no reason to not play with SDR dongles today. When you can buy one as cheaply as I did for around $13, and I bet a year later today much cheaper, why not?
I am not a shill, but rather as a fellow RF guy that loves new tech, we should buy these suckers up and play and experiment with them and see what all is possible.
When you figure you spend +$200 for a half decent SW radio, or even a SW/VHF/UHF scanner, why not spend literally a few bucks to get one of these SDR "TV" dongles and setup the software and play around? Anyways moving on.. One of the best antennas I have tried so far for these SDR dongles is the fan dipole antenna. Just like with HF using a fan dipole covers many frequencies. For VHF and UHF they work equally well IMHO. For others the bowtie antenna works equally well. I have not had the ability to compare both, but I am willing to bet they work equally well for reception. After all they are based on the same principal basically, increase bandwidth by either more elements or a conical element.
For HF converters work really well as I showed in the original post. I am listening to my converter built into the same box as my dongle right now and its reception on HF is almost equal to my DX398 Radio Shack radio.
BTW, my Uncle Al wants to know where to place the knobs? He's worried about how hand capacitance might affect regeneration with the thing.
LOL. Yeah it is quite easy to fabricate an upconverter so you can listen to HF on these dongles. My design is a little more complex because of the odd chip I used, but there are far better and simpler designs one can use. I just happened to use what I had laying around in the junk box and this chip works great for the purpose.
Another Update: Anyone willing to install Linux Mint 17 or its relative Ubuntu releases can now get GQRX directly from the software channel by simply clicking the software manager in the menu and searching for GQRX. It will install all the necessary GNUradio stuff. It is pathetically simple to setup now.
Amazing how a few years ago I had to compile the software by hand and spent a few days setting this stuff up. Now it is simply a matter of clicking "Install" in the package manager lmao.
Wow how a few years can change things. GQRX is also updated with some new features in the software channel release since I first posted this.
Just remember you may need to black-list the linux kernel RTL2832U stuff since modern linux kernels now support the TV stuff directly, and if you want to use it as an SDR you have to black-list the kernel from loading the driver on boot automatically. Lots of documentation on this of course and outside of the scope of this thread.