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Where to find the $20 Software Defined Radio?

A while back I wrote a blog post about the availability of $20 software defined VHF/UHF radios in the form of re-purposed USB digital television dongles.

Now-days, with the improvements in software and documentation, the hardest part is finding the right dongle. What you order from EBay, and what you receive, can be two different things and only some of the dongles are suitable for use as VHF/UHF software defined radios.

So, I was pleased to see that at least one hobbyist electronics supplier has sought out and supplies a suitable device for SDR at a fair price :

Adafruit has available the USB dongle and “antenna” suitable for experimentation for $22.50, not far from the EBay (direct from China) price.

Click here to go directly to the product page: Software Defined Radio Receiver USB Stick – RTL2832 w/R820T

No, I didn’t receive a free evaluation unit and I don’t work for Adafruit … I’m just glad to see these useful devices available from a local company with an increased chance of you “Getting what you paid for.”

Adafruit also helpfully stock the adapter cables to convert the less common MCX antenna connector into the much more common BNC connector: MCX Jack to BNC RF Cable Adapter

Shock and Awe – The story of electricity.

Amateur radio has a long history, going all the way back to wireless experiments in the late 1800s. However the study of electricity has its roots in the observation of natural phenomena and stretches back much further.

I ran across this excellent three part documentary detailing the story of the discovery of electricity. The presenter is Jim Al-Khalili, currently Professor of Theoretical Physics and Chair in the Public Engagement in Science at the University of Surrey. He not only knows his stuff, he is also an interesting and engaging speaker.

The documentary runs for three hours but is worth your time if you are interested in the story of electricity and the people behind its discovery and history. I hope you find it as enjoyable as I did.

At 522,000,000 miles per watt, Voyager 1 might be the ultimate in QRP.

At 522,000,000 miles per watt, Voyager could be the ultimate in QRP … if you have the right antenna.

For most HAMs the experience of seeing sub-one watt WSPR signals decoded from across the globe is enough of a thrill. However, the fine folks at the National Radio Astronomy Observatory have taken this a little further and used the Very Long Baseline Array radio telescope to precisely pinpoint the position of the Voyager 1 space probe.
While the layperson might see detecting the glimmer of 22 watts across the vastness of space miraculous, the amateur radio community can see this feat as the natural evolution and refinement of the technology and medium we know and love.
From nrao.edu:
Earlier this year, the National Science Foundation’s Very Long Baseline Array telescope turned its gaze to NASA’s famed Voyager 1 and captured an image of this iconic spacecraft’s faint radio signal. The Green Bank Telescope also detected Voyager’s signal, picking it out from the background radio noise in less than one second.

Astronomers using the National Science Foundation’s (NSF) Very Long Baseline Array (VLBA) and Green Bank Telescope (GBT) spotted the faint radio glow from NASA’s famed Voyager 1 spacecraft — the most distant man-made object.

According to NASA’s Jet Propulsion Laboratory (JPL), the VLBA imaged the signal from Voyager 1’s main transmitter after the spacecraft had already passed beyond the edge of the heliosphere, the bubble of charged particles from the Sun that surrounds our Solar System.

Using NASA’s Deep Space Network, JPL continually tracks Voyager and calculates its position on the sky, which is known as the ephemeris. Since the VLBA has the highest resolution, or ability to see fine detail, of any full-time astronomical instrument, NRAO astronomers believed they could locate Voyager’s ephemeris position with unprecedented precision. This is unrelated to Voyager’s distance from the Sun or position relative to the heliosphere.

The initial observations, which were made on February 21, placed Voyager very near, but not precisely at its predicted location. The difference was a few tenths of an arcsecond. An arcsecond is the apparent size of a penny as seen from 2.5 miles (4 kilometers) away. The second observations on June 1 produced similar results.

“It is possible that these observations are at the milliarcsecond [one-thousandth of an arcsecond] level, or better,” said NRAO scientist Walter Brisken, who led the observations with the VLBA. At 11.5 billion miles — Voyager’s approximate distance at the time of the initial observations — one milliarcsecond would be roughly 50 miles across.

Voyager’s main transmitter shines at a feeble 22 watts, which is comparable to a car-mounted police radio or — in visible light — a refrigerator light bulb. Though incredibly weak by the standards of modern wireless communications, Voyager’s signal is astoundingly bright when compared to most natural objects studied by radio telescopes.

“The ability to pinpoint the location of Voyager and other spacecraft is critical as we explore the inner Solar System and beyond,” said Brisken. “The NRAO’s VLBA has the capability to do this vital task with unprecedented precision.”

Voyager 1, which was launched in 1977, is now headed away from the Sun at a speed of about 38,000 miles per hour.

In a remarkably sensitive complementary observation, the NRAO’s Green Bank Telescope (GBT), which is the world’s largest fully steerable radio telescope, easily detected Voyager’s signal, picking it out from the background radio noise in less than one second.

“Voyager is the first man-made object to penetrate the interstellar medium, and we really want to be able to receive the data from this new frontier,” said NRAO scientist Toney Minter, who oversaw the Green Bank observations. “This information will provide many clues about how the interstellar medium behaves and how the Sun interacts with it.”

“NRAO’s instruments have the capability to provide the most accurate position information of distant spacecraft like Voyager,” said NRAO Director Tony Beasley. “The remarkable sensitivity of GBT and VLBA’s sharp vision are essential for discovery but also have unique capabilities that have enabled us to make this contact with one of humanity’s most ambitious missions of exploration.”

The VLBA is a system of radio antennas located across the United States from Hawaii to St. Croix. The antennas work together as a single telescope nearly 5,000 miles across, giving the VLBA its ability to see fine details. Only seven of the VLBA’s full complement of 10 antennas were used to make these observations.

The 100-meter GBT is located in the National Radio Quiet Zone and the West Virginia Radio Astronomy Zone, which protect the incredibly sensitive telescope from unwanted radio interference. The GBT observations were made by NRAO scientists Toney Minter and Frank Ghigo, and Green Bank Director Karen O’Neil.

From Backblocks To High Seas

I came across this great piece of history via the Google+ page of Cristian YO8TNB and had to share it here for others to enjoy. I have a soft spot for New Zealand, being so close to my country of birth, and I particularly noticed the carefully cultured accent of the announcer. On a more serious note, this video is an invaluable record of the wired and wireless technology used in 1939 and the procedures for transmitting a message from land to sea.

Philco Tropic Model 3012

Last weekend I attended the Houston Vintage Radio Association holiday dinner & picked up a Philco Tropic Model 3012 during the fundraiser auction. I had let a few other radios go without placing a bid and was beginning to think I might go home empty handed when I saw the Philco “on the block”. A few seconds later I was the proud owner of this vintage receiver.

Philco Tropic 3012

Information on this model seems a little scarce, however the style of case was introduced by Philco in 1951 and used in their line of AM/FM receivers for many years after that. This particular example is a transformer-less AC/DC set with a potentially live chassis and the unusual (to me) lineup of 14Q7, 7B7, 14B6, 35A5 & 35Y4 vacuum tubes.

What prompted me to bid on this particular radio was the inclusion of two shortwave bands in addition to the typical AM broadcast band. The dials are marked off in meters which also appealed to the ham radio side of my interests.

After attaching a short length of wire as an antenna I was able to pick up signals across the two SW1 & SW2 bands so I’ll be interested to see what it can receive with a long wire antenna at night.

After a gentle cleaning with dilute mild detergent to remove dirt I rubbed in some beeswax polish to restore the original gloss. Sadly the plastic dial is cracked in the middle but I can look past that given its a little more unusual than the typical All American Five receiver.

Being over fifty years old I wonder what this radio has been used to listen to and what stories it could tell. Perhaps it gave some youngster his or her first taste of ham radio, listening to shortwave stations and AM QSOs until they received the final demand to, “Switch that radio off and GO TO BED!”

Get your head in the cloud.

Even though my day job is completely centered around Information Technology I still miss changes and shifts in technology that happen practically under my nose. As much as I hear vendors speak about “The Cloud” I haven’t had much time to investigate and discover if this “new technology” is something I can put to use.

If you already know what “The Cloud” is then you can skip the following paragraph, otherwise please read on:

The easiest way to understand the cloud is to think of it as a utility, like electricity. When you plug a device into a wall outlet, electricity flows. You didn’t generate the electricity yourself. In fact, you probably have no idea where the electricity was generated. It’s just there when you want it. All you care about is that your device works. Cloud computing works on the same principle. Through an internet connection (the equivalent of an electrical outlet), you can access whatever applications, files, or data you have opted to store in the cloud–anytime, anywhere, from any device. How it gets to you and where it’s stored are not your concern (well, for most people they’re not). 

By Rama Ramaswami, Dian Schaffhauser (http://campustechnology.com) 10/31/11

There is no end to the stream of interesting projects that are being developed “in the cloud” and its hard to keep track of them all. Some projects have turned into things that we’re all familiar with; Flickr, Facebook & Twitter are a few examples. Some appear and vanish like the proverbial “Flash in the pan” and, since you generally lose access once they run out of steam, it can be disappointing if you have invested any time in those applications.

I’ve collected a few cloud based applications/services here that might be of interest to the radio amateur and/or experimenter. They look like they should stick around for a while and have already reached a fair level of maturity:

circuits.io: Described as a free circuit editor in your browser, it is actually a lot more. You can not only design practically any kind of circuit using just a web browser, you can turn that circuit into a printed circuit board and then BUY that PCB board online. Several different technologies had to come together to make this into an effective tool. This tool is fairly new but is becoming very popular. Hopefully it will stick around and continue to mature into something great.

WebSDR: While arguably not a “cloud application” it does allow you listen to software defined radios, using a web browser, from anywhere you have internet access.
There are multiple sdr receivers located across the globe using a variety of receivers and antennas. Some are tuned to the HF bands while others cover VHF & UHF bands.
This is an invaluable free service provided by institutions and individuals at their own cost.

APRS.fi: The distributed network of Automatic Packet Reporting System stations, repeaters, clients and map servers could be considered to be “of the cloud” before the cloud even existed. With an APRS equipped radio you can log your position from a GPS, over the air & through another ARPS receiver. This is then sent out (usually) across the internet to other systems which in turn can map your location or update other APRS clients or radios. APRS has also been extended to include the ability to text message which is particularly useful in locations where cell phone SMS messages or email are not possible!

Echolink: Like APRS, Echolink links the Internet to amateur radio. However Echolink links the audio and PTT (push to talk) signals from a radio or software client to a radio in another physical location. If you’re stuck in a hotel room or another location without access to a radio you can still “get on the air” using an Echolink client on your Windows, Linux, iOS or Android computer & handheld device. Most Echolink connected stations are VHF/UHF but there are HF stations connected as well. Echolink is not designed to replace radio to radio communications but instead increases the connectivity of amateur radio operators and allows hams, who otherwise would not be able to operate, the pleasure of getting on the air.

As you can see, some of these “cloud apps” pre-date the idea of cloud computing by quite a while. Just another example of amateur radio folks being ahead of the curve without even realizing it.

The $20 Software Defined Radio

Introduction:

Despite my interest in boat-anchors I do find myself peeking ‘over the wall’ from time to time and taking a look at new and emerging technologies. After several demonstrations from friends I had become convinced of the incredible potential of software defined radios and even found thinking about owning one … one day.

Perhaps the best known SDR in amateur radio circles are the FLEX rigs from FlexRadio. I had the chance to see a FLEX-3000 in use during Winter Field Day 2011 and had to admit that, barring the lack of knobs & dials, it was a very impressive rig!
One thing stopped me from running out and buying one straight away was the cost and perhaps the notion that once the new had worn off I would regret the significant outlay required to own the blue box. So, I shelved the idea of owning an SDR and found other things to occupy my time.
This changed when a post on www.reddit.com/r/amateurradio/ mentioned an unmodified digital TV receiving USB device that had been used as a software defined receiver in the 60MHz – 1.7GHz range. The best part was the cost, around $20 for most examples of this kind of device. Finally software & commodity hardware had come together to deliver useful receiver that everyone can afford.
The nuts and bolts:

There are specific parts required to put together your own $20 SDR but I will document what I used to get mine running and hopefully you can follow along.
Hardware: The device that I used was a Ezcap EZTV668 DVB-T Digital TV USB 2.0 Dongle purchased from DealExtreme. The part was shipped from Asia and I gather from reading else ware that DealExtreme is a middleman and not the actual supplier. Be prepared to wait a while if ordering from this supplier, my Ezcap took about 3 weeks to arrive but I have heard that a month or more is not uncommon.
The upside is that shipping is free and your purchase involves 0% tax, this really IS a $20 SDR.
This particular DVB-T dongle uses the RTL2832U chip which is required for use as an SDR, other dongles with this chip may work but if it does not have the RTL chip it will NOT work currently.

Software (Linux) : After poor results with the software running on MS Windows I moved across to Linux and got it working well there. I can’t point you to a single howto for this because I used several different guides and tried a few things before it started working. The most helpful, and probably all you really need, are the build-gnuradio script which gets hardware support and gnu-radio running and the “Getting Started With RTL-SDR” page by Tom Nardi which covers installing Gqrx. All the software used is in development and requires familiarity with the command line to install and use at the moment.

Software (Windows) : I had another shot at getting the MS Windows software running and stumbled across the excellent website http://rtlsdr.org. Rtlsdr.org mentions using a new version of SDR# software which worked very well! 
I would recommend following the instructions under the Windows Software section, this had me up and running in a matter of minutes. Follow the instructions EXACTLY, I made life hard on myself by not paying attention to details and I think was responsible for my earlier issues.
Going further – Antenna : The stock antenna that is supplied with the Ezcap EZTV668 is sufficient for testing but you’ll want to add something a bit more substantial for regular use. You may even want to remove the existing (hard to find) antenna connector from the board and install a standard connector and a less flimsy metal casing. This will help with RF shielding and temperature stability. 
If you are going to use a larger antenna, especially an outside antenna, you’ll want to check to make sure a protection diode has been fitted to the input. The Ezcap EZTV668 is a very inexpensive device and others have found units in which the protection diode was not fitted to save costs.
Going further – 160M – 6M ? : I’ve just seen an interesting blog post titled FunCube Upconverter where the author, George Smart, has built a converter allowing the reception of 160M – 6M using the FunCube dongle. The FunCube is functionally the same as the RTL dongles available for $20. For any home brewers out there this could be a great project as George has included all the details including schematics and board artwork required to build the converter.


Update : Thanks to a link from Neil W2NDG to an EBay sale I’ve been able to track down a pre-assembled HF up-converter on this page : New HF Converter Kit for the SDR Fun Cube Dongle The price seems to be 45 euros, or about $55 US.

I’ve had a lot of fun using the $20 SDR to listen to AM aircraft traffic, local repeaters, emergency services and amazingly good quality broadcast FM stereo programming. Its easy to see, with an SDR, just how wide a radio broadcaster is transmitting and move your filter bandwidth to match.

Hopefully this is just the beginning of inexpensive SDR hardware that the radio community can re-purpose and re-engineer. 

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