Posts Tagged ‘Hacking’

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

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. 

Something old, something new.

Something old …

As a young boy in Australia my two favorite hangouts were my grandfather’s shed or practically anywhere that electronics were sold. The two largest electronic component retailers in my home town were Tandy (Radio Shack) and Dick Smith Electronics. They both sold kits, tools, ‘100 in 1 Labs’ and other assorted gear but Dick Smith eventually became known as the experimenters store due to their greater range.

Original Radio Shack calculator
Tandy is now almost vanished after their aquisition by Woolworths (Despite also owning its competitor Dick Smith) and has converted or closed most of the locations. 
One of the things I have to remember Tandy by is a handy resistor color code calculator. It saw a lot of use in past years while I built kits and experimented but not so much nowdays.
This device also calculated inductor values when flipped over which was handy for some of the older equipment I came across.

If you would like to make one of these yourself then Adafruit Industries has created a PDF document you can print and cut out for create your own resistor value calculator.

The PDF file is available from Adafruit Industries or a copy is also here. Once you print it out, a little cutting and folding should produce something like the example of the right. The Adafruit design uses brass paper fasteners (remember those?) but any fastener could be used that would allow the wheel inside to rotate freely. It would be best to print on heavy card stock if you have the ability as it will give the calculator some strength.

Something new … 

If you happen to have one of those new fangled iDevices you can download Circuit Playground. It has a few more features than the old Radio Shack calculator and looks great on the iPad.

More features are being added but the list at the moment includes:

  • Decipher resistor & capacitor codes with ease
  • Calculate power, resistance, current, and voltage with the Ohm’s Law & Power Calc modules
  • Quickly convert between decimal, hexadecimal, binary or even ASCII characters
  • Calculate values for multiple resistors or capacitors in series & parallel configurations
  • Store, search, and view PDF datasheets
  • Access exclusive sneak peaks, deals & discounts at Adafruit Industries

You can download it from the iTunes Store or, if you have an Android, you can check out ElectroDroid for similar functionality.

As time goes on there are more and more useful utilities available for electronic experimenters on iOS and Android devices. Since more and more equipment today is becoming computerized do iOS and Android devices  represent the future of test equipment?

iMSO-104 iPad Oscilloscope

Ham Radio and Mesh Networks

Lately I’ve been fascinated by the capabilities of mesh networks. The ability to quickly create ad-hock computer networks could be an invaluable resource for amateur radio operators in general and particularly for emergency communications (EMCOM)

Linksys WRT54GL Router

The particular device and software I have been experimenting with is the Linksys WRT54G router and HSMM-MESH firmware from http://hsmm-mesh.org/.

Installing the HSMM-MESH firmware changes the way the Linksys router functions and allows it to automatically connect to other HSMM routers in a mesh network. No special configuration is required after setting your callsign. All TCP/IP configuration is pre-configured, even down to automatically assigning addresses to connecting clients.

Mesh Network Diagram

Mesh networks are highly fault tolerant. Every router in the network is aware of every other router and has the ability to move network packets through from one unit to another provided there is a link, or chain of linked routers, between them.
In the diagram to the right each router is represented by a numbered circle. If router number 6 were to fail then network packets that needed to move between router 1 and 7 would travel through routers 2 & 3 or 5 & 10 until 6 was repaired. All this happens automatically and quickly enough so that there is no disruption to the traffic.

Anything you can access on a normal computer network can be made to work on a mesh network. Some of the services that have been demonstrated include email, voice over IP (VOIP), video conferencing, file sharing, web servers & groupware applications.

With simple modified antennas the modest output power from the WRT54G (100 to 200mW) can be used to reach distances of many miles or tens of miles with directional antennas. Mounting the router on a mast in a sealed enclosure can reduce losses from long cable runs while running off 12V power makes them compatible with ham radio power sources including solar and wind power.

The example to the left is from NG5V located on hsmm-mesh.org and consists of an omni-directional external antenna and a lawn sprinkler controller box from a popular home improvement store.

Did you know that … Frequencies used by channels one through six of 802.11b and 802.11g fall within the 2.4 GHz amateur radio band. Licensed amateur radio operators may operate 802.11b/g devices under Part 97 of the FCC Rules and Regulations, allowing increased power output but not commercial content or encryption.

I hope to acquire a few more WRT54G routers and put together a mesh network in the Katy TX area as a resource for experimentation and education in an area not normally touched upon by regular amateur radio operators. Who knows what the future holds & it behooves us to investigate this technology and bend it to our own needs.

The Amateur is Progressive … He keeps his station abreast of science. It is well built and efficient. His operating practice is above reproach.

Jeri Ellsworth video “Secret to Learning Electronics – Fail and Fail Often”

I came across this video by Jeri Ellsworth via the Make blog and I was so impressed with the content I thought I would repost it.  Listen to what Jeri says, there is some great advice here.

Ottawa Mini Maker Faire 2010

Ottawa Mini Maker Faire logo

For readers local to my home area you may be interested in this exciting and free event in Ottawa this weekend. Full details can be found on the Artengine website. The essential details are:

Dates and times: Nov. 6th and Nov 7th, 12pm to 6pm.

Location: Arts Court 2 Daly Ave. Ottawa, ON K1N 6E2

If you are not sure what makers do or what goes on at a Maker Faire take a look at this video of the 2010 Kansas City Mini Maker Faire

Videos of Akihabara

Tokyo Hackerspace has recently released these videos of a tour of Akihabara in Tokyo and they have done a viral tour of some of the major hacker blogs like Make and Hackaday.  If you have not already seen them then they are worth the time watching as Akiba of Freaklabs gives a great tour of this part of Tokyo which is brimming with stores that sell tools, electronic components and everything else for the hobbyist, maker, hacker and engineer.

The full collection of 24 videos are on the Tokyo Hackerspace website.  The video recording was made in HD so if you have a good bandwidth connection try the 1080 HD version on full screen. Here are a couple of the videos that I found particularly interesting.  First an amateur radio store called ‘Rocket Radio’

This next video shows a collection of indoor stalls that sell a wide variety of hobbyist items.  The location reminded me of a British indoor market, but instead of clothes and food here you can buy radios and enclosures. A collection of ‘candy stores’ for hobbyists.

I had heard of Akihabara but was stunned watching these videos how many stores there are.  I am sure it is unique in the density of electronics and construction retailers.  I would be interested to hear from anyone if they know of a collection of electronic component stores similar to this elsewhere, particularly in North America.  No doubt there were smaller collections of shops like this after World War II when the surplus gear hit the high street.  I know in London, UK, Tottenham Court Road had a concentration of such stores and I remember my father taking the family there when we visited London in the 70′s when I was a kid.  I believe that Shudehill in Manchester, UK, also had electronic component stores around that time  (again I recall a visit with my father) but they had all gone except for a TV and Radio store in the 80′s when I was a student there.

Thanks to Akira of FreakLabs, Patrick of Work in Progress and Tokyo Hackerspace for bringing us these videos.


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