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Australian TV Tuner Offers 4 RTLSDR Tuners in One Internal Card
Over at RTL-SDR.com is a report of a fascinating development with the DigitalNow Quad DVB-T Receiver, apparently well suited to working as a very powerful multi-SDR solution.
I just wanted to let you guys know that the Digital Now Quad DVB-T Receiver (http://digitalnow.com.au/product_pages/Quad.html) works. It’s a PCI-e card with 4 tuners on it, linked up internally via USB. This has pleased me no-end – I might finally be able to get DAB+ working on my media centre!
I had to add the following line to librtlsdr.c
{ 0×0413, 0×6680, “QuadDVBT” }
I wouldn’t be surprised if this patch makes its way onto the slightly more user-friendly Windows pre-compiled drivers before too long. If you live in Australia, or don’t mind paying for shipping, you could have one for AU $179, with the Australian Dollar roughly at parity to the U.S. version. For $45 per tuner it’s a great looking integrated solution and is much more elegant than a USB hub and a stack of dedicated dongles. Looks like this one has a PAL connector.
Kegerator with Arduino-Based Beer Level Indicators
Andrew of Andrew’s Telephony/IT Blog came up with a fascinating project where he built a 3-tap kegerator out of a 7 cu. ft. GE chest freezer, an Arduino, and a variety of flow rate sensors to display exactly how much beer is left in any keg at a given time. It’s a very in-depth project, and it looks like it’s turned out both awesome and functional.
Go check it out!
Bad Capacitors Strike Again
I’m working on another Bose 901 Series 1 equalizer. It looks to be the same manufacturing run as the first one I wrote up last July, uses the same components, and those components look like they’ve had the same failure mode.
The rather dubious EM-branded capacitors have the same discoloration on the top middle I saw on the other Bose, as well as on the Farnsworth K-262P which had been repaired once before. I’m curious what the physical failure is, as the discoloration would suggest to me overheating, but that seems very unlikely in this circuit and application. Newly manufactured replacements aren’t likely to have this problem as the film technology has improved significantly in the last 40 years.
Hardware Pong Mod Makes Smaller Paddles
While browsing Hack-a-Day, I ran into an awesome hack for the original Pong game. One enterprising hobbyist built his own Pong from scratch following the schematics. It’s a big job but it’s manageable since it’s all discrete logic. I’ve just been re-watching That ’70s Show and in one episode Red and Kelso modify the Pong to make smaller paddles. I was shocked to learn this is both feasible, and even somewhat believable for them to have done in their garage with a screwdriver and a soldering iron.
A neat discovery to add more storage to a laptop.
I acquired a few HP ProBook 4415s laptops which had been scrapped, and decided to rebuild them into working machines. I’ve been needing a new personal/media laptop for a bit, and these are capable little machines with an HDMI output for connecting to my home theatre system.
While cruising eBay for missing trim panels I stumbled across something I’d never seen before – an extremely easy way to add a second hard drive or SSD to any laptop currently fitted with an optical drive: optical drive adapter caddies!
Remove your existing CD drive, drop your new hard drive into this caddy and slide it in where the optical drive used to go. It’s that easy – expanded capacity. Laptop surgery isn’t always for the faint of heart, and this also offers a good way for a road warrior to expand capacity or add a backup drive. Since optical media is really falling by the wayside, unless you watch a lot of disc-based movies on your laptop it’s unlikely you’d miss the optical drive.
I searched around some more, and it looks like these adapters are available for most relatively recent and popular laptop models. I’ll probably buy one for the next time one of my laptop hard drives needs to be upgraded.
Shortwave Radio Reception with the RTL-SDR Dongle
I bought and did a quick setup on my RTLSDR dongle using SDR# a few weeks ago, where I used it to listen to FM radio stations around my area and a few public safety frequencies. That’s all well and good, but I’m much more interested in shortwave listening – when the weather is good, I can pick up a fair number of stations on my Hallicrafters receiver and there’s even more out there that I can’t tune in with that old equipment.
The RTLSDR tunes from around 64MHz up through around 1800MHz, but shortwave frequencies are much lower – only up to around 30MHz. Using an RF mixer, it’s possible to shift the signal into the RTL’s tuning range. Portuguese designer CT1FFU developed a mixing upconverter which adds 106.25MHz to the incoming signals, shifting them up into the correct receiving range and filtering out signals about 50MHz to prevent interference. His version comes as a kit which requires surface-mount soldering, but German retailer Wimo offers mostly-assembled versions of the kit which only need the antenna terminals and power connector soldered.
Finding those adapters was a bit challenging – I have a helical antenna which terminates in that alligator clip, feeding into a coax break-out, with an SMA-Coax converter. On the other end is an SMA gender-changer and an SMA to MCX adapter. Ultimately I ordered them from eBay and they work as intended. The USB port provides the +5V power supply for the converter’s operation but otherwise isn’t connected.
Reception is acceptable. With the aid of the SDR software, I can see where signals are more readily, but issues with my antenna setup and local interference are keeping it from performing as well as the Hallicrafters. I can identify human voices on more stations, but it seems there are fewer I can actually listen to with this equipment. I’ll probably try building a tuned loop antenna similar to this one, and see what I can do with better noise rejection and directionality. I might also add a low noise amplifier after whichever better antenna I end up using.
If anyone has a favorite, easy-to-build loop antenna for 10-160M I’d love to hear about it.
World’s Most Complicated FM Radio [RTL-SDR]
After many hours of trial and error, I’ve turned my computer into one of the most complicated FM radios imaginable – and it’s nearly free. With just a cheap ($20) TV tuner based on the Realtek RTL2383 chipset and some free software for Windows/Linux/Mac, you can have your own Software Defined Radio receiver that can decode nearly every type of transmission imaginable from 50MHz-1800MHz, with the right antennas.
I’m using it to listen to my local FM radio station, KNDD 107.7 The End.
In this graph, you can clearly see the HD Radio sidebands (HD1 and HD2) as well as the main carrier. It’s present in both the waterfall, and the waveform. The sidebands are digitally encoded on either side of the analog carrier on the center frequency. This station is centered on 98.9 MHz (KLCK-FM/ HD1/ HD2 “The Click”) and plays a a mix of Top 40 and Alternative/Rock.
I’ll be posting more about RTLSDR in the future, including a guide on getting set up with RTL-SDR. In the meantime, back to experimenting!
Free Mapping and Tracking for Android [My Tracks]
Beautiful weather has finally arrived in the Pacific Northwest and I’ve been taking advantage of it as often as I have time. One thing about living where it’s grey and rainy for so much of the year, it really almost forces me to go outside and be active when it’s nice out. I’ve been riding my bike around, and wanted an easy way to keep track of my stats like speed, distance, which trails I was riding and altitude. Turns out there’s a free and easy way that integrates well with Android: Google My Tracks
My Tracks uses your phone’s GPS to record your position and plots it on a map, where you can upload it to Google Maps or export your track as an industry-standard KML file for analysis in another application.
You get a print out of your statistics at the end, and can optionally insert markers with interval statistics on a custom schedule. The app has been around for a few years but has become much easier to use lately. My last ride was 12.9 miles long at an average moving speed of 7.5 miles per hour:
Total distance: 20.78 km (12.9 mi)
Total time: 2:56:35
Moving time: 1:43:56
Average speed: 7.06 km/h (4.4 mi/h)
Average moving speed: 11.99 km/h (7.5 mi/h)
Max speed: 34.62 km/h (21.5 mi/h)
Average pace: 8.50 min/km (13.7 min/mi)
Average moving pace: 5.00 min/km (8.1 min/mi)
Min pace: 1.73 min/km (2.8 min/mi)
Max elevation: 179 m (589 ft)
Min elevation: 93 m (304 ft)
Elevation gain: 984 m (3228 ft)
Max grade: 12 %
Min grade: -17 %
Recorded: 5/26/2012 12:21 PM
The application also integrates with a Polar brand heart rate monitor over Bluetooth to record heart rate statistics along with the other information. I don’t have that option yet, but plan to add it fairly soon. This is a great free app that everyone should know about. It’s not just useful for mapping a trail, either – you could use it to mark where you left your car, see where you’ve been in an amusement park, or record the location of interesting landmarks you see while wandering around the city. Check it out!
The Canadians Invade: Highway Advisory Radio Interference in Seattle from Saskatchewan (CBK)
Flammable cargo was prohibited under the Washington State Convention Center on I-5 last weekend according to the large Smarter Highways signs along SR-520 in Washington, as there’s some sort of maintenance happening. There’s a highway advisory radio station on 530 AM and I tried to tune in to see what it had to say about it.
.jpg/200px-Thruway_Info_(1).jpg "Highway Advisory Radio")
As it turns out, the station was completely unintelligible due to bad interference. I could just barely make out the fact it was a highway message, but not the contents, in my car radio. With my GE F-135 radio, I couldn’t pick up either so it was time to break out the big guns, my Hallicrafters 8R40 attached to an 85′ helical antenna and managed to bring it in quite clearly.
The station beat very closely with 530AM in my receiver making a very obvious beat note, but they identified themselves as a CBC station a couple of times and were playing PRI’s The World. Some digging about where CBC stations are located, and I was able to identify the interfering station as CBK AM 540, a 50 kW clear channel station broadcasting out of Watrous, Saskatchewan - about 1100 miles away!
Clear channel stations running that high power at night can definitely propagate that far – or further, an experimental station in the 1930 was able to cover the entire western hemisphere and was known to take requests from as far away as Buckingham Palace. There’s nothing that can be done in this case as the interference is coming from a licensed user in another country and happened due to natural atmospheric conditions. I guess the right thing to do is just hope there’s no important traffic information being broadcast during the nighttime DX window.
CBK-AM is the furthest distance AM broadcast station I’ve yet received. I should probably keep a map of some kind.
Spotty GPS is Interesting
I’ve just returned from Whistler, BC for the season-ending weekend on the downhill mountain bike park, and wanted to track my progress using Google’s free My Tracks application which records your GPS position on the map for review later. I’ve used it successfully many times to keep track of my biking stats and see my trail runs, but it seems to have had some trouble up in the mountains of Canada.
At the very top are the markers indicating where I actually was. All the other pins were recorded at the same time, but seem to have no particular relationship to anywhere I was at any time during the trip. Since Canadians have almost third world Internet, I kept data off to avoid $10/MB roaming charges. Android GPS devices receive some amount of GPS assistance from towers setting up, so this lack of a cell connection may have resulted in the unit using bad GPS data. Or, it was just a weird bug – it’s impossible to tell. The weather was perfectly clear and we were on exposed mountain faces, so there shouldn’t have been an interference or coverage issue.
I was quite impressed with the top speed I managed on my bike of 496.0 MPH, and a min-max elevation change greater than the Space Shuttle’s orbit.
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