Radio Australia Digital Test

In this age of information over the internet, the role of short wave broadcasting is being questioned. We thought that the internet would kill off Amateur Radio but instead low cost computers have led to an explosion of interest in digital modes over HF.

Countries that wish to prevent their citizens from reading news from external points of view are able to easily filter or even turn off the internet and while they can jam short wave radio, it turns out that digital modes can get through when voice would not.

VOA has been doing tests in recent months and tonight Radio Australia did their own test on 7.410 MHz at 6:30pm Australian Eastern Time and here in Sydney I received it perfectly.

I decoded with fldigi:

As you can see, decode is perfect.



I remember as a teenager decoding RTTY news broadcasts which used to be a regular feature of shortwave, perhaps it's time for a new era of digital news over short wave taking advantage of robust new modes and widely available decoding software?

Beaglebone black first impressions on MacOS

I'm a bit of a sucker for a cheap unix computer. In recent months I've been playing with Raspberry Pi devices but ran in to problems with audio over the USB. When the $60 Beaglebone black went on sale, I couldn't resist.

This board, which is about the size of an Altoids tin, features:

• 1GHz ARM Cortex-A8 processor
• uHDMI video socket
• uSD card socket
• 2GB on-board storage all ready to boot
• 5V in socket
• 2 USB sockets
• Ethernet socket

To get started, I've done the following:

• Plug the board in to the USB port on my Mac using the supplied cable (no other power is needed for the board)
• A USB storage device mounts and all the documentation and drivers are available. Open START.htm to read the documentation.
• From the Drivers folder, there are two drivers, one for serial over USB and the other for a network connection over USB. I already have the serial FTDI driver so I installed the RNDIS driver (which seems to be an Android open source thing).
• Unmounted the BEAGLEBONE disk, unplugged it from USB.
• Re-plugged the USB and waited for the drive to mount.
• At this point I could ping 192.168.7.2 and load http://192.168.7.2
• In terminal ssh root@192.168.7.2 (hit return for password)
• Plugged the board into a hub on my network with an ethernet cable
• ifconfig shows that the board now has an IP address and can reach the internet
• opkg update
• opkg upgrade # this runs for some time (I left it over night)

It's marvellous that the board has enough storage on-board to boot up linux and there is a socket for extra storage. Angstrom linux is a mystery to me but I'm going to give it a go and maybe switch to something more familiar to me later if I hit a wall.

Later...

Hmm, I left the opkg upgrade running over night but in the morning I notice that it didn't complete correctly - looks like it lost network connection.


 * opkg_install_pkg: Failed to download perl-module-unicode-collate-locale-da. Perhaps you need to run 'opkg update'?
 * pkg_run_script: package "bonescript" postinst script returned status 1.
 * opkg_configure: bonescript.postinst returned 1.
root@beaglebone:~# reboot

It did not reboot. I've tried with the ethernet cable disconnected (a user reported this as a possible issue). I have to go to the office so will come back to this and report when I figure out how to re-flash.

Today, I picked up a 4GB uSD card and followed the instructions here to re-flash the built-in on-board flash and all is well.

MacOS

The provided instructions are rather focussed on Windows for imaging a uSD card for re-flashing but I was able to do it on MacOS as follows:

Use 'diskutil list' before and after inserting the card to figure out which /dev/diskX it is.


$ diskutil unmountDisk /dev/disk2
Unmount of all volumes on disk2 was successful
$ sudo dd if=BBB-eMMC-flasher-2013.05.08.img of=/dev/disk2
Password:
7143424+0 records in
7143424+0 records out
3657433088 bytes transferred in 12416.160438 secs (294570 bytes/sec)

It's rather slow, this took 3.5 hours.

I like the way the default linux registers the beaglebone on mDNS (bonjour) so I can find it on the network like this:

ssh root@beaglebone.local

Incidentally, these things really do fit in a lolly tin, here's mine in a "Fisherman's Friend" tin along side a Raspberry Pi.

Resources

There is a big list of projects.  Angstrom Linux has a marvellous list of pre-built packages. I notice that gnu-radio is there...

PA0RDT Mini-Whip E-Field antenna

A recent presentation at the WIANSW Home Brew group about receiving on the 630m band mentioned that a very small E-Field antenna works almost as well as a full size antenna at these very low frequencies.

I wrote off to Roelof Bakker and ordered his pre-built "Mini Whip" antenna (plus another for local ham James, VK2JN). The circuit is very simple and Roelof has published it but I decided to go with his selected parts and weather proof construction on this occasion.

A few weeks later and the antennas arrived. Construction of the external probe part and also the power injection box are both very solid. BNC connectors are used everywhere.

The antenna came with a "9V" out 230V plug pack with european round prongs.

This is an active antenna with a small area of copper for receiving that should be mounted a bit above roof line on an insulating pole. Power is sent up the co-ax and is injected with a little box in the shack.

At first I had trouble - it turned out that there is water in my co-ax and the 15V inserted in the shack was just 3V at the antenna! (Amazingly I've been having WSPR contacts on 20m for months with this arrangement).

I find that the PA0RDT Mini Whip works best at 40m and lower frequencies. It's not quite as good as a full size dipole but has the benefit of being broad band. Here's a video of the parts and a bit of local reception on 40m.


If you don't have room for a full size antenna and are interested in lower bands I can recommend one of these active antennas.

Here's how I receive Ross, VK1UN who is about 750km away on 80m WSPR:

Given the tiny size of this antenna, it's amazing to receive anything at all on 80m in a suburban house.

Wearable computers for health

Inspired by colleague Jason Crane, I've started wearing a little clip-on bluetooth connected dongle from Fitbit.

The device itself is quite small and I barely notice it clipped to my shirt - how long until it goes through the washing machine?

It records how many steps I walk each day plus how many floors up climbed. If you wear it at night (they have a wrist strap that makes it comfortable) it records how "efficiently" I sleep.

The device stores data until synced over bluetooth 4 (very low power) using an app - I'm using the iPhone app which is good but crashes rather a lot at the time of writing.

The app uploads the recorded activity to a web site where it can be graphed in even more ways than in the iPhone app, plus you can friend people and enter in to a bit of friendly competition.

The scary thing is how much of my day is spent totally idle sitting in a chair staring at a computer screen.

I am over weight although thankfully not "obese" at this stage. Wearing the tracker does motivate me to climb the stairs where possible and walk to the shops on the weekends.

Bluetooth 4 is a good technology. The device lasts all week even though it's listening for a connection from the phone app at all times.

This week I purchased the Fitbit scales. They connect to the home Wifi network and by simply standing on them it measures my weight and uploads it to the site. The most impressive bit (for me) was how it was configured and given the details of my Wifi network by running an app on my computer. I'm not quite sure how this was achieved as clearly scales don't have much of an input device.

Of course Fitbit isn't the only game in town, there's Nike, Jawbone, Basis, Striiv, Larklife and many others.

All this current interest in wearable computing, like Google Glass and the rumoured Apple watch, are good things if they help us to avoid turning into the blobs like in the Pixar Wall-E movie. Computers have freed us from physical activity, now hopefully they can help us stay active enough to live.

WSPR Watch for iPhone updated

I'm pleased to announce that a new version of the iPhone App "WSPR Watch" is now available in the App store.

New features are:

• Sort spots by Time, distance, SNR and Km/W
• Show only recent spots from 2 hours, 1 hour, 30 mins or 15 mins
• 600m band

Plus there's some cosmetic and operational improvements. WSPR Watch is free and pulls its data from the old database page of WSPRnet.org (thanks to those folks!).

Thanks to Will and Ross for suggestions and testing.

iOS seems to download files over Wifi 3.5x slower than Android

I hope I'm mistaken about this but my experiments seem to suggest that iOS downloads large files significantly slower than an Android device on the same Wifi network.

For the test I download a 70MB test jpeg file in the Chrome browser on both an iPad Mini running 6.1.3 and a Nexus 7 running 4.2.2. The Wifi network is an Apple Airport Express running 7.6.3.


Android downloads the file in 91 seconds,  iOS takes 314 seconds.

I forgot to show it in this video, but the Android version is really there at full resolution if you tap on it.

I've repeated this test using Safari on iOS and it's the same so I think it's something to do with Wifi or the TCP stack.

Has anyone else noticed this?

Fibre to the premises or to the node?

The complex and expensive national infrastructure project to create a National Broadband Network in Australia is underway. Not surprisingly it is taking longer and costing more than initially hoped and now the opposition is proposing to cut costs by cutting an important corner.

Rather than doing the hard part, taking optical fibre to each home, they propose to run fibre to nodes and re-use existing copper to get to houses. This approach will deliver an improved internet at a lower cost but both only in the short term.

To me, it's like building a highway system with dirt road off-ramps.

Looking back at the history of internet speeds it's clear that speeds grow logarithmically and there is not sign that this will slow or stop. It's inevitable that the last mile of copper will be a choke point and a future government will have to come back and finish the job.

ABC Radio National Breakfast aired interviews with me and finance correspondent Sheryle Bagwell where we looked, in turn, at the technical and financial analysis of the alternate plans.

As I said in the interview, this is not really about politics, it's about the relentless march of technology.

630m operation and Class E at Home Brew Group

Two excellent talks at the ARNSW Home Brew Group meeting today. The main talk was by Nick, VK2DX, who talked about getting on the 630 meter band (472-479kHz).

Nick talked about his long history of listening to interesting things he's seen on the waterfall including over the horizon radar and non directional beacons. Getting on air with such a low frequency is a challenge anywhere but particularly in a dense metropolitan area.

The challenge is the antenna and matching to it. Ironically, while the best antenna is something huge like a beverage antenna, the second best is a tiny E-Field probe like the PA0RDT mini whips.

Nick uses a vertical antenna that is resonant on 80m but with the addition of a huge 600uH loading coil (60 turns on a bucket), a home built variometer and an impudence matching transformer he's getting to QLD, SA and NZ using the WSPR mode.

The supporting talk was my regular Mike, VK2BMR who talked about his experiments making a tesla generator operating in class E.

Mike is getting great efficiency, which is the great benefit of Class E, and his biggest challenge seems to have been to build attenuators and dummy loads that can handle the power he's generating. I was hoping for a demonstration with a bit of indoor lightning but maybe next time.

As always, thanks to the organisers for another great day at Dural.