Friday, May 31, 2013

First test with cheap $5 AD9850 DDS board and Arduino

News of the availability of very low cost AD9850 DDS boards from China via eBay has swept the home brew radio community in recent weeks. These chips alone were quite expensive and the surface mount soldering was a challenge.

Now the chip, mounted on a nice carrier board, with 125MHz crystal, is available for a very reasonable price. Here's mine sweeping a few frequencies near 10MHz:


The Arduino code I used is from NR80 which in turn is based on code from Andrew Smallbone.

I simply powered mine from the 5V on the Arduino and it seems to work just fine.

Our plan is to make a little crystal replacement board for QRP purposes with a multi-position switch to select the frequency.

Purchased a blank Arduino shield board and have now mounted the DDS board nicely for future software development.


Sunday, May 26, 2013

Melbourne meetup with homebrew legend VK3YE

While in Melbourne for the fabulous "One More Thing" conference this weekend I had the pleasure of breakfast with ham radio home brew legend Peter Parker, VK3YE.

Gracious with his time, Peter brought along a number of recent projects including the famous "Beach 40" and a new fixed frequency SSB transceiver he dubbed the "knobless wonder" that has been recently completed.

Peter works in the public transport industry, (may I say how impressed I am with the Melbourne MyKi system), his knowledge of the network is impressive.

We talked of many things including cross-overs between amateur radio and public transport including Tony Sanderson, VK3AML, and the videos made by Dave VK3ASE of the Glenhuntly station crossing.

Peter is a self-taught radio electronics engineer who is performing a great service to all would-be home brew designers.

Here's some previews of the "Knobless Wonder":


Nice crystal filter array there.


Here's the popular Beach 40:


Thanks Peter for your time and generousity. Keep up the great work!

Update

Thanks to Bill of Soldersmoke for the mention.

Good news: Peter has updated the Knobless Wonder circuit and published a video here:



The circuit is here.

Friday, May 24, 2013

A wonderful One more thing conference


Really enjoyed "One more thing" again this year in Melbourne and at the pub afterwards ran in to Luke Anear who pulled out a Google Glass device much to my amazement.

I put on the Google Glass headset and found the display incredibly clear. Despite the noisy pub environment, even with a band playing the speech recognition worked very well.

After returning to Sydney I introduced Luke to Marc Fennel who followed up with a great video story about Glass on SBS2's The Feed.

Wednesday, May 22, 2013

Looking forward to One More Thing...

On Friday I'm off to the "one more thing" iOS developer conference in Melbourne. Last year was great. At the time I was only a part time iOS developer, now it's 24/7.

Developing apps for smartphones, more than any other software I've worked on, is a team effort where programmers work closely with designers. I love the way we iterate and what is only learned by playing with the app as it comes together.

The phrase "one more thing" references something that Steve Jobs used to do sometimes at, what seemed like, the end of a keynote speech where he would reveal something amazing. Past "things" have been the MacBook Air, Apple TV, Powermac and Airport.

WWDC is a few weeks away and there is much discussion in my office about what Apple might announce to fill the product void that has opened up since the iPad Mini last year. We can be confident that pretty much all laptops will be refreshed with the new Intel Haswell chipsets, we can hope that a new MacPro line will begin and that HiDPI (Retina) screens will come to the desktop.

I think there are some important technology transitions taking place that Apple has chosen to wait for rather than bring out products that will be vastly superseded in a few months: Thunderbolt - which is jumping in bandwidth to 20Gbps, presumably enough for 4K video, plus the ability to put cards - such as video cards, in the monitor; Intel's new generation of CPUs that reportedly will use 1/5th of the power of the previous generation in laptops, and large high resolution displays which will have taken time to come down in price.

On the software side, I can't wait to see what's in MacOS X 10.9, Xcode, and of course iOS 7 under new management.

While it might be nostalgic to hear Tim Cook say "one more thing", perhaps it best left to a bunch of us in Melbourne this Friday.

Tuesday, May 21, 2013

MacOS X Calendar knows time zones!

Just discovered a great feature of Apple's Calendar application - you can add an appointment with a time in another time zone and it converts to local for you. Create a quick event with a time zone:



And it gets added to your calendar in local time:


I can't tell you how many times I've messed around figuring out when a keynote will be in local time.

Apple software often looks simple, but is really deep.

Saturday, May 18, 2013

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.




And here's reception from Colombia:



Here's my reception on Sunday night:



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?

Information about similar tests in the future can be found via the VOA Radiogram blog.

Monday, May 13, 2013

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...

Saturday, May 04, 2013

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.