Thursday, August 28, 2008

On the bench - double sideband exciter

I recently constructed the Bitx20 kit and so far, despite willing help from the Yahoo! group, I've failed to get it working.

dsb.jpgIt's hard debugging a densly packed circuit board, so I decided to build a duplicate transmitter chain ugly style as you see here.

This is most instructive for me. It's laid out pretty much as the circuit diagram and I can easily measure at any point.

The Bitx20 is a marvellous design and there are lots of handy guides to construction and tuning around but, for me, what's missing is a circuit diagram with both DC and AC waveforms at every stage in both transmit and receive mode.

Anyhow, it's all for the best. I've often built a kit that's just worked first go and really it doesn't teach me anything. I'm hoping that after getting something similar going in this way I'll be able to go back and compare with the PCB version and figure out what's wrong.

Sunday, August 24, 2008

Blue mountains amateur radio Winterfest

Spent a very pleasant morning at the Blue Mountains Radio Club Winterfest.


Great weather (I was expecting to freeze) and a great turnout.


Lots of junk to look at and try not to buy (even at very good prices).


Lots of vendors there too, who seemed to be doing pretty well. Great to chat to a few folks and share a sausage sandwich.


In the end all I bought was a couple of books but did lots of tire kicking. I'll certainly be back next year. Congratulations and thanks to the organisers. Great to see Tim Tuck, VK2XT, who I've known for many years as a co-worker and had no idea he was a ham!

Chinese Embassy site links to a Trojan page

Picture 5.pngMy daughter noticed this, thankfully we are running MacOS X here.. If you visit the web site of the "Embassy of the People's Republic of China in Australia" there is a "Useful Links" item to "China Association for Preservation and Development of Tibetan Culture", sounds very positive.

However, if you're in Firefox, which checks sites with Google to see if they are known for bad things, you see this:

Picture 6.png

If you click through, Google provides the following advisory:

"Of the 1 pages we tested on the site over the past 90 days, 1 page(s) resulted in malicious software being downloaded and installed without user consent. The last time Google visited this site was on 08/22/2008, and the last time suspicious content was found on this site was on 08/22/2008.

Malicious software includes 5 trojan(s). Successful infection resulted in an average of 15 new processes on the target machine.

Malicious software is hosted on 10 domain(s), including..."

(I won't link to any of the bad domains here though).

So, either the site controllers want to install a trojan on the computer of people interested in Tibetan culture preservation or the site has been compromised by someone without their knowledge.


I discussed this on ABC Radio National this morning.

Tuesday, August 19, 2008

Where are all the induction cookers?

induction.jpgApart from a rice cooker, the other gadget we picked up during our stay in Hong Kong is an induction cooker.

You don't see them in stores in Australia for some reason.

Now that the big element on our electric stove top has died, again, I've brought it out of retirement.

Induction cookers work by inducing an electric current in the metal base of the pot that's sitting on it. This means that the heat generated in that metal is transmitted directly to the food being cooked rather than being partially lost in the kitchen. As you can see from the picture, the device itself remains cool.

In use, the induction cooker is very responsive and includes some advanced features for running a program of temperatures over time, but we never use those.

I read on Wikipedia that induction cookers are twice as efficient as electric elements or gas cookers, [although citations are needed].

The only downside is that it only works on pots with a thick, non-laminated base. If the pot isn't suitable the cooker sits and blinks until it feels something it can induce.

Works nicely with my coffee maker:


I wonder why they aren't in the stores here?

Three ideas for the Olympics

Medal auction

It's reported that each Olympic gold medal in the last 20 years has cost Australian tax payers about 40 million dollars. I hear that the UK is now reaping the rewards of extra investment. Why not save a lot of bother and just auction the medals off the highest bidder?

Anything goes

Many events in the past have been won with the aid of performance enhancing drugs, advanced computer modelled training, or special suits or shoes. Complex rules currently control which techniques are legal and which are illegal. No doubt new drugs, for example, are being used this year that won't be detected until after the event.

Why not remove all the rules and let the teams pull out all the stops. The most performance enhanced, steroid soaked, android, with atomic shoes would win - if they don't have a heart attack first.

True competition

If the medal tally is really a measure of the performance of the people of a nation, perhaps no preparation should be allowed. In the days leading up to the Olympics, representatives should be picked at random from each country. These true representatives of the country would compete with only a brief explanation of the event before it starts.

Oh, and praying should be banned as presumably that is performance enhancing.

Then we'd have a real Olympics.

Sunday, August 17, 2008

HF antenna height improvements

antenna.jpgDid some work on my 20m (14Mhz) dipole antenna and managed to raise it about another meter above the (2nd story) roof.

The difference is clearly noticeable in reception, the background noise level is reduced - meaning I can hear stations I previously couldn't and early reports of my transmission are that my signal is perhaps 1 S point higher. (I'm a bit wary of that observation as HF radio is extremely variable).

Note that 1 S point is four times the power.

I shouldn't be surprised that the extra hight helps, there's lots of research on this, but I didn't expect it to be so clear.

This new support is the pole from a free standing netball hoop, then an iron pole, and finally an aluminium pole. Up the top is a pulley so I can easily raise and lower the dipole balun with ease.

Anyhow, I'm happily back on 20m PSK31, chatting near and far on 25W.

Incidentally, I'm tired of getting RST reports of "599" all the time. Firstly on PSK31 it's pretty meaningless (a better measure is IMD dB), and secondly how on earth can I be S9 all over the place?

Saturday, August 16, 2008

Enhancing video by using still images of the scene

I don't normally do this but there is some amazing work being done at the University of Washington.

Using Photographs to Enhance Videos of a Static Scene from pro on Vimeo.

Spotted on CrunchGear.

I was impressed by smile and blink detection in my little point n shoot. That's nothing compared to what these folks are doing.

They take some still images of a scene and then a video. The still images, including HDR images, can be used to enhance the quality of the video scene. There is also a brilliant image stabalisation system that works after shooting.

My only question is just how much of this requires operator skill and how much is automatic?

Friday, August 15, 2008

Stop printing phone books 2 - You can't opt out!

PhoneBook.jpgIt's a year since I posted about how I thought printing phone books and distributing them was a waste in the days of the on-line phone directory.

As I researched I discovered that you can opt out by contacting Sensis on 1800 810 211 and opting out. So I did opt out, but here we are, a year later and they delivered the White pages again.

Who's paying for these unwanted giant print runs? What is the impact on the environment? Why is it apparently impossible to opt out?

According to the Australian Bureau of Statistics (2006-07), the internet is widely available in households, 31% had dial-up access and 68% had broadband. (Does that make 99% or do some households have both?).

In 2006-07 5.1 million households have home internet access, (it went up from 2.3 million in that period so no doubt it's even higher now).

Sensis "Green Office" program is not working. I've contacted them about this and received an acknowledgement but so far no actual reply.

Thursday, August 14, 2008

iTunes movie rentals in Australia - at last!

So happy to finally see iTunes movie rentals in Australia. I immediately jumped in and rented a movie through iTunes for AU$3.99.

Picture 1.png

It took 65 minutes to download, then I had to transfer it to the Apple TV.

On Apple TV I chose the movie and pressed play, it went away and authorised, then... a black screen and no sound. The movie was playing, I could pause and play and see chapters. Hmm.

In the end I did a reset settings and it played.

Quality is ok, not HD but no annoying artefacts in the one I'm watching now. $4 is a reasonable deal (plus my internet bandwidth of course). The main problem is the small range (700 by some reports), compared to my current provider QuickFlix with 32,000.

Some movies are only available for sale which seems weird.

Once a movie is downloaded you have 30 days to start watching, once you start watching you have 24 hours to view it (which didn't impress me when I had a blank screen).

Tuesday, August 12, 2008

Alien DAC + Chu Moi = Headphone bliss in a box

Regular listeners will know that I'm always searching for high quality headphone audio. In the past I've built a CMoy amplifier and an Alien DAC USB audio device.

Yeah it's a bit rough but it fits nicely under my computer monitor.

box finished.jpg

It was time to put them together in one box and dispense with the excess wires.

I started with some 0.5mm sheet aluminium:

box sheet.jpg

Marked out to make a box 50mm x 100mm x 100mm. It was cut with tin snips and simply bent over the edge of a bench by hand. The sides were joined using angle aluminium stock drilled 4mm and tapped.

box filled.jpg

For now I'm powering the amp on 12V supplied by an external AA battery pack with 8 cells. Can't wait for GreenPlug to arrive..

I thought I was doing the right thing choosing metric screws but even in a metric country the range is severely limited and I've had to saw off the rather long machine screws I got.

This is not a bad way to make a small project box. Even 0.5mm aluminium feels pretty rigid with the help of the angle stock.

Sounds great with my HD560s by the way.

Amazing first iPhone bill from Vodafone Australia

bill.pngI've just received my first bill for iPhone 3G from Vodafone Australia.

As you can see it's rather excessive. I was unsure about what my data usage would be so I initially signed up on a business capped plan that would give me 500Mb per month.

There's a number of anomalies here, according to the online usage Vodafone say I'm entitled to 500Mb and that I've used 12.11Mb so far with 487.89Mb remaining:


On the phone it reports a total of 98.2Mb:


From the 15 page bill I've been sent, it looks like their billing system is continuing the old practice of charging in units of 5 minutes for any internet traffic:

Picture 2.png

Certainly not the way it's expressed in the plan agreement.

Presumably I'm not alone but I'll hop on the phone to them today and try to sort it out. Wow, that iPhone sure does increase data usage.


Did anyone else experience this?

Update 1

Lara seems to be having hickups this morning.. Anyhow, it turns out that when I purchased the iPhone, which can only be done on an iPhone plan, it was not immediately put on the iPhone plan but rather stayed on my old (high data cost) plan until the end of my billing cycle.

Gavin at Vodafone politely told me that nothing could be done and that I should talk to the store where the phone was purchased to take it up with them.

I've now spoken with Reggie at the dealer and he was sympathetic and said he'd call Retail Support about the issue and call me back...

Update 2

Reggie called back to let me know that the problem has been escalated to the "iPhone Taskforce" who are working through these issues. They will call me in about two weeks and I shouldn't worry about the bill in the mean time.

Update 3

Thanks to "tester" for the link to a thread on Whirlpool where "Kirsty from Vodafone" says:

"Hi guys,

Vodafone addressed the issue some of our customers have experienced with purchasing their iPhone cap plans midway through their normal billing cycle in a press release dated 25/07/2008. In the past, plans were only changed on the bill cycle date. We acknowledge that this is not practical for customers signing up for the new iPhone 3G caps. From 23 July, anyone signing up for a iPhone 3G cap will immediately be able to enjoy the benefits of their new plan, rather than waiting for their bill cycle date.

Vodafone is reviewing the excess data usage of it's customers who signed up to an iPhone 3G cap mid way through their bill cycle, and will waive any charges that would not have been incurred if the customer had been able to use their iPhone 3G cap, with its voice and data allowance, from the outset."

This is certainly good to hear.

Update 4


I'm pleased to report that my bill has been re-issued and I've received a credit for $1,500 on that bill.

Monday, August 11, 2008

Working with Django 1.0 and Google App Engine

logo160.pngI've taken some time off regular work to build, a site where you can find and review your local coffee shops.

To build this new site, I decided to use Google App Engine and Django.

Right now, Django is racing towards the version 1.0 release and it's changing fast. Unfortunately, due to some constraints in the runtime and the fact that you have to use Google's Database, it's not all smooth sailing.

Most things are working quite well, and the site is very responsive (certainly to django hosting I've tried elsewhere), but I've run into some roadblocks when I come to upload image files.

On App Engine you can only run pure python code, so using the latest Django I see log entries like this:

Could not import "fcntl": Disallowed C-extension or built-in module

More seriously, there is no local file system, so when I try to upload an image file, it fails with:

NotImplementedError: This class/method is not available.

When django tries to get a temporary file like this:

self._file = tempfile.NamedTemporaryFile(suffix='.upload')

Which is fair enough.

Anyhow, it's early days and there's lots of other people playing with this technology. Certainly it's a great deal from Google and I'm totally excited about the state of Django. I'm in geek heaven.

Sunday, August 10, 2008

Back on 20m, doing PSK31 and Bitx20

Picture 2.pngMy primary antenna for the past few months has been an 80m dipole. It works pretty well and I hear lots of regular groups chatting but I really miss my PSK31 contacts.

There is a digital mode range on 80m (3.620 - 3.640) and I've been calling CQ there for some time but have only had one PSK31 contact on 80m and that was a conversation I stumbled across on 3.66Mhz.

The other reason to abandon 80m for now is that I've just constructed a bitx20 transceiver and am trying to get it going.

As you can see from the waterfall on the right, there's lots of PSK31 activity on 20m and I'm seeing US stations pretty well here at 3 in the afternoon.

Saturday, August 09, 2008

Apple store opens at Chatswood

GeniusBar.jpgDropped in to the new Apple store at Chatswood Chase this afternoon and ran in to well known blogger Ben and his wife (trying to get his hair cut).

On the way there I walked passed the excellent Maccentric store that has taken care of us so well in Chatswood for many years. Maccentric has a 10% off store wide sale but I must report that it was looking pretty empty.

The new Apple store, even at 3pm in the afternoon was extremely busy. Several of the staff have been imported from the US, presumably to kick things off on the right foot.

It must be tough for an existing store when your supplier opens up within a block of you. I hope they got plenty of notice and perhaps some help in moving if they so choose.

The guy that served me had a badge saying "Ask me about MobileMe" so I did.. he apologised and said that while there were still some bugs, the major outages hopefully are over. I asked about my problems with the backup phase of my iPhone sync and he wasn't able to help.

The store looks great, I'm sure they'll do well, and it seemed like a good size for the number of products.

Wednesday, August 06, 2008

iPhone 2.0.1 still not quite right yet, 2.0.2 better

Like everyone I had a few annoying issues with the original software but I still feel it's the best phone/pocket internet device, I've ever used.

One of the most annoying little issues I've had is that syncing the phone would hang during the phone backup. Once I thought it was going to finish without me cancelling but then a call came in.

My update to 2.0.1 went smoothly and during my first sync I hoped the problem would be gone but no. Amusingly the log says:

not the droid.png

Backups still don't complete so I've done this:

defaults write DeviceBackupsDisabled -bool true

Anyhow, my problems aren't nearly as annoying as Ben's so I count myself lucky.

The phone does seem smoother with 2.0.1, the annoying pauses have gone away and I think the 3G switching problem I had might have improved a bit.

Update 2.0.2

After a day with 2.0.2, I'm pleased to report that it drops back to 2G in my bad 3G signal environment much more smoothly than before.

It still won't backup my phone, so I've disabled that.

The Console log says:

20/08/08 10:40:13 AM [0x0-0x27027][365] MobileDevice: receive_message: Could not receive size of message: 0 Unknown error: 0
20/08/08 10:40:13 AM [0x0-0x27027][365] MobileDevice: _read_callback: Could not receive message
20/08/08 10:40:13 AM [0x0-0x27027][365] MobileDevice: send_message: Could not send message size: Bad file descriptor
20/08/08 10:40:40 AM [0x0-0x27027][365] Created child to sync device with pid 738...

And it hangs at that point.

Jury duty - well worth while

I've just completed a short stint as a juror on a criminal trial here in NSW.

On several occasions in the past I've been called and have either got out of it or not been balloted. This time it was all go.

The case was a federal crime, importing drugs into the country. I think the jurors all felt deep sympathy for the defendant and the predicament he'd ended up in.

Out of this experience I have gained respect for the legal system, the police, barristers and most of all for the ability of 12 citizens, chosen at random, to work together to decide facts that will have a major impact on someone's life.

Parts of the process were a little tedious, sometimes gross, but always enlightening.

We've all seen way too much court room action on TV, it wasn't like that at all. We all took notes and back in the jury room it was a bit like a comprehension test where we gently formed a view on what we had seen and heard.

In the end we found the defendant guilty without too much deliberation, but as we said our farewells outside we all wondered what would become of this poor man.

Sunday, August 03, 2008

Building a BITX20 20m SSB transceiver

The current project on the bench is a single sideband transceiver for 14Mhz. It's a kit from Hendricks.


I'm following the instructions and testing as I go rather than one big "smoke" test at the end. So far receive/transmit switching works, the audio amplifier and mic pre-amp and mixer work. Very encouraging.

I first heard about this design on the Soldersmoke podcast. It's by Ashhar Farhan VU2ESE, his article is here.

There is much to commend this circuit, coming out of India it is designed to use low cost easily obtained components. Ashhar comments that if you can't get (or afford) torroid transformer cores, tap washers may be substituted.

amp.gifThe circuit is "bi-directional" in that it uses the narrow crystal filter for both receive and transmit and switches amplifier stages using diode switches. The amplifier stage is pretty much the same throughout so despite the switching it's pretty easy to see how it works.

The kit I'm constructing is revision 3 and has push pull IRF510s in the output so it should deliver about 10 watts which is quite substantial with a reasonable antenna on 20m.

I plan to build this into a box including the frequency counter from Doug N3ZI mentioned earlier.


Construction is going well although I found a few missing and substituted components in the kit.


I'm looking for a signal on 20m to use for receive alignment.