Monday, September 29, 2008

80m QRP Beacon on the air

After biting off more than I could chew a few times recently, I've successfully built a QRP (low power) beacon for 80m.

beacon.jpg


It's on air at the moment on 3.686Mhz sending a morse ident with my email address so I'm hoping to get a few signal reports.

I think it's putting out about 250mW.

There are some obvious faults, I can hear chirp, clicks and when it's off carrier from the oscillator leaks out to some extent.

The keyer is an Atmel AVR ATMega816 which is complete overkill in this case.

The circuit is very closely based on Alan VK2ZAY's design except that I didn't have any 2N7000s so I've used a single IRF510 with a bit of bias.

I used perforated board with just a copper spot under each hole and it went together rather well (for me).

beacon board.jpg


I don't speak morse yet, but here's what I'm sending:

morse.png


Anyhow, please tune in to 3.686Mhz and let me know if you can hear my slow morse.

Update

Hi Peter,

Read about your 80m QRP beacon mentioned on hamnews and had a listen.

It’s peaking about S5 in Canberra. I’m using a TS-480SAT with a 40/80m trapped dipole. Here is some of what I decoded using Ham Radio Deluxe DM780 software:

LE EK*E PM VK2TPM VK2TPM PLS EMAIL RPT PETER DOT WARKS AT OBOX COM THIS ISE A QRP BEANION TRANSMISSIOLE VK2TPM VK2TPM VK2TPM PLS EMAIL RPI PETER DOT MARKS AT POBOX COME THIS IS A QRP BEACON TRANSMISSION DE VK2TPM VK2TPM VK2TPM PLS EMAIL LPT PETER DOT MARKS AT POBOX CON THIS IS T *RP DEACON N E IS E UK2TPM VK2TPM VK2TPM PLS EMAIL RPT PETER DOT MARKS AT POBOX COM THIS IS A EQRP BEACON ARANSMISSIXD DE VK2TPM VK2TM VK2TPM PLS EMAIL RPT AIETER DOT MARKS AI POBOX /OM THIS IS A QRP BE P EHANSN ESSIO N DE VK2TPM I ERM VK2TPM PLS EMAI D RP E NETER DOT MARKS AT POB3X COM E I IS A QRP BEAON TRANSMISSION DE VK2TPM

As you can see I’m missing/badly reading some characters and have interference but the message is coming through, probably be better received by a human than a computer…but I’m no morse code expert…

Had QRM from SSB and another CW signal nearby by managed to filter most of it out.

Regards

Ian Sinclair VK1DI

Update 2

I'm taking it off air while.

Sunday, September 28, 2008

Valve technology needed for post nuclear sked

john.jpgThe NSW home brew "trash n treasure" meeting today at Dural was great thanks to the work of John Hale VK2ASU (left) and Stephen Lowing VK2BLQ (below).

Together they presented on the theory and practice of constructing using valve technology.

John handed around common valves including a tiny device and told the story of his first home made valve radio. The theory of how valves work, by using heat to emit electrons and then using charged grids to control their flow in the vacuum chamber is at once, both simple and sophisticated.

stephen.jpgStephen talked about where to pick up common valves even today and showed some of his past projects which are beautifully constructed.

The board he's holding here is a regenerative receiver that is powered by batteries including just 9V for the plate voltage.

It was pointed out the the electromagnetic pulse from a nuclear explosion (or even a devices specifically designed to generate an EMP) will kill most modern technology and if we want to have a chance to participate in the post apocalyptic radio skeds we'd better get on and build some valve equipment.

table.jpg


Luckily, the group that turned up managed to fit into the air-conditioned WIA hut today, but it's great news that the construction of a larger shed on the Dural block is finally going ahead.

DSC00901.jpg


I can still remember valve equipment (aside from that big tube at the front of televisions until recently), but my children have no idea about this technology.

minitiature.jpg


It won't be long until all living memory is gone.

Saturday, September 27, 2008

The best hi fi system

tognetti.jpgLast night we were fortunate to have a wonderful experience - we sat in on a bit of a rehearsal of the Australian Chamber Orchestra.

I was able to sit right in the middle with the orchestra very close and all around. The communication between the players and Richard Tognetti, all done with body language and eyes, is fascinating.

The most impressive thing for me was the quality of the sound. I listen to too much music through small computer speakers and headphones, but it's amazing what poor reproduction even good headphones produce compared to the real thing.

There is a richness of tone from a bow being drawn across a string, I think the cello in particular, that doesn't seem to come across in recordings.

I recall hi fi sales blurb that used to claim that certain systems were "just like having a symphony orchestra in your living room", the reply was always to ask if that was really desirable as they'd drink your house dry.

Wednesday, September 24, 2008

One tree dies, an antenna will live

tree.jpgToday is tree lopping day. We're getting rid of a pesky liquid amber and a pine tree. Both of these shade the garden.

The huge gum tree is staying but I noticed that the tree men climbed the gum to tie ropes to liquid amber branches to control their fall. I had a bright idea and have asked them to run a line for me over a very high branch in the gum tree. "No worries" they said.

This means I'll have a loop of venetian blind cord going right up that very tall gum tree which I can use to raise up awesome long wire antennas or support one end of an 80 dipole.

These tree lopping guys are both smart and fit, here's a time lapse video with one frame taken every sixty seconds.



The job's done and I can definitely recommend Aura Tree Services they were efficient and professional. Great blokes too.

We have a lot more sky now and I'm back on 80m with good reports.

When I mentioned I'd made a stop motion video they were very interested and I gave them a CD with the high quality video on it.

Update

The loop of venetian cord is in place so I can easily hoist things up 10m or so.

I first tried an end fed long wire but the noise on 80m was bad, so I've put up my old 40/80m trap dipole with one end up in the gum tree and the other end over the house to a tree in the street.

The new antenna is working really well. The extra height has further reduced noise, I've had some PSK31 contacts on 40m (7.040) and am hearing some magnificent signals on 80m.

Monday, September 22, 2008

BaristaReview site build

logo160.pngI'm pleased to report that I've built a real application in Django on Google App Engine.

BaristaReview is a site that I've always wanted, specifically to let me find (and review) coffee shops near where I am.

Although it's loaded with Australian cafes to start with, it's not localised except for it being in English.

The great benefit to me of Google App Engine is the low cost of entry and ultimate ability to scale right up to whatever success we might achieve without having to supply any hardware ourselves.

It's been a fascinating little project with lots to learn about:


  • Google App Engine

  • Google Maps and geocoding

  • Django 1.0

  • Serving images from a database

  • memcache(d) for caching images

  • integrating blogger into a sub-domain



There's still lots to do, not to mention the iPhone version people keep asking for, please let me know if you see bugs or unexpected behaviour.

Google App Engine is a little new and I do run into a few issues deploying sometimes, but generally the site seems to perform pretty well.

Please look up your favourite cafes and if they aren't there, go ahead and add them!

Saturday, September 20, 2008

Trying to build transmitter for 20m

A personal objective for a long time has been to have a radio contact with a home made transmitter. After many false starts I've focussed on a transmitter for 20m.

The oscillator now works nicely. Early attempts, it turned out, were running on totally the wrong frequency, that's now fixed (with a different circuit) and the waveform looks nice and puts about 1V peak to peak into 50 ohms which I think is 2.5mW.

oscillator.jpg


The next step is to raise this level up to a few watts so that I can be heard at least by VK2BVS who lives near by.

In a burst of foolish enthusiasm, I added a gain stage followed by a class C driver and an IRF510 final, rather messy but the box will be good for the next iteration.

amplifier.jpg


Alas the final oscillates magnificently, presumably my construction is far too spread out. I'm not deterred by this and will have another go this time using a design from Drew Diamond rather than random circuit snippets found on the internet.

I feel I'm making real progress, despite no outright success, my debugging skills are improving with experience.

Wednesday, September 17, 2008

Fence troubles

treeFence.jpgLast week's demolition of the back yard went so smoothly (if a little behind schedule) that I was starting to think that I had the knack of dealing with trades people.

With the demolition, the fencing and the (still to come) tree lopping, I went through the local papers and chose three companies to get quotes from. The winner was on a combination of the price, clarity of the quote and how much I liked the person (Geoff) who came out.

I won't name them, yet, but the fencing company that won the fierce contest to replace the old wire fence with a new colourbond fence has different people doing the quoting to the people who do the work.

Today the worker guy Bill came out and balked at the amount of work required to clear the brush along the fence line.

guy.jpg


The quote said it would take 1.5 hours, he feels it's at least a day's work and I'd have to agree. Some of the brush, as you can see above, is really quite substantial trees.

My first inclination was to simply cancel and engage one of the other quotes, but the materials have already been delivered and I fear this could get messy.

Anyhow, the worker guy has now left and the company is coming out to have another look... more breaking news as it comes to hand.

Update

Today, Friday, I decided to keep ringing "Pete's Local Fencing" of Collaroy until I got some kind of commitment that something was going to happen. After four calls, I'm told that Greg will pop by either Saturday or Monday to take a look, and that the job has been given to Matt to do.

Update 2

It's Tuesday. Greg didn't turn up. I left a message on Monday but they didn't ring back. Called again and Greg is in the yard for about an hour and will call me.. (I doubt it).

Monday, September 15, 2008

Cleared the back yard

Previous owners of our house felt compelled to fill the back yard with stuff. We've now cleared it and are on our way to a nice garden.

Here's before:
before.jpg


And after:
after.jpg


A few trees to go and then it's time for a veggie patch.

If you're in Sydney and looking for a company to do demolition, I can personally recommend C.J.E. Excavation & Demolition - very professional, polite and efficient.

Lost another hard disk - we love Time Machine

disk.jpgWe seem to lose a laptop hard drive about every twelve months and yesterday my daughter lost the drive in her MacBook.

There was music, documents, bookmarks, settings and of course a few vital assignments in progress.

A few years ago this would have been a devastating event but the good news is that Apple's Time Machine backup system is so simple to use that she actually does back up. She had done a backup the morning of the loss.

The drive was out of warranty so I trotted off and bought a replacement, re-installed Leopard and restored from the external Time Machine backup.

The process was smooth and easy. Great stuff.

Update

I tried to get over the air Time Machine backup to work but kept getting an error saying it was "unable to mount" the server. It turned out that my problem was that I'd already mounted the server (in order to set it as the backup volume in TM). Unmounting it before starting the backup appears to be doing the trick.

The first backup looks like taking 5 hours for me.

Update 2

We now have wireless TM backups working from two laptops to a drive connected to an Airport Extreme. It's obviously not as fast as a local drive and I'm not sure what happens if you put the computer to sleep with that disk mounted, but it's certainly convenient.

Sunday, September 14, 2008

Current Dr Who series is excellent

Picture 1.pngI remember being really scared by the Daleks as a young child, and I've always had a soft spot for Dr Who.

This current series started out looking a bit like the high production value was out of balance with the plots but the last three weeks, here in Australia, with the two part "Silence in the library" and "Forest of the dead", and last week "Midnight" were really great.

7:30 Sunday nights ABC1.

Friday, September 12, 2008

Backyard sun path stop motion

I'm trying to figure out the best part of the garden to put the vegetable patch so today I recorded a full day of stop motion video using a little Nikon point n shoot.



It's not looking too good unless we do some serious tree downsizing. Of course it will be better in summer.

As you can see the removal of the swimming pool is pretty much complete, just some topsoil to come.

This stop motion feature of the Nikon coolpix is excellent. The camera ran from about 6:30am until after 5pm without going flat. None of my other cameras seem to have this ability.

Incidentally, I searched for something to turn a series of still pictures into a movie and couldn't find much. It turns out that good old QuickTime Player has this feature built in:
Picture 1.png


You just open any image in a folder containing the series, choose how many frames per second you want:
Picture 2.png


And you have a movie.

QuickTime Player is such a strange application, it does lots of useful things that make it more than a player.

VK2BVSs Awesome antenna

vk2bvs.jpgI've been pretty active on 14MHz again lately, mostly PSK31 where I chat with VK2ATC, VK2VFV, VK2PN, and if he gets back on, VK2ZAY. It's an amazing mode where, this morning I chatted with UA0QGG in Russia on just 5W.

Was tuning around and heard very very strong signal from VK2BVS who is quite near by. Today I dropped over to inspect his impressive antenna array. He's on all HF bands from 160M up and uses two collections of inverted V antennas connected together.

I don't think I'd get away with such a structure, err flagpole, here but it's something to aspire to.

Thanks Sam for your hospitality.

Wednesday, September 10, 2008

Reclaiming the back yard - removing the pool

When we moved in, we really didn't want a pool, but it came with the house.

I've maintained it for more then ten years, mostly cleaning leaves, adding chlorine, fixing pumps and supplying electricity.

It was the electricity that finally tipped me over the edge. As part of a daughter's school project we went around and measured the power consumption of things around the house. The pool pump, which runs between 5 and 8 hours a day uses 1,600W.

The other funny thing about this house is that aside from the pool, which really chops up the back yard, there's a two-car garage - in the back yard.

before.jpg


We decided to get rid of both monstrosities in one go. I'm working from home to the sound of jack hammers, but already I'm excited about the prospect of a larger back yard space and more sunlight.

during.jpg


This should be over in a few days, a new fence goes up next week. Later we'll add a small garden shed to take all the implements which are currently stored in a tent:

during2.jpg


When the subsiding has settled, we have grand plans for a small vegetable garden. I've been listening to the excellent digitdownunder podcast for tips and ideas.

I'm thinking of one of those built-up style beds where you don't have to grovel on the ground to work on it.

Tony sent me some information on seeds, small fruit trees and a compost bin he recommends. So much to learn.

I am a bit worried about the lack of sun, you can see the shadows from the large trees here:



I plan to do a full day stop motion to see where the problems are soon.

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.

winter1.jpg


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

winter2.jpg


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

winter3.jpg


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

winter4.jpg


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.

Update

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:

pot.jpg


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:

usage.png


On the phone it reports a total of 98.2Mb:

IMG_0003.PNG


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.

pastUsage.png


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

7-September-2008

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 BaristaReview.com, 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 com.apple.iTunes 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].com.apple.iTunes[365] MobileDevice: receive_message: Could not receive size of message: 0 Unknown error: 0
20/08/08 10:40:13 AM [0x0-0x27027].com.apple.iTunes[365] MobileDevice: _read_callback: Could not receive message
20/08/08 10:40:13 AM [0x0-0x27027].com.apple.iTunes[365] MobileDevice: send_message: Could not send message size: Bad file descriptor
20/08/08 10:40:40 AM [0x0-0x27027].com.apple.iTunes[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.

bitx20.jpg


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.

Update

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

bitxcomplete.jpg

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