Simple 40m Direct conversion (DC) receiver

I'm very inexperienced at home building radio projects. Inductors, in particular, seem rather mysterious to me. Microprocessor projects seem much more predictable, signals are either on or off, but radio circuits may or may not be resonant, may or may not oscillate, and they certainly change whenever you try to measure anything.

The book "Experimental methods in RF Design" by Wes Hayward and others (aka EMRFD) it truly an inspiration and after reading it for months, and a few false starts, I've just completed the very first project in the book, a 40m (7MHz) direct conversion receiver with just two active components.

The design uses an NE612 oscillator/mixer to do most of the job and an LM386 as an audio amplifier suitable for driving headphones. NE612s don't have a lot of dynamic range so the only gain control is a pot at the antenna that serves as RF attenuator and overall "loudness" control. This works really nicely.

I can't reproduce the circuit here, but it's Figure 1.9 in EMRFD and uses only a handful of components. The design is very similar to this one.

My implementation is very ugly construction and I've mounted it in a rather over-engineered box with a transparent lid - I thought it might be a good bit of home brew art to show at the Wyong show.

Challenges

This project has taken some time to get started. First I soldered a trimmer and an off the shelf inductor the the board and attempted to confirm to myself that it was resonant at 7Mhz. I couldn't get a dip on my dip meter and couldn't see any sensible voltage peak when sweeping an RF oscillator. I was stumped for weeks.

(Thanks to VK2ZAY for his encouragement during this frustrating stage).

So I decided to follow the instructions...

I wound my own inductor using a toroid but still had trouble coupling to it. In the end a single loop of wire (soldered into a loop) running through the toroid and then around the coil on my dip meter worked and resonance was found. A few extra capacitors later and it was in the right place. This is a major breakthrough for me!

Next I built the circuit for the oscillator (active components inside the NE612). Holding a short wave radio near the circuit and sweeping the tuning cap quickly showed that it was indeed oscillating nicely.

Finally, an LM386 was ratted from another project and the audio stage built. It all worked on the bench, and would receive my GDO, so I installed it in a box and powered it from external batteries.

It stopped working.

Turns out the NE612 is a little voltage sensitive and my re-chargeable 4 AA battery pack had dropped in voltage. Fresh batteries and it now works.

The sound is very pleasant and there's no doubt that it's very satisfying to listen to a radio you've constructed yourself. Here's a recording of ZL2JR from New Zealand and some tuning around here.

A Chat with Ben and Pete episode 13

Pete's ham radio holiday. This episode we chat about:

• The Coffs Harbour radio expo
• Apple cripples DTrace
  • Mac OS X and the missing probes: http://tinyurl.com/2lpm58
• iPod Touch 1.1.3 experiences
  • The secret life of firmware 1.1.3: http://tinyurl.com/ywpab4
• Company’s stock plummets after AdSense account disabled
  • Google Boots IncrediMail…: http://tinyurl.com/2×565h
• Sun acquires MySQL
  • Press Kit: http://tinyurl.com/3b7bor
  • In a Vortex: http://tinyurl.com/345auv

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• Everything else: http://tinyurl.com/ysgksw

Coffs Harbout Radio Expo

Attended the Coffs Harbour radio expo on Sunday.

While a lot smaller than the Wyong field day I'm looking forward to in a few weeks, it was a fine event with lots to look at including some excellent home brew electronics and a diverse trash and treasure sale.

I've been looking for an RF signal generator and was very pleased to pick up a nicely built Electronics Australia design which includes a frequency counter for $25.

There were lots of books on sale and I purchased a slightly damaged copy of the RSGB Radio Communications Handbook at a good price. A great read.

The home brew display, which regrettably didn't have anyone with it to talk to when I was there, had a fascinating 80m double side band transceiver and a little portable whip with antenna tuner built in - rather like those suspicious "miricle antennas" you see advertised.

Lee Andrews was there selling rigs and seemed to be having a good time, it's a pity he doesn't get to Dural from time to time if only to keep his mood positive.

A great day, I'll be back next year with any luck. Photos.

Currently on holiday at Coffs Harbour

Might be a little slow to respond this week as I'm on holiday at Coffs Harbour. Catching up with some friends and family and most importantly the radio expo on Sunday.

It's raining quite a bit here but the fun news is that the carnival is in town. A great old fashioned show with all the authentic gear. They certainly weren't making money when we visited last night - more staff than customers.

I'm sitting in the local internet cafe with about 10 others with internet addiction. Tried using their supplied windows computers but they are so bogged down with anti-virus measures that I gave up and today I'm pecking away on the eeePC keyboard (but with an external mouse).

See you next week.

MacWorld 2008 Keynote live blogging the live blogs

04:22 (local time) Engadget seems down.
04:23 Techcrunch is doing a fine job, a wireless backup device.
04:24 Macrumourslive has a feed that updates part of their page regularly. iPhone SDK coming February.
04:25 Only my friend Andrew is logged in to iChat down here, I think he was here last year too.
04:26 New iPhone software today. I'm running iTunes with my iPod Touch to see if there's anything there yet.. no.
04:27 TechCrunch just put up a picture, gosh Steve is wearing a black turtle-neck skivvy and jeans - what a surprise!
04:24 Some clouns at Cunning.tv claimed to be sending out video of this, but they're unreachable.
04:33 More iPhone software stuff, which has previously leaked. MacRumoursLive doing a great job.
04:35 Can't ping Engadget, not sure if that's normal. You'd think AOL's servers could handle this but no apparently. acblogs.web.aol.com.websys.akadns.net 18 packets transmitted, 0 packets received, 100% packet loss
04:36 What! I have to pay to get a software update for my iTouch?
04:39 iTunes Movie rentals! Great, but when will it come to Australia?
04:42 Movies will be available 30 days after DVD release, hmm, that's not really moving technology forward, I thought this might replace DVDs. Just checked with software update, nope.
04:46 Apple TV Take 2 No computer required. Just checked apple.com, there's still just something in the air. Gosh those AppleTV slides have a lot of words on them, I think Steve is loosing the plot in terms of minimalist presentation style. Perhaps he's got Bill Gates working for him now?
04:51 Engadget just reloaded, they have good commentary but I haven't been able to read it until now. They have a broken image in their page.
04:52 MacRumoursLive have ads in their feed. I guess that's fair enough.
04:55 He said there were four things to show: Leopard uptake success, iPhone success, iTunes movie rental, I count one important thing so far.
04:58 The Unofficial Apple Weblog is trying to load in my browser but going extremely slowly. Their coverage looks good but if you can't read it.. MacRumoursLive wins the liveblog hands down from here.
05:00 Apple TV update is free, well that's nice. Out in 2 weeks, so it's still got bugs.
05:04 "Fox wanted to make great movies, and get them into as many people's hands as possible" yeah but not until 30 days after physical distribution. They still don't get it, I'm surprised Steve went along with that backward step.
05:10 Worlds thinnest notebook! Now that's what we had a sleepless night for.
05:15 MacBook Air sounds awesome. I'm preparing my script for ABC Radio National breakfast.
05:20 First photos of the Air are up. Looks pretty ugly to me, are the keys really black?. Oh no, another video plug - Micro DVI. Converting units so it's 4mm to 19mm thin. You can "borrow" the optical drive from an existing machine (including a Windows box), very nice. 5 hours battery life - excellent!
05:26 US$1799 converts to AU$2002 (well, we'll see about that) Pre-order today, ships in two weeks.
05:28 I go to the Australia Apple store but it's down right now.
06:04 I'm done. See you next year.
PS: I seem to be updating my iPod touch, not sure at what point it's going to ask for money..
Well done to MacRumoursLive for the best live blog of the 2008 MacWorld keynote.

A Chat with Ben and Pete - Episode 12

CES, Wikia and more.
This week we chat about:

• Low cost laptops. Has the OLPC project created a new category?
  
  • Everex Cloudbook: http://tinyurl.com/26bfje
  • Lenovo has one for China: http://tinyurl.com/22w8up
  • Hasee Q540X notebook: http://tinyurl.com/2xao9m
  • Intel’s Classmate PC: http://tinyurl.com/ystz7h
  
  
• CES. Is it just a bunch of thin displays?
  
  • Loren on the Gizmodo stupidity: http://tinyurl.com/2h9tvb
  • CEA bans Gizmodo staffer: http://tinyurl.com/2xg5xc
  • Multitouch trackpad: http://tinyurl.com/yrxrpj
  • Gibson’s self tuning guitar: http://tinyurl.com/2xub9f
  • Mitsubishi’s Laser TV: http://tinyurl.com/256np6
• Xubuntu on the EeePC
  
  • eeexubuntu: http://tinyurl.com/ywpnry
  
  
• Wikia, Jimmy Wales’ Google killer?
  
  • Wikia search engine: http://tinyurl.com/yp2fss
  • Arrington calls is a complete letdown: http://tinyurl.com/yw4zko
  • Why Wikia will change search: http://tinyurl.com/37he7j
  • A nice frontend to the MacOS firewall called WaterRoof
    
    • Check out WaterRoof: http://tinyurl.com/2mxl39
  • Parallels Server in beta and runs virtualised Leopard on Apple hardware
    
    • Report from the Unofficial Apple Weblog: http://tinyurl.com/2vm6cq
  • Mac file transfer application Interarchy hits version 9
    
    • Check out Interarchy version 9: http://tinyurl.com/2y8dt5
  • Sun to reduce data centres to zero by 2015
    
    • Brian Cinque: http://tinyurl.com/3yoyzk
  
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Free single sided ATMega8 PCB design

Here at marxy.org I make printed circuit boards using the rather low-res iron on technique so I went looking for a single sided board design with no fine tracks. For example I can't reliably run a track between two IC pins.

Please correct me if you can, but I couldn't find a design out there so here is my contribution.

The circuit is a minimalist design, the chip runs without a crystal. I find this fine and given that ATMega8 series chips ship with their fuses set for the internal oscillator I'm surprised that more people don't do this for non time critical applications.

Aside from four links, there are only a few components: 10k resister on the reset pin to +5v, a 100nF capacitor across the power rail, and a 1k and LED on the power to show that the board has power. So the LED and 1k resistor are optional.

I bring out all 8 lines of Port D and some spare ground connections along a board edge, Port C 0-5 are also available as are Port B 1 and 2. The pins used for programming go to the standard 6 pin header.

The square pins are pin 1.

There is a PDF version of the design here.

I laid out this board in OmniGraffle and the file is here.

You are free to use this design for whatever you want and hopefully improve on it. I did find some great PCB designs out there but they are all both double sided and often have very fine tracks which are beyond my home fabrication capabilities.

AVR Butterfly Mac experience

I've been learning about the Atmel AVR microprocessors recently and ordered a very nifty little demo board called the AVR Butterfly. I bought mine from Mouser for US$21.

The board is handy in that it has an LCD display, a clock, temperature sensor, noise maker, 5 way switch (kind of a pokey little rocker), and a place for a light dependant resistor. (It no longer ships with an LDR as I guess they contain lead).

It comes flashed with a very comprehensive demo program that fully demonstrates the capabilities of the CPU and supplied hardware. The source code is in C and has been ported to gcc.

I installed the avr-gcc tool chain with this installer and use the java AvrFlasher with a Keyspan USB serial adapter at 19200 baud. Note that I needed to set line endings to LF in AvrFlasher's serial settings for things to work. Until I tried that I was getting mysterious flash failed message with no clue about what was wrong.

This board is an absolute bargain for the price, and the display is a great feature, but aside from working with the naked chip, like my favourite the ATMega8, my vote overall goes to the Arduino board.

A chat with Ben and Pete - Episode 11

Scoble’s fuss about Facebook and more.

This week we chat about Facebook locking out Robert Scoble for trying to extract his contacts, using OpenWRT in client mode, is OS X killing Linux as UNIX desktop environments, signs that BluRay might win the format war, Google’s distributed computing, and Pete reviews two books.

Interesting links talked about in the show:

• Techmeme thread on the latest Facebook issue: http://tinyurl.com/39tx4g


• Plaxo’s notification spamming: http://tinyurl.com/2fozv9


• OpenWRT client mode howto: http://tinyurl.com/7z7qx

• Is Apple killing Linux on the desktop: http://tinyurl.com/2wn7gj


• Top 5 Engadget posts for 2007 are all about Apple: http://tinyurl.com/2e7h9c


• Warner Bros. goes BluRay exclusive: http://tinyurl.com/22rdh6


• David Lynch and watching movies on the phone: http://tinyurl.com/2yzqpr


• Jeff Dean’s talk about Google’s infrastructure: http://tinyurl.com/2ehe3b


• Similar Google developer day talk: http://tinyurl.com/2onu6e


• RESTful web services: http://tinyurl.com/24pssf


• The Django Book: http://tinyurl.com/224gkg

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Thanks Ben for production.

Getting started with Atmel ATMEGA8-16

I mentioned in a previous post that I've been interested in learning about the Atmel AVR microcontrollers.

To get started I purchased an already constructed Arduino board and had a good experience using it's USB/Serial programming from my Mac.

I don't feel satisfied until a controller board has been built from components, here's what I did.

• Purchased an ATMEGA8-16 from the local Jaycar for AU$19.95
  
• Built a minimal circuit based on the Arduino but without the USB stuff.
• I kept the power LED and bypass capacitors but that's all
• Built a simple PC Parallel port programmer based on this circuit (yes, just two resistors!)
  
• On a Fedora 8 machine, did "yum install avr-gcc avr-libc avrdude"
• Add your user to /etc/groups under the lp group so you can access the parallel port
• I followed the excellent instructions by The Real Elliot here to get a sample program going and make a Makefile.
  

One thing that caught me for a while is that while plugged in to the programmer, the chip doesn't run. I'm sure I can fix that by adjusting the reset line or something.

I've also changed the fuses on a chip so that I now get "avrdude: AVR device not responding", still trying to figure out how to get out of that issue.. All good fun.

Amateur Radio NSW Home Brew meeting

Here's some video from the ARNSW Home Brew meeting last night at the children's party room at McDonalds at North Paramatta.

Hopefully, this will convey the flavour of these meetings - a lovely bunch of blokes.

A chat with Ben and Pete - Episode 11

FlickrFan, the death of hi-fi and more.

This week we chat about the surprisingly technical Stephen Fry, Dave Winer's new application created using his OPML platform, FlickrFan, experiences with Kubuntu and KDE4, AOL cans Netscape Navigator, booting linux from a USB flash drive, and the death of high fidelity music.

Interesting links talked about in the show:

• Why I love smart toothbrushes and loathe internet plug-ins
• FlickrFan
• Hugh’s reaction to FlickrFan
• OPML Editor
• Kubuntu
• AOL to discontinue Netscape browser development
• BBC article about Netscape
• Puppy Linux
• rEFIt boot loader for EFI-based machines (Intel Macs)
• The death of high fidelity

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• Facebook: http://tinyurl.com/2qtf3z
  
• Everything else: http://tinyurl.com/ysgksw

Killarney Heights space program

A very entertaining morning - thanks Pete and kids!

On a hot Killarney Heights morning, our intrepid gang of space heroes set out on a mission to launch a rocket high into the air. It was dangerous, possibly even fool-hardy (well, that's what my wife was suggesting).

The video shows just one launch but I think we did six until enough pieces had fallen off that the rocket became unstable in flight and was lost, presumably in a low earth orbit.

Newspapers not for breaking news any more

I remember a time when the morning newspaper had a box, outlined in red, with breaking news that was occurring as the paper was put to bed.

This morning, the Sydney Morning Herald arrived on the doorstep missing one of the biggest stories of the year - the assassination of Benazir Bhutto.

Now, I listen to the radio over night so it felt like the story was quite old by the time the paper came and it was surprising to see no mention of it.

In Wikipedia it is reported on her page that she died at 6:16pm local time, which is 12:16am Sydney time (a bit after midnight). Had the paper's front page been set in stone already?

Was the biggest story in the world the fact that NSW police didn't want a water cannon, or that the PM went to the cricket and didn't seem to enjoy it?

I know it's the silly season, but news doesn't stop and in recent years we've had some really big stories at this time of year, including a tsunami.

For three years I subscribed to Time magazine and there is some value to a publication that shows the news of the past week in a way that lets you get a feeling for what has transpired without any pretense of having the very latest news.

It's hard, (for me), to see the value of a broadsheet daily news paper. Our paper recycling bin is pretty much full of it. Perhaps it's time for a daily journal of opinion and analysis that doesn't pretend to have the news of the day any more.

Variable DC regulator V1

I'm getting really sick of those little "wall wart" power bricks for everything. My collection is getting silly, particularly as the multi-voltage ones seem to never quite have all the voltages I want.

My recent purchase of an Asus EEE PC is a good case in point, I imported it from Hong Kong so it has a power brick with a dodgy mains adapter plug on the back of it. This device needs 9.5V DC to charge - none of my existing adapters will provide this - hence this week's mini project.

It's a classic LM317 variable DC regulator in a box with a knob. The circuit is straight from the data sheet here. In my version I have 100R for r1 and the potentiometer is 1K. On the input I have a bridge rectifier so I can plug either polarity in to it without fear. Construction is on a tag board, probably a heatsink and some ventilation holes will be needed but the LM317 is well protected against over temperature and current problems.

I'm calling this project version 1 as it turns out it can't supply the 2.3A needed to charge the EEE PC, still useful for other things, but a version 2 is going to be needed for my original objective. Looks like I need an LM150 or LM138 for that.

A call for cheaper public wifi

We're staying at a nice hotel for xmas. The kids and I can't live without our internet fix for even 24 hours - is that addiction?

The internet is available here (Sydney) but only via an ethernet socket and it's AU$30 per day!

While I'm away, it's the Asus EEE PC for me, while my daughter in the next room has a PowerPC iBook running Tiger.

Obvious solution: plug the iBook into the wall ethernet, system preferences, sharing, internet tab, share internet connection over Airport - works really well. (Don't forget to adjust power management to avoid sleeping while plugged in).

While I'm on this topic, why don't cafes have free wifi? I've seen it in one cafe using an Unwired connection. This is presumably a very easy to deploy solution, an unwired (pre-WiMax I think) modem and a wireless router to share it in the cafe. Surely whatever the cost of this to the business would be outweighed by the extra sales to people staying longer to use the internet.

Finally, if we must use a commercial Wifi connection, provided by the same people that provide our home connections (Optus, Telstra) then why can't we log in with the account we already have at home?

Anyway, enough moaning from me, merry Xmas.

A Chat with Ben and Pete, episode 9

The Google Talk Babel Fish and more.

This week we chat about Google Talk's automatic translation service, developer frustration with the Android SDK, Firefox 3 and the large number of bug fixes, the Mac security update breaking Ben’s proxy functionality, Apple legal getting testy with Fake Steve Jobs and Think Secret, SSH configuration coolness, and comparing Windows and Mac vulnerabilities.

If you’re still listening, there’s a treat at the end of the show. We chat about the production and publishing of this podcast.

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Thanks Ben for production.

I'll be appearing on ABC Radio National Breakfast with Steve Cannane on Thursday this week to talk about electronic book readers.

Arduino controller board on a Mac

Having played with PIC microprocessors for many years and had good times with the 16f628, it's been hard for me to jettison that knowledge and move to another chip even though it looks much better.

The Atmel AVR chips are low cost but designed for running code generated by "normal" compilers like good old gcc, rather than the PIC chips that need hacked c or basic compilers that know how to use that banked memory.

I use a Mac and always feel like a second class citizen when it comes to software and hardware for embedded systems. Make magazine featured a little board called Arduino that carries an ATMega168 chip.

It's the fastest "greet postie" to "das blinken lights" joy I've ever experienced.

Here's my list of observations so far:

• The Arduino is open source so you can make your own
• I bought the Diecimila for AU$37.50 with it's USB connection
• Chip programmed with a boot loader so it is re-programmed via serial (over USB)
• The boot loader is freely available so you can burn it into your own chips
• There is an IDE for Windows, Linux and the Mac that works really well
• The IDE for Mac comes with the driver you need for the USB interface
• IDE has gcc-avr built in
• It links against AVR Libc
• Language is most of c
• Syntax colouring
  
• Seems actually to use a c++ compiler
• Has some useful built in functions for doing i/o
• Comes with libraries for things like printing to serial (and you can do serial comms to the board in the IDE so that's how you debug)
• There are third party libraries available for stuff like digital servo control
• Libraries are installed by simply dragging them in to a folder
• The board can be powered by USB or a separate supply 6-12V
  
• When you compile your source the output, including the intel hex file is dropped into a folder with the source so you can even burn it to another chip with your own programmer

What held me back from trying the Atmel AVR chips is the fact that there's so many of them! Where to start? Well, it seems like the ATMega8 is a good start. All the tools are free and if you have a PC with a parallel port you can make a really simple programmer.

Incidentally, I ordered my Arduino from Little Bird Electronics here in NSW on 9-December and it only turned up today 20-December. I think that's a little slow.

A look at Sun's Blackbox

Attended a very nice function by Sun at Darling Harbour in Sydney today to take a look at their server in a shipping container.

Racks are squeezed into a standard shipping container in a front to back packing arrangement. Between each rack are fans with heat exchangers that cool the air by using cold water. So the air flows into the front of one rack, out the back, through the heat exchangers and then in to the front of the next one.

Water is much more efficient for removing heat than air. I note that the standard unit contains a dehumidifier...

Racks slide out for access to both front and back. It's a clever idea and achieves higher density than you get in a normal data centre.

The warm water is cooled either in a building's system or in an external cooler and then it re-circulates. The air flow is a loop inside the box too so it all stays cool when closed.

Applications include things like:

• Temporary data centre (perhaps for the Olympics or to render a film)
• Building a data centre in a car park or warehouse (because you don't need an expensive space with false floors and airconditioning)
• Door stop
• Paper weight

It's a clever idea, although there must be some consternation about Google getting a patent on the same idea. Sun is a much more interesting company than it was a few years ago, there was a genuine buzz of enthusiasm from staff and customers at the event today.

Django Book 1.0 as an A4 PDF

I've been hanging out for this book for more than a year.

Having just done a formatting pass through it, I can confirm that it's truly a great piece of work. 

I ordered it over 12 months ago and can't wait to get the printed copy in my hands but in the mean time, I've grabbed it and done some basic formatting to turn it into a PDF with a useful table of contents which I present for your download entertainment here.

My reading of the licensing is that this is perfectly OK, and indeed others have done it, but they are in strange non-metric formats and none that I've seen have a useful (clickable) table of contents.

(If I have done the wrong thing, please let me know ASAP and I'll remove it).

I did the formatting rather manually by copying the web pages into Apple's Pages. Must say, Pages is a superb word processor these days and I have no desire to run anything else again.

A Chat with Ben and Pete - Episode 8

Amazon SimpleDB, Google Knol and more.

This week we chat about hulu.com and viewing long-form videos using flash, VoIP on the iPod Touch, Web services interfaces into databases, the Amazon SimpleDB announcement, KDE4, USB vs. Firewire, “upgrading” to Windows XP, and Google’s unit of knowledge.

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80m loop antenna experiment failure

Just a brief post about some experimentation that has failed.

I've been trying to build a loop antenna for 80m (3.5Mhz) to reduce local electrical noise.

The idea was a 2m diameter square loop built from 1m lengths of electrical conduit. First I built with 1 turn and a 300pF polyvaricon capacitor and it resonated nicely at about 20Mhz. Next went to 3 turns and it seemed to resonate around 9Mhz, then 4 turns and I can't get this thing to resonate at all.

No idea what I'm doing wrong or why this won't work. The family is a little bemused about the structure in the back yard - I tried to pass it off as my version of a Xmas decoration.

I did learn a bit about conduit - there are two main kinds around, electrical and water. Water pipe is designed to carry water under mains pressure so it's much stronger.

Update: Check out Alan's excellent response. I will get back to this project soon.

A Chat with Ben and Pete - Episode 7

Project Blackbox, Songbird and more.

We chat about the world of XWindows on Leopard, Sun’s Project Blackbox, developments in the python based web framework, Django, more wake from sleep problems with the Mac, an iPhone MMS application, the Google charts API, and an amazing iTunes clone, Songbird.

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Bus driver of the year 2007

What an honour, to be driven by the Bus Driver of the Year 2007. We know because he has it embroidered on his shirt sleeve.

Richard drives a shuttle bus around a local loop that includes some retirement villiages. He's amazing in that he seems to know everyone's name and is completely patient with those who take a while to get on or off.

When I took this shot, he said "this isn't going to turn up on MySpace is it?". I said no, not MySpace.

A chat with Ben and Pete - Episode 6

Facebook Beacon, Google Maps and more. We chat about routers, Peter’s domain woes, Facebook backs down on Beacon, Google and the FCC 700Mhz auction, Google maps and cell triangulation, offline web apps, an interesting SPAM solution, broadband over powerlines and the Eee PC launch. Golly!

We’re now listed in the iTunes directory. Click here to subscribe directly in iTunes.

Also check out the Facebook group. Click here.

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Thanks again to Ben for production.

Tracks for evaluating Hi Fi

Headphones and the amplifiers to drive them have become a bit of an obsession around here. For me, Alastair started it here for me. 

Clearly my hearing is not as good as it was when I was in my teens but there is a visceral pleasure in high quality audio even now.

Not all music shows it up and here is a little list of tracks I use to evaluate a new amplifier or headphone. It doesn't mean that these are particularly Hi Fi tracks, just that I know them and they reveal the differences for me. YMMV.

• Jean Michelle Jarre, Equinox Part 4
• Ry Cooder, Bop Till You Drop, I think it's going to work out fine.
• Eagles, Hotel California, Hotel California - not really Hi Fi but so familiar that I can pick difference easily and hear the bad edit in the middle
• Keith Jarrett, The Koln Concert, Part 1 (well any part really)
• Dire Straits, Love Over Gold, Love over gold
• Music for the Funeral of Queen Mary, John Eliot Gardiner; Monteverdi Choir, March 1
• Steely Dan, Remastered: The best of steely dan then and now, Hey Nineteen
• Talking Heads, Stop Making Sense, Psycho Killer
• Eric Clapton, Unplugged, Tears in Heaven

Hmm, maybe this list reveals something about me rather than Hi Fi evaluation. Anyhow, it's my little list for what it's worth.

A chat with ben and pete - podcast episode 5

Latest episode of our podcast, we discuss:

• Amazon Kindle
• Australian Election
• Google developer podcast

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On traditional media I reviewed the Asus EEE PC in the morning on Radio National Breakfast with Fran Kelly you can hear it here.

Chu Moy Headphone amp PCB design

I've built a number of Chu Moy design headphone amplifiers over recent months and recommend them so highly to friends I end up giving them away. Previously written up here.

Ugly construction is fine for one or two off, but it was time to try manufacturing a printed circuit board.

When I last made a printed circuit board, it was done photographically, by exposing a chemical resist to ultra violet light. Having just dismantled my dark room, it was time to try a different technique.

I used some blue "press-n-peel" transfer film. The design was done manually in OmniGraffle, printed on the film with a little HP laser printer, ironed on to the board on a wool setting, etched and drilled all in a couple of hours.

This technique works pretty well, I've had a little trouble with the ironing phase, the transfer moves a bit when I iron it on. On one occasion I had to rub off the bad transfer and iron on again. The instructions say to set the iron to polyester, but our iron doesn't have it so I set it to wool.

The actual circuit for this board uses two OPA134 amp chips (rather than the dual chip) and a TLE2426 rail splitter. I don't include any volume control as the device driving it, generally a computer or digital player has one.

I present here revision 2 of a PCB design. It works but could be more compact and has two links. PDF here, OmniGraffle source here. Note that the writing will be mirrored on the copper side when you make it. (I haven't figured out how to mirror text in OmniGraffle..) 

You are free to use these for any purpose. (Let me know if you improve it).

Be careful that your printer is close enough to 100%, I suggest test printing and lining up the 8 pin IC which is the only critical spacing.

Sorry for the break in transmission

marxy.org expired and for various reasons I didn't realise until it was too late. Unfortunately it has taken five days for me to get it back and running again.

Very sorry to anyone who came to this humble blog over recent days. I'll try not to have this happen again.

Dismantled my darkroom - a sad day

I'm a habitual early adopter in every area except one, photography. I stuck with film long after it was becoming clear that digital was superior. Digital isn't better in every way, but that's a whole other topic...

Looking back at my prints I can see that I was somewhat blind to the dust and scratches that would not go uncorrected in these digital days.

I've had a darkroom in the house, on and off, pretty much since I was in my early teens. Many deeply satisfying hours have been spent huddled over the enlarger, with my fingers in the chemical trays, and walking with dripping prints to the laundry to wash. I will miss just having the room there, even though a year has gone by with no activity.

Digital equipment goes out of date within months, some of my darkroom gear is technology that hasn't changed in 40 years.

I'll still keep a few film cameras, they are pieces of industrial art. I wonder if there is a film processing service that develops the film and sends back a really high quality negative scan? Last time I tried Kodak Photo CD it was very disappointing.

A Chat with ben and pete - podcast episode 4

Latest episode here.

Advertising, Outages, Android and Eee PC.

We chat about Time Machine, Back to my Mac (still not working for us), the Rackspace outage, the Android SDK and I have an Eee PC.

Subscribe.

Asus Eee PC mini review

I've just spent a full day using the new Asus Eee PC as my main desktop computer. It was a surprisingly smooth experience.

This tiny laptop, with just a 4Gb solid state drive and 512Mb of RAM is amazingly snappy to use.

The built-in screen and keyboard are tiny but usable if necessary - today I plugged in an external USB keyboard, mouse and screen. The video output goes up to 1280x1024 and looks just fine.

All the applications I need are built right in, including:

• Firefox web browser
• Thunderbird email client
• OpenOffice word processor, spreadsheet, presentation package.
• Pidgeon instant messenger client
• Skype telephone
• KDE's excellent file manager
• KDE's nice terminal

The Xandros linux distribution browsed my network well and found printers and samba shares with ease. Sometimes finding the local WiFi network was a little slow but worked in the end.

While there is only 1.3Gb of disk space free for documents, it was easy to mount a shared file system (included NFS) or plug in an SD card for document storage.

As a command line user, I welcome all the standard utilities such as ssh, wget, python (regrettably only 2.2.4), nano, java, and about 1600 others.

Criticisms

It's hard to complain about a highly portable notebook that costs just AU$500. Of course it would be nice if the screen was bigger and took up the available space, you can't make the keyboard larger without increasing over all size, the trackpad defaulted to a very insensitive setting but that was soon fixed.

Scanning for wireless networks seems a little slow, but gets there in the end. There are rather a lot of icons in the system tray and the overall look of the KDE based desktop looks unnervingly like Windows XP.

I'd like to leave a large SD card in the slot all the time, but each time I start up it pops up a dialog asking what I want to open it with - probably a work around involving fstab but this needs a gui solution

The single click button below the track pad seems very stiff and I've just realised that it's because it's actually a rocker switch with a left and right button part. Perhaps a little clue such as a line in the middle would avoid this mistake.

Conclusion

I'm writing this post on the device right now, still getting used to the keyboard, but certainly very usable. The only moving part is a small fan so it's very quiet, strange not to hear any disk activity at all.

I think these low cost but feature packed Linux based devices represent a new category of consumer devices. Cheap enough to give to the kids without taking out extra insurance, powerful enough for real work.

A chat about the Google phone

This morning on ABC Radio National, I had a chat with Fran Kelly about the new Google phone platform. You can hear it here.

A Chat with ben and pete - podcast episode 3

GPhone, AWS and Linux.

The big news of the week is the launch of the Open Handset Alliance and the Android OS backed by Google. We chat about its possible effects on the market and the developer scene. Other topics discussed include GMail IMAP, Amazon Web Services and Redhat, the Asus Eee PC, Radiohead and Fedora 8.

Subscribe here.

ITunes feature creep getting out of control

iTunes started out as a fantastic tool for organising, searching, browsing and playing digital media files. The ability to browse by genre, album, date added and so on, was a revelation to me - and it was really fast too.

But now, iTunes has changed so much the name doesn't even suit it any more. 

Here's my list of features that have ended up in what used to be iTunes:

• Update firmware in telephones
• Purchase electronic books
• Synchronise calendars
• Monitor RSS feeds
• Share music on the local network
• Burn CDs
• Enforce parental controls on content
• Backup phones and one model of iPod
• Movie rentals soon too?

Does this sound like feature creep to anyone else?

When Apple created iSync and the whole Sync Services concept, it sounded like we would get a single place for doing that hard task of synchronising our computers with our portable devices.

Of course it's more extreme on Windows where an install of iTunes also installs QuickTime, I think they should extend this software beach head and also install Safari 3 (weird how it's still a beta even though Leopard has shipped).

It's easy to be a critic, so here's what I'd suggest:

• Split up the iTunes functionality, give us back that simple media player with fantastic slicing and dicing features
• Create a "device manager" that is responsible for talking to devices, including media players, Apple TVs, phones, cameras, tablets, and doing the syncing that needs to be done.
• Put the iTunes store on a web site and just make it part of the general excellent Apple online store experience, sure you can link from tracks but don't make me shop inside that little box.

iTunes must be well overdue for a re-write, I still see the old watch cursor from classic days so my guess is that it's still a carbon app - that must be a nightmare code base to work on!

There's no doubt that the iTunes team has been the first to show us new user interface features that have ended up in the OS: smart folders, live search, and now coverflow. That must be a hot team, but I think it's time to split up and focus.

VNC client built right in to Leopard

After installing Leopard I've been gradually re-installing the apps I need only as required. Just now I wanted to connect to a server via VNC and was about to re-install ChickenVNC but instead thought I'd try something...

We know that Leopard supports screen sharing and that it's built on top of VNC. It turns out that you can do a Command-K in the finder, connect to server, and use a url like this: vnc://hostname to connect. If it's not running on the default VNC port of 5900 you can add the port in the usual way as shown in the picture.

As dreena is a a linux box, I get a warning dialog box as shown. The client seems very snappy and works nicely.

When I connect to an old Panther MacOS X Server it works just fine and obviously doesn't give the warning about keystroke encryption. Digg this.

Update
I've noticed that the built-in VNC doesn't interoperate too well with the RealVNC server for windows. In this case Chicken Of the VNC seems to start up the session much faster for some reason.

A chat with ben and pete - podcast episode 2

Episode 2

We discuss our thoughts on MacOS X 10.5 a week into installing it. Topics covered include Time machine experiences, launchd, Mac malware, XCode 3 and more DTrace. The big news of the week is Google's OpenSocial API and we chat about our thoughts on all things social.

Subscribe

GNUstep quick start on Linux

I'm enjoying tinkering with Cocoa on my Leopard Mac and I thought it might be fun to take a peek at Objective C and the framework on Linux in particular for developing command line tools.

My thinking is that it would be nice to develop the code under XCode and then just compile for Linux if I can figure out where the frameworks diverge and keep to compatible code.

Here's a quick start guide for Fedora Core 5 assuming that you already have the basic gcc (I'm sure it's basically the same on others):

• sudo yum install gcc-objc
• wget ftp://ftp.gnustep.org/pub/gnustep/core/gnustep-startup-0.18.2.tar.gz
• tar xzf gnustep-startup-0.18.2.tar.gz
• cd gnustep-startup-0.18.2
• sudo ./InstallGNUstep
• Edit your ~/.bash_profile to add the line . /usr/GNUstep/System/Library/Makefiles/GNUstep.sh
• (note the leading dot in the line above)

Here is a little test program, called first.m:

#import <foundation/foundation.h>

int main(int argc, char** argv, char** env)
{
NSLog(@"Hello");
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

NSMutableArray * array = [NSMutableArray new];
[array addObject: [NSString stringWithString:@"one"]];
[array addObject:[NSString stringWithString:@"two"]];
[array addObject:[NSString stringWithString:@"three"]];
[array addObject:[NSString stringWithString:@"four"]];
[array addObject:[NSString stringWithString:@"five"]];
[array addObject: @"six"];

NSEnumerator * e = [array objectEnumerator];
NSString * string;
while ((string = [e nextObject]))
{
NSLog(string);
}
[pool release];
return 0;
}

Create a file called GNUmakefile:

include $(GNUSTEP_MAKEFILES)/common.make
TOOL_NAME = first
first_OBJC_FILES = first.m
include $(GNUSTEP_MAKEFILES)/tool.make

Then make and run:

[marksp@homelinux first]$ make
Making all for tool first...
Compiling file first.m ...
Linking tool first ...
[marksp@homelinux first]$ obj/first
2007-11-04 04:38:40.246 first[1257] Hello
2007-11-04 04:38:40.276 first[1257] one
2007-11-04 04:38:40.277 first[1257] two
2007-11-04 04:38:40.278 first[1257] three
2007-11-04 04:38:40.278 first[1257] four
2007-11-04 04:38:40.279 first[1257] five
2007-11-04 04:38:40.279 first[1257] six

The same code can be built in Xcode and will run on the mac.

The GNUstep framework is very well documented here. 

One immediate incompatibility I ran into was the starter code for a Foundation command line tool ended with [pool drain] instead of [pool release] - a little DTS humour no doubt!

A brief review of XCode 3

Spent much of Saturday getting in to XCode 3 which ships with Leopard. My project was to build a Cocoa native version of the AppleScript Studio app I built last week to read and ultimately control a Yaesu FT-817 radio via a serial interface.

Having used Microsoft's developer studio, Borland's C++ Builder and the beloved Metrowerks CodeWarrior, the old XCode seemed like a step backwards in programmer friendliness.

XCode 3 is a major step forward. 

It's taking me a little while to stop fighting it and go with the new work flow. Here's my observations:

• You don't really need to go to the debugger window, variables are now inspected by rolling over them. The open up so you can inspect structures within objects very nicely.
• The output console doesn't open automatically and until I found it I used the system-wide console to view my NSLog() printouts. 
• Interface builder has been completely re-written and the vast array of available NIB objects are available in an easily searchable window.
• I'm having a bit of trouble with the synchronizing between my XCode project and Interface Builder, I end up putting declarations in my .h file and dragging it to IB each time.
• There's a handy link at the bottom of the IB window to take you to the XCode project.
• When there are build errors they appear in red balloons right in between lines of your code. At first I found this a bit annoying but now I think it's pretty clever.
• Code focus is where you put the mouse in a little left margin and blocks of code are highlighted - it's a bit alarming when you first do this by accident but now I think it's neat.

Still to try out

• Cocoa 2 with garbage collection and automatic synthesis of getters and setters.
• Project versioning - although I'm loving having Time Machine taking care of me all by itself (tip, watch the console for a while and see all the clever things it's doing)

Cocoa compared to AppleScript

It took me a lot longer to get this going in Cocoa compared to AppleScript mostly because I had to figure out how to drive the serial port. In AppleScript I found an extension that did it all for me, in Cocoa I found some classes from Andreas Mayer and others that are fantastic.

In AppleScript I used the idle handler, in Cocoa I had to use NSTimer.

I'm really enjoying Cocoa now that I'm up and running. It feels really solid and my only complaint is the sheer richness of the library, it's getting really huge and when you can't remember the method name you have to hunt through a huge list. It would be great if code completion could first show the most commonly used methods rather than the whole list.

We desperately need a new edition of Hillegass.

A chat with ben and pete - podcast episode 1

Together with the always interesting Ben, we've decided to join the weekly podcast gang, starting off with some discussion of our Leopard experiences. 

Click here to add it to iTunes.

I'll also be appearing on ABC Radio National Breakfast at around 8:05am tomorrow, (Thursday), discussing the Leopard vs. Vista vs. Linux operating system competition.

You can hear this chat here.

An AppleScript studio application

AppleScript studio is kind of the Visual Basic of MacOS X. (I'm sure some people will correct me firmly on that statement).

In order to try it out under Leopard I picked a simple project to give me something to shoot for.

I have a little Yaesu FT-817 that supports a remote control serial protocol they call CAT. It's 4800 baud, 8 bit, 2 stop bits. Each packet is 5 bytes, the last byte being the command and the other bytes are the data to go with it.

My objective is the program shown above, it periodically retrieves the current frequency and mode from the transceiver and shows it.

To interface with a common PL-2303 USB serial device, I installed the excellent (and free) Serialport X scripting addition. Thanks Art Coughlin!

To install you create a folder called ~/Library/Scripting Additions/ and stick it in there.

Prototyping was done in straight AppleScript until I was able to read and display the frequency. Next to XCode where I created an "Applescript Application". It reminds me a bit of HyperCard, you open the .nib file and in the Applescript properties tab you can set a handler for a button to call an "on clicked theObject" method in your script for example.

After some frustrating messing about, I've achieved my objective. Once you've chosen the serial device an idle handler refreshes the frequency. 

To make the built application run on a machine without the Serialport X applescript already installed you need to bundle it in the application. Thanks to the instructions here I was able to automate this. Note that I needed a -r after CpMac to copy recursively.

I find the AppleScript language frustrating for reasons I can't fully fathom, this "Applescript for python programmers" table was a great help to me as I'm very comfortable with python.

For what it's worth, I've put my xcode project here, hope it helps someone.

Leopard, great, but not totally without problems

Ben and I were first in line at MacCentric at Chatswood in Sydney to buy MacOS X10.5 Leopard today.

I rushed home and installed it as an upgrade on my Intel iMac. An upgrade takes quite a long time.

When done, Spotlight didn't seem to be doing anything. For some reason it had excluded my internal drive, a preferences change was required to fix this.

After removing my internal drive from the exclude list it seems to be taking hours to index. After an hour it's only 3% done.

So far, all my applications work just fine. Safari seems clearly faster than before, Mail is good. I showed my daughter some of the new features in iChat and she collapsed in laughter when seeing fish swimming behind Ben - this OS is going to be a hit for all the wrong reasons I think.

Tried to get started with Time Machine backups but I need a really big drive by the looks of things. Fair enough.

I ran in to some problems with .Mac syncing. I kind of got stuck in a loop resolving conflicts.

It's a pity that a new install these days involves indexing a large drive which takes time and kills the CPU for some time (hours). This gives an impression that things are going slowly - perhaps this phase should be deferred until the user has played with all the new toys for a while.

Anyhow, lots of new things to play with: Spaces looks great, I do like the new Dock, Mail seems more capable, and I can't wait to learn about Cocoa 2.0. A fun weekend lies ahead...

Updates

I've done a few installs now and here's my notes on an updated machine:

• Installs are much faster than an update
• I've had some minor problems with PPTP VPNs (for one thing the connect/disconnect menu item gets a bit confused) I've also had traffic stop and attempting to ping then gives me some error about being out of space.
  
• iTunes has hung on me
• Previously I built my own python but this causes problems for xcode
• I can't build python 2.5.1 at the moment - compile error
• All my apps just work

Due to the messing I've done under the hood, such as building my own python in the past, I'm now backing up and preparing to do a fresh install.

Dxpedition with OziPole at Sydney's North Head

Alan VK2ZAY and I went bush this morning in search of a low noise HF location where we could play with antennas, balans, tuners and annoying flies.

I recently built the excellent Ozipole kit and this was a good opportunity to try it out, primarily on 7Mhz.

I've been searching for a location close to Sydney but as far as possible from power lines and houses and Fairfax Walk at North Head seems perfect.


View Larger Map

As expected, this was a superbly low noise location, and as it was the Scout Jamboree of the Air today there were tons of stations about. Unfortunately VK2WI was on low power on 40m and pretty hard to hear.

We played with several antennas and generally had a pleasant time. Notes for the next outing:

• Take a table of some sort
• Shade if possible
• Find a way to carry the gear, (the battery is rather heavy)
• Something to repel flies
  

It was wonderful to hear stations perfectly clearly at less than S1, at my home they need to be overwhelmingly strong to be heard. I'll go back to this location - any other suggestions around Sydney would be most welcome.

Thanks Alan for the fine company. He has blogged about this outing here, which refers back to this post so I hope the internet doesn't get runaway feedback and explode.

Update: Turned on 80m this morning at home at 6am and there is no noise. Here's a sample. So the band noise at my QTH must be from an appliance or power supply or something. I need to go hunting for it and I'm also reading up on receiving loop antennas that might let me null out the signal.

Linux on a low end laptop

This weekend I've been playing with an old IBM ThinkPad 600X. It has 300Mb of ram, 12G hard disk, 450Mhz Pentium 3 processor, dead li-ion battery and no built-in ethernet or wireless.

My goal is a machine for use on ham radio, most likely running one of the psk31 software packages. I'd also like to be able to use a web browser and check imap email.

There are some very tiny linux distributions around but I figured I'd like something fairly rich so I've been playing with xubuntu which can run in 128Mb of ram. My approach was to use the Ubuntu 7.10 (release candidate) alternative install - as the live CD wouldn't install and then install xubuntu-desktop as explained here.

The normal Ubuntu desktop, Gnome, eats 250Mb before you start up any extra applications. Xfce, used in Xubuntu, eats 244Mb so I don't see much benefit in not running gnome. (I must be missing something here...)

The show stopper has been sound. Sound out works fine, sound in doesn't seem to function. I can see lots of other folks running old hardware with the same problem. I'm using a Lucent PCMCIA wireless card that Ralph kindly sent me. (It actually has an antenna socket on it!). This was detected just fine and works really well. Ubuntu seems to be lacking some user interface for seeing wireless networks though.

Bottom line: A 450Mhz legacy laptop is perfectly usable with Ubuntu. Firefox is everything I want (with a plugin it even plays YouTube videos reasonably), OpenOffice is great and just gets better every month, Evolution email is fantastic, and the overall desktop experience is really solid.

If I wasn't addicted to MacOS and hanging out for Leopard, I could use this desktop every day.

Oh, and I really hate that little IBM nipple mouse thing. Trackpads are much better.

Cleaned the very dusty case up with eucalyptus oil which can dissolve all the sticky gunk under the silly "made for windows 98" and "Intel inside" stickers.

Getting started with PSK-31 on Mac

PSK-31 is a recent digital mode that is very efficient in terms of bandwidth use and is excellent for keyboard to keyboard chatting on noisy HF.

I've been listening around for the distinctive warble sound on 80m and 40m for some time and hadn't found anything I could decode, then I read about 14.070Mhz (20m) and that seems to be where the action is. Several strong stations were heard without trouble.

A simple wire dipole for 20m was constructed and strung between two trees. I have a Yaesu FT-817 portable rig which has a mini-din 6 data jack on the back so an interface box (pictured above) was constructed. As I run a Mac the excellent cocoaModem software is in use. To key the transmitter, (as the FT-817 doesn't support VOX on the data port - a great pity) I first tried making a simple vox circuit but in the end used cocoaPTT which toggles the RTS line on a USB serial cable. One diode was used to save the radio from the +ve swing, so it just pulls PTT low to transmit, otherwise no electronics, just soldering, seems to work fine.

I called CQ, running just 5W into a very flaky antenna and was immediately called back by JA2LCN in Ogaki City, (this person seems very active).

If you run Windows there is lots of software about for PSK31, there's also some Linux software with a reasonable GUI.

In use, you leave the radio tuned to 14.070Mhz and watch the waterfall display. When you see a signal you click between the lines and start reading. It seems like a very nice way to chat, particularly if you can touch type. (A lot of receive errors I noticed now seem to be bad typing in retrospect).

I note there's some interesting kits around for minimal, low power transceivers designed for PSK31 use specifically. It's interesting to consider that a little board like this, a roll of wire, antenna tuner and a laptop and you can chat half way around the world pretty easily.

HF QRP pleasure with an FT-817

I've just spent a few very pleasant days south of Sydney at Gerroa.

We hired a house on a hill looking out over the beach and I took a Yaesu FT-817 and a slightly modified MFJ random wire tuner along for fun (all I did was add banana sockets for attaching a wire to it).

I strung out about 20m of wire from the balcony to a piece of wood in the yard and it tuned up nicely on 80m, 40m, and 20m. Had a few contacts running just 2.5W (on the in-built rechargeable batteries).

80m is blotted with interference at home. At this location it was magnificently quiet until about 5:30pm when bad televisions get turned on. I really want to find a location with no noisy power lines or TV sets to disturb by HF listening.

Only a few contacts, mostly listening. Just before we packed up I tuned around on 2m and found a very active local community.

Spent the time reading the ARRL Handbook, 2007 and a book by Melvyn Bragg, both really dense and fascinating.

On our last morning, went for a walk with my wife who slipped on a ramp and broke her leg. So quick, so easy. My thanks go out to the good folks of Gerroa who helped us to a car, a doctor and a hospital.

It's amazing how easily we can be injured. Such fragile creatures.

Degen DE1103 shortwave radio mini review

Can a low-cost digitally controlled radio have the same feel as an analog receiver?

The audio/touch combined feeling that you get while tuning across short wave in the evening on a true analog radio is much more usable than the chop/chop/chop effect experienced on low cost digital radios - until now.

The benefits of a digital radio, accurate frequency read out, full band coverage, and memories are great, but if it's painful to tune around it's just not worth it.

I picked up a Degen DE1103 for AU$159 from the very friendly AV-Comm here in Sydney. Significantly more expensive than I've seen them on eBay, but it came with a local power adapter and a smile on a Saturday morning.

The good:

• Very sensitive, in fact it overloads on the AM broadcast band (there's a switch for local which must be used).
• Comes with re-chargeable AA batteries which can be charged in the unit with the supplied power adapter. It has a timed charge system built in.
• Includes a generous long wire antenna and cloth pouch.
• Tuning up and down the dial is really smooth, you would think it was an analog system.
• Direct input of frequencies using the row of number buttons.
• Remarkably good on single side band.
• 0xFF memories (255)
• Short wave broadcast bands for easy finding of the big broadcasters.
  

The bad:

• Audio volume is adjusted by pushing a button and then using the tuning knob.
• Mine doesn't sit flat, there is a pop out stand, otherwise it rocks when laying flat
• The big digital simulation of a short wave band dial is pretty funny really, tuning is actually continuous.
• A little cryptic to operate, eg: memories are recalled by pushing a button and spinning the dial. I'd like to store frequencies in those buttons on the front but they just seem to do direct frequency input.
  

In summary, it's a good little radio. Perfect for travel, with decent sound and great sensitivity. I wish manufacturers would make appliances easy enough to use that you don't need a manual at all - you do with this one.

I wish we had an iPod short wave radio.

Ultra high quality headphone amplifier

I read Alastair's post about high quality headphones with great interest. 

After finding the excellent Headwize site, I rushed down to Jaycar this morning for bits, and built the cmoy headphone amplifier (in an Altoids tin, with space to spare, as shown above right).

What really got me was the data sheet for the OPA2134 operational amplifier from Burr-Brown which says, in part, "The distortion produced by OPA134 series op amps is below the measurement limit of all known commercially available equipment."

Further: "THD+Noise is below 0.0004% throughout the audio frequency range, 20Hz to 20kHhz".

My experience.. 

• This is easy to build. I did a hack job, as you can see above, and it worked perfectly first time.
• I'm driving Sennheiser HD 212Pros.
• Ripped some CDs at AAC 256kbps as sample content.
• iPod shuffle has noticeable hiss
• iPod 30Gb has less noise
• Switching the headphones between the iPod direct and via the amplifier makes the iPod sound relatively dull.

It's hard to explain, but this little amplifier gives a real sparkle to the sound. It's not artificial or boosted in any way, but things like cymbals sound quite different - better. Sometimes there is too much bass for my liking.

Other notes:

• Jaycar don't advertise the OPA2134, I went to buy the NE5534AN which is in their catalog and they gave me what I really wanted as a substitute - excellent! (AU$3.95)
• This chip is broadband, when I touch the input it picks up all sorts of hum, I expect that it will be susceptible to RF from things like mobile phones and will need to be in a well shielded box (Altoids tin for example) with filtering to avoid picking up hash.
• I used "ugly construction" which works well for RF projects so it's probably pretty stable as it's all ground plane.
• Didn't bother with gain control as I figure whatever is driving it has it's own volume control. Mine has a bit too much gain for my listening levels.

So, one more thing to carry on the train.. thanks Alastair.

Update

I've spent a very entertaining evening re-importing some of my old favourite CDs at 256Kbs/AAC and of course listening to tracks in different headphones. There is a story around about how your brain works harder listening to music which has been compressed for space (no, not level - that's another topic). Basically masked parts of the audio are removed to reduce the data rate, but in fact you miss those parts of the signal and have to imagine them yourself.

In my youth I was very interested in "hi fi" and well remember the arms race that would follow the upgrade of one component in the system: a new moving coil cartridge would show up the noisy amplifier, upgrading that would show up the speakers, and so on.

Recent years have seen my music move totally on to computers and mostly in to headphones. Loud speakers are always a compromise existing as they do in a room that resonates to some extent. Little computer speakers have advanced tremendously in recent years and work damn well at low level. Headphones can reveal detail and texture in an audio track that will be missed on even the most high end speaker system.

With the falling cost of storage it's now time to re-import my CD collection at a higher bit rate - or perhaps I should just bite the bullet and go loss-less at last.

Update 2

Hmm, not sure if the higher bit rate AAC is worth it for me. I created this test which chops back and forth between 128Kbps and 256Kbps every ten seconds and I can't tell the difference. Of course I'm getting old and probably not listening in the best equipment.