Friday, February 29, 2008

Listening to a satellite on a hand held receiver

satellitePass.pngI've heard about the amateur satellites for years but never tried to listen in. I guess my assumption was that a directional tracking antenna would be required, but it seems with at least a recent device, AO-51, that's not the case.

It only passes over for a few minutes, when it does, and you find out where it is here. I entered latitude and longitude for Sydney (34 south, 151 east) and clicked predict.

This morning there was a pass that looked perfect so I wandered out into the back yard with a hand-held receiver tuned 435.3Mhz and with the antenna positioned horizontally, I was able to hear snippets of people talking.

Sorry about the poor quality, this was recorded with a little dictation recorder held up to the speaker.

Anyhow, this is very encouraging. I understand it's even possible to talk back through the satellite with a hand held. The uplink is on 145.92Mhz.

Because of doppler shift, you have to tune up as the satellite approaches and down as it runs away.

There's a nice page of suggestions on the Amsat site.

Tuesday, February 26, 2008

A great low power FM transmitter

FMTransmitter.jpgSaw this little FM transmitter for the broadcast band on the Make Blog.

I often want to listen to the Sunday ham radio broadcast but it would be great to not have to sit by the rig for the whole duration so I've used an iPod FM transmitter to relay the audio but they have very short range, even with an antenna added.

Turned out I had all the required components in my junk box. Built the oscillator first and it just worked right off, then built the buffer stage.

This circuit has an RF buffer stage so touching the antenna won't pull it off frequency. Running on a 9V battery it puts out enough power to cover the house. It's getting hard to find a spare frequency but I put it down near 88Mhz and it works very nicely.

I really love the aesthetic of "ugly" construction and it's so quick to throw together these little projects. I did release the smoke on the buffer transistor by accidentally using a 1K bias resistor in place of the 100K but after a small explosion that was fixed.

This design is to be recommended, it worked without any problems (except those of my own making) for me other than a bit of stretching of the oscillator coil to get it on band and it seems exceptionally stable given the construction.

If you tap the board it transmits a lovely metallic "clang" sound from the coil but that's to be expected.

I remember many years ago building JostyKit transmitters which had the coil etched onto the circuit board.

Sunday, February 24, 2008

A Chat with Ben and Pete - Episode 18

WiFi Balloons!
This week we talk about:
  • Microsoft opening up?
  • Google news for video?
  • GSM encryption broken
    • Researchers at a Black Hat conference in Washington claim to be able to listen in to GSM phone conversations with $1000 worth of equipment
  • Balloon WiFi
  • Document collaboration with SubEthaEditDocument collaboration with SubEthaEdit
Subscribe in:Full shownotes at http://tinyurl.com/23qk6e

Friday, February 22, 2008

PSK-20 kit completed.. finally

psk-20.jpgI ordered the PSK-20 kit, a PSK31 crystal locked transceiver for 14.070Mhz (the most active spot for PSK31) from SmallWonderLabs back in October 2007. Three months later it arrived.

It's a great radio. Plugs directly into your line in and out on a computer, I'm using a USB audio adapter as shown above and a Mac with the excellent CocoaModem software. Transmit comes on when you start sending, an inbuilt vox, which is great as my other arrangement involves an external vox box I put together to drive my Yeasu radio.

Construction wasn't completely smooth for me. One part, a surface mount 1uH inductor was missing and a bit difficult to source locally. Once complete the receiver worked right away but I had no output on transmit.

I traced RF through to U8, an MAR-3 surface mount rf amplifier that came already soldered on to the board. Mini-Kits were able to send me a couple within days. Still no rf out, it seemed like the output power transistor Q11 an MRF261 was dead. And it seems I'm not alone in this, at least back in 2001.

Found it difficult to find a substitute until VK2ZAY kindly offered me a 2SC1969. The leads are BCE instead of BEC so there's a bit of air sculpture going on but it works and I'm certain it's putting out at least 5W.

I did write to SmallWonderLabs about my problems but he hasn't replied so far.

I would certainly recommend this rig, it would go really well in a travel kit with a laptop, a wire to hang out the window and a small end fed tuner.

The box is excellent, definitely order it. All metal and the board is mounted by sliding into a rail.

Yes, I had a few challenges getting it going but the benefit is that I'm familiar with how it works and improved my skills somewhat. Perhaps all kits should have some bugs?

Update: I did get a reply from smallwonderlabs and today 14-Mar-200 the missing inductor and a replacement MAR-3 have just arrived.

Monday, February 18, 2008

Turned professional blogger

google_sm.gifAn exciting day!

I've just received my first ever payment from Google for AdSense revenue from my blog. Oh sure, it's only $12 but it's a milestone.

I don't blog for money, obviously, I really just blog as a way to keep notes on what I've been up to and thinking about. It is spooky sometimes to look back at your own blog posts, presumably people who write a diary have the same sensation.

Blogging is maturing, the proportion of search hits that come from blogs rather than other types of sites is going up and the material is useful and often very well thought out.

It seems amazing that not only do I not have to pay to have this blog, on my own domain even, but that they actually send me money.

For other bloggers, you might be interested that I currently get just over 100 viewers per day and my top story was about the VNC Viewer built in to Leopard, presumably because it was dugg on Digg.

Thank you for reading, I hope there's something here that's interesting.

Saturday, February 16, 2008

Wyong field day 2008

HomeBrewDisplay.jpgJust returned from another excellent Wyong field day. I'm sure attendance is going up again - despite a rather threatening sky.

This year I participated in the NSW Home Brew display and was proud to show off my little 40m Direct Conversion receiver. Amongst all the vendors selling little black boxes it's great to see there are still a few of us wielding the soldering iron.

Attended a talk on the new digital radio system D-STAR. Although the presenters were very enthusiastic about it and their demo, which included talking to a bloke in England on a little hand held, went well - I can't help worrying that this system is based on a proprietary audio codec and that there are no manufacturers except Icom at this point.

When a bloke expressing interest in software defined radio applications asked about the codec, the presenter dismissed the question by saying "it's not proprietary, you can just buy the chip" so I don't think he gets the point.

There are also some signs that the engineering has a way to go, it was stressed that we must leave four seconds before replying so the system can do some handshaking, and further if you accidentally "double" with another station the repeater will go off air for several minutes!

I didn't come away empty handed, picked up a book on receiving antennas and also a wonderful Tektronics 2246 100MHz CRO which will be a great help with the kids science homework..

Friday, February 15, 2008

Built a PVC pipe laptop stand

LaptopStand.jpgI'm using a laptop at work and have been searching the shops for some contraption to lift the laptop up so the screen is at eye height (I'm using an external keyboard and mouse).

Couldn't find anything I liked but searching on the net turned up a simple design for a stand constructed of PVC pipe. Marvellous stuff! Easy to cut, easy to join. I'm not using glue or anything, just friction will hold it together enough and still leave it with the ability to be pulled apart for carrying in my bag.

It droops forward a little (in the configuration shown here) which is fine. The laptop feels pretty secure on there but I am considering wrapping some rubber bands around the corners to give a little extra grip.

This little project went so well, I decided to make one for my wife as well (ideal romantic gift for Valentine's day I thought).

Another perspective on piracy


Denis Price, owner of "The Picture Show Man" twin cinema at Merimula gave an insightful talk on ABC Radio National tonight, but I feel he's missing an important point.

Denis has seen a "large chunk" of his market disappearing. I have great sympathy for him and can fully understand his interpretation of what he is experiencing - but I think he's missing the point.

The estimates of lost revenue by the record companies, studios and game makers are based on an assumption that everyone who has taken a copy of their works would have actually paid retail price for that work at current retail prices for physical copies. Clearly that's not the case.

Secondly, if Denis thinks that his cinema would be full except for the piracy of movies on the Interrnet, then how does he explain the fact that DVD/BluRay copies aren't available at the same time as the movie release? Surely if everyone was satisfied with the cinema experience then surely movies would be on DVD on the same day of the cinema release.

A new movie can be enjoyed in a variety of formats: iMAX, Digital Cinema, Standard Cinema (like Denis's), High Definition home cinema, standard definition TV, iPod Touch/iPhone, or iPod Video, and many others.

Sure, the film maker would like us to see their art in the iMAX cinema, but the reality is that not all of us will.

Downloading a movie from the "Internet" isn't free - users pay for the bandwidth, and it take real effort and concentration to locate and organise the download. Users must install special software and jump through all sorts of hoops to view the content.

The fact that Denis sees lots of people doing all this doesn't mean that they are criminals, it means that there is a clear consumer demand to get the content they value in new ways. Content providers have not kept pace with what consumers want and consumers will find a way until the providers come on board.

When a new movie comes out, I want to be able to choose how I will view it. Some movies should be seen in a wonderful cinema. Other movies might be best watched on the bus on my portable digital player. The point is that I want to pay the creators of this content but currently I can't.

If we can't buy the content in the format we want, well, I guess we'll look for other alternatives. That's not a threat, it's a marketplace that is being shunned by retroactive suppliers who refuse to keep up with the age of the internet.

The old model of distribution of content, where physical copies are shipped around the world is just silly.

Denis Price says "Indeed, we've now reached a tipping point." but he's got an axe to grind and he's picked the tipping the wrong way.

The cinema experience, where we go to a place with a great digital projector, great surround sound, great seats, and the vibe of experiencing the movie with other movie lovers I hope will live on - but it's just one of many possible ways to consume content.

Often when I go to the cinema, I get over priced food, out of focus projection, way too many ads, and bad seats plus annoying compatriots.

I respect creative people and I want to pay them their dues. We live in the age of the Internet and instant gratification. There is a huge opportunity here, don't fight it, satisfy it.

I urge you to read what Denis had to say. But I think the other perspective should be expressed.

Wednesday, February 13, 2008

Sorry, now for the Republic

Kevin Rudd said sorry today, on behalf of all Australians.

It was moving. Went very well, I was impressed.

Now it's time to address the other big issue in Australia - we should be a republic.

Last time we had a referendum we didn't get to vote properly, I think we should get another go at it.

Saturday, February 09, 2008

Built a better PSK31 interface box

pskVoxInterface.jpgStarted playing with PSK31 on my mac last year as reported earlier. As I said, I'm running the excellent CocoaModem software.

Until last week I was using the RTS line on a USB serial cable to key the transmitter which made for rather too many cables on my desk so I've jumped in and built a better interface box that has a VOX for keying PTT and includes level controls for both send and receive audio.

The box includes my old audio interface with 600/600 ohm transformers for audio in and out and ads a VOX board I built from a jaycar kit. Initially I ran in to some RF effects that caused the PTT relay to drop out during transmit, but the addition of RF chokes on all inputs and some bypass capacitors seems to have cleared up the problems.

On the back is a 5 pin DIN plug so I can make leads to connect to my rigs. To start I've made an Icom data cable.

So far I've had contacts with New Zealand and Queensland and can hear people in WA, SA and Victoria. We've had a lot of rain recently and I'm not sure that my home constructed balun has kept out the water. (The TV used to black out when I transmitted and it isn't any more - so in my book that's a bad sign...).

Very much hoping to catch up with VK3SL, Les, in Melbourne if he gets set up.

Thursday, February 07, 2008

Wonderful documentaries by Louis Theroux

Since I discovered this series, about a week ago, I've become addicted to the BBC series by Louis Theroux- "Weird Weekends". They are charming and best of all seem to be available here on google video.

As an Australian viewer, (and note that the series hasn't turned up here as far as I know), his style reminds me of Andrew Denton. Covering topics such as UFO hunters, swingers, white supremacists and gambling, mostly in America, Louis is able to charm his subjects and get them to reveal their surprising world views.

Louis is not a "pure" journalist though, he does show his reactions and sometimes takes people to task. Clearly he invests considerable time becoming friends with the characters and he isn't afraid to become involved. In a piece on cosmetic surgery he even goes under the knife himself.

You wouldn't see Ray Martin doing that eh?

If anyone's listening in Australian television programming, can we please have this series and also the wonderful "Flight of the Conchords".

Both highly recommended.

Wednesday, February 06, 2008

MacBook Air in Australia

My MacBook Air arrived this morning. Shipped direct from Shanghai. I do love it - light enough to carry around every day but with a lovely full sized keyboard and screen.

The remote DVD/CD software, which you install on other machines from the first install DVD works nicely. I didn't think I'd need it until I tried to install from a shared iWork 08 disk and it told me that it wouldn't let me do that.

Random thoughts so far:

The screen is really bright. The keyboard has FKeys for keyboard illumination brightness (I've never had a laptop with illuminated keys so maybe this isn't new). It has a disk eject key but it doesn't eject the remote disk. 2Gb of RAM is a good thing of course. The magnetic property of the magsafe power plug are a good thing in that they make it easy to plug in - it jumps to the right spot.

Part of the "thin" effect is an optical illusion. For me, being light weight is more important than being thin.

The big trackpad seems good, haven't fully tried all the features but two finger scrolling works very nicely thank you.

Great that it came with video adapters for both VGA and DVI, I'm sick of buying those. I think I'll have to buy the ethernet USB device to fit in with some workplaces.

At the office where I'm working at the moment I've hit a terrible networking bug that crashes anything that uses WebKit when I try to use a Microsoft authenticated proxy (even Dashboard crashes) so I've held off installing the 2007 security update in the hope that the problem started there - will report back with an answer in a few days. Update: Yes I can confirm that the crash bug when using an MS Authenticated proxy is not present before you apply "Security Update 2007-009, version 1.1". So, if you must use one of these proxys DO NOT apply this security update.

I'm being frugal about space but really 80Gb is quite sufficient. I won't be using this for my music or photo collections. I've installed my favourite apps and I still have 50Gb free.

Hey, it's missing the little Apple remote! Well, we have plenty of them so no problem here, and yes it does respond to a remote and Front Row is all there as you'd expect.

Too early to tell about battery life but right now it's showing 3:42 remaining.

These things will sell very well in my opinion.

Update: The single USB port is really high power, and that's handy. I have a serial ATA case that I've always had to plug in to two USB ports or a plug pack to power, turns out that the USB port on the Air is rated to 500mA and powers it without any problem.

Monday, February 04, 2008

A Chat with Ben and Pete - Episode 15

Microsoft! attempts! to! acquire! Yahoo!(sorry El Reg)
In this episode we chat about:Subscribe in: