Tuesday, December 28, 2010

Portable ham radio station gear

We spent Xmas at Fisherman's Paradise (presumably AKA "Fish Hell") so I was keen to enjoy some ham radio reception without all the electrical noise of a big city.

Here's my portable kit:

go pack.jpg

It's hard to beat the Yaesu FT-817 for portable operation, all HF bands plus VHF and UHF, about 350mA on receive, built-in rechargeable batteries and lots of advanced features in there (if you can find them in the menu system).

I also take a sealed lead acid battery and a small solar charger which is easily able to top it up.

Co-ax and wire dipoles are coiled on mains extension cord holders (a great buy at Bunnings). I took antennas for 20m, 30m and 40m.

To get the wires up in the trees I use a "Bait Caster" (no, it's not a sling shot) to fire a sinker on heavy fishing line right over the tree and then I connect a line to the dipole leg end and pull that up. This system works really well but the local bird life likes the new perches a bit too much:

20m antenna.jpg

The noise floor was very low, usually S1 or below, compared to S7 here in Sydney, but even this location has some TV sets that pollute the spectrum.

My thanks to Henry, VK2HE, who heard my callback to the VK2WI Sunday broadcast and passed on my details. Henry was about 1,000Km north of me and could hear me pretty well on 5W mid morning.

Amazing what a bit of wire and 5W can do.

Tuesday, December 21, 2010

Eye tests with nifty microphotographs

Eye tests are pretty cool these days. This week my eye test involved a photo being taken of my retinas and the guy got a nifty image which he was happy to email me.

MARKS Eye scan.jpg

Those light dots at the top of the right image (my left eye) are due to age and are not currently a problem.

At the end of the measurements I asked if I could have a copy of the test (so I could have a go at ordering much cheaper glasses on line). He scribbled the copy of the prescription down so roughly I had to quiz him on what the numbers were.

It's the law that the prescription is to be available to the patient but clearly there's a racket here where the testers railroad you into paying huge margins to their associated glasses supplier.

Spectacles and frames seem to me to be vastly over priced. Perhaps they should charge for the services rather than ripping us off for the frames and lenses?

I've ordered a pair of glasses through the associated shop but I thought I'd have a go at online as well so I can compare. I'll let you know how that goes.

Monday, December 20, 2010

Wagner AX-200 manual antenna tuning unit

Old mate John Beeston was upgrading the radio gear on his yacht and kindly passed the old manual antenna tuner to me. It's a Wagner AX-200 Manual Antenna Tuning Unit clearly designed for matching to the back stay short vertical wire.


This is a fantastic tuner for long (or not so long) wires. I threw up about 5m of random wire and laid down a short counterpoise and this gadget matches it on 40m perfectly and it's easy to tune by ear and then peak using the meter or the rig's SWR meter.

So far I haven't been able to find any reference to it on the internet and would welcome any specifications you might have.

There's a bit about Wagner on the net from Malcolm Haskard.

I can see that physically it looks very similar to the ATU1A. Here's a picture from an eBay auction:


If you stumble across one, I'd recommend it although it's not small enough for use as a travel tuner.

Friday, December 17, 2010

Microsoft PHP Developer Survey

It was nice to see Nick Hodge at the PHP Unconference and he gave out some nice 8GB USB sticks with the slogan "Windows+PHP Platform of choice" on them.

Along with the gift was a scrap of paper with a url asking us to do a survey about Windows as a platform for PHP. One of the questions seems a little tilted to me:

Screen shot 2010-12-17 at 2.38.32 PM.png

Good luck to them with this push but I think if they're going to charge for the platform they need to be able to demonstrate clearly the value we get for the extra money.

Sydney PHP Unconference

I attended the Sydney PHP group's unconference last night held at Google. It's my first "unconference" although it's a pretty popular idea around the world.

Basically, rather than having formal presentations scheduled for the conference, the attendees write topic ideas on sticky notes which are then stuck on a board in columns for the groups.

We join the group with a topic of interest and while the person who posted the idea kind of moderates, it's really a free flowing discussion.


It worked better than I expected, although the groups were a bit big for detailed discussion.

I heard some interesting stuff and there were a few "alternative" views (people who don't like frameworks and would rather write everything from scratch every time for example).

Not being a user of PHP, it was fun to hear clues about how threatened many of the users are by the work being done in Django and Rails. (CakePHP sounds like a good response).

Thanks to the organisers and sponsors which amazingly included Google, Microsoft, and Yahoo. (Good work attracting that bunch!). DMSBT bought the pizzas.

Wednesday, December 15, 2010

MacOS Snow Leopard in VirtualBox on Linux

os list.pngI have an irrational desire to see MacOS running on alternative hardware. It's always disappointing but never the less I was boggled to read that it's now supported on VirtualBox 3.2 and later.

Strictly speaking VirtualBox supports MacOS X Server which can be legally virtualised, but I created a VM, stuck in my Snow Leopard DVD and following just a few simple steps from here or here, now have a real Mac experience on my old Lenovo Ubuntu laptop.

Basically, you need to grab an Empire EFI boot ISO to boot from and it in turn sees the install DVD. You need to use Disk Utility to format the virtual disk and finally when you do boot you need to boot from the EFI ISO each time and simply press right arrow and Return to kick off the booting.

mac on linux.png

I did a normal system update without incident. Networking works right out of the box, no sound though. The mouse is rather too sensitive but usable. Booting and shutting down is rather verbose and it doesn't properly power off.

I would never choose this over my MacBook Air but it's nice to know it works.

Wikileaks technology

This morning on ABC Radio National Breakfast, now with the Chaser's Julian Morrow, I had a chat about some of the technology behind Wikileaks. You can listen here.

Julian is hosting RN breakfast over summer and I'll be joining in each Wednesday to talk about tech.

Thursday, December 09, 2010

Terrorist Watch: Casio F-91W

I wanted a low cost digital watch and a bit of research turned up fascinating information about an old favourite, the Casio F-91W which first appeared in 1991.


It's a simple, readable, watch with a battery life of more than five years.

The Wikipedia article reveals that this watch is reported to be favoured by those interested in building time bombs! Surely this is a testament to its reliability and hack-ability.

Picked one up for AU$21 on eBay and can recommend it, for telling the time at least.

Tuesday, November 30, 2010

Photography, brilliant project case and a fire breathing dragon

The last ARNSW Home Brew group meeting at Dural for the year and quite an entertaining one at that. Stephen VK2BLQ stole the show with the brilliant idea of using old CD drive housings to build home brew equipment in.

Aluminium angle stock makes the ends perfectly. He's nicely built a CW transceiver. I'm kicking myself for throwing some of these out even in the last few weeks.

John Hale gave an excellent talk on photographing projects or really any device of small size. Here he shows the use of a seamless background and a telephoto to avoid distortion.

I'm pretty happy with my Ricoh for close up work like this. (Detail from Stephen's rig).

I rambled about wire dipoles, pulleys and cleats but the most surprising talk was about the building and operation of a fire-breathing dragon head.

Thanks as always to the organisers and the WIA.

Monday, November 29, 2010

wsprnet.org is down

Sadly, it looks like wsprnet.org is down and has been for an hour or more at the time of writing.

I notice that it has been struggling a bit lately, in particular since the WSPR story made the front page of QST.

Hopefully it isn't too serious. I certainly miss it.


It's back up.

Sunday, November 28, 2010

WSPR analysis with gnuplot

Just posting this for my own reference really. I find that spreadsheets don't really cope with lots of data to plot so gnuplot is the way to go, but it's a little hard to figure out.

I want to plot Ross VK1UN's reception of my WSPR signal using the data on the site. Here's the output I want (pretty much).


To get this, I go to the wsprnet.org site, run a report of my transmissions and vk1un's receptions of me. Then I copy the table data from the web browser and paste it into a text file called "wspr.txt", then I run this python script to clean it up ready for gnuplot.

import csv

INFILE = "wspr.txt"
OUTFILE = "data.txt"

infile = csv.reader(open(INFILE, "r"),
delimiter = "\t")
outfile = csv.writer(open(OUTFILE, "w"))
for row in infile:
timestamp = row[0].strip()
call = row[1].strip()
sn = row[3].strip()
receiver = row[7].strip()
#print("'%s': '%s'" % (timestamp, sn))
outrow = (timestamp, sn)

Then I run the following gnuplot commands to draw the graph above.

set terminal png size 405, 320
set title "40m WSPR VK2TPM - VK1UN"
set output "WSPR.png"
set xlabel "DATE"
set ylabel "S/N"
set xdata time
set timefmt "%Y-%m-%d %H:%M"
set xtics format "%d"
set datafile separator ","
plot "data.txt" using 1:2 title 'S/N' with points

One thing that eludes me is how to get the date xlabel to change once a day. Any tips most welcome.

By the way the plot shows two days on the half wave dipole followed by one day on the half size G5RV. Not much between them. (Well, not enough data to tell).

Here's VK6ZRY's reception reports:


Saturday, November 27, 2010

Electronic technical books will win quickly

I've been lying in the hammock reading my ARRL Handbook and noticed the CD Rom in the back. It turns out they give you a complete copy of the book in PDF format.

Dragged it over to iTunes and found that it is very readable on the iPad. One problem, dear ARRL publishers, is that the files are simply called 01.pdf, 02.pdf and so on, with no metadata. Happily, iTunes can edit the metadata quite easily (although it seems to feel that it's editing music files).


Reading such a big heavy book on the iPad is much nicer than trying to hold the big heavy book up, plus you get search (well, within each chapter).

PDF is OK but the text can be a little small, it would be great to have an ePub version. Quite frankly, I never want the physical book again. It won't be long before most technical book buyers feel the same way I think.

Wednesday, November 24, 2010

Google search results with page preview

I just got this Google preview display next to my search results.

(click to enlarge).

It pops up quickly as you roll over the result line. Not all sites have previews but lots do.

Sunday, November 21, 2010

CZH-05B 500mW FM transmitter

I like to listen to the VK2WI Sunday broadcast. It's part of my weekly routine. This week I was able to listen to it lying in a hammock thanks to a new arrival, a small FM transmitter purchased on eBay.


It's synthesised for frequency stability. At 500mW it saturates the house but doesn't go much past the neighbours. On the back there is a BNC connector and it comes with a little antenna. No doubt an external antenna would extend the range.

Internally, construction is of a very high standard:


It came with an over the top switched giant power supply. There is some hum evident in the signal but no doubt that could be improved with a regulated supply.

Over the years I've built many little FM transmitters but they always drift to some extent. It's nice to have something stable like this.

I think there could be a market for a radio station that broadcasts selected podcasts, my latest discovery is The Changelog. Now I can just make my own.

Saturday, November 20, 2010

Sony Reader PRS-350 review

101335.jpegSony kindly sent me a loan PRS-350 for review this week.

The PRS-350 is a small e-ink book reader, less than the size of a novel (5"), but with a "paper white" touch screen. The display is 800 x 600 pixels and capable of reasonable grey scale display and of course works nicely in daylight. It has 2GB of built in storage.

The review unit I received was pretty grotty from previous users but cleaned up well with a damp cloth. I guess that's the drawback of any touch screen - including the iPad.

Around the rim, the device has slide power switch to wake it up, a stylus top right, one of the various micro-USB connectors (the same as the HTC phone I use which is handy but not the standard one used on many devices, and a reset hole.

On the front there are buttons for previous and next page, home, text size and options. I'd be inclined to make the next and previous page more prominent as they'll be used hundreds of times more than the others.

When you first plug it in to your computer, two storage devices are mounted, one with applications that download the software installer (a good idea - rather than directly installing an old version of the software),

Screen shot 2010-11-20 at 7.59.47 PM.png

another with a mysterious directory with "database", "Digital Editions" and some pdfs with the user manual and instructions on how to get content.

Screen shot 2010-11-20 at 8.00.22 PM.png

Unfortunately you don't seem to be able to simply drag content to the reader so software needs to be installed.

Screen shot 2010-11-20 at 8.00.07 PM.png

The installer wants to reboot the machine, I'm on a Mac here, and that always worries me as it indicates it's going to install something that runs in the background. Sure enough, after reboot, even when not plugged in there is a program running called "Reader Library Launcher". There is no uninstaller.

The "Reader Library" software shows your library on the computer, a status display of any transfers, your local disk and an ebook store:

Screen shot 2010-11-20 at 8.08.14 PM.png

Clicking one of those links simply opens your web browser at their store, so it's not an immersive experience like Kindle or iTunes. The instructions on the Borders store for "Reader Users" are a bit scary:

Screen shot 2010-11-20 at 9.34.02 PM.png

I mostly purchase books from O'Reilly in ePub format and for some reason you can't just drag them in to the application, you need to "Import" them.

For me, ePub has emerged as the winning book format, with its ability to reflow the text around graphics and the open nature of the file format (a zipped xml file) it's what I look for in a book reader.

The Sony PRS-350 does a good job with my test epub file, dithering the colour images down and showing the text styles nicely. The touch screen means that links work the way you expect without having to move through a page link by link.

It's great having search but the keyboard is a little cramped and the slow updating of the e-ink display makes this kind of user interaction a little clunky.


The device is good, it handles even large ePub books well and does a good job with fonts and images. The software is not so good, the integration with stores is poor and even books you own can't be just dragged to the window or the device.

The touch screen, even on a matt display works well and I can see why an iPad owner would want one for times when they want to read in daylight.

RRP is AU$229 which seems fair but not quite in "impulse purchase" range.

Thursday, November 18, 2010

Melbourne fancy airport road thingy

Not sure what this is called but it's fantastic.

G5RV compared with dipole using WSPR

It's hard to measure one antenna against another on HF due to the huge variations in conditions even minute by minute.

Recently I bought a half size G5RV multi-band (compromise) antenna and while it's incredibly convenient my feeling is that while reception is as good, people just don't hear me as well.

To test this, I used WSPR on 40m to record the S/N that people hear me with running 1W.

This graph plots 1 nightly cycle of transmission on the G5RV followed by two on the old 40m wire dipole.

wspr chart.png

Higher up the chart is better and there are outliers, but the average of reception seems markedly better on the simple dipole on average.

More samples need to be taken and my analysis needs to be better thought through.

Sunday, November 14, 2010

QSL Cards arrived - a blast from the past

I've never played the QSL card game, where you send a card off to people you talk to on Amateur radio to confirm the contact. Recently an envelope arrived stuffed with QSL cards people had sent me in recent years.



Scan 1.jpg

Thanks Dmitry, UA0LQI (I think) in the Russian Far East. I remember when I was a kid listening to short wave I sent off to Radio Moscow and received a lovely QSL card back from them - my parents were appalled and thought I'd be tagged as a Communist for life!

Scan 3.jpg

Thanks Pierre F5GPE in Grenoble, France.


A charming design from VE3HMK.

These contacts are all from a period when I was pretty active on 20m PSK31.

Thanks to the VK2QSL Bureau, greatly appreciated.

Monday, November 08, 2010

Half size G5RV arrived

A half size commercial G5RV just arrived from ebay seller capitalstoresaustralia. It seems well constructed, certainly better wire than the zip cord I normally use.


It hangs pretty well in the space I have between the tree and the house where my 40m dipole went. On the MiniVNA you can see the SWR plot:


SWR seems good on 40m and 20m and fair on 10m. I can't see how you'd use it on 15m.

Perfect day for hanging antennas:

antenna weather.png

Happily it's south of me, however there is tons of static crashes so it's a bit hard to evaluate the antenna at the moment. I'm running WSPR on 20m and so far reception is excellent.

I paid AU$61.21 all up which seems a bit much for some bits of wire but overall I'm happy with what I got.


Well, that didn't last long. It's very windy here tonight and the antenna is down. It broke at the junction between one wire leg and the central connector. To be fair, it's pretty interesting weather here at the moment:

Sunday, November 07, 2010

Tet-Emtron wire dipole centre pieces

I picked up a few of these excellent plastic wire dipole centre pieces from Tet-Emtron at the last Gosford field day and I'm now starting to figure out a good way to use them.


Wing nuts are the answer.


I've been using perspex sampler squares but these are really well thought out and constructed. I've now cut and tuned wire dipoles for 40m, 30m, and 20m and with my pulley and cleat system it's pretty quick to change them over.

Best time for an HF contact using WSPR Data

I'm hoping to have a contact with old friend VK3ZZC and to figure out the best time to suggest a sked I look to the WSPR data between my station and Ross VK1UN/1 (who's actually located in Melbourne at the moment).

I grabbed the historical data of Ross receiving me from the WSPR spot database and plotted it in local time.

Sydney to Melbourne spots.png

Although Ross spots me all through the 24 hours, the best times are 5am and 7 to 8pm.

It would be nice if it was a little easier to grab the data for this kind of plot, but it's a very useful resource.

Saturday, October 30, 2010

Dual-band "fan dipole" for 40 and 30m

I've been having great success with 40m WSPR with my 1W going right around the world (at certain times of the day) but much of the WSPR activity is on 30m.

Today I ran a second wire dipole cut for 30m below the main dipole suspended with strings cut for 30m and connected to the same coax.


It worked out pretty well and I'm keen to see how it goes over night. That plot is from a MiniVNA which makes it very easy to get everything adjusted.

There's a half G5RV on it's way and I'm looking forward to getting more bands but it's unlikely that I'll see the exceptionally low SWR I get with my simple wire dipoles.

Looks like it's working nicely:

Screen shot 2010-10-30 at 5.37.36 PM.png

As the "grey zone" approaches it gets better:

Screen shot 2010-10-30 at 6.59.06 PM.png

A nice balance of hearing and being heard. I'm running 1W here and have just been spotted by W1BW 16,209Km away. (The earth's circumference is 40,000Km, so I'm on the way to the other side).

Screen shot 2010-10-31 at 6.19.07 PM.png

I'm using a new centre connection with screws so I can switch wires more easily.


Sunday, October 24, 2010

Visit boat supplier for wire dipole supplies

A new wire dipole for 40m has gone up at chez marxy.

As it's suspended by the wire itself I decided not to use a balun in order to avoid the weight. The coax to wire joins are attached to a perspex sample square the local perspex supplier appears to happily give away. It's soldered and the whole lot is smeared with silicone bathroom sealant.

The wire is held at the ends with 3mm braided cord from the boating supply shop. They sell 100m for $30 and I find cord made for yachts survives the weather better than venetian blind cord.

At each end I have a pulley mounted on the house and tree.

Finally, for ease of fix and release, I've mounted cleats suitable for 3mm cord.

All this makes it very quick and easy to raise and lower the dipole.

This (no balun) wire dipole seems to be working extremely well, at least according to my wspr spots. I called back on 40m after the VK2WI broadcast  this morning and they clearly heard me better than I could hear them. Despite the lack of balun I'm not getting RF in the shack.

I notice that the resonant dip is very sharp but I got it resonant at 7.1Mhz without too much trouble.

All the bits and pieces from a boat supply shop are tested on ships at sea and seem far superior to the stuff I get at the local hardware store. The tension on an antenna is much less than what a sail causes and the ability to survive salt air means that it will last in my yard.

Monday, October 18, 2010

HF Radio lives, and is fast, at least for the military

Thanks Nigel for pointing this out. They say the've made HF communications so easy to use that no specialist knowledge is required. No mention of antennas though.

Sunday, October 17, 2010

Higher quality aerial imagery at nearmap.com

This was mentioned on the VK2WI Sunday broadcast. They have aerial imagery that is higher quality than what you get on maps.google.com and it's updated every few months by the look of it.

Here's a sample near Circular Quay.

Screen shot 2010-10-17 at 11.07.57 AM.png

If you go to nearmaps.com it's worth trying different dates as the quality varies and sometimes exposure is out.

Saturday, October 16, 2010

Shelves in the shack, thanks SolderSmoke

On a walk this morning I listened to a brand new SolderSmoke podcast, back after taking a break while Bill's family moved back to the US.

My workbench was such a mess that it's been hard to get in there and melt solder. Basically, I need to dispose of some junk or add some shelves.

shack before 016.jpg

I took the easy option and put in some nice new shelves.

shack after 015.jpg

It's really not cramped, it's cosy.

We've had big wind here in Sydney and one leg of my 40m wire dipole has fallen off so my next priority is to fix that.

It was great to hear the podcast again, and Bill, I think your audio on the old laptop running Ubuntu is the best its ever been. I wish you'd put out a podcast every day.