Mini field day at Dural

Attended the mini field day at the WIA NSW Dural site today. Beautiful weather for it, a good turn out, got some useful bits and pieces though nothing major. Quite a few car boot sellers oddly selling complete HF setups with older style rigs.

The home brew team got together with a bit of "show and tell", I brought along my MMR-40 and compared notes with John, another builder. Stephen, VK2BLQ, showed an experimental 80m short vertical which we tried to tune up by using the "pin through the insulation" technique of finding the right spot in the coil.

Alan, VK2ZAY, told me he'd built a tiny 2m AM transmitter Fredbox last night and when we got home I could hear it at my place, which is about 5Km away. Not bad for an estimated 30mW!

Gosh, during the writing of this story Blogger appears to be down for several minutes. Could Google be fallible?? It's giving 502 Server Errors.

Alan wrote up the day here, he scored some excellent bits and pieces I should have been more alert.

Built a 40m SSB transceiver kit: MMR-40

Since having a wisdom tooth out on Tuesday I've been laying low this week and took the opportunity to construct a kit.

Shown at right during construction, the MMR-40 from Hendricks QRP kits is a great little kit transceiver. Mine was missing a couple of diodes but was otherwise complete. I had a few problems getting the receiver going due to the fact that I hadn't read the errata and mistook the different zener diode for one of the missing diodes and experienced some very strange voltages that affected the transmit/receive switching circuit.

After a long night of hair pulling I joined the Yahoo MMR40 owners group and posted a question about my symptoms. Very quickly Tom replied from a Blackberry with a pointer to the problem. Great stuff.

I find building kits is a great way to get familiar with components and in particular diagnosing problems helps me greatly in understanding the circuit. I never dreamed that I could build an SSB transmitter. Still some work to do to get it all lined up but it seems to be putting out a few watts.

An interesting part of this design is the permeability tuned oscillator where part of the inductance is varied by screwing a brass bolt in and out of the coil. You can see it at the bottom right of the image above. Counter-intuitively, to me, is that frequency goes down as you wind the bolt in. The good thing is that you get slow change over turns of the knob and it seems remarkably unaffected by hand capacitance.

Update: After swapping out the mis-placed zener the receiver was still a little disappointing. Turned out that like others I had followed the layout diagram and installed a 22pF capacitor at C18 which caused T1 not to tune up. The only other oddity is that if I turn my variable supply up much above 12V the receiver mutes, not a big deal.

Anyhow, the receiver is working really nicely and is sensitive enough to hear all that bad band noise on 40m, which is all you need really. I'm not confident that my transmitted SSB is right yet, it puts out power when I talk but doesn't look like real SSB just yet.

A simple modification has been to install a stereo headphone jack that cuts off the speaker. Builders should note that the speaker really comes to life when you put it in the box and close it, very soft on the bench on its own.

I'm enjoying this but I think the kit errata needs an update. The design is very clever in that it re-uses lots of components for both receive and transmit but it lacks a block diagram so I've tried to create my own here.



(Click for a larger version). Please send me corrections!

Incidentally, wisdom tooth removal went very well - the wonders of modern dentistry.

Built a roll-up 2m j-pole antenna

I saw Dom Bragge's posting about a 2m J-Pole antenna made out of 300 ohm TV ribbon and thought I'd give it a go.

Although the design specifies 51 inches in length, Dom notes that other builders have found this resonates too high in frequency and they suggest you start at 52 inches. I did that but found that the lowest SWR was at 148Mhz so even that's too short.

Perhaps 300 ohm twinlead material is different to the original designer.

I do have one contribution to make on this topic, it's really hard to strip the insulation from this twinlead. The insulation seems very strongly bonded to the conductors and they always rip out for me. The solution is to melt your way through with a soldering iron.

Some toxic vapour comes off but it seems pretty easy to tin the wires after the plastic melts away. Shown above is the bottom of the antenna where the co-ax connects and the shorting bar at the base. The melting works quite nicely as you can see.

Thanks to Dom for the pointer to this simple and highly portable VHF antenna design.

The Nature of Photographs - mini book review

Spotted this wonderful book this morning. "The Nature of Photographs" by Stephen Shore, subtitled "A Primer".

The reproductions of photographs is fantastic in this high quality publication from Phaidon. Works are by the author and many others including Robert Frank, Walker Evans, Cindy Sherman, Lee Friedlander, André Kertész, William Eggleston, Garry Winogrand, Bernice Abbott, Dorothea Lange, Alfred Stieglitz, Diane Arbus, Eugene Atget, and even the great John Szarkowski is in there.

Well structured and simply stated, this book has given me a good structure for appreciating photographs. Packed with insights that in retrospect seem obvious. For example, the artist starts with a blank page and must fill it, the photographer starts with the clutter of the world and must simplify it.

Progress on the 80m challenge transmitter

Finally making progress on the NSW Home Brew group's 80m challenge project to build a 20W 80m AM transmitter.

I'm a bit daunted as I have never made anything that puts out more than about 500mW and have very little RF experience, but progress is finally being made.

A design has been cobbled together based on the Hendricks QRP TwoFer design, built for 80m.

So far I have the oscillator and a buffer stage running nicely and I'm looking for an RF power transistor to get to 2W. I can't seem to source a 2N2553 or 2SC799 so I've ordered from the U.S. but disappointingly they say it won't ship for up to 3 weeks.

The smoke from an MPF102 was released along the way due to wiring it in reverse.

In other news, I picked up 20m of RG213U co-ax from the MWRS at a great price. I've run this through a hole, up between the double brick walls, through the ceiling and to my newly stretched out 40/80m dipole upstairs.

Reception is great but when I transmit all hell breaks loose from RF getting into audio amplifiers. Once again, my long wire antenna looks like being the most practical transmitting system here.

MacMorseTutor version 0.00001

As part of my elaborate procrastination about learning morse code I've started writing my own tutor program for MacOS X. So far it sounds out the text you type in a field, displaying the character it just played after the audio.

It is available for your evaluation pleasure here.

This is just the start, planned features are:

• Drill characters by playing and then displaying them.
• Test by playing and then having me type the letter.
• Give positive and negative feedback after typing the letter.
• Controls for speed and spacing.

I know almost nothing of Cocoa programming but I find it a very easy environment to work in. Can't wait for WWDC.

Python decorators a simple example

Python decorators are a wonderful syntax for wrapping one function in another. I had a bit of trouble understanding the documentation, which often seems to involve talking about the history of how the syntax evolved rather than cutting to the chase and giving a simple example.

Specifically, I wanted to know how to get access to the arguments to the function I'm decorating in the decorator. Here's my example, at the top is the output:

"""
Example decorator that gets function arguments.

>>> decotest.py

>in mydecorator
>Function decorateme has been wrapped
> args = hello this is request
> kwargs = {}
>request = hello this is request
decorateme got request = hello this is request
>finished wrapped function
"""

def mydecorator(f):
   print ">in mydecorator"
   def wrapper(*args, **kwargs):
       print ">Function %s has been wrapped" % f.__name__
       print "> args = %s" % args
       print "> kwargs = %s" % kwargs
       request = args[0]
       print ">request = %s" % request
       f(*args, **kwargs)
       print ">finished wrapped function"
   return wrapper
     

def test():
   request = "hello this is request"
   decorateme(request)
 
@mydecorator
def decorateme(request):
   print "decorateme got request = %s" % request
 
if __name__ == "__main__":
   test()

Teac DV-B420 receiver creates bad RFI

Ever since I started hanging up antennas here, I've been plagued with a terrible, pulsing, interference across 40m.

Walking around with a short wave radio seemed to show that it was coming from somewhere near my house. It seemed to come from the mains, it was very strong near our meter box which has some suspiciously new meters in it. I could hear it at the next power pole down the street but not at my neighbor's meter box.

I decided to turn off the power to the house and while walking around looking for things that should be shut down before turning off the power I noticed the signal got very strong near a TEAC DVB receiver, model DV-B420.

When I unplugged it, the broadband, pulsing signal vanished.

What's worse is that this box makes the interference even when turned "off". As with many modern appliances, there is no true "off", it just stops putting out video. My guess is that it's a little switching power supply that just keeps going. Thankfully, this device isn't required at our place any more.

Some searching reveals that I am not alone in noticing interference from these devices.

Antenna activity

To maximise my procrastination on the morse code front, I've spent the weekend improving the antenna situation here. There are two HF antennas, a 40/80m trap dipole, and a recently improved (by lifting it high into a tree with a squid pole) long wire.

The long wire was used with an excellent Emtron matcher but with just a wire counterpoise in place of a real earth. I had a lot of RF in the room so I've now run that wire down to an attachment on a copper water pipe in the yard pretty close to the house. See picture above.

The dipole was in a sharp V shape from the middle of the house to two trees in the back yard, but with the help of the squid pole and a daughter, I've swung one arm right around, over the house and hung it from a tree in front of the house. So now the dipole is nicely in line and up pretty high.

The feed point is on a TV gutter mount on the second floor, the arm that goes over the roof just grazes the peak of the roof and the ends are both about 3m up. Pretty much as good as I can manage without a tower.

Disappointingly, a comparison with the long wire shows that the long wire antenna performs much better. The coax feed line to the dipole is RG58 but it's crummy stuff with aluminium foil mixed with only a few strands of copper in the shield. Next step is to upgrade that coax.

Morse code at Manly Warringah Radio Society

Attended a Wednesday meeting of the MWRS. Great fun, a lovely group of blokes. I asked about learning Morse code and was treated to a live demo which included a contact with someone in Texas.

Pictured here is (if I've got this right) Russel Clarke VK2BYN and, on the iambic keyer, Yves Bernier VK2AUJ.

Russel confirmed that there's no easy way to learn Morse, I was so hoping for a pointer to the tape I could play under my pillow while asleep that would have me wake up with the knowledge.

On another topic, my thanks to Mike Bell from the home brew group for very kindly posting me some 3.6884Mhz crystals so I'd have no excuse not to build the 80M challenge.

Learning Morse Code, MorseBlog anyone?

I'm learning Morse Code. It's hard getting started.

Amazingly, given that it's no longer required for Amateur radio, there is a lot of morse to be heard on the HF bands.

Last week I bought a key (pictured) on eBay. There is a ton of software around to help and that seems to be a good way to go. For now, I'm using Koch Method CW Trainer from G4FON along with the companion program KochRx.

In these programs it sends from a given number of letters and you type in what you hear. When you start going mad, you stop and it compares what you typed with what was sent and tells you how far you got before an error.

I'm keen to learn the code at high speed (but with big gaps for now) so I can scale up in the future.

What I'm looking for is software that:

• Teaches a character by playing the sound and showing (or speaking) the character
• Plays the sound and I type the character
• Rewards me if I get it right
• Corrects me when I get it wrong
• Reviews characters already learnt
• Repeat, adding more characters
  

So far I haven't found this, any pointers would be greatly appreciated.

When I learned to touch type, I did a course. It was tedious but the group helped me get through it. There's lots of on-air practice, but I'm no where near that stage yet.

This post was brought to you by the letters K, M and R. -.-, --, ._. (which is all I have so far).

Organizing electronic components

I had a plastic box full of resistors collected over the years. When building some project, one of the hardest things for me is finding the right components in that jumbled mass. In the past I've tried tackle boxes with lots of drawers, but there's never enough for all the different resistors and they often need their leads bent to fit.

Found a great thread on slashdot on this topic where someone suggests this method.

I bought a bunch of 15cm x 9cm snaplock bags and a box that fits them nicely. Spent some time sorting out the collection (only resistors done so far, capacitors are next).

The plastic bags have a nice place to write the values on them and all. This system is very compact and if you get a value to file that fits between two others it can be simply inserted without the need to move all the drawers.

The point has been made that this probably isn't a good idea for static-sensitive components, but I just thought I'd put them in the bag inside their anti-static bag or foam pad.

No doubt this whole exercise is really just elaborate procrastination.

New longwire hoisted by squid pole

The yard is filling with antennas. I think they look great. There is a very tall tree at the back of the block that I've been trying to run a long wire up to. Today I spent AU$39 on a 6m squid pole at a fishing shop.

Squid poles are great devices, it telescopes out from about 1.5m to 6m. Standing on top of a 2m ladder, holding the end of the 6m squid pole, I managed to feed two sinkers attached to a string over a branch. Yay! Not easy.

A 20m line goes to the bedroom on the second floor into an Emtron antenna match. There is a counterpoise of about 3m running down to the ground.

I'm able to tune this up nicely on 80m, 40m and 20m. I came up on 40m just now and had three quick contacts: Blue Mountains, Victoria and a guy down the road! Apparently you can get 18m squid poles, but they are significantly more expensive.

Ha, just noticed that if you google for squid pole, the first link relates to antennas, it seems they are also used sometimes for fishing.

Home work space

This is a response to Alastair's excellent workspace post. My little home office is a mess. I have three main hobbies: photography, computers and ham radio. They all compete for space at home.

Regrettably I don't have a nice window to look out of at a calming garden so I've added a second screen to give me a wider panorama.

From left to right: A monitor supported by books I try to keep in my unconscious. Above, on the wall, a print from the master (well from his 8x10 negative). An Intel iMac. Altoids I'm munching to make way for electronics projects. iPod loading up with too many podcasts to get through. (I've recently ditched Scoble and Calacanis as they make too much).

On the right, below puzzled daughter Catherine, is my radio hobby. An MFJ-902 travel tuner (excellent), an FT-817 I had a great time with while camping, an old Emtron tuner that I only learned how to use from the instructions that came with the MFJ tuner, a receive only tuner just being used to hold things up, and finally my boxed DRM receiver.

The transceiver is tuned to 80m via a long co-ax run through the wall, then ceiling and out to the top floor to a very narrow trap 40m and 80m dipole. Lots of activity these days on HF.

DRM Dream.exe on linux works nicely

I'm sitting in front of a shiny new install of Ubuntu 7.04 listening to the Radio New Zealand International digital broadcast on 7145kHz in perfect clarity.

This Ubuntu version is very slick as we've come to expect. For some time I battled to build the Dream receiver source code on this system without joy. Lots of roadblocks for me, mostly to do with Qt. Almost as an afterthought I installed the Wine windows emulator and tried the pre-built windows binary, after adding only a few DLLs (MSVCP60.DLL and qt-mt230nc.dll), it was up and running.

Sound in and out all just works out of the box and it runs indefinitely. Playing with the UI, for example, changing sound settings, causes it to exit, but it's perfectly usable.

Regrettably, Darwine isn't quite up to supporting this application just yet, seems to be missing some functions in the 3d graphics area which I think are used in those fancy spectrum displays. Can't wait for the day I can run this on my Mac.

HF portable radio propagation while camping

Just returned from a couple of nights camping at Coolendel near Nowra in NSW. I took along some battery operated ham radio gear and constructed two antennas. The "good" antenna was a center fed half wave dipole for the 40m band fed with TV twin lead carefully suspended between two trees, the other was simply a long wire, perhaps 25m long, thrown into a tree with sinkers on the end.

As seems to be the way for me at the moment, the simple long wire worked much much better than the carefully made dipole. My guess is that using TV twin lead is a really bad idea even though my antenna tuner has balanced antenna connections.

With just 2.5W I easily had a contact in Melbourne and could hear very strong stations in Hawaii, New Zealand and every Australian state except WA.

The most striking thing, aside from the low power needed to communicate 1,000km, is just how quiet the band is out of the city. There is so much RF interference at my home QTH that it's difficult to hear many stations.

The random/long wire tuned up really well on 40m and 20m using an Emtron tuner I picked up on eBay, I've constructed a tiny tuner of my own, in an Altoids tin, but currently it doesn't work as well as the "bought one".

Built a tiny 80m AM transmitter

I've been attending the Amateur Radio New South Wales Homebrew Group meetings recently, both on air and in the flesh.

Most entertaining. This year they have a "challenge" (not a competition!) to build an 80m AM 20W transmitter. I haven't done any electronic construction for years and haven't really attempted RF projects.

To warm up for this challenge, I've just completed a tiny 80m AM transmitter based on a circuit found here.

This is my second attempt, the first time around, I tried to build it from the limited parts I had around. If the circuit said 5k1, I'd use 4k7, and so on. Anyhow, it didn't work so I went and bought the right bits and now it does work. The only substitution is that I used 2N2222a transistors in place of 2N4401s.

This is also my second project using the "Manhattan Pad" technique which I'm very comfortable with now.

FatBlog 75.1

Yeah, I know, not statistically significant.

Fairwell DRM, hello fingerprinting?

I'm as happy as everyone to see that it's going to be possible to buy music without DRM. I've only purchased a few tracks as I regard buying with DRM as being like renting rather than buying.

This move will surely stimulate more content sales, and perhaps better, will open up the market to iPod alternatives that will play your purchased content.

The purpose of DRM is to make it hard to pass on the content, the downside is so bad (honest customers losing the ability to play stuff they paid for because they upgraded or something) that it could be that less intrusive alternatives are being sought.

The obvious one to me is content fingerprinting. Add a unique customer code to the data in the content that doesn't affect the play but can be used to trace where the copy came from. Sure, there'll be ways to strip them out in the end, but for most consumers, if they know their purchased tracks can be traced back to them it will dissuade them from "sharing".

I'm making this up, it might not be on the agenda at all, but it is possible.

Apple TV arrived in Sydney

My Apple TV just arrived here in Sydney.

Not much I can say so far except the box is pretty nice. It shipped on the 20th and just arrived now, a bit longer than expected.

Later: Now that I've got it going, here's my impressions:

• Very easy to set up, booted, on the network, shows a number that you key into the iTunes you want to pair it with.
• By default it started syncing all my Music. I didn't buy this thing to play music on the TV so I've changed that default.
• iTunes immediately tried to sell me music videos, which is about all there is in Australia at the moment, I fell for it and bought a few clips.
• The TV trailers are tantalising, Lost, Grey's Anatomy, etc etc. Of course we can't buy any of these in Australia. Grrr...
• The interface lags a little but probably because it was madly trying to sync my music library.
• Visually, looks lovely.
  

We don't have cable TV and I'm prepared, keen in fact, to spend the money that would have gone on cable, on purchasing shows I really want to see.

Issues:

• It doesn't play everything I can play in iTunes. Not sure why, I've got a quicktime movie in my library that won't sync over.
• Some videos, including movie trailers from Apple lose their Video/Audio sync pretty badly.
• iTunes kind of forgot about my iPod for a while. Had to re-boot the iPod, seems ok now.
• They need a black version, after all, most flat screen TVs come in black.
• Why doesn't the volume control work? The nifty remote control only has 6 buttons and two of the don't do anything.

I'm happy with the product and very much enjoyed watching video podcasts in bed last night. Can't wait to buy a TV show or movie.