Sunday, December 27, 2015

Codan 6924 Mk2 on 40m

Picked up a Codan 6924 Mk2 at Dural a few months back. Always wanted one of these lunchbox radios. The IF is 1650kHz so by feeding a 5450kHz signal from a bench VFO in to an empty crystal socket I'm able to tune 7100kHz (for example).

It sounds a bit wobbly, but it's a good start.

The next step is to put together a little DDS oscillator small enough to be mounted internally. I'm not sure if I should try one with multi channels or just make separate ones to replace crystals.

I've now got it receiving 40m quite well using a DDS VFO with programmable offset that I purchased on ebay last year and badly boxed up.

Tip: You power it on while holding the CAL button to set the offset.

Saturday, December 26, 2015

WSPR on Ubuntu 15.10 using WSJT-X

The original WSPR software is an amazing construction, built with c++, Fortran, lots of library code and the UI is hung together with python. I've battled with building it and getting all the dependencies resolved in recent years.

Joe Taylor has re-written the suite as a C++ application that does not just the QSO modes but also the WSPR beacon mode. Here's a few notes on getting it going on Ubuntu 15.10.

Full documentation is here, but below are my abbreviated notes.

Grab the package from the URL on this page:


Install it:

sudo dpkg -i wsjtx_1.6.0_amd64.deb 

I recommend you install the time synchronisation software ntp like this:

sudo apt-get install ntp

Apparently you also need the kvasd decoder:

sudo add-apt-repository ppa:ki7mt/kvasd-installer
sudo apt-get update
sudo apt-get install kvasd-installer

Then you get a text menu with install and test options:

I ran WSJT-X, switched to WSPR-s mode. When the first 2 minute cycle ended I got an alert saying "/usr/bin/wsprd Error loading shared library".

To resolve that I installed the library:

sudo apt-get install libfftw3-bin libfftw3-dev

I have no idea if -dev is required but sometimes it has helped in the past in other contexts.

Now all seems well and I'm merrily decoding WSPR beacons.

This runs nicely on an old MSI U200 laptop with a dual core 1.2GHz processor. The short but wide screen doesn't particularly work well with the dual window design of WSJT-X but it quite usable and seems to decode very well.

Wednesday, December 23, 2015

Low cost 45W HF linear amplifier kit

I can't resist the low cost electronics kits out of China these days. On the bench at the moment is a 45 W HF linear for US$20.

My kit was missing the large capacitor and had extras of many of the surface mount components. The strips were marked with the values.

It's a familiar design with a pair of IRF530s in push pull on the output. The surface mount components are tiny and I have run in to a few problems with bad connections due to my giant sized soldering iron but it has come together.

The instructions are machine translated from Chinese and are quite amusing.

Here's some excerpts:

* I will Stress that the fourth point is Pandora's box, and you will feel good, if you do well. But if you do it not very well, you will reinstall after buying a new one!
* The welding way should be correct, no mistake, and no
* Postscript: Pay more attention please, because of the discreteness of component, the initial conditions may be not the optimization. In order to make discharge waveform best, experienced worker can make adjustments. In practical use, you must insert low pass filter after outputting, and filter the higher harmonic.

At this point I'm debugging the input stage which isn't biased correctly for some reason.


OK, I had destroyed Q3, a 2SC3357. I've roughly replaced it with a random NPN transistor and now for 2V in I see over 50V peak to peak out. The waveform looks pretty bad but that's mostly coming from the input stage having a totally wrong device in there. They are easy to source so I've ordered a bunch more.

So, it looks like the kit is good. I had one bad surface mount joint but otherwise it seems to have come together ok.

Sunday, December 20, 2015

WSPRnet down up down...

The fantastic JT65 mode which is used for the WSPR beacon network relies on the web site at

For several years, but dramatically lately, the site has been down. is both a Drupal based discussion board with key information about WSPR but more importantly a database of sports reported by the client applications.

At the time of writing, the site reports:

346,759,392 total spots
326,804 in the last 24 hours
7,653 in the last hour

It wouldn't be so bad if just the discussion forum was down, but when the site goes down we lose the reports from remote stations as well. This could be critical for hams tracking beacons on balloons and of course is now relied on to get a view of propagation around the world.

The problems have not gone un-noticed not just in the forums (when up) but also on Twitter.

JT65 creator Joe Taylor posted on the site this morning:

"This excellent web site is written and maintained by Bruce Walker, W1BW. We haven't heard from Bruce in quite some time; presumably he's very busy with work or other obligations.
I get frequent emails from people saying something like "I applied for a WSPRnet account and received a confirmation email telling me approval was pending. Then nothing... Can you help?"
I always tell people to contact W1BW. But I can guess what happens, because I can't raise Bruce by email, either.
I think we need a volunteer who knows web programming to pitch in and help, perhaps sending Bruce a priority letter by FedEx or something to get the process started.
-- 73, Joe, K1JT"

I'm the author of an iOS application "WSPR Watch" that crawls the site to report spots and in the past I've tried to contact the site administrator to make sure I am being kind to the site. I was unable to get a response.

The site is well designed and has a great deal of functionality for displaying, searching and mapping spots.

The spot upload web service works like this:

function wspr
tcall ZL3DMH
dbm 37
tgrid RE66
drift 0
date 151219
dt -0.7
rcall vk2tpm
version 3.00_r2328
sig -19
rqrg 14.0956
time 2304
tqrg 14.097178
rgrid QF56of


1 out of 1 spot(s) added
Processing took 65 milliseconds.

What's to be done?

The Drupal based discussion forum is fine and should remain as is, but I think that the spot database should move to a different domain and be backed by a cloud based scaleable architecture. The project should be managed by a team in the open.

The spot database should provide APIs both for client apps and reporting apps (like my WSPR Watch and iWSPR). These APIs should require a license token and be protected from overuse.

Hopefully can return 301 Moved Permanently responses and the clients will jump over to the new API if not there will be a period of disruption but in the end we will end up with a system that can take us all forward.

I'm here to help as are many others. I'm grateful to the work done by Bruce Walker and I hope he's ok. What's the next step?

Reading a GPS with Arduino

Bought a u blox neo 6M:


Works well:

Even inside the house it found 7 satellites (I’m not sure if that’s the max).

I used the TinyGPS++ library

The "Device" example was my start. Turned out that my GPS baud rate is 9600.

When I first built the gps example the compiler printed some warnings (something about can't inline a static) while building the software serial library. At first glance these looked like errors but in fact they were just warnings and once built the first time all was clean on subsequent builds.

I've heard other hams complaining that the library they want to use won't work with the latest Arduino IDE and to overcome errors they resorting to running old versions of the IDE to overcome these problems - which of course leads to other incompatibility problems.

Struggling a bit with number to string conversions but starting to drive a little display now:

Sunday, December 06, 2015

Simple copper pipe loop for 40m

After several false starts, including complex schemes involving stepper motors and long rods, I've settled on a very simple design for a loop that nicely covers 40m.

The loop is about 1m in diameter, a cat is shown for scale.

Contrary to some other designs, I've put the coupling at the top. Two turns on a FT-114-43 toroid. (Since this picture I've anchored things with some cable ties and removed one turn to get a lower SWR).

The tuning is at the bottom. I needed an extra 180pF to get this on to 40m. A larger knob is better, a reduction drive would be even better. (Tuning is very sharp).

Here's a rough drawing of the circuit:

Sitting at the table in the back yard yields decent reception - not as good as the full size dipole - but not bad.

The 3m length of copper pipe was a standard cut length at the local hardware store.

To find where the loop was resonant and make sure it was working, I used a miniVNA pro  and the vna/j software. I'm running Ubuntu Linux and ran in to some problems getting vna/j running. The trick is to remove the open source Java implementation and install the version from Sun. Also there's the JNI libraries that are required the Arduino IDE that needed to be removed to get it running.

Here's the plot showing the SWR dip at 7.1Mhz to 1.4:1. The KX3 tuner nulls out the mis-match without problem.

I've transmitted up to 50W SSB without any bad things happening.

Thursday, November 12, 2015

Another visit to the Kurrajong Radio Museum

I visited the fabulous Kurrajong Radio Museum once in the past with my partner in tow and while she found it "mildly amusing" I thought it was time for a repeat visit.

I contacted Ian via the email on the site to organise the visit in advance and he was most gracious with his time and knowledge.

With Mal, VK2BMS and Robert VK2ZNZ in tow we met up with Jules, VK2EXT for a grand tour. Some photos from the day:

Sunday, October 18, 2015

SDRPlay receiver with SDR Console

Since eliminating the annoying interference I was suffering, I've returned to the pleasure of tuning around on HF. A while back I bought the US$150 SDRPlay receiver. Getting it going with some of the common software is a bit of a trial due to the proprietary driver that's needed.

SDR Console is a very nice SDR receiver program that works out of the box with SDR Play. (Be careful on their site, they accept ads that portray themselves as bogus "download" buttons).

SDRPlay is more expensive than the RTL-SDR TV dongles but it's really worth it. They have a 12 bit A/D and capture a much larger part of the spectrum so it's easier to see the whole band and find stations.

Here's what AM shortwave stations look like.

And here's 40m LSB on an active Saturday afternoon.

A tiny snippet of video shows how it looks when running.

I'm running this on a Lenovo ThinkPad X201 with Windows 10. It's a Core i5 processor at 2.4GHz with 4GB of RAM. The software reports only about 4% CPU so there's plenty of headroom. You would struggle to run this on a cheap netbook.

One tip - there are keyboard commands for moving the IF and tuning up and down but they're disabled by default. There's a setting and then you can use PageUp and PageDown to move IF and arrow up and down to tune. Fine tuning is by holding the Control key.

Monday, October 05, 2015

Locating the source of local HF interference

In recent weeks my reception of HF radio, particularly on 40m (7MHz band), has been marred by nasty broad band interference. I had thought it was from a neighbour's TV.

Using a portable shortwave radio with a strength meter, I walked around the house trying to find the cause but it just seemed to be strong everywhere that mains wiring went.

After shutting down all computers I turned off the house main switch and the interference was gone.

By plugging things back in, one by one, I found the culprit.

Many of us suffer HF interference and the more computers and appliances we have the more likely it is, but this experience shows that it can be located and removed.

Saturday, October 03, 2015

Sydney meetup with Peter VK3YE and Stephen VK2BLQ

A rare pleasure today to meet up with home brew hero Peter, VK3YE, who was visiting Sydney.

Stephen, VK2BLQ and I caught up for a chat and Stephen brought along a phasing receiver for Peter to inspect.

We had an entertaining discussion on many topics and I hope one day to get Peter along to an ARNSW Home Brew Group meeting for some sort of chat.

Thanks Peter for all your great work to help ham radio and home brew on the web sitevideos and all the articles in various magazines - we really appreciate your efforts and encouragement.


Peter mentioned that he was close to publishing a book about QRP operation and that book is now available on Amazon. Minimum QRP is well worth a read.

Peter shares his considerable practical experience of ham radio in an easy to read and informative book. It covers equipment (including commercial and home brew), antennas, bands, propagation, modes and operating procedures that give the reader valuable tips on how to enjoy success in the challenging art of low power operation. The focus on QRP is, of course, valuable for operators working at all power levels.

Peter has always been generous with his contribution to the hobby of amateur radio and this book adds to the information available to newcomers. I look forward to more from VK3YE in the future.

Great cover by the way.

Tuesday, September 29, 2015

Everything looks better from a drone

Last weekend I was invited to film a friend's property from my drone. I'm a pretty poor flyer but the result is nice. It was a fabulous day for flying.

Thursday, September 24, 2015

A weekend away at the faded Hydro Majestic

Pip and I took advantage of a "Spring Escape" in a "Heritage room" at the Hydro Majestic in Sydney's Blue Mountains.

Not being from Sydney, I don't recall the glory days of old but do remember years of passing the place while it was being refurbished.

At $167 per night, the "Heritage" rooms turn out to be a nod to our convict heritage. As one reviewer on TripAdvisor writes, "there's hardly enough room to change your mind". We rang reception and paid considerably more to upgrade to a more spacious room with a nice view of the car park.

The staff were nice and presumably we're not the first to react this way to a room even they refer to as "compact".

There's not much to do at the place but compete for a chair that gives a glimpse of the pleasant view.

Some cushions would be a nice addition. The free Wifi is very slow but functional.

Drop in for a glass of wine on the way to an AirBNB but I don't recommend staying here. Staff were nice though and General Manager Ralf B is amusingly responsive on review sites.

Sunday, September 06, 2015

ozQRP MDT Double Sideband transceiver kit review

I learned of the Minimalist Double Sideband Transceiver (MDT) kit from the video review by VK3YE and thought it might be a fun project.

The price is $75 but it includes everything you need except a microphone. The parts are well packed and clearly marked. The circuit board is excellent quality and all parts fitted well.

The manual is very clear and I found construction quite smooth.

The only confusion I experienced was figuring out which way around the BD139 transistors go in the board (the label side is closest to the edge of the board).

I spent a lazy Saturday on and off doing the build in short bursts. Late in the afternoon I was tuning around and the direct conversion receiver sounds excellent. The carrier nulling was easy and from what I can hear off air transmit audio sounds good. So far no one has responded to my CQ calls for a report but I'll get back to you when that milestone is passed.

It's a great kit for a constructor with at least a little experience. A very compact rig that could be good to take on a hike.

Update: First contact with Mal, VK2BMS who said the audio sounds good although a little basey - which is probably more due to the microphone than anything. Mid dial was 7.10604 so that's good to know.

With the second varicap link open mine covers 7.090 - 7.127MHz. Tuning is quite sensitive so I wouldn't want more range without a multi-turn pot so I think this is a good range.

Just had another contact with Ian, VK3AXH in Ballarat who gave me a 5 and 3. He's running 200W and I'm running about 2W DSB. He commented that the rig is "doing a remarkable job". I do find that after switch on it drifts a bit but it's a pleasure to use.

Tuesday, September 01, 2015

Radio data link for $1

John, VK2ASU, showed a little data link he'd built at a recent home brew group meeting at Dural and I've started experimenting.

Here's the transmitter.

They only say it’s on 433MHz but mine seems to be on about 433.9112. I can pick it up on a little hand held scanner and given that there’s no antenna connected the range seems excellent. There is a plated hole to add an antenna. I make it 17cm for a quarter wave.

I’m using RadioHead’s ASK mode here.

With an arduino sketch example.

These are the modules I bought for $1 (including postage) on ebay.

Applications of such a link are things like sending back temperature or battery voltage readings from remote sensors.

My plan is to slow down the transmission rate, test on uhf and then get it to work on 40m with the Frog sounds transceiver.

Saturday, August 22, 2015

Helping a soon to be new ham in Bowral

Recently I had a very pleasant train trip to Bowral to assist and old friend, and soon to be amateur radio operator, William.

I was able to make the full return journey using my Opal card at no cost, which was an unexpected bonus.

William lives on a nice sized block near the centre of Bowral. Here he is in a very nice shed.

By the time I turned up, William had the rig up and running with a run of coax to a simple dipole in the back yard. I was very impressed with how far he's got. Electrical noise seems to be a significant problem though.

I brought along an antenna analyser and it turned out that the dipole was rather short for 40m and was nicely resonant at 9MHz. We replaced the simple centre connection direct to co-ax with a proper balun and made a longer dipole.

Unfortunately the two trees are a little close together but we managed to get everything going (after the picture above was taken) by having down hanging ends. (Also I did put the co-ax through the strain relief on the balun.

Here's William's operating position:

I responded to a call and had a good contact with a chap in Victoria who gave us 57.

The electrical noise could be from high voltage power lines running just a house away or it could be from an appliance in the house - more investigation is required.

Thanks William for the hospitality and I look forward to our first on air contact.

Sunday, July 26, 2015

ARNSW Home Brew Group meeting

Another interesting meeting today with lots of "show and tell" and a talk on filters. Here's some photos.

Bob had a high quality component analyser with probes that work with surface mount components.

The room was enthralled as always.

A prototype weather station with links from the remote sensor working over Bluetooth.

Convenor Peter VK2EMU at the helm.

John VK2ASU demonstrated a wireless link running over 432MHz using a $1 transmitter (but he recommends a more expensive receiver).

Stephen, VK2BLQ has constructed an amazing SSB phasing transmitter for 80m.

Eric showed the new Powerpole distribution box from the Waverley Amateur Radio Society.

The full kit is $35 - much cheaper than commercial equivalents.

Cameron, VK2CKP, showed his arduino controlled rotator.

Eric talked about filters and why you shouldn't open email enclosures while running Windows.