Tuesday, 22 October 2013

Arduino Sudden Tx Shield Available Now!

I am delighted to see Kanga's announcement that the Arduino "Sudden" Transmitter Shield is to be launched at the Rishworth G-QRP Mini-Convention at the weekend...


You met my prototype in this post, where I promised that, once the commercial kit was ready, I would "post the complete schematic, in true open-source spirit".

Well - here it is...


As you see from the schematic, the shield hosts not just George's transmitter circuit but also a power supply (to derive 5V system power from the "12V" radio supply) and a flexible input buffer/amplifier arrangement, to allow the transmitter to operate with a range of RF signals (including - of course - those from the Kanga / m0xpd DDS Shield).

The transmitter puts out just under 2W - as I confirmed yesterday by sending WSPR signals on 30m which were received in Tasmania (again) and Venezuela!

There are complete design files (including an Eagle PCB design, suitable for single-layer construction - as in the prototype) on the "Occam's Micro" support page

You can meet the new transmitter shield on the Kanga Products stand at Rishworth.

See you there!

...-.- de m0xpd

Sunday, 20 October 2013

Occam's Dagger

You've heard about his Razor - well now William is tooled up with a new blade - meet "Occam's Dagger"...


It is just as sharp as the original "Occam's Microcontroller" rig, but it packs a much bigger punch in terms of functionality.

Using the extra opportunities presented by the 16*4 alphanumeric display and three push buttons (which could be added to the mix as there were some I/O pins freed up by the display's I2C interface), I've built a menu-driven User Interface. This takes the "root" display from the Kanga Enhanced VFO project, as recently hacked to make a beacon...


and adds Receive Incremental Tuning...


the ability to switch between two "VFOs"...


the choice of CW or CW(Reversed) modes...


band selection (top band through 20m)...


choice of automatic CQ message (CQ, CQ(/a), CQ(/p), CQ QRP and CQ FISTS)...


and keyer speed ("dit" length in milliseconds)...


All of this functionality is controlled with the main rotary encoder and the three buttons...


In normal operation, the rotary encoder changes frequency whilst the left and right buttons move the frequency cursor (to change the digit which the rotary encoder is adjusting). Pressing the "CQ" button initiates an automated CQ call, which can be aborted by touching the key or paddle. Pressing the rotary encoder's push-button invokes menu mode...

In menu mode, the left and right buttons navigate between menus, whilst the rotary encoder selects values in each menu - either adjusting a continuous variable or selecting from a list. Pressing the rotary encoder's push-button exits menu mode.

The rig uses the "stack" of shields  familiar from the original "Occam's Microcontroller" rig...


but, unlike the original rig, Occam's Dagger uses the recently prototyped Sudden Tx shield and a new Rx shield based on g3rjv's "Sudden" receiver, now under development. 

Here's the prototype PCB for the new Rx shield, produced by a guy who was offering a PCB milling service through ebay (seems the service isn't available at the moment - so I can't give you a link)...


More details on the receiver will follow in a later post - suffice to say (for the moment) "it works"!

All of the above was produced to illustrate the principles described in the "Occam's Microcontroller" article, which is an open-source project. The components of the user interface which distinguish it from the previously published rig are shown in the following schematic...


The Arduino sketch which powers Occam's Dagger ("Occams_Dagger_0v1.ino") is available for download here . Copy it if you like or - better still - adapt the methods for use in your own experimental rigs!

I unsheathed the dagger for the first time yesterday afternoon, and answered a CQ from g3mck. Turns out that Gerald (who gave the Dagger 559) was in "Oakham" - not "Ockham", but remarkably close!

You can come and meet Occam's Dagger at the G-QRP Rishworth convention next Saturday - see you there!

...-.- de m0xpd

Saturday, 5 October 2013

Following Noble Tyre Prints

Having quoted from the book in my recent article in SPRAT, I was pleased to spend last week in "Five Red Herrings" country.

I was staying just outside Gatehouse of Fleet, at the West Lodge of the Cally Estate - a beautiful place for a holiday (although persons of a nervous disposition might find the interior decor a little overwhelming).

One day, the XYL and I decided to follow the suggestion Wullie Murdoch had given to Lord Peter in Chapter 2...
"Ye maun tak’ the coast-road through Creetown to Newton Stewart ... and turn to the richt over the brig and then to the richt again at the signpost along the road to Bargrennan and juist follow the road till ye turn over a wee brig on the richt-hand side over the Cree and then tak’ the richt-hand road.

We, of course, were starting from Gatehouse rather than Kirkcudbright, but we followed the route as best we were able from there on. Words in italicized yellow are from DLS, the remainder from me.

"(W)e passed through Gatehouse, waving a cheerful hand to the proprietor of the Anwoth Hotel...


As you see, the Anwoth is now called "The Ship Inn".

Next, we "climbed up beneath the grim blackness of Cardoness Castle"...


Joining the west-bound A75, we "drank in for the thousandth time the strange Japanese beauty of Mossyard Farm, set like a red jewel under its tufted trees on the blue sea’s rim"...


Mossyard now farms not just cattle and sheep but also tourists, with cottages and lodges for rent. Its "strange Japanese Beauty" is a reference to the conspicuous stand of sycamores, visible from the main road. Unfortunately, the equally conspicuous red barn (which, I was told, explains Dorothy's "red jewel" similie) has recently been demolished. 

We pressed further along the A75 to find "the Italian loveliness of Kirkdale, with its fringe of thin and twisted trees and the blue Wigtownshire coast gleaming across the bay".  


Unfortunately, much of  Kirkdale's Italian loveliness was obscured by typically dreich Gallovidian weather! 

Behind Kirkdale (and actually before it in a strict, sequential itinerary) is "the old Border keep of Barholm, surrounded by white-washed farm buildings"


Recent renovations have seen the grim granite painted - diluting the contrast with the adjacent farm buildings.

Following the text, we drove on west, always aware of "the huge hump of Cairnsmuir rising darkly over Creetown."


Whilst we were aware of it, we couldn't see Cairnsmore at this point - the picture above was actually taken a couple of hours later from the road between Creetown and Gatehouse Station, near Falbae.

"Then the open road again, dipping and turning – the white lodge on the left, the cloud-shadows rolling, the cottages with their roses and asters clustered against white and yellow walls; then Newton Stewart, all grey roofs huddling down to the stony bed of the Cree, its thin spires striking the sky-line. Over the bridge..."


"and away to the right by the kirkyard, and then the Bargrennan road, curling like the road to Roundabout, with the curves of the Cree glittering through the tree-stems..."



"...and the tall blossoms and bracken golden by the wayside. Then the lodge and the long avenue of rhododendrons – then a wood of silver birch, mounting, mounting, to shut out the sunlight. Then a cluster of stone cottages – then the bridge and the gate..."



The bridge is reached from a right turn off the A714, some 8 miles north of Newton Stewart, near a place called "Clacheneasy" and - fortunately - it is no longer gated!

We followed DLS' description of the route, climbing "the stony hill-road, winding between mounds round as the hill of the King of Elfland, green with Grass and purple with heather and various with sweeping shadows". 

Just like Wimsey before us, we "pulled up as (w)e came to the second bridge"..


where we found not just The (Water of) Minnoch but - surely - the self-same point on that river where Campbell's corpse was discovered (in fiction, at least).

I had always read FIVE believing "The Minnoch" to be a product of Dorothy's imagination. 

Last year, whilst holidaying in nearby Ballantrae, I discovered it is a real river. 

This year, simply by following what turned out to be clear instructions in the text, I found what I am convinced is THE PLACE - a beauty spot which Dorothy surely visited as a tourist herself some 75 years ago.

Here's The Minnoch, looking upstream (i.e. North) from the "second bridge"... 


The Minnoch was in glorious spate after rain the night before. There were any number of points where an artist might wish to erect an easel and from which might slip to an unfortunate accidental death - or from which (s)he might push an already dead fellow artist's corpse to simulate the same accident!


For others repeating this pilgrimage, the second bridge actually takes you across The Minnoch to the visitor centre at Glentrool (or, at least, a mile-or-so east of the village of Glentrool)...


We managed to park our car rather more easily than Lord Peter did, as grass verges are now supplemented by a car park, and the visitor centre provided a fine bowl of soup and pot of tea. Our "cup of happiness was full. (We were a couple) who loved simple pleasures

...-.- de m0xpd

Friday, 27 September 2013

Occam's Microcontroller

I just arrived home from work to find that our beloved SPRAT has landed on my doormat, in its 156th issue. Perhaps your copy has arrived too.

I am delighted that it contains what the editor, George, g3rjv, generously describes as my "Major Article", which I've given the intentionally oxymoronic (some might just say moronic) title:
"Occam's Microcontroller"...


The article explores the use of microcontrollers within simple QRP projects. One such simple project is the little rig, pictured above (and gracing the front cover of SPRAT 156), which was built to demonstrate the article's ideas.

Neither the article nor the initiatives connected with it deny or detract from the work which experimenters with special digital interests and expertise are conducting in the area of  
"QRP Computing" - 
"If I have seen (any distance at all) it is by standing on the shoulders of giants." 
The present Occam's Microcontroller article deals in simple, accessible ideas of interest to all QRP experimenters, especially those contemplating taking their first steps with digital methods.

The link with our dear Franciscan, William (of Occam /Ockham), is through his famous parsimonious principle, which G-QRP members may have seen paraphrased on various club artefacts such as carrier bags (and indeed on George's email 'signature').

I've taken liberties with the club logo and an image of William from painted glass to produce the icon above, which also serves as a new fixed link at the top right of these ramblings to a dedicated support page of resources for the article, containing full details of the rig - code, hardware and more.

If you're not a G-QRP member, the support page provides links for you to join (and you can download a copy of the article too).

George mentions in his editorial that I have been given the honour of speaking at this year's Rishworth QRP Convention, where you have chance to come and meet the rig pictured above!

...-.- de m0xpd


Thursday, 26 September 2013

Suddenly, best-ever beacon dx

Last weekend I saw my new Arduino Sudden Tx Shield and the DDS Shield sitting on the bench and an idea struck me - I'd work up a beacon which combined some of the flexibility of my multi-mode beacon with the simplicity of the Arduino beacon.

I took the code I'd developed for the Kanga enhanced VFO system and hacked it to make a beacon capable of sending QRSS FSK-CW, QRQ CW and WSPR.

 Here's the set-up on the bench...


I had arranged for the software to use VFO A of the Kanga Enhanced VFO for the CW transmissions and VFO B for WSPR.

Here's the screen in close-up during the "Rx" phase between transmissions...


Notice the band display at lower right - not only could I adjust the frequency of the transmissions (to fit between other signals showing on the grabbers) but also I could change bands at will (as you'll see later in this post). Here's the display in transmit mode - in this case I'm sending the usual QRSS FSK-CW as you see at the top of the screen...


I started on 40m in the evening of 23 September and immediately got some decent reports on WSPR and QRSS - here's the overnight performance from 23 - 24 September...


Gratifying and consistent with the sort of results I'd obtained before with other beacon systems (Blogs passim) here at m0xpd (although I'd never before been spotted in Bermuda - thanks John, vp9ni !)

 I decided to exercise the flexibility of my new system and switched to 30m for the night from 24 to 25 September and was rewarded by my best-ever beacon performance...


I was so excited by the journey to Oz that it took me a while to notice that Dick, vk7dik, is actually further away in Tasmania. Brilliant.

Also the little beacon had bagged some nice new reports from Greenland and the Canaries (where I've never "been" before). Note further how Chris, 4x1rf (who has received my beacon signals before) spotted this new system's output in Haifa on both 30 and 40m - thanks Chris!

After that exhilarating performance, the next day (today) was a wash-out.

Changes in propagation conditions are seen by the sudden-ness (pun intended) of the "cut-on" as reception wakes up - as seen in this example at pa1gsj...


I also noticed a slight droop in the frequency during the course of reception at the same grabber - a rough "guesstimate" of the gradient suggests the VFO is drooping by about 0.8 Hz/minute (during the transmit phase) in this application...


This is interesting, as its the first shred of non-ideal behaviour I've seen in the DDS module - perhaps it doesn't like sitting close to the 2N3866 sweating away on the nearby Tx shield.

All-in-all a really pleasing result.

Now for the good news - I'm going to be making the beacon software freely available for you to download and use as part of the supporting materials for the joint Kanga / m0xpd projects.

It will be a great application for the DDS Shield and (once we get round to completing it) the Sudden Tx Shield.

Watch this space.

...-.- de m0xpd

Thursday, 12 September 2013

Arduino DDS Shield Available Now!

Delighted to see that the Kanga / m0xpd Arduino DDS Shield is available for purchase NOW...


Even more delighted to see that Kanga is offering it at (what seems to me to be) a very attractive price!

I've posted some details of construction, testing and applications on the Kanga Resources page.

There are more exciting developments in the pipeline - watch this space!

...-.- de m0xpd

Sunday, 1 September 2013

Sudden Transmitter Shield

After the fun and games with my original Arduino Transmitter Shield and experiments with an ugly version of George, g3rjv's "Sudden" transmitter, I've now closed the loop and built the first prototype of a "Sudden Transmitter Shield"...

The shield includes a buffer/amplifier stage on the input, allowing it either to derive RF from the "RF Bus" which is a common feature of all my Arduino devices (driven by the Kanga/m0xpd DDS Shield) or from any other source (such as a mixer for sideband signals). The shield also hosts a power supply to derive 5V for the Arduino from the conventional "radio" 12V power supply. The DDS Shield is pretty power-hungry and when its 5V is derived from the 12V line by a linear regulator, there's quite a lot of power dissipated - so I think it best to have all the "hot" objects (like this regulator and the PA final) on one shield, where they can sit basking at the top of the "stack".

The keying arrangements follow those used in my own "Ugly Weekender-derived" Tx shield, whilst the remainder of the circuit follows George's words and music closely.

Here's the system with the individual functional blocks annotated...



You can see that I've not fully populated the Rx Mute section - 'cos I've no 2N7000's in stock!

Anybody who doesn't know the Sudden can learn all about it (and learn a lot of useful practical tips besides) by downloading the excellent construction manual from the G-QRP site.

On test, my Sudden Transmitter Shield delivered a nice clean signal through a test 40m Low Pass Filter, when driven by a 7 MHz signal from the Kanga/m0xpd DDS Shield running in the Kanga "Enhanced VFO".

It produced "a shade less than 2 Watts", just as George said it should...


We're looking at ways of making this transmitter shield available for purchase as a kit - once that's sorted, I'll post the complete schematic, in true open-source spirit!

 ...-.- de m0xpd