Monday, 25 April 2016

RSGB Awards

Spending a few days up in M-land, during which time I have been proud to receive a brace of awards at the RSGB Annual General Meeting.

The first was the Wortley-Talbot Trophy...


which, I'm told, was given for 'outstanding experimental work in amateur radio', specifically for my 'Parallel IF' article in RadCom back in January 2015. There was an FA Cup semi-final fixture played on Saturday and the trophy rather put me in mind of the Soccer prize!

The second award was the Don Cameron G4SST Memorial Trophy...


awarded (according to the RSGB's nice letter) for "outstanding contribution to low power amateur radio communication" and specifically for "actively passing on (my) knowledge to others in the field, including Digital QRP".

The Don Cameron award shuns the traditional trophy format and takes instead the more sensible shape of a CW rig with integrated paddle, all mounted on a plinth. It was nice to see my name on a new engraved plate on the plinth, along with the great and the good of British QRP - many of whom I am honoured to count as friends. The big 'cup' had been engraved too.

I couldn't help but massage my vanity by taking a picture of my two awards...


Whilst here in Glasgow, the XYL and I have taken the opportunity to steal a pleasant 'city break' weekend away from the pressures of work, visiting the many museums and architectural delights of this great city.

One of the real highlights is the Necropolis, where the great and the good were buried in earlier years...




From this 'City of the Dead', high on a hill over St Mungo's Cathedral, you get good views over today's living, vibrant city.

Come to Glasgow - to get an award or just to enjoy an interesting visit to a fantastic, welcoming city.

...-.- de m(m)0xpd

Sunday, 10 April 2016

A Beacon on the Internet of Things

Well - I just got my new beacon closer to where I want it: responding to remote "on / off" commands delivered from anywhere in the world via the internet.

I used the tutorial on openhomeautomation.net as the basis for my solution, which now allows me to send an enabling command to the beacon of the form:


As you see, this is just a http command issued from a browser address line - but it can easily be issued by any web application. The red x's conceal my beacon's 'i-d' - I don't want you to hack into it and turn it off! The beacon 'wakes up' from power on or reset in disabled mode and will not start transmitting until I have issued an enabling command of the form above.

Although Open Home Automation's tutorial is about remote switching a physical, hardware relay, my beacon enablement is all achieved in software. I have made no hardware modification to add the remote enable / disable feature. 

When the beacon receives the enable command, it responds with a simple message in JSON format:


The name is a nice, human-readable confirmation that it really is my beacon responding.

If I want to shut down operations, I just send a similar command to disable transmission:


which stops the action and prompts an acknowledging message:


 
Obviously, this is only the first step to what will one day be a nice, custom interface but it works, so heck - it's time to test it... 

I checked that I really can 'Man' the 'Manned Experimental Propagation Transmitter' even when I'm not actually 'in the building' this weekend. In the inset on the map below, you can see your humble servant enabling and disabling the beacon remotely from Flamborough Head Lighthouse, some 120 miles from the shack and the beacon...


All worked f/b.

The beacon is still getting all its timing information from an NTP server on the 'net as well as responding to my remote 'commands'. It feels like it is now at the qualifying level where it really is out there on the Internet of Things (as opposed to just some little micro with a WiFi connection).

In the meantime, the beacon has been putting in a good performance, reaching out to the antipodes and South Africa...


and to Greenland...


and doing its ordinary QRSS stuff in between WSPR transmissions.

As I have said before - big thanks to all those who receive and report WSPR and other beacon modes: all these Tx experiments would be worth nothing without the continuing efforts of receiving stations.

...-.- de m0xpd

Sunday, 3 April 2016

No Rest for Fools

Well - fools day is gone, but I'm still Rappin'...

I've used some more wire wrapping wire to move the DDS module onto a more permanent home on what is now revealed as 'The Connected Beacon'...


Nice one SolderSmoke - even better than spaghetti trees!

...-.- de m0xpd

Saturday, 2 April 2016

The Connected Beacon

I've put my new esp8266 module to use - in a multi-mode beacon which is connected to the internet...


Here you see the module on its programming board (as previously described), hooked up to an old faithful AD9850 DDS module, the output of which is running through a prototype of the Kanga / m0xpd Tx Shield (and through a 30m filter, which is out-of-shot).

Some simple code, derived from the Occam's Beacon software, previously published, is running a multi-mode beacon on 30m, putting out WSPR, QRSS and vanilla CW on a 10 minute cycle. The novelty (for today, at least) is the fact that the system derives accurate timing information (critically important for WSPR) from the internet, which it accesses through my home WiFi.

No more messing around with pressing a reset button just at the right moment. No messing with those chocolate teapots called 'real time clocks'. No messing with GPS modules (which are fine - but not so easy to use from the north-facing window of my shack).

Just power up and go - the system looks up the time from the NIST Time Servers, using code hacked from this example. Then the system checks every once in a while to ensure it is still on track with 'internet time'. Works a treat!

Whenever you play with a new beacon, there's always a childish thrill as the very first spots are returned...


and - as I said - this is a multi-mode system, so there was also a first QRSS sighting. In this case, a partial grab (of just the '0xpd' part of my call) by Mikael, SA6BSS, over in Slutarp...


followed, ten minutes later (and when the crystal module in the AD9850 had reached better thermal equilibrium) by a complete grab...


The spots and grabs keep coming - even as I write, I see I've just crossed the pond to GĂ©rard, VE3GF...


Now - of course - the ability to get the time from the internet isn't my motive for setting up this beacon. It is just the first step in a development process. But I've made that first step and done something new and useful.

Talking of new things, I see that Bill and Pete have big plans for SolderSmoke, making a 'major change in direction'. It all has something to do with Wire Wrapping (remember that??!??). Well - ironically, and quite by chance, my little programming board for the esp8266 was made with some old wire wrapping materials I found in the junk box...


Here you see the back side of the board and a couple of the reels of wire wrap cable I used to wire the whole shooting match up - along with the old wire-wrap tool I used to strip the insulation off the end of the scraps of wire before SOLDERING (no actual wire was wrapped in the making of this blog post).

Hopefully, the heavy involvement of wire wrapping materials (not to mention the 'on trend' nature of hooking radio beacons up to the internet) will make this material acceptable to my good friends at the WireWrapRap...

Good Luck with the new venture, guys!

...-.- de m0xpd

Update:

I left things running overnight and had a pretty good bag at 09:00 UTC...



Special thanks to John, vk5ev and Andrew, vk5mr, for copying the new connected beacon down under. Now it's time for some engineering work... 

 

Sunday, 20 March 2016

Late Adopter of Things

After the dusty relics of recent posts (tubes, slide rules, etc) it is time for something more 'on trend'...


I was pleased to meet Richard, g0vxg, at the recent "Radio Active" rally and it was he who told me I should be checking out Expressif''s ESP8622. Accordingly, the notorious late adopter put in an order via the internet.

The devices have been making their way toward me ever since and the proverbial 'slow boat' just docked...


As you can see, I chose to buy some ESP8266s with a mounting PCB, which allows for the unit to be mounted via 0.1 inch headers on my beloved solderless breadboards for simple prototyping. This extra expense was no expense at all, as the whole enterprise cost less than a pint of best.

The ESP8266 (for those who cannot be bothered to follow hyperlinks) is a WiFi chip with an integrated micro, which can be programmed via the Arduino IDE. It has its own (limited) I/O capabilities. It has been described by some commentators as the Arduino killer. Obviously - I had to try it - but in order to try it, you need to program it...

Of course, given my purchase, I could plug it into a solderless breadboard. But I decided i) that I didn't want to commit a breadboard and ii) that I needed something a little more permanent.

So...


A scrap of perfboard (which had been rejected at work because it had been ordered in error, by somebody who thought it was stripboard - I rescued it from the trash can and gave it a loving home) gives, in turn, the ESP8266 module a home. Also, there is provided the two push-buttons, required to pull the ESP8266's Reset and GPIO0 pins to ground and manually cause it to enter the FLASH mode, in which it can be programmed using a USB to TTL module, which plugs in at bottom left, according to the recipe that can be found all over the 'net. The ESP8266 can be powered either from the programming module's computer or by the pair of AA batteries in the holder at the right of the photo (the ESP8266 is a 3v3 device).

However, pressing buttons is very yesteryear - so I was pleased to find a description of a simple circuit on www.arduinesp.com which also is implemented on the board above. The entire 'programming' side of my board is as described below...


You change between 'manual' and 'automatic' programming by inserting links on the jumper. I found the little twin transistor circuit worked perfectly as described on www.arduinesp.com - apart from one additional step...

It was necessary to set the Reset Method to 'nodemcu' in the 'Tools' drop down menu of the Arduino IDE:


Once this is understood, you can go ahead and plug in your FTDI board and get coding within the familiar Arduino development environment.


Here you see the little red USB to TTL board, with an extra flying lead to connect to the 'Ready to Send' and 'Data Terminal Ready' lines (the latter is also available on the edge-facing pins - but I did it this way for convenience). The little solderless breadboard hosts an LED for the inevitable 'blink' programs which form the subject of microcontroller programming 101...

There is a blink example described on www.arduinoesp.com - which is a modified version of the blink example in the built-in Arduino resources. But what's the point of this? You might as well just use an Arduino! To get added value from the ESP8266, you need to start to exercise the WiFi functionality. Fortunately, doing that is super-easy...

I found a great tutorial on www.openhomeautomation.net and - within minutes - I was able to hack it to control the LED in the photo above over the internet from a browser on my phone...


The browser page is served by the little ESP8266...


This application is only for local control (i.e. over your own WiFi network) but www.openhomeautomation.net goes on to explain how to extend control over the entire internet.

This is incredible - here we have a device, which costs less than a beer, which can be used to do all sorts of neat stuff, of which controlling an LED is really just the beginning. Applications limited not by cost or size (Richard's server, including its power supply, was hiding in a matchbox). Not limited by technology at all - just by imagination.

Genuinely exciting.

...-.- de m0xpd


Sunday, 13 March 2016

ECL86 Amplifier Test

Every once in a while, life in general and my shack in particular gets into such a mess that I can hardly breathe. At times like these my long-suffering XYL comes to my rescue and helps me to tidy things up. We had a bit of a tidy today and I found some goodies - including the old ECL86 AF amp prototype and a dummy load for AF amplifier testing.

After the tidy up was completed, I treated myself to a little gentle play at the bench, by hooking up this little tube amp to the 'new' HT supply. First (after fixing all the broken wires) I just listened to it, then I connected it to the dummy load...


Just as with RF experiments, cheapskate audio engineers find it difficult to get hold of perfect dummy loads. In the case of AF, there isn't a problem with inductance (as the frequencies are so low that wire-wound power resistors can be used for amplifier testing to first order of approximation, at least). However, exactly as we can't find 50 Ohm resistors straight out of the E series for RF, there similarly aren't 8 or 16 Ohm resistors to emulate ordinary nominal speaker loads.

Fortunately, 10 Ohms is close enough (and we don't get standing wave patterns on speaker cables, HI HI), so that's what I've always used to model an 8 Ohm speaker...


Note that as well as the ordinary 4mm binding posts, my 10 Ohm dummy load has a BNC socket, which allows me to read the voltage across the load. This allows me to simply measure - for example - the voltage gain of an amplifier, which I took the opportunity of doing for my little toy triode/pentode amp...


It offers about 32dB of gain over a pretty narrow bandwidth, which is fine for the voice applications for which it was conceived.

Now I have to tidy away this little amp - which is making the place look a mess and getting in the way of any real work. Then I have to go and say 'thanks' to the XYL.

...-.- de m0xpd

Sunday, 6 March 2016

Beer and Filters

I'm planning to show off my nice old Pickett N-515-T to some students in a few days time. I think I'll need a hook to get them interested and one sure way of attracting the attention of engineering students always used to be beer...


As is well known, empty (or part-empty) beer bottles, exhibit a nice acoustic second order resonance, analogous to the electrical resonance of an LC filter...


Reflecting the analogy, the resonant frequency is determined by exactly the same equation  I presented in the recent post on my beautiful old slide rule, where the 'capacitance' is the acoustic compliance of the volume of air in the body of the bottle and the 'inductance' is the acoustic mass of the 'slug' of air in the neck.

The equations for these parameters are...

in which rho is the mass density of air and c is the speed of sound.

Air is surprisingly 'heavy' stuff - such that its density at the ordinary temperatures and pressures in which you're likely reading these words is around 1.22 kg per cubic metre and the speed of sound is around 340 metres per second. V is the volume of air in the 'body' of the bottle, l is the length of the neck and S is the cross-sectional area of the neck.

There are a bunch of other details, which I'll not bore you with - such as the reason for saying 'acoustic' compliance above. Also, the length l needs an 'end correction' (an additional length), to account for the radiation of sound from the open end of the bottle and the cross sectional area of the neck is not constant in the Bud bottle pictured above, such that specifying S isn't easy!

Taking a look at the bottle through half-closed eyes (and noting it was specified on the label to hold 330mL), I came up with some very ROUGH ESTIMATES of V=295 e-6 cubic metres, l=0.09 metres and S=3.14 e-4 square metres.

These produce the following equally rough values for the 'capacitance' and the 'inductance' (don't worry about the units):

C = 2.09 e-9
L = 347

I tried to solve for the resonant frequency of (the air inside) the Bud bottle on the Pickett N-515-T (I wonder if that's been done before?) using exactly the same steps as previously described.

We start with the rough estimate on the Decimal Point Locator...

First, we find the capacitance of 2090 pF, since there isn't a nanoFarad scale (I've indicated 2000 pF by my green line and red circle)...


then we move the slide until the 2090pF lines up with 347 H on the slide. This is difficult to do, as 347 Henries would be one big mother of an inductor, so the scales didn't run that high, stopping at 100H.

Fortunately, there's clear space above 100 Henries and we can easily see how the logarithmic scale works so, extrapolating from the decade 10:100, we can 'imagine' the decade 100:1000 (which I've labelled in blue on the photo below) and position the slide approximately...


Then, we should be able to read off the resonant frequency from below the arrow...


it is around 200 Hz.

For more accuracy, we can multiply together the 'inductance' and 'capacitance' to find the LC product...

 
 to get 7.25 (e-7) and set the hairline of the cursor over this value on the cursor on the 'H' scale...


The resonant frequency is directly read from the D scale to be around 187 Hz.

Blowing over the beer bottle, in traditional bar-room style, whilst running a tuning app on the iPad, revealed an actual frequency of 196 Hz ...


so this model - and the rough estimates of sizes - was reasonably accurate.

The bottle is (as many will know) an instance of what is called a Helmholtz resonator, after German physician and physicist Hermann von Helmholtz. Hermann was way too dignified to blow over bottles in bar rooms - here's an image from my copy of his 'On the Sensations of Tone...', showing his equivalent of the Bud bottle...


He even arranged a nice little 'Guttapercha' tube to direct the blowing!

It is nice to see that the Pickett N-515-T is good for more than electronics. I wonder if many other folks have done acoustics on it - or taken it into the bar?

...-.- de m0xpd