Archive

Archive for October, 2013

Building the OpenQRP kit….

October 25, 2013 1 comment

Day 1Sat down at the workbench this morning and began to build the OpenQRP kit.  The components are conveniently packed into little bags, each labelled with a section number (1 – 19) corresponding to construction stages, both on the parts list and build instructions, both of which need to be downloaded from links on the Kanga website here: http://www.kanga-products.co.uk/index.php?option=com_content&view=article&id=76&Itemid=78.

Today I completed the first five sections which all relate to separate voltage regulators within the unit.

Section 1 provides the analogue ground and consists of a couple of resistors and some smoothing caps.  One of the caps is a tantalum and it is important to ensure that the polarisation is correct (long leg is positive (+)).  Fairly easy to mount on the board though.

1

 

 

Section 2 provides the 12V DC input, including the socket and again some smoothing capacitors.  It is important to ensure the socket fits flush to the board otherwise it may not meet up with the hole in the case later.

2

Section 3 provides the 5V digital input for the CPU of the board (Arduino).  Most of this is done with a 78LO5 and some smoothing caps again. Again ensure all electrolytic capacitors are fitted the correct way around.

3

Sections 4 and 5 provide analogue voltages of 6V and 8V respectively.  It is noted that the build instructions were actually incorrect here (section 4), suggesting that one of the capacitors was placed elsewhere on the board and not where it should be.

4

5

So after day one we have a few parts completed on the board but it is still very much vacant.  The next stage will be more testing as it is constructing the Arduino based CPU and relevant controls for on board programming. However the progress so far can be viewed in the last image here.

Day 1


October 30th:

Finally got onto stage 6 today.  This consisted of building the CPU and adding the push button controls and key jack prior to inserting the ATMEGA32 (Arduino) chip.

Firstly I checked the voltage points for all the previous stages and after confirming they were correct inserted the components for stage 6.  Checking the voltage across pins 7 and 8 of the IC socket I confirmed that it was 5V and then inserted the chip.  The photo shows a much more populated board and I eagerly await some more free time when I shall be able to move onto stage 7.

OQRP_30-10

November 2nd:

This morning I got round to completing stage 7.  This consists of fitting the display (2 * 16 LCD) and contrast control to the board.  The display did have to be matched up to the cut out on the front of the case so some care was taken here.  Once mounted power was applied to the unit to ensure that something happened and, lo and behold, the start-up screen was displayed showing the firmware version (E) and the pSOC chip version.

7 (1)

Next is the VFO stage.  A little more to this one – resistors and capacitors first, including CT3 – a small orange miniature trimmer – , followed by the varactor diode and Q9 (NPN).  The coil, L5, a 6.0uH inductor was wound and temporarily tacked to the back of the PCB  whilst testing.

8 8b

Once all were populated on the board the unit was powered up and the oscilloscope probe was used at TP4 to check for a nice 2.1MHz sine wave. All ok so far.

03/11/2013:

First thing I did today was fit the VFO Buffer.  This only really consisted of a couple of transistors plus a handful of resistors and capacitors.  What it did mean though was that it enabled the unit’s frequency counter to operate and display the VFO frequency on the LCD display.  The pictures say it all really.  It is notable that the VFO frequency is actually below 7MHz and slightly unstable at this stage.

9 9b

I then went on to do the RIT/Tuning stages.  The RIT is operated through a balanced resistive bridge and a CMOS controller.  I used a 10K linear POT as a temporary tuning control to check this stage and noted that once completed the VFO became much more stable (rock solid) and the frequency was more in the range required.  Again the pictures say it all really.

10b 10

04/11/2013:

Two further stages were completed today.  Firstly was stage 11.  This provides the 12V on key down.  Not a lot to it really, a few resistors and capacitors plus a couple of transistors – Q3 and Q4 – which are MOSFETs.  As these are rather easily damaged with static (ESD) I donned my anti-static gloves for this stage.  Powered up the unit, plugged in my paddle and checked for a 12V swing when the paddle was closed.

11

Next was stage 12 – TX Mixer and 1st Driver.  A bit more complex this one.  I do think it would have been made easier if the holes on the circuit board had been closer together for the multi-layer ceramic and smaller ceramic capacitors as the leads had to be stretched to fit in.  However, after installing the crystal (Y1) for the TX offset and the two transformers T1 and T2, the unit overall is beginning to look more like a radio.

12

November 6th:

worked through four stages today.   Firstly, stage 13, the PSoC Controller.  This was a fairly simple stage – two capacitors, a resistor and the PSoC IC (8 pin DIP).  So what does this stage do?  Well firstly it gave the LCD a backlight and made it much easier to read.

13

I then moved on to check the VFO and adjusted the coil to tune it to an LF of 6.995MHz and a HF of 7.085MHz.  Painting the coil with nail varnish holds the coils in place so all good.

Once the VFO was sorted I moved on to stage 14.  This is the Low Pass Filter and antenna switch.  The LPF consists of two wound toroids (makes for sore fingers) 17 turns on each and six small capacitors.  This is followed up with the antenna switch which consists of 3 MOSFETs, 1 resistor and 2 capacitors plus the BNC antenna socket.  All went together relatively easily.

14

I then moved on to stage 15 the Audio Amplifier.  The main component of this is the TDA7205A IC (8 pin DIN) op amp.  Associated components are a handful of capacitors and the speaker/headphone socket plus 3 resistors including RX2 the audio level control.

15

Lastly today was the audio filter another IC and some very precise (1%) resistors and capacitors.  However, once fitted this gave me a decent sidetone on key down so I can monitor my sent CW at least :-).

16

Stage 17:

Spent a while today (7/11/13) putting stage 17 together.  This is both the 1st RX Mixer stage and the crystal ladder filter.  I checked all the components against the list and noted that there was a surplus capacitor.  I placed this to one side in case I had miscounted and worked my way through.  First things to go on were the capacitors.  Quite a few of these and some are very tiny so again I have to be grateful for the high power magnifying glass I have in the workshop.  After fitting all the capacitors, still no mention of the surplus one.

Following this, I fitted 2 small inductors – L1 and L2 before fitting the IC – a SA-602 mixer.  this was followed by four crystals and then by T4 and T5.  Suddenly the spare capacitor came to light – the PCB is misprinted and the earth line on the second can is missing so it is used on the reverse of the board to link the tag to earth.

17

I also purchased a tapered round file this morning as the holes in the case aren’t quite big enough to accommodate the controls.  A single twist of the file was enough to widen them sufficiently to enable the rotary controls (Tune, RIT and RF Gain) to be fitted into the front panel.

08/11/2013:

So onto stage 18.  This is the 2nd RX mixer and differential amplifier.  Quite a bit to it actually with many small components.  The capacitors are very small and it is necessary to use a magnifying glass to read the values.  It is fairly important to get them the right way around and remember, the tantalum capacitor is electrolytic.  It was good to note that the demodulating circuit is the same as that used in the first ever crystal set I built – a diode ring.  Those basics that you learn always come back into play.

18

It was then time to fix the controls (Tune, RIT and RF) to the board and the front of the case. Nine pieces of wire were used here of varying lengths although the required lengths to be cut are noted on the instructions.  Powering up at this stage the unit looks quite good.

18 (2)

Finally attached an antenna and , using a local source, set up the RX section.  I actually fitted an antenna to the BNC socket, plugged in a speaker and tuned up my TS-480SAT to 7030kHz CW and sent a short CQ (5W out).  I noted that the frequency on the display was only 0.02kHz out – not bad at all really.  Anyway, the received tone was good and the decoder did its job perfectly.  I need to find a way to increase the gain a bit more as it needed a very strong signal to receive it.

And the board so far looks quite good, as can be seen from the photo.  The empty part on the far side is for the TX finals which will be done another day.

18 (1)

10/11/2013 – Final Stages:

Set on with constructing the final TX stages today.  First in were all the components including Q5 (IRF510 power MOSFET), Q2 (2N2219A TO-39 NPN) RX-1 (Transmit bias) and T3 (IF Transformer), omitting L4 at present.  this practically filled the board.  I checked the output waveform from the gate of Q2 and then set the bias voltage to 4.5V.  Once done, I wound L4  – this is a bifilar coil wound on a FT50-43 toroid former.  The four legs/leads of the coil were inserted into the relevant holes on the board and soldered in place.

I then fitted the board back into the base of the case and connected Q5 to the heatsink.  Once done I fixed the case completely and applied the decals to front and rear as can be seen in the photos.

19 (1)

19 (2)

Tomorrow, all being well, I shall set the TX offset and adjust the bias to give maximum output to complete the unit.

11/11/13:

Bit of bad news today I’m afraid.  I started out full of good intentions and fitted a power meter and dummy load to the unit and powered up.  This was time to set up the TX bias properly and check for an output.  I set the radio to tune (c/1 + pb6) which gives a 6 second key down) and adjusted T1 and T2 to give maximum output.  Unfortunately, the circuit went into thermal overdrive and the PA transistor blew.  Bright sparks, smoke and the smell of burnt silicon.  Turned everything back to minimum and now awaiting delivery of a replacement PA to fit in its place tomorrow.

12/11/13:

Set to and removed the blown Power MOSFET and proceeded to reset the radio tuning and bias properly.  First things first, I re-adjusted the BFO and tested the RX and decode functions. Absolutely lovely as can be seen by the image below.

RX and Decode

The H visible between the CQ and the callsign was sent as a test character.  This was all sent using my FT-817 on low power so as not to overload the RX circuit.  I then checked and reset the bias voltage before inserting the new Power MOSFET (PA) all well this time – I didn’t mange to (ahem) blow it up.  The picture below shows the completed circuit board.

complete

The overall size of the unit inside its case is ideal for a small home set up or portable use.  It is roughly the same width and height as an FT817 and a little bit less deep.  It is also very lightweight.  You would only need a 12V power source at approx. 2A DC and an antenna and key.  The photo below shows it sitting above a FT817 for size comparison.

BY3C8s0IMAAEnuU

 

Advertisements

OpenQRP inside the box

October 24, 2013 Leave a comment

openQRP1Arrived this morning from Kanga kits UK.  Only ordered yesterday – how’s that for service? anyway, upon receiving the package and opening it up I got my first glimpse of the PCB I shall be working on.  The components are inside the metal box which will encase the completed project.

OpenQRP Transceiver Project

October 24, 2013 Leave a comment

Yesterday I ordered an OpenQRP transceiver kit from http://www.kanga-products.co.uk/.  The full details of this kit can be found here: http://www.kanga-products.co.uk/index.php?option=com_content&view=article&id=76&Itemid=78.  Basically it is a 40m QRP CW transceiver built around the Arduino microprocessor.  The kit is supplied as a selection of components plus the case and controls.  The full parts list is 6 A4 pages long so I shan’t go into details here.

As I progress through construction of the kit I shall keep a running blog of it and then describe the results as I use it.  If completed correctly it will incorporate a CW decoder with a running message on the LCD screen for both RX and TX….

Visual Studio 2012 vs what came before

I started off, many years ago, programming in Commodore BASIC (Vic 20, C64) and then progressed onto GWBASIC and such before delving into C as a programming language. I first used Borland C and then moved onto Borland Turbo C. This gives a little bit of a background of my programming history.

I took a break for some years as other things got in the way and then took it up again with the advent of Visual Studio 2005. This was a little different as it involved a little object oriented programmingand something called C# that was a new language to me. The thing with C# is that it replaces the traditional C language and adds Windows forms as well as the more traditional console type execution. The fact that the forms were available predefined within the SDK also made programming somewhat easier and the end product more user friendly with a half decent GUI.

In 2007/8 a new beast was released called Visual Studio 2008. this time the new version of Visual C# included LINQ or Language-Integrated Query.  this enabled direct integration with the .NET Framework collections, SQL Server databases, ADO.NET Datasets, and XML documents, enabling the creation of greater databases and easily shared routines across the MSDN .NET framework.  It also introduced the ability to adjust the properties of any given object using the associated XAML code.

I gave the 2010 version of Visual Studio a miss for various reasons and the next update I got was the new Visual Studio 2012.  As a rule I use the Express version until I decide to go out and exchange hard cash for a professional or ultimate version.  The first thing I noticed was that whereas previous issues had been a single SDK, when I downloaded the VS2012 Express from www.microsoft.com I was only able to see templates for metro style apps for the Windows8 Store and no generic Windows form apps or WPF templates.  I put out a general query through twitter and discovered that I actually needed to download a second SDK – Visual Studio 2012 Express for Desktop.  Anyway, on doing this I found that I now had all the usual generic templates albeit spread over 2 SDK’s.  Also it is worth noting that Visual Basic 2012 is now a full Object Oriented Language and now has much the same power as C# or C++.  Not quite the same as previous versions of Visual Basic so if you do update from VB5.0 or whatever you have quite a learning curve to progress through.

Anyway, I do like Visual Studio 2012 now I am getting the hang of it and may make some software available either as freeware or shareware at some stage before going on to full professional development again.

Thank you for taking the time to read this.