Winter's icy grip

Cold air from Scandinavia brings freezing weather conditions to Poland with temperatures well below 0C. I recorded -16.5C overnight last night and -21C is forecast for tonight. Although today was clear and sunny the temperature was still only -10C to -12C. Sun illumination level was high today, making it possible to receive some nice images transmitted by the NOAA weather satellites. I received the one shown above from NOAA18 at 1131gmt on 137.9125MHz.

Bootloader in action

After programming a boot-vector and boot-block into the PIC microcontroller's flash program memory, I used a bootloader to upload my application code to the PIC from the PC using its com port, the level converter, ( featured yesterday ), and the EUSART, ( enhanced universal synchronous asynchronous receiver transmitter ), connections on the PIC. The top picture shows all the project hardware, looking a bit untidy by now.
To check, I read back from the PIC to the bootloader the entire contents of program memory, ( actually also data eeprom and config ). The screen capture in the lower picture shows just the first portion of this, from address 0000hex to address 00DFhex. On looking at this I can see that the bootloader has highlighted the boot-vector code, at address 0000hex - 0003hex; the high priority interrupt vector and low priority interrupt vector are still at 0008hex - 000Bhex, and 0018hex - 001Bhex respectively. My PIC type, com port and speed are correctly declared in the bottom right corner. I notice that the time taken for the flash memory 'read' was 35 seconds. I'll configure com2 for a higher speed to reduce this, although I won't be reading memory very often. I recall that, earlier, 'writing' took only 4 seconds.(*)
It'll be interesting to use the bootloader for programming instead of the ICD2, which of course will still be essential for debugging.
All this has got me thinking about the download area on my eventual (?) website !
( My thanks to Microchip Technology Inc. for the freeware serial bootloader AN1310v1.04 )

* Update, 11 February : I subsequently changed the speed of com2 from 9600 to 115200 bits per second; now write and read times have been reduced to 0.942 and 2.975 seconds respectively.

PC talks to PIC projects

Today I built a CMOS/TTL to RS-232 level converter using a Texas Instruments part, MAX232N, driver/receiver chip in a 16pin DIP package. Now, provided that the PIC is self-programmable, ( which indeed my PIC18F4550 is ), it will be possible to connect my PIC applications/firmware to a PC serial ( com ) port, or via a USB (*) adaptor.The purpose of this interface between PC and PIC is, ( after making a bootblock in the program memory ), to use a bootloader so that a PC can read, write, verify, modify etc the PIC's software; or software updates downloaded from the web can be installed by a user anywhere.
The schematic and track layout for a double-sided 2.1 x 1.6 inch circuit board show the MAX232 in a 16pin SOIC package.
(*) Although I am usually 'game' for a challenge, I have put on hold indefinately any of my attempts to make a USB interface.

First birthday

 

Today the blog is one year old - Happy Birthday, Radioworm !
During the last 12 months there were 50 postings made, the hit-counter shows 1759 pageviews and visitors came from Europe, Middle East, Asia and USA. "Circuits", 27th March, leads the popular posts table. This was a post that I was undecided about publishing at all !
In that time the frequency synthesiser has dominated my construction projects.
My activity 'on the air' on longwave has been the most newsworthy; country "firsts" were reported on January 8th, and an award received in recognition of my achievements, 6th February. My personal favourite post is that of the extreme loading coil, 19th February. Of all the pics of my longwave radio station which I sent a magazine columnist, I wish he hadn't chosen to publish the one of the coil.
On the 20th April I saw the volcano eruption in Iceland from space, thanks to the weather satellites.
In the next twelve months I plan to develop a family of synthesisers including basic models and more advanced variants, build a new antenna for longwave, complete the 700 watt transmitter amplifier for 144MHz, and make my first amateur radio contacts via the moon; all of which will be posted here if they come to fruition. So it seems I shall be in this corner of the workshop quite often !

DDS #2 on test

Today I continued with the development of the second prototype frequency synthesiser. I have added the facility of changing the tuning step size in real time.
It is shown being tested on the work bench alongside "MyDev2", ( PIC18F4550 microcontroller ), and "ICD2", ( debugger and programmer ).
The output voltage at 137.7KHz is a 1.32v peak to peak pure sine wave across 300 Ohm. There is no output low-pass filter and I think this is the reason the output level is about twice that of prototype #1, which incorporates such a filter, probably introducing significant residual capacitive reactance.

More "firsts" on longwave

Yesterday evening, Szigy, callsign YO2IS, in Timisoara, Romania, 710 kms away, and I had a contact on the 2190m longwave band, which we will claim as the first ever Romania - Poland contact on that band, thereby adding Romania to my two prior "firsts" with the Czech Republic and Belarus.
I copy part of Szigy's email which he sent to me soon after our meeting 'on the air', particularly because it emphasises how challenging amateur radio communication is on longwave; as I know only too well myself, even over distances of just a few hundred kilometres. Szigy wrote:

"Dear Steve pleased to run a fine QSO with you, the very first SP-YO on 2.2Km. Signal was nice but with a deep QSB on the midle of the QSO. At the beginning had some problem with a flashover in the teflon feedtrough my window, it take one hour to change the isolator.Will send you a direct QSL in the next days. Once more thanks for the new one ! Have fun on VLF it's always a big chalenge, gl."

One of the challenges is typically the use of short inefficient antennas, ( because of the nearly 2.2km wavelength ), causing high voltages of several KV to appear at various places in the antenna system. Unluckily for Szigy during our contact, he had to take time out to tackle a problem of insulator flashover !
Earlier this week, I cleared ice and snow from my antenna in order to make it useable once more; but even then I had a flashover problem which I was able to prevent happening again, and fortunately nothing went wrong at my end during the contact with Szigy.

Stop press: In the last few minutes I have achieved another "first", Estonia. Incredible conditions on longwave this weekend, and some stations active making the most of them. What a start to 2011 on 2190 !

Meteor scatter using the Quadrantids

The Quadrantids meteor shower, which appears to come from the direction of  the old star constellation of Quadrans Muralis near the Pole Star, has just intersected with the earth, as it does every year on the 4th January. I used the ionised trails produced as individual meteors burnt up in the earth's atmosphere to reflect my 50MHz radio transmissions to make contact with other radio amateurs in Denmark, Slovenia, England and the Netherlands by exchanging short, ( for obvious reasons ), text messages with them. The data transmission mode is called WSJT/JT6M, and I used the 500 watt amplifier featured on 25th January and 12th May 2010.
The screen shot shows one of Dick's, ( callsign G1CWP ), signals which I received during my contact with him in West Sussex, in the UK at a distance of 1451kms from me. The burst of signal has the characteristic profile of having been reflected by a meteor trail with its steeply rising leading edge as the trail quickly forms and peaks in intensity, followed by a more gradually falling trailing edge as the intensity subsides until the event is over.
I try to participate in all the major meteor showers during the course of a year; Quadrantids ( January), Lyrids ( April ), Perseids ( August ), Orionids ( October ), Leonids ( November ) and Geminids ( December ).

DDS deadline met

I have completed the first prototype of the dual-band frequency synthesiser, ( just before my self imposed deadline of the end of the decade ), by writing the last piece of the software to tune the output frequency up and down in 1Hz or 10Hz steps. This function works perfectly; whatever the actual output frequency, it precisely matches the frequency indicated on the display, as of course it should do. So 2010 will end on that happy note. But what about the future ?
This first prototype is what I would consider as a ' concept and technology demonstrator'. For the second prototype synthesiser I have decided to change to a more sophisticated PIC microcontroller, and one that has not been in production all that long, e.g., the Microchip PIC18F4550, which will allow me to implement more features. In fact I have already completed about 25% of this prototype , based on "MyDev2"; see posting on 2nd November.
Concerning software, until now I have been programming in Microchip's assembler language. Using 'C' language is probably a better choice in future. I have absolutely no prior experience of 'C'; but what I do know is that its command syntax is more descriptive than assembler, and the code is not type specific to any one manufacturer's microprocessor families. Some of the extended functionality I want for the second prototype is better suited to 'C' and would be extremely difficult to program in assembler for a novice programmer as myself. The PIC18F4550 can be programmed in both assembler and 'C'.
Back to the present, and the first prototype is shown in the upper picture placed on top of my longwave transmitter with which it will be used to gain some operational experience which may suggest improvements or further development. The middle picture is the post-filter rf output voltage displayed on an oscilloscope, showing a 656mV peak-peak pure sine wave. The lower picture is the output frequency of the synthesiser as I tune it from 137700Hz +/- 50Hz in 10Hz steps.

Stepping up and stepping down

A few hours ago I took my frequency synthesiser project a significant step nearer to completion. I had a 'eureka' moment; not actually in the bath but instead while waiting to go Christmas shopping with my daughter.
A long time ago I had programmed the PIC microcontroller to show the frequency on the liquid crystal display. The number crunching sequences needed are binary to binary coded decimal ( bcd ) conversion, bcd to ascii, and finally, supression of any leading zeros to prepare the number for display.
For weeks I had been baffled why I couldn't achieve this repetitively in order to step the displayed frequency up or down in response to clockwise or counter-clockwise turning of the rotary encoder; the only difference being to include multiple byte addition and subtraction. This I have now managed to do. It's a great result for me and so good to see on the display. Now I can enjoy Christmas and not be distracted by searching for a solution any more.
This was one of the last two crucial issues to be resolved; the other being to increment / decrement the tuning word by the same step size for sending to the synthesiser chip, which should be straightforward. So I ought to be able to complete the prototype frequency synthesiser this month - famous last words !

XiWANG - Chinese for hope

I had my first radio contact using a satellite as a repeater in 1997, and since then have made a total of 582; an average of less than 45 per year. So I have not been very busy using satellites which have to compete for my time with my many other amateur radio operating interests and construction projects. It usually needs the launch of a new satellite to get me interested again. Such was the case recently when China launched its first amateur radio communications satellite, called XiWang-1, ( Hope-1 ), on 15th December 2009.
Commissioning of this satellite finished in early September 2010, when it was then brought into operational service, using the broadcast callsign BJ1SA-11 and message board callsign BJ1SA-12 with uplink in the 145MHz band and downlink in the 435MHz band. Soon afterwards, I began listening to its beacon transmission in morse code and decoding its data signal, for example,
BJ1SA-11 To DL8DR [21:07:48]
OK DL8DR\\D
BJ1SA-12 To BBSTAT [21:08:05]
Open BJ1SA-12:1
BJ1SA-12 To OZ7SAT [21:08:15]
BJ1SA-11 To PBLIST [21:08:28]
PB: DL8DR\\D
This week I have enjoyed making my first two-way radio contacts through this "bird"; so far with other amateur radio stations in Italy, Norway, France, Belgium and Hungary. I have already received a radio contact confirmation card from one of them.
The antennas I am using are crossed dipoles, ( uplink ), and helical, ( downlink ); both are home-made and can be seen in the picture which I posted on 11th May.
PS. 11th December. After my initial euphoria my enthusiasm has been dampened by the fact that the cw/ssb transponder seems to be turned off for long periods.

Four on longwave

Most weekends, except in summer, I am transmitting my radio signal on longwave, ( 2190m / 137.7KHz ), and hoping someone will reply. Usually my signal goes unanswered as no one else is about; but last night Marek, a Polish radio amateur, callsign SP2OVY, from near Gdansk, called me. I had never received his signal before. So I assume that he has only recently begun to transmit on longwave. To my knowledge there are now 4 Polish stations, including myself, who have transmitters for the 2190m band; though I am aware of a few others who monitor on receive only. Two years ago I was the only one active on longwave in Poland. So the numbers are gradually increasing.
The distance between Marek and me is only 277kms; but I was happy my signal made it that far as snow on my antenna had significantly detuned it. We had a successful 2-way contact, ( report "O" bothways ), ending in the early hours of this morning.
The screen capture shows his slow morse ( QRSS ) signal to which I have added the letters; of course 'E' and 'N' were the following two letters on the next screen capture, ( not shown ).
I am still using the same home-made transmitter and antenna which I featured on the blog on 25th January and 19th February.

Adjustable voltage for the ex-PC PSU

The discarded computer power supplies which I modified, ( see January 26th and March 7th ), are very useful items of equiment to have on the bench in the workshop; 12V for my frequency synthesiser project and 5V for microcontrollers. They are, of course, fixed voltage supplies. There will be times when other voltages will be needed. I am thinking in particular about 9V and 3V. So I made an adjustable series voltage regulator to connect externally to the 12V power supply. The regulator uses a linear voltage regulator IC, RCA type CA723CE, or National Semiconductor type uA723CN; both have identical pin assignments, and are directly interchangeable, ( same package outline 14pin DIP ). Unfortunately two different, separate circuits are needed to provide 3V and 9V; the difference being the connections between the resistive potential divider and the error, ( "long-tailed pair" differential ), amplifier. For the time being at least, I decided to make just a 9V version for permanent use, ( the output voltage is adjustable between 8.43 - 9.81V ); but I also built a 3V version on experimenting board to check it, ( the output voltage range was 2.8 - 3.6V ).
The xA723Cx IC on its own can provide a maximum of 150mA output load current. This is insufficient for general purpose use on the work-bench; more current should be available. So the IC drives a 'pass' transistor rather than the load directly; but the output will be 0.6V less. Just about any power switching transistor capable of passing a few amps is suitable. From my stock I pressed into service an ancient and hitherto unused Motorola type BU326A, rated at maximum 8A, and fitted it to a small 2.9degC/W heatsink.

AF Marker Generator

I have four 2048KHz quartz crystals, probably originally in some old 32 channel PCM telecomms equipment, and was thinking how I might use them, or at least one of them. I also have the same number of CMOS logic binary divider ICs, types HCF4060BEY and CD4060BE. 2048 = 2e11; dividing it by 2e12 ( 4096 ) will produce a 0.5KHz square-wave from the divider chip.
In my circuit, the crystal is used in a 2048KHz oscillator to clock the divider chip and the 0.5KHz square-wave is taken from the /4096 output on pin 1. A resistive potential divider reduces the level of the square-wave to 1.05V on the output phono socket.
As a square-wave is the sum of harmonically related sine waves, in the frequency domain there will the fundamental 0.5KHz signal and its odd numbered harmonics; 3rd, 5th, 7th, 9th etc. For my purposes the most useful signals are the fundamental, 3rd and 5th harmonics; 0.5KHz, 1.5KHz and 2.5KHz respectively, as these lie within the AF band 300Hz-2.7KHz typically used in radio communication, and can be used as accurate frequency calibration markers.
I have connected the marker generator to the sound card in one of my PCs in order to display the audio spectrum. With the cursor arrow placed as accurately as I can manage on any one of the signals, e.g. the 3rd harmonic near the band centre, and reading off the frequency there is a frequency error of +7Hz due to the inaccuracy, compared with the nominal, of the sampling rate of the sound card input.
After that slight digression I had better get back to PIC programming, or maybe I'll make a start on putting together the pre-amplifier, ( see June 16th ).

On display

Seeing is believing ! I programmed the frequency synthesiser, which I am in the process of building, for an output signal on 137.700KHz. Both the display on the Thandar PFM200A frequency counter, ( connected to the output ), and the display on the synthesiser, ( connected to the microprocessor ), agree. What a relief.
The next task is to make it tuneable up and down, ( probably in 1 and 10Hz steps ), implement band changing and at the same time make sure the display updates correctly.

MyDev2 replaces MyDev1

PIC18F4550 version

PIC18F4685 version

Schematic - note Vcc connection depends on usb-powered or self-powered application

Development boards for microcontrollers are essential for debugging code and checking hardware peripherals before committing to the final build-configuration.My first microcontroller development board, which I called "MyDev1", has served me quite well; see 25th January. It is a typical, solderless, experimenting board; component leads are a push-fit into the holes. Its limitations, however, began to become apparent; noisy, intermittent connections, lack of flexibility and a real nightmare if I had ever attempted to use it with 40 or even 28 pin microcontrollers and interfacing with several hardware peripherals at once. Having unreliable connections is a really bad situation when the microcontroller is waiting, or looking, for changes.It was therefore time to upgrade to a better system; so I have produced "MyDev2". Now it is much easier to reconfigure for different peripherals, e.g. display, keypad, rotary encoder, comms ports, and to check their operation. Of course, I haven't omitted the LEDs, and "MyDev2" has many, ( different colours for different ports ), as it is always nice to see pretty lights as a visual indication of I/O port output state ! I could not avoid solderless connections entirely; but those are of a high reliability using good quality pin-headers.
"MyDev2" connects to the Microchip ICD2, ( In-Circuit Debugger No.2 ), for programming and debugging operations, thereby replacing my original home-made programmer, ( see 25th Jan, 8:06PM, purple box ).
Using a development board I was easily able to change between two mechanical rotary shaft encoders, ( control with knob ), from different manufacturers, choose the more appropriate one for my final application, and 'fine-tune' the PIC code to suit.
Incidentally, the microcontrollers featured in the pictures above are 40 pin Microchip parts, ( lower ) type PIC18F4685-E/P, and ( upper ) type PIC18F4550-I/P which incorporates a USB interface.

SMD soldering success

I have used the tools and materials described in my posting on 20th August to solder successfully in place the frequency synthesiser chip, ( encircled in the picture ); an amazing result, considering it was the first SMT component I had ever attempted to solder, ( since being properly equipped ), and I had only 'perfected' my technique on a scrap piece of circuit board a few moments earlier !
The chip is Analog Devices Inc. 50MHz CMOS complete direct digital synthesiser type AD9835 which measures 5.1mm x 4.5mm and has 8 connection pins on each of the two longer sides to be soldered.
The mixture of 'through hole mounted' components and SMD on the same board is convenient and acceptable for prototyping. With this first SMD soldering success behind me I shall, in time, convert the circuit board completely to SMT in a future version.
Now let me see if the code I have written, ( see 17th May ), to control the chip will actually get it to do what I want.

Matchbox

During the summer I don't operate my amateur radio station on the low frequency bands, ( 80m, 160m and 2190m wavelengths ); the atmospheric noise, mostly from thunderstorms within a radius of about 4000kms from me, just doesn't give a pleasant listening experience, as well as blotting out the weak signals which I need to hear. Conditions in winter for radio communication on these bands are much better, particularly for making very long distance contacts. My favourite time for concentrating on these bands is around the time of the autumn and spring equinoxes. I am starting to get excited as such conditions will soon be arriving again.
I use the same antenna on each band, namely a vertical, aluminium pole which rests on an insulator at its base. Over the years I have collected many useful insulators of this type, both ceramic and glass, by looking on the ground at the bottom of telephone poles.
I have just cleaned the insulator, ( a white, ceramic one ), checked and weather-proofed the connections to the antenna, confirmed that it is resonant on my preferred frequencies and impedance-matched to the 50 Ohm coaxial feeder cable from the transmitters.
The matching networks, ( a tapped coil for the 80m band, a L-C 'L' network for the 160m band ), are located inside the storage container with lid, otherwise known as the "Matchbox", at the foot of the antenna, with the exception of the loading coil for the 2190m band which is too large to fit inside.
Perhaps this year I will reach my target of making contact with 160 different countries on the 160m band.

ESD and SMD

Many modern electronic components are vulnerable to electrostatic discharge, ESD, and may also be miniscule surface mount devices, SMD, ( typically with dimensions of only a few hundredths of an inch ), for circuit boards using surface mount technology, SMT. The synthesiser chip, which I referred to on 17th May, is both. Since then I have assembled the necessary tools, materials and aids to work successfully with such components.
On the heat-resistant anti-static work mat I've placed some other ESD accessories; wrist-strap, anti-static brush and earth plug.
For soldering and handling I have a 48 watt temperature controlled soldering iron, tips with sub-millimetre pointed ends, 0.38, 0.56 and 0.70mm diameter solder, solder-wick ( size AB ), liquid flux, solder paste, iso-propyle alcohol for cleaning off flux residue, tweezers and a swivel mounted vice. Regarding the vice, mine has a groove along the length of the jaws, making it ideal for holding circuit boards.
Obviously it is fundamental to be able to see the SMT components properly. So to help me in this regard, and also for inspecting my work, I've collected various types of optical aids, handheld and hands-free, with magnifications from x1.5 to x20. The adjustable 2.5 watt LED light will illuminate the work surface without too much glare or shadow.
All that is now left to chance is a steady hand !

ISS and I-Gate

The International Space Station, ISS, has been very easy to see just after dusk for the last few evenings. The first module, called Unity, was placed in orbit in 1998.
About September 2005 I became registered as an authorised Internet Gateway, ( I-Gate ), for traffic relayed by the ISS, and seeing the ISS recently rekindled my interest. With my laptop connected simultaneously to a radio transceiver and the internet I can receive and pass on to an internet server messages, beacons, locations, and weather reports from ground-stations, sent via the ISS.
The first couple of lines of text show that I sent traffic to an address APRS via ARISS, ( the ISS ); the content is my ground-station location and a text string stating that it is an internet gateway, digital repeater and weather station. The next two lines show that 2 seconds later my transmission was relayed by the ISS, which inserted its callsign RS0ISS-4, and was received by me and any other ground-stations in range of the ISS at that time.
In lines 5 and 6, I sent a kind of greetings message to everyone, and again, 2 seconds later, receive it back. I have in the past sent personal messages to specific stations and weather, ( 'WX' ), reports; but on this occasion I didn't leave myself with enough time to download weather data from my weather station to the laptop, before the ISS was above the horizon.
It is not possible to 'I-Gate' ones own transmissions; another 'I-Gate' has to do that. My first transmission contained coordinates; so when an I-Gate in the Netherlands received it, I could then be plotted on the map. Look for the green star with 'D', meaning digital repeater. The station UT1HZM in the Ukraine appears on the map only thanks to me; I received and 'I-Gated' his transmission. A station in Belgium, using my email address, subsequently emailed me.
Quite a few stations were active during that particular ISS pass over Europe yesterday between 2139 and 2154 CET. Some of them, ( white 'WX' in a blue circle ), were transmitting weather reports.
All up and down link transmissions to and from the ISS took place on a frequency of 145.825MHz, +/- Doppler shift, with a data rate of 1200 bps, AX25 packet unprotocol information, ( UI ), frames. I used a 50 watt transmitter, TNC-2 terminal node controller with the TNC-laptop interface running at 9800bps, and 'white stick ' antenna; the software packages are AGW Packet Engine, UISS and UI-View.
Perhaps this evening I will send a weather report for all the world to see !
Click on the post title link for more information, the latest maps and traffic from the last two hours or so.

Noise factors

Having achieved over the years considerable success with radio communication on the VHF bands using terrestrial modes of radio-signal propagation and reflecting my signals from the ionised trails formed by meteorites as they burn up in the earth's atmosphere, I am considering a new, formidable, challenge; reflecting my signals from the moon, to be able to contact amateur stations on the other side of the world on VHF. Signals received via the moon will be very weak, however, and at present noise may be a limiting factor. All radio signals are received in the presence of noise, from external atmospheric, man-made and galactic sources as well as that added by the receive equipment itself. Even an electronic component, such as a resistor, lying unconnected on the work-bench generates noise at the sub-atomic level, unless kept at a temperature of -273C ! Powered-up equipment at room-temperature is much noisier. I had been wondering if my equipment would be sensitive enough to receive signals reflected from the moon from other stations, as well as my own, or would they be buried under the noise and be undetectable.So I carried out an assessment of the noise performance of my VHF receive set-ups, for 50, 70 and 144MHz frequencies, and found it to be poor in each case. The noise is excessive for consistently successful 'moonbounce', though there is always the possibility of the occasional 'freak' contact. My assessment method, using my 144MHz set-up as the example, is shown in the upper picture.
I can't control external noise, but fortunately there is still a remedy; fit a low noise receive signal pre-amplifier as close to the antenna as possible. I set about designing one, first for 144MHz, based on a low noise n-channel dual gate mosfet transistor, type BF991, which is specified to 200MHz, ( circuit shown ). With a noise figure of 1.28dB and sufficient gain, this little amplifier should do nicely and allow a signal power of 1.306x10e-4 picowatts from the antenna to be detected with a signal / noise ratio of 10dB in a 2400Hz receiver bandwidth ! I will need to modify the circuit for the other two frequency bands mentioned, just by changing the attenuation of the 50 Ohm pad and the values of the frequency dependent components.
So three preamplifiers in all - my list of circuits to build during next winter just keeps growing !