Compliments always welcome

I have just received an unexpected email from Michal, a Polish radio amateur, callsign SQ7JZI, who has been monitoring my longwave transmissions recently. He wrote, " Incredible VLF signal to 137KHz, congratulations. What equipment do you use ?"
Of course I had to tell him, and encourage him to radiate his own signal. Then there will be 3 from Poland on the 2190m band.
Signals on this band are rare; still none at all from many of Poland's neighbouring countries. I hope someone from there will one day be able to change that. It would certainly add interest.

Circuits

This evening I have been transmitting on longwave, waiting for a contact partner, but none appeared, although I know that my signal was being received in Nuernberg, Germany, 745 kms away.
While waiting, I realised that until now I had never placed on my blog a circuit diagram for any of my construction projects; and yet there might be some visitors who would like to copy some of my designs.
Although the picture can be enlarged by clicking on it, whether I do this again still depends on the clarity.
Anyway, I try it at least once, with the circuit schematic of my GS31B 50MHz amplifier from 4 years ago. ( see also 25th January 2010 ).

My Russian toys

Though not dolls, there is nevertheless a progressive increase in size.
They are Russian made high power triode tubes, ( thermionic vacuum tubes, valves ), ideal for use in VHF/UHF transmitter power amplifiers, and significantly cheaper than western alternatives.
So, from L - R, the ones I have are type GI46B, GS31B and GS35B; in each case the suffix 'B' denotes tube variant suitable for forced air cooling, with or without the finned anode cooler. ( An 'A' here would mean water-cooled ).
The GS31B is a spare in case the one in my 50MHz amplifier, ( see post of 25th Jan, 7.23pm ), fails one day.
I am currently building an amplifier for 144MHz using the GS35B.
I haven't decided what to use the GI46B for yet. If I can obtain a second one, then making an amplifier for 432MHz using both tubes with their outputs combined would be an interesting construction project.

International Space Station

I was sitting in my radio room while wondering what to do next when I saw a radio contact confirmation card on the wall. Perhaps because it has been there a long time, I rarely notice it. As it may be of interest to the many visitors to my blog, I have put it here. The card shows the International Space Station, ISS, of course, and was sent to me as a memento of a conversation I had with Bill McArthur, the Mission 11 (?) commander, as the ISS passed over on 27th November 2005 at 11.00am.
I guess the ISS has grown in size since then !

Frequency synthesiser

Having decided on all the additional functions I want, ( band change, tuning step selection, PTT and output filter ), and the switches and connections that will be needed, during the last few days I have progressed further with the frequency synthesiser project from the experimental and development stage, ( see 25th January ), to the first, ( boxed ), prototype. The green, back-lit, dot-matrix liquid crystal display gives a particularly pleasing appearance. The source code still needs some refining. The inset shows new code being uploaded via the 'in-circuit serial programming' interface, ICSP.

Weather bad, longwave good

Tonight it is snowing again. The large coil is outside and connected to my antenna, but has little protection from precipitation. Although the weather is poor, radio propagation conditions on longwave tonight have been good. I have just completed a contact with Gerhard in Austria. The screen shot shows him calling me at the start. The other horizontal lines are sidebands from the LORAN-C navigational system on 100KHz. There are LORAN-C sites in coastal regions of northern Europe. We have to put up with its interference until the system is supersceded by GPS. The sound it makes is like a steam locomotive travelling at 100mph. To our advantage, however, these 'lines' give a useful indication of propagation conditions on 136KHz, and were strong and clear tonight; hence the possibility for my contact with Gerhard.
My signal was also picked up 745 kms away in Nuernberg, Germany !

Home-made PCBs

I made a printed circuit board, (PCB), today as part of the same construction project reported on 25th January. The quality achieved when making ones own boards in the kitchen at home can be remarkably high. I use silkscreen printing and photographic methods of production depending on the nature of the board. If I need a copper ground plane, (as in this case today), in order to equalise earth currents because radio-frequency signals will be present, I adopt the photographic method. If there are only to be tracks present, then the silkscreen printing method is quicker.
The picture shows the silkscreen layer, (top), for component locations, then the track pattern, (mid), and finally the etched board ready for drilling and populating. Click on the picture to enlarge it.

Modifying PC PSUs - finishing off

Recently my electronics workshop in the cellar has become just warm enough to visit to complete the modifications. Since the posting on 26th January, I have chosen to use 30 Amp Anderson Powerpole connectors for the red/black 12V output terminals; fitting a LED 'power-on' indicator and non-slip rubber feet underneath completes the work.
( Thanks Richard for donating the original. )

Friday night activity night

Yesterday evening the first activity period on longwave took place, to encourage Polish radio amateurs with longwave receiving and/or transmitting equipment to meet up "on the air". I think that in Poland only myself and one other guy can transmit on 2190m wavelength. Amateurs' antennas for this wavelength are relatively short and inefficient. So we have to transmit information slowly in a very narrow bandwidth to have any chance of being picked up. As an example, the screen capture shows how my slow morse signal, ( 4 sec dot , 12 sec dash ), was received by another Polish receiving station during this activity period.

Extreme loading coil appears in ham press

A description and picture featuring the massive loading coil I use with my Marconi antenna for 136KHz, have recently appeared in RadCom, the monthly magazine of the Radio Society of Great Britain, RSGB, December 2009, page 29. ( click on the post title to visit the RSGB web site ).
The main winding consists of about 400 turns on a 15cm diameter, 108cm long, sewer pipe and has multiple tapping points. The rotatable variometer winding inside is made from 37 turns on a 11cm diameter plastic water-pipe. The upturned plastic food container on top keeps water out.
The impedance matching network to the 50 Ohm coaxial cable feeder from the transmitter uses an ETD44 transformer core with a 9 turn primary winding and a 20 turn secondary winding. I can obtain a perfect match with this method, though occasionally there is slight detuning of the antenna system owing to environmental effects, requiring readjustment of the variometer.

Award arrives

The award that I mentioned in my last posting has just arrived by post; very colourful it is too. It will look even more impressive when framed and hanging on the wall in my radio room.

136KHz Award

PZK, the Polish national amateur radio society, has awarded me with a certificate in recognition of my achievements in longwave radio communication. And I even get a mention on the PZK web site http://www.awards.pzk.org.pl
( click on post title )

Europe in the deep freeze

I captured these images from today's early afternoon passes of the NOAA 19 weather satellite.

Putting old computer power supplies to good use

ATX type switching power supplies which have been removed from redundant computers can be easily modified to provide useful +/-5V and +/-12V ( also not so useful +3.3V ) DC fan-cooled bench supplies delivering around 300 watts in total. Voltage regulation of all rails is controlled by the regulation of the +5V rail, which needs to be permanently loaded with a resistor of about 10 Ohms rated at 3 to 5 watts. The power unit I am modifying is almost complete; just needs some nice red and black output terminals to be fitted and then it's ready to take its place on the workbench.

Amplifier for 144MHz

Another project on the bench is a transmitter power amplifier for the 144MHz band based on the Russian ex-military GS35 triode tube, ( centre top ), and which should be capable of an output in the region of 700 watts. The bias board ( right ) is completed, as is the control and switching board, ( left ); but the project is on hold. Despite my great endeavours, I cannot locate a source for the needed 2000 volt, 2 KVA eht transformer !

New design in progress

This is my current project which is still at the very early stages of development. I am hoping that eventually it will become a frequency synthesiser. For the first time I am using a programmable integrated circuit, PIC, which is basically a microprocessor using a reduced instruction set of around 40 commands. I am writing and testing the source code, burning the PIC, rewriting and retesting etc. Keep a look-out for future progress reports.

Winter at the antenna farm

This winter is very long and harsh. I patiently wait for suitable weather to work outside on my antennas. I really must put up a large loop antenna for longwave when the weather improves. Part of the vertical antenna for the 160 and 80 metre bands is just visible through the snow covered trees.

Longwave station

This is the operating position for the 136KHz longwave transmitter. The VLF SWR meter sits on the transmitter case, and the 25V 20A power supply is behind.

Single side band generator for the longwave transmitter

Uses the phasing method for ssb generation. CMOS logic integrated circuits ( D type and J-K type flip-flops ) produce the rf phase shift; a passive R-C phase shift network takes care of the audio phase shift. Plessey SL640 mixers are used. The prototype is shown undergoing tests. It is now fitted inside the transmitter case at the rear left. When it's connected to the PC soundcard, data, encoded as audio tones, can be transmitted.

Longwave transmitter

This transmitter for the 136KHz, ( 2190m ), band is another of my creations. It is capable of producing 350 watts from four IRF640 power mosfets with a 50V DC power supply. With this transmitter, I was able to complete the first longwave two-way communication ever accomplished in the history of the universe between Poland and Belarus, and Poland and the Czech Republic. Many thanks to my contact partners, Andrei and Ruda, for being at the other end of these historic contacts.