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.

50MHz transmitter power amplifier

This home-made amplifier for 50MHz uses the Russian ex-military GS31B triode tube, producing about 500 watts output. It really is a fantastic performer. I remember some noteable reception reports of my signal, namely, "599+++ on my ground plane", "599+30dB" and "remarkable signal", from Belgium, England and Norway respectively !