This signal is broadcasted by the DCF77 time signal transmitter in Germany and used by most radio controlled clocks in western Europe. Soon I heard some signals, one of the strongest was the pulse-per-second signal at 77.5 kHz. I tuned my receiver to the 30 meter band and tuned the oscillator and filters of the converter.
The converter’s output was connected to the antenna connector of my IC-718 shortwave transceiver. Since I did not have a suitable antenna yet, I took a 50 meter extension reel to act as a small receiving loop antenna and connected it to the input of the converter. I finished the converter and with just eight days left I put it to the test. I immediately started building the VLF converter. This reminded me of converters for VLF reception, and soon (early December) I decided to get my ham radio station prepared for the next SAQ transmission on Christmas Eve. My setupĪ fellow builder gave me a bunch of parts he didn’t use anymore, including some mixers and lots of crystals.
HOW TO BUILD A VLF RECEIVER SOFTWARE
A complete different solution is a piece of software called SAQrx, which turns your PC soundcard into a VLF receiver. Another way to receive VLF stations is to obtain a vintage radio which includes the VLF band, like the 45 kg Murphy B41 and the less heavy Telefunken ELK 639, both capable to receive VLF from 9.8 kHz. The most common solution to solve this issue is adding a VLF converter, which transponds the VLF band to a higher, more convenient part of the radio spectrum. For example, the Kenwood TS-590SG has a VFO which goes all the way down to 30 kHz, but the receiver is not able to handle signals below 130 kHz (as stated in the tech specs listed in its manual). But there is more, like active receiving loops and ferrite based antennas.Īdrian PA0RDA owns a Telefunken ELK 639, on this picture the (V)LF receiver is activated.īesides the antenna, the other concern is probably the receiver the VFO of your radio may run down to the VLF band, however the receiver itself is not able to handle these low frequencies, and/or the radio’s internal band filters will probably cut off these frequencies. A good example is the Mini-Whip by PA0RDT, which is a very simple yet great performing antenna for VLF. It can be easily placed on a balcony, in the attic or on a tonkin stick in the garden. No, you don’t need a huge antenna, indeed you can build a very small active antenna, maybe just 4 x 10 cm. There are two things to consider: the antenna and the receiver. Receiving VLF stations like SAQ is fairly simple, but not straightforward. Simplified visualisation of the radio spectrum, with the VLF band on the far left.
At such moments lots of radio enthusiasts tune their radios to 17.2 kHz to copy the telegraph message. The power is driven into a large antenna, which looks like a power transmission line of almost 2 km.Īt least two times a year the machine is powered up by volunteers (veterans) of the Alexander Association to broadcast a message to the world, typically in the early Summer at Alexanderson Day, and on Christmas Eve. At this level the transmitter is running very relaxed, since it is originally built to speed up to 40 kHz with a maximum output power of 200 kW.
HOW TO BUILD A VLF RECEIVER GENERATOR
The gear box causes the generator to produce an AC current of 17.2 kHz with an output power of about 80 kW. It is a true machine, with three main parts: a 500 HP electrical motor, a gear box and a generator. The so-called Alexanderson transmitter is everything you don’t expect of a transmitter. From 2004 the radio station is classified as a world heritage site by UNESCO. In 1996 the transmitter was finally shutdown, after more than 70 years of operation. Later the transmitter was used for submarine communications. It operates on a very low frequency: 17.2 kHz (!). Its first transmitter came on air in 1924 for telegraph communications with Radio Central, New York. SAQ is the callsign of the Varberg Radio Station at Grimeton, Sweden. The Alexanderson Alternator, which generates the 17.2 kHz carrier ( credits).
0 kommentar(er)
