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frequency range 135,7 kHz ... 137,8 kHz. Until now my transmitter consists of a FT-757-GX and a 1:100 frequency-divider. The resulting signal is low-pass filtered and amplified by an old HIFI-PA to a power of about 20 Watts. The signal goes into the 2-turn link winding on the bottom of the loading coil. The antenna current is about 270 mA. |
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the estimated radiated power (ERP) ist about 3.6 mW. Because of the very low radiated power the most efficient mode seems to be slow telegraphy (SCW) with dot lenghts of 3s ... 5s. For reception I am using the DSP-receiver KWZ-30 by Kneisner&Doering usually with an IF-Bandwidth of 50 Hz. The best receiving-antenna so far is the GPA50 shortwave groundplane on top of the roof. The capacity of the coax-cable (2.2nF) is compensated at 137 kHz by means of a series choke of 500 yH. The atmospheric noise lies about 10 dB over the noise-floor of the receiver. The man-made noise level is usually sufficiently low with this antenna. The audio of the receiver is fed into the soundcard of a PC. On the PC runs a software (GRAM) that does a FFT-spectrum-analysis of the audio signal. The resulting bandwidth of the system is only 0.3 Hz when a 16k-FFT is selected. With the additional averaging function of the program it is possible to detect signals that are absolutely not audible. The detected signals are presented in a graphical form. |
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is made of 100 turns massive 1,4 mm diameter copper wire. |
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