DL2KCL longwave-page  (part 1)

homepage | longwave | solar eclipse 1999  | link-page | software

Here is a description of my amateur radio longwave-experiments in the
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.

transmitter configuration

The radiation resistance of the antenna is about 0.05 Ohm and
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
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

The antenna loading-coil (6 mH)
is made of 100 turns massive 1,4 mm
diameter copper wire.

my longwave-log

next page