CLAIM OF ZL TO VE1 AMATEUR LF DX
20 December 2001
On Saturday 15 December ZL6QH transmitted a low speed frequency shift keyed
test signal in the 136 kHz band, as a beacon transmission for all hours of
local darkness. John VE1ZJ managed to receive and positively identify
signals from ZL6QH. The path length from ZL6QH near Wellington to VE1ZJ in
Sydney, Nova Scotia has been calculated as being 15,645 km.
VE1ZJ received the LF signal using a 10 metre vertical with top loading,
high impedance pre-amplifier, low pass filter and a TS-850 receiver. The
demodulated audio was fed to a computer sound card for filtering and display
of the signal using Argo software.
Weak signals were first received by VE1ZJ at 0845 UTC, which was some 40
minutes after ZL sunset at 0806 UTC and some three hours before VE1 sunrise
at 1150 UTC. Best reception was from 1045 to 1138 UTC.
Previous best DX for ZL6QH was confirmed reception by Dexter W4DEX two weeks
earlier, over a distance of 13,633 km. W4DEX received ZL6QH again but
generally not as well as the previous time. In June and September ZL6QH was
received by VE7SL, when the test frequency was 184.4 kHz, but since then the
ZL6QH signal has not been received at all, despite operators being ready to
try for an LF/HF cross-band contact if propagation was satisfactory at the
time.
The ZL6QH transmitted signal used frequency shift keying, with 0.4 Hz
frequency shift. The uniquely coded transmission consisted of repetitive
sending of QQQQQ. sent as 137.7900, 137.7900, 137.7896, 137.7900 and then a
gap, with all elements being of 120 seconds (2 minutes) duration. This
means sending a single Q takes ten minutes.
The ZL6QH LF signal was generated using a modified TS-850SAT, in SSB mode,
fed with audio from a lap top PC, using soundcard software developed by
Steve VK2ZTO. TS-850 frequency control was by means of a high performance
TCXO master oscillator. The low level LF signal from the TS-850 transverter
port was fed to an external LF power amplifier, and the output power was
around 500 watts. The radiated power is estimated to be 4 watts. The
antenna was a long wire at the Quartz Hill club station, which is run by the
Wellington Amateur Radio Club. The ZL6QH operator was Mike ZL4OL.
The next test from ZL6QH in the 136 kHz band will likely be in mid January.
Bob Vernall ZL2CA
Organiser of the ZL LF DX tests
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