A SECOND CLAIM OF ZL TO VE
AMATEUR LF DX 26 September
2001
On
Saturday 22 September ZL6QH, ZL3PN, ZL3JE, ZL4OL and AX2TAR (VK7ZAL) transmitted
test signals in the 165 - 190 kHz band, for so-called trans-Pacific tests. Various DX listeners had prior knowledge
of the schedule of individual test frequency and coding used by each
station.
As
occurred in the 30 June trans-Pacific tests, Steve VE7SL managed to receive
signals from ZL6QH before VE7 dawn.
This time VE7SL obtained an Argo capture of both frequencies of the DFCW
transmission. The path length is
estimated to be 11,709 km.
Refer to the associated Argo
graphic. The ZL6QH signal is in the
lower half of the screen. The
transmitted signal used dual frequency keying, with 0.4 Hz frequency shift. The uniquely coded transmission
consisted of repetitive sending of QQQQQ… sent as 184.4001, 184.4001, 184.3997,
184.4001 kHz and then a gap, with all elements being of 120 seconds (2 minutes)
duration. This means sending a
single Q took ten minutes.
The
Argo graphic of the VE7SL reception shows inverted audio FSK , but otherwise
agrees with the dot length, sequence and frequency shift of the ZL6QH
transmission. The explanation for
the inversion is that the Icom IC-R75 receiver used by VE7SL happens to give
inverted FSK in the audio output when used in the normal CW mode. VE7SL used an RF signal generator to
subsequently verify that an Argo trace (showing receiver audio output) went
lower in frequency when the RF frequency went higher. Note that the parallel vertical red
lines in the centre of the Argo graphic are a software option for selecting
either short or long "ticks" and once selected, a tick stays on the screen. The left side of the long tick is close
to 40 minutes before the 1401 UTC sunrise at VE7SL. The signal faded rapidly about 3 minutes
after sunrise. It was still dark in
New Zealand at VE7 sunrise.
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 5
watts. The antenna was a long wire
at the Quartz Hill club station, which is run by the Wellington Amateur Radio
Club. The ZL6QH operators were
Andrew ZL2BBJ and Bob ZL2CA.
ZL6QH is seeking permission
to transmit in the 136 kHz band, which could widen the scope of testing beyond
"trans-Pacific", and give European listeners a better chance at receiving
amateur LF DX from down-under.
Bob
Vernall ZL2CA
Organiser
of the Trans-Pacific tests
