26 September 2001

On Saturday 22 September ZL6QH, ZL3PN, ZL3JE, ZL4OL, ZL4MD 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


Further comment and screen shots by Rick Warnett  P29KFS, from Papua, New Guinea

Attached the fade in (our sunset) and fade out (NZ sunrise) traces.

I have a three turn 6 x 6M loop as a diamond frame which hangs from a suitable tree in my back yard and is rotatable 
It has a small 25:1 Z match toroid transformer which feeds coax back to the shack. 

I use a WJ HF1000 receiver set to CW 56Hz IF bandwidth, BFO 1000Hz and an MFJ784 DSP AGC / noise eliminator /
passband filter to feed audio into a generic sound card in an older Pentium.

The midnight trace is NOT overload !! You may be able to explain it ? I think it is to do with Doppler shifting of the signal on reflection....... but not certain.

Rick Warnett,  P29KFS