Re: LF: hunting IK1HGI on LF

[Markus Vester <markusvester@aol.com>]

Thanks Domenico.

Yesterday evening we had monstrous QRN, but a faint and stable line became visible on my opds between 4 and 5:30 UT. An opds-32 detection requires about 15 dB for the central carrier of the 50% AM transmission, equivalent to 21 dB for a pure carrier in 0.47 mHz. We have been detecting IK1IGI frequently here, and I'm indeed interested to attempt an EbNaut decode. The best time may be around noon (i.e. now), when dayrime skywave is strongest and QRN hasn't built up yet.

Best 73,
Markus

-----Ursprüngliche Mitteilung-----
Von: Domenico IZ7SLZ <iz7slz.domenico@gmail.com>
An: rsgb_lf_group <rsgb_lf_group@blacksheep.org>
Verschickt: Fr, 23. Jun 2017 11:28
Betreff: LF: hunting IK1HGI on LF

Hi LF,

in these days, Tony IK1HGI from JN45jj, is transmitting some (not announced) EbNaut test message on LF and he is active in op32. He is using a very stable exciter formed by a GPS Neo-7 which time port TP5 has been reprogrammed to output directly the operating frequency (i.e. 137493,000 Hz).

I invite all interested LF operators to try this solution becouse it's cheap, easy to built and it works !

Riccardo IW4DXW, who had this idea, is writing some

post to the group with his indications on buffering the TP5 signal, obtain a BPSK and ASK modulator, reprogramming the GPS parameters.

Erp transmitted by Tony is low due to very short antenna placed on his balcon, short cap-hat wires,  poor ground system and low power output (around 70 W) with some mismatching.
So catching  his signal is a challenge for me in JN80nu (abt. 920 km).

Last night i saw some traces of his signal on my opds Spectrum Lab waterfall but no opera detections were possibile even by reducing thresholds in opds.ini.

I have also used Paul Nicholson's vlfrx-tools programs to record the audio coming from LF receiver. Then i tried this morning to obtain  4 hour-long  FFT  centered on IK1HGI qrg after filtering and blanking the signal. 

I got an evident peak that i'm almost sure that comes from Tony.

These are the commands that i have used (i'm new on vlfrx-tools so i hope do not make big mistakes):

vtread -v -T2017-06-22_23:40,+16000 /media/iz7slz/Storage/ |
vtfilter -v -h bp,f=1500,w=2000 |
vtblank -v -a2 -d0 -t10 |
vtnspec -v -f 1493 -w0.02 -r6.25e-5 > spectrum.dat

that vtblank settings comes out after many attempts.

73, Domenico IZ7SLZ