klubnl.pl

[email protected] list outage

The [email protected] email reflector doesn’t work, the last post is from 1 september 2019.

We hope this is a temporary outage due to patching of the CVE-2019-15846 vulnerability in Exim.

An archive of this list is avaliable on this page.

How Cave Communications works

Due to the ongoing (on 20 august 2019) rescue operation in the Wielka Śnieżna Cave in the Tatra mountains we decided to write about cave communications.

Rocks and soil attenuate radio signals well. Despite of this some means of communications in caves and mines are needed.

The attenuation rises with frequency. Normal VHF communications gear can’t be used, sometimes the distance can deteriorate to meters, depending on the geology and shape of tunnels. Of course cell phones are totally out of the question too. Shortwave radio behaves only a bit better.

Much larger distances can be achieved using low frequencies.

Continue reading “How Cave Communications works”

SAQ Alexanderson Day transmission on 20190630

A video of the SAQ Alexanderson Day transmission on 9:00 UTC 20190630.

Received at SQ5BPF QTH Warsaw/Poland KO02md.

E-field active antenna, vlfrx-tools and Spectrum Lab receiver

Transmission at 9:00 UTC:

Transmission at 12:00 UTC:

ULF 2970.1 reception record

Stefan DK7FC transmitted at 6 aptil 2019 20:25 UTC at 2970.1Hz. The TX power was 487W into a 1130m ground dipole antenna. The ebnaut transmission parameters were:

f = 2970.1 Hz
Start time: 06.APR.2019 20:25:00.3 UTC
Symbol period: 6 s
Characters: 7
CRC bits: 16
Coding 16K21A
Antenna current: 2.4 A
Duration: 02:04:48 [hh:mm:ss]

The signal was received by Jacek / SQ5BPF in Warsaw/ Poland KO02md, at a distance of 976km!

After the filtering and noise blanking was optimised, the signal could be decoded:

sq5bpf@jitter:/stuff2/sq5bpf/vlf_stefan2$ vtcat -p < stefan_2970_1 | vtfilter -a th=4 -h bp,f=2970,w=2200 > ../vlf_stefan2/pliktmp6


sq5bpf@jitter:/stuff2/sq5bpf/vlf_stefan2$ vtblank -v -d0.0007 -a20 -t 50 < pliktmp6 | vtmult -f 2970.1 | vtresample -r 240 | vtresample -r 10 |vtraw -oa | ebnaut -dp16K21A -r10 -c2 -v -k16 -S6 -N7 -PS -L 50000


vtblank: selected channel: 1 = -:1
vtblank: channels: 1, sample_rate: 48000
vtblank: hfactor: 0.000e+00
vtblank: afactor: 20.000
initial reference phase -89.4 amplitude 7.496e-04
phase 0 0 0 0 0
vtblank: end of input
vtblank: dropsum 0 64750004, nfp 359999999
vtblank: dropfactor 0 1.799e-01
found rank 14143 ber 4.2548e-01 Eb/N0 -2.5 M -2.143712342e-02 ph 0 0,0,0,0 [DK7FC/P]
carrier phase: -10.6 deg
carrier Eb/N0: -0.4 dB
carrier Es/N0: -15.33 dB
carrier S/N: 15.63 dB in 133.5 uHz, -23.11 dB in 1Hz, -57.09 dB in 2.5kHz
elapsed 92

The message was: DK7FC/P

Link to Stefan’s email:

https://klubnl.pl/rsgb_lf_group-archives/html/rsgb_lf_group/2019-04/msg00042.html

Record distance for a VLF transmission from an earth dipole antenna.

Recently we’ve done a successful transmission from an earth dipole on 8270 Hz.

This is the first amateur transmission on VLF from Poland which has been received in another country. This is also the record distance for a transmission using a ground dipole antenna – over 1330 km.

Link to Paul Nicholson’s post about it: https://klubnl.pl/rsgb_lf_group-archives/html/rsgb_lf_group/2019-03/msg00025.html

Link to Paul’s VLF milestones list: http://abelian.org/vlf/amateur-radio/

This is probably the first VLF signal which has been transmitted from Poland after World War II. We are not aware of any military or other transmissions. Before the war we had the Babice Transatlantic Radiostation (callsigns AXO/AXL/SPO/SPL), which was similar to Grimeton/SAQ.

Complete archive of 20 years of the RSGB LF Reflector

The RSGB LF Reflector is the most important group for low-frequency enthusiasts. For many years list members have been witnesses to milestones in the 136kHz, 73kHz, 500kHz, 472kHz, VLF and lower bands. Many posts have great historical significance.

When we created the KLUBNL.PL website, one of our most important goals was to create a publicly available archive of this list: https://klubnl.pl/rsgb_lf_group-archives/html/rsgb_lf_group/

In the beginning this archive spanned from 2014 up to now. Recently we imported archives kindly donated by Dave G3YXM and Markus DF6NM. Thanks to them the archive now spans from February 1999. 20 years of radioamateur longwave (and medium-wave) radio history!

End of NDB BIA on 474kHz

Sadly the NDB BIA on 474kHz in service at Rzeszów Airport has been turned off.

For many years the carrier at 474kHz and the sidebands at 473kHz and 475kHz were used by polish radioamateurs to check their 630m equipment. Foreign radioamateurs used this NDB to judge the propagation to Poland.

This will change the way we work in the CW segment in the 630m band in Europe. Up to now we had to use 472-472.7kHz or around 473.5kHz, and a narrow filter was necessary. After BIA is switched off we can use the whole 472-475kHz segment, also with wider filters.

DK7FC ground dipole experiments on VLF

Stefan DK7FC did a succesful transmit experiment utilising a ground diole on VLF. This resulted in a really strong signal on our Warsaw grabber (over 900km distance):