Propagation research on 5 MHz produces some interesting results

April 23rd, 2014, Published in Articles: EngineerIT

 

Hans van de Groenendaal, ZS6AKV, South African Radio League

Propagation research undertaken by radio amateurs on 5 MHz showed some early and interesting results using the weak signal propagation reporter software (WSPR) .

Stewart Moss and Nico Janse van Rensburg

Stewart Moss and Nico van Rensburg.

Almost a year ago the South African Radio League (SARL) obtained a licence from the Independent Communications Authority of South Africa (ICASA) to do propagation research on 5250 and 5260 kHz to support the World Radio Conference (WRC15) agenda item 1,4,  which will consider a possible new allocation to the amateur service on a secondary basis within the band 5250 – 5450 kHz.

The ICASA Council supports the propagation research project and is sponsoring  the South African Radio League  with a licence for 5250 and 5260 kHz  until 31 October 2015, just as the WRC15 conference will get under way.

To support the agenda item frequency sharing studies on the impact to other services currently allocated in the band and in the adjacent bands will need to be carried out. It is also important to show why radio amateurs need an allocation at 5 MHz which is in between the 7 MHz and 3,5 MHz band and could possible solve  the problem of communication when the other two bands are not suitable during certain times of the day. In  South Africa this is an important consideration  for  HAMNET, a division of the SARL, which provide communication during emergencies and disasters.

In the 1950s and 1960s some unusual propagation conditions were found in a study along the coast in the George area. The research at that time showedthat that good propagation occurred during the late afternoon over paths up to 500 km with a very low noise level.

Various methods of research were considered but ultimately it was decided to  put the major effort into a software program called WSPR. WSPR (pronounced “whisper”) stands for “weak signal propagation reporter”. It is a computer program used for weak-signal radio communication. The program was initially written by Joe Taylor, K1JT, but is now open source and has been developed by a small team. The program is designed for sending and receiving low-power transmissions to test propagation paths on the medium (MF) and high frequency (HF)   bands. Transmissions carry a station’s callsign, Maidenhead grid locator (a geographic co-ordinate system), and transmitter power in dBm. The program can decode signals with S/N as low as -28 dB (in a 2500 Hz reference bandwidth). The WSPR signal itself occupies 6 Hz wide signal. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet.org, which includes a mapping facility.

ZS5JT - ZS6KTS March 2014.
Fig. 1:  This shows that there is propagation around the clock between Durban and
Kempton Park with peaks in the early morning and late afternoon.
ZS1AGF - ZS6KTS March 2014.
Fig. 2: This shows the path between Cape Town and Kempton Park, some propagation
in the early morning and early evening.
ZS6AF - ZS6KTS March 2014.
Fig. 3:  Locally in Gauteng there is propagation almost 24 hours with
a sharp dip in the early morning hours.

Stewart Moss (ZS6SGM) said that KARTS received a lot of support from UK and European amateurs who have been working with WSPR for some time.  During March 2014 he analysed some of the first WSPR results which showed interesting propagation conditions which were not expected and did not shown up on the standard propagation predictions. He said that was all the more reason to do research on this band.  On the international front the longest distance achieved with WSPR on 60 m was 13 800 km.The SARL worked with the Kempton Park Amateur Radio Technical Society (KARTS) which designed and erected a beacon station at its club facilities in Kempton Park, Gauteng. The station can transmit in the WSPR mode, PSK31  and using slow morse code. PSK31 or “phase shift keying, 31 baud” is a popular computer soundcard-generated radio teletype mode. It is used to conduct real-time keyboard-to-keyboard chat, most often using frequencies in the high frequency amateur radio bands. PSK31 is distinguished from other digital modes in that it is specifically tuned to have a data rate close to typing speed, and has an extremely narrow bandwidth.

Working at KARTS with Moss is Nico van Rensburg (ZS6QL). Van Rensburg said they have had help from a number of people who are part of the KARTS club. These members have contributed to the installation, testing of the beacon and technical assistance with aspects the beacon. He said that they  are planning to develop tutorials which will encourage more radio amateurs and shortwave listeners to become involved in WSPR reception. “We need more participation over a long period to build up a better picture.”

Details of the tutorials can be found on www.amateurradio.org.za/propresearch.htm

 

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