NVIS PROPAGATION UNDERSTAND THE BASICS
Radio Communication via Near Vertical Incidence Skywave propagation can be used for communication over a wide area. It is very well suited for emergency communication. It uses frequencies between 3 and 10 MHz with amateur allocation in the 5 MHz particularly attractive. Two propagation researchers, Ben Witvliet and Rosa Ma Alsina-Pages wrote an interesting paper with lots of reference to other papers for additional reading.
You can download it here
New 5 MHz allocation for amateur radio agreed at WRC15
New allocation for amateur radio service in the frequency band 5351.5 - 5366.5 kHz will maintain stable communications over various distances, especially for use when providing communications in disaster situations and for relief operations. The South African Radio League has worked closely with ICASA and carried out propagation studies on two frequencies licensed by ICASA for this purpose.
It is not clear when the new allocation will be made available an replace the two frequencies that ICASA allocated to members of the SARL. The current two licensed frequencies are 5260 and 5290 kHz . ICASA have indicated that access to the new frequencies will likely only be from next year. The SARL has discussed an interim solution with ICASA and has submitted a motivation to expedite the allocation. In agreement with ICASA we still use 5290 and 5260 MHz
ACCESS TO 5MHz
SARL Members will have access to 5 260 and 5 290 kHz on registration requiring the completion of a registration form which can be downloaded here.
Once completed please email it to firstname.lastname@example.org. Processing time is a max three days.
All registered users are listed here
Latest version V1.03 can now be down loaded here
If you are interested in the mysteries of propagation then WSPR is the tool at your disposal. To experience this fascinating tool, all you need is an SSB transceiver, simple antenna, a sound card interface to connect the transceiver to your computer and internet access.
WSPR is short for Weak Signal Propagation Reporter and is pronounced “Whisper”.
It is important to note right away that WSPR is not a QSO mode. It is used to broadcast a position, call sign and power level and see who hears and decodes it. The receiving station can work out how far the signal travelled and how strong it is on the receiving end.
The mode that WSPR uses is called MEPT-JT. MEPT means Manned Experimental Propagation Transmitter. The JT part is Joe Taylor's initials. Joe Taylor K1JT also developed the mode WSJT which is used for “moon-bounce” communication. In 1993 Joe Taylor shared a Nobel Prize in Physics with Russell Hulse, for some work they did in their field of Astrophysics. He obtained his license as an Amateur Radio operator as a teenager and as a result became interested in radio-astronomy.
This tutorial covers the reception and decoding of WSPR only. TX will be covered in later tutorial. Download it here
STUDIES OF IONOGRAMS SHOW SUPREMACY OF THE 5 MHZ BAND
The ionograms generated by the South African ionosonde network clearly illustrate the supremacy of the 5 MHz band for short range, near vertical incidence skywave (NVIS) communications under certain conditions. These typically happens during the morning and late afternoon when the 7 MHz band does not support short range, sky wave communications and the 3.5 and 1.8 MHz bands suffer from high noise levels.
During the middle of the day the 7 MHz (and 10 MHz during high solar activity) band is typically the most effective medium for short range, sky wave communications.
Permanent access to the 5 MHz band will ensure that the amateur radio community can efficiently contribute to emergencies requiring short distance communications beyond line-of-sight as typically required in hilly and mountainous terrain.
The South African ionosonde network is unique in Africa and place South African radio amateurs in the very fortunate position to monitor reigning, short range propagation conditions and to improve their skills and experience accordingly.
An article by Hannes Coetzee illustrated with ionograms is available for download here