AMATEUR RADIO

SA radio amateurs embark on a next
gen beacon programme
Current beacon in Bethlehem – antenna structure

VHF and UHF radio propagation remains a mystery; even troposphericand sporadic-E propagation are not fully understood, with new longdistance communication distance records being broken. The enquiring
nature of radio amateurs has over many years resulted in informal researchwith setting up beacons and monitoring signals. But this hand-to-mouth wayof doing this has not really delivered the kind of data to make meaningful andscientific findings. All it’s really is showing is that long distance communicationof frequencies above 30 MHz is possible and does regularly occur. The
answer to the conundrum is to set up a reverse beacon network to monitorbeacons.
Reverse beacon monitoring has always been a major requirement formonitoring a beacon and has been discussed over the past two-plus years at
various workshops arranged by the SARL and AMSATSA. The initial outcomeof these deliberations was to monitor CW beacons using software like CW
skimmer, but experience gained through actual testing has shown a number offlaws with this approach. The major flaw is that CW skimmer software is not
100% reliable when it comes to decoding. It requires a fairly strong signal
before the software actually begins decoding the received CW signal. Aural
reception of a weak CW signal can already take place way before theskimmer software starts to decode the signal.
These findings encouraged members of the SARL VHF work group to startexperimenting with digital modes like FT8 and JS8Call on VHF and UHF, andthey found that the reception and reporting of the signals heard could takeplace at very low levels. This therefore seems to be a much better solution fora beacon than continuing with a traditional CW beacon.

Next generation beacons
Drawing on experience from international amateur radio groups with similar
objectives, the work group found that the PI4 mode would meet therequirements and the journey to next generation beacons.
Next generation beacons generate a machine generated message (MGM)similar to WSJT-X and other digital modes. There are already numerous digitalmodes available, however testing and experience has shown that the various
digital modes have been developed with specific types of propagation in mind
and do not all work equally well for different propagation types.
Pi4 has been developed specifically by the next generation beacon project
team in Denmark for VHF propagation and above. Pi4 is short for
PharusIgnis4. The name PharusIgnis4 comes from the ancient words forbeacon, lighthouse and fire - Pharos (from Greek to Latin Pharus and comingfrom the lighthouse of Alexandria), Ignis (Latin: fire) and 4 for the four FSK
tones.
Pi4 is also compliant with the International Amateur Radio Union (IARU)
Region 1 VHF Committee, which accepted one minute mixed-mode beaconsequence.
Pi4 makes use of four tones, as does JT4 and WSPR, however there is adifference in the spacing of the tones and on which tones syncing takes place.
Pi4 is free, allowing any radio amateur who is set up for digital modes toeasily receive, decode and report on the signal received. It is available as astandalone package called PI-RX and has been incorporated in the MSHV
software package also used by a number of VHF and above enthusiasts.

EngineerIT | November 2020 | ??

AMATEUR RADIO
Extra bonus
The MGM signal generated by the next
generation beacon does not only generatea Pi4 sequence, it also generates thebeacon ID in CW and sends out afrequency accurate tone. The beacon
therefore caters for automated receptionof the Pi4 digital sequence, aural receptionof the CW ID and a frequency accurate
signal that can be used to check theaccuracy of the receiver.
The amateur radio license
requirements are to have frequency
measurement equipment, but the quality
and accuracy of the frequency
measurement equipment is not specified.
Most affordable frequency checking
equipment is fine for HF frequencies,
however as one moves up to the higher
VHF, UHF and microwave bands,
frequency accuracy and stability becomes
critical and can be the difference between
making a contact or not. Most operators
have no idea how far off-frequency theirradios actually are, and having a method tocheck their equipment against a frequency
accurate signal is an added bonus.
Ideally the next generation beacon
programme requires that beacons are set
up in many locations. The SARL decided
that the priorities are Cape Town, Northern
Karoo and Bethlehem as this would
provide the best opportunity to study thenorth south propagation path. Bethlehem
has been chosen as a test site by the VHF
work group for the following reasons:• It is a reasonable distance away fromthe centre of VHF/UHF activity inGauteng. This is important as VHF
active radio amateurs constantly
monitor the beacon to determine
when suitable propagation is available
to make long distance VHF contacts.
• The site is owned and controlled byradio amateurs.
• The custodian of the site, Rickus deLange ZS4A, is a VHF and above
enthusiast and an active member ofthe VHF work group.
• There is already an established CWbeacon located on the site withantennas pointing towards Gautengand KZN.
• The current CW beacon in Bethlehem
has been used for all the current
testing that has taken place since itwent live almost a year ago.
• The current CW beacon has also
provided propagation reports fromsome unexpected areas and this has also helped with the decision to change the directionof the KZN antenna to point towards the SW, where there is more VHF and above active
amateurs who can monitor the beacon and provide much needed reception reports.

Reverse beacon monitoring network
Once the first next generation beacon network is operational, work can start on thedevelopment of a reverse beacon network. This will require developing an inexpensive
receive dongle Raspberry Pi driven receiver with an internet connection to a central serverwhere the information can be stored. Software development will be required to set up analert system to generate SMS or telegram messages.

Student research
Weather and tropospheric propagation are closely related and the collected data will offer
many research opportunities for high school learners and students who are looking forinteresting science projects.

Next generation beacon hardware

The NGNB platform consists of the following functional blocks:• VCO-PLL which provides a stable GPS disciplined frequency reference to the DDS.
• The DDS (direct digital synthesizer) generates the modulated signal at the desired
frequency.
• GPS is used to provide a reference frequency to the VCO-PLL, as well as timing for theDDS to ensure accurate timing of the message being generated by the DDS.
• RF amplifier to amplify the DDS output, along with the necessary RF filtering as
required in any RF power chain.

Crowd funding
The SARL has provided funding for the first beacon. However, the project will have to rely
on crowd funding to accelerate the project. AMSAT SA has launched a crowd funding
project on behalf of the SARL VHF work group. Contributions can be made fromwww.amsatsa.org.za/nextgenbeacon by clicking on the pay button for R50, R250 or R1000.
Your contribution is appreciated and will be acknowledged.
nFor more information email vhfnews@sarl.org.za
FT8: http://physics.princeton.edu/pulsar/K1JT/wsjtx.html
PIA: http://rudius.net/oz2m/ngnb/
Reverse Beacon network: http://www.reversebeacon.net/
JS8call: http://js8call.com/
After CW (Morse code)

EngineerIT | November 2020 | ??