Page 26 - EngineerIt March 2021

AMATEUR RADIO

Beacon monitoring by the next generation beacon project team in Denmark for VHF and above propagation.
Having beacons are however only part Pi4 is short for PharusIgnis4. The name PharusIgnis4 comes from the ancient words for
of the solution and one needs to have beacon, lighthouse and fire - Pharos (from Greek to Latin pharus and coming from the
a better reporting system than the Lighthouse of Alexandria), Ignis (Latin: fire) and 4 for the four FSK tones.
haphazard, incidental reporting by a radio PI4 is also compliant with the IARU region 1 VHF committee, which accepted one
amateur who just happens to hear a minute mixed mode beacon sequence.
beacon. This data needs to be collected PI4 also makes use of four tones, as does JT4 and WSPR*. However there is a
in a more scientific way.
Reverse beacon monitoring has
always been a major requirement for
monitoring a beacon and has been
discussed for more than two years at
various workshops.

The initial thoughts were to monitor CW
beacons using software like CW Skimmer,
but experience gained through actual
testing has shown the following flaws with
this approach:
1. CW Skimmer is not free software
and at $75 per license, it is out of
reach for most amateurs who want to
monitor beacons.
2. It has been discovered that CW
Skimmer is also not 100% reliable
when it comes to decoding and that
a fairly strong signal needs to be
received before the software actually
begins decoding. Aural reception
of a weak CW signal can already
take place long before the skimmer
software starts to decode the signal.
These findings encouraged the members
of the SARL VHF work group to start
experimenting with digital modes like
FT8* and JS8Call* on VHF and UHF
and they found that the reception and
reporting of the signals heard could take
place at very low levels. This therefore
seemed to be a much better solution for a
beacon than continuing with a traditional
CW beacon.
This experience led the work group
to next generation beacons that use the
PI4 mode.

Next generation beacons
Next generation beacons** generate
a machine generation message
(MGM) similar to WSJT-X* and other
digital modes. There are already
numerous digital modes 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. The beacon antennas currently in use for the analogue beacon in Bethlehem ( Mid Tower)
Pi4 has been developed specifically will be re-used for the next generation beacon.

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