DMR (Digital Mobile Radio)
The most common use of the Digital Mobile Radio (DMR) communication mode in ham radio is where an analog voice signal is converted to an AMBE +2 Vocoder compatible digital signal. This signal is then sent to a DMR repeater that is connected to the internet. It is then sent to a distant repeater that is connected to the internet which retrieves the digital signal and transmits it to its local destination. The received signal is then decoded by the DMR targeted listener to an analog voice signal which can be a remote party somewhere else in the world.
There are several modes for DMR including simplex which may have a communication distance of only a few hundred yards. Simplex may also be used in unlicensed operation because of its short transmission distance.
The site listed below will provide significant detail on how DMR works and how to get started In DMR.
FT8
FT8 is a digital weak-signal communication mode used by amateur radio
operators, designed to enable reliable contacts even under poor
propagation conditions or with low-power equipment. Developed by Joe
Taylor (K1JT) and Steve Franke (K9AN) and released in June 2017 as part
of the open-source WSJT-X software, it has become the most widely used
digital mode in the hobby.
The mode utilizes 8-tone frequency-shift keying (8-FSK) modulation
within a narrow 50 Hz bandwidth, allowing signals to be decoded with
signal-to-noise ratios as low as -20 dB to -24 dB—well below the
threshold of human hearing. This efficiency enables operators to
exchange essential information, such as call signs, grid squares, and
signal reports, in highly structured 15-second time slots, completing a
typical contact in about 90 seconds.
FT8 operates primarily on HF (High Frequency) bands but can also be used
on VHF and UHF. It is not a conversational mode; rather, it is a
semi-automated tool optimized for DXing (long-distance contacts),
propagation analysis, and award chasing. Its success lies in its ability
to facilitate global communication with minimal power and antenna
requirements, making it accessible to operators with limited resources
or in high-noise environments.
Radio Direction Finding
Amateur Radio Direction Finding (ARDF), also known as fox hunting or
radio orienteering, is an amateur racing sport that combines radio
direction finding with the map and compass skills of orienteering.
Competitors use a topographic map, a magnetic compass, and a directional
antenna receiver to navigate through wooded terrain and locate hidden,
low-power radio transmitters.
The sport is governed by the International Amateur Radio Union (IARU)
and typically involves finding up to five transmitters that broadcast
unique Morse code identification signals on either the 2-meter or
80-meter amateur radio bands. Participants are individually timed and
must determine their bearing to each transmitter, often using
triangulation or signal strength measurement, before reaching a
designated finish line in the shortest possible time.
While traditionally associated with amateur radio enthusiasts, the
activity serves practical purposes beyond sport, including training for
emergency response personnel and helping to locate sources of illicit or
interfering radio signals. Unlicensed individuals can often participate
in casual “bunny hunts” or pedestrian events, as the activity primarily
involves receiving signals rather than transmitting them.