ML-91 NVIS Roof Rack Antenna System
Q-MAC Electronics has pioneered the world’s first folding roof rack HF SSB antenna. The Q-MAC ML-91 NVIS Roof Rack Antenna is a technological breakthrough in vehicle-based HF radio communications. The ML-91 is without doubt the best type of antenna for vehicular NVIS (Near Vertical Incidence Skywave) operations and is effective in overcoming the skip zone common in whip based antenna systems.
The ML-91 is a magnetic half loop antenna which predominantly radiates RF energy towards the ionosphere, making it ideal for NVIS propagation. Skip zones are eliminated and coverage, with the correct selection of frequency, is virtually continuous from 0 to 1000km or more.
HIGH PERFORMANCE
Q-MAC’s ML-91 is significantly more efficient than any whip-type vehicle antenna, producing considerably more transmit and receive power. The received signal relative to whip antenna systems varies between +10dB and +14dB. Antenna current in a typical whip system at the base is 1.5 Amperes, whereas the antenna current in the ML-91 loop element approaches 15 Amperes.
The radiation pattern of the ML-91 has low angle nulls toward each side of the vehicle, effectively reducing noise from adjacent power lines which commonly affect vehicles driving on remote roads that have high voltage distribution lines in close proximity. Q-MAC’s ML-91 also magnifies the received signal strength, giving a higher overall performance than any vehicle whip antenna system. The receive bandwidth is narrow (Hi Q) which helps to eliminate noise from adjacent channels common on conventional systems.
INTEGRATED ROOF RACK
The ML-91 roof rack has been designed by Q-MAC as an integral part of the antenna system. The ground plane for the antenna is a heavy-duty aluminium mesh floor, which is welded to the frame bars, maximising current within the radiating loop. Using a closed magnetic loop antenna design, the ML-91 effectively shields and isolates vehicle ignition noise thus providing greater clarity in communications. Whip based systems rely on the vehicle chassis for ground and as a result commonly suffer from induced electrical noise.
OPTIONS
Coax cable: 30m RG58 coax cable
COMPATIBILITY
For use with the Q-MAC HF-90 and HF-90M transceivers
Propagation using whip antenna system and ML-91 NVIS Roof Rack Antenna°