CHA F-LOOP 2.0
Page 5
Even under optimal conditions, there is a gap between where ground waves end (around 40 to 90 miles) and the
sky wave returns to Earth on the first hop (around 300 miles). NVIS propagation can be used to fill this gap. The
frequency selected must be below the critical frequency, so NVIS is can normally only be used on frequencies from
around 2 to 10 MHz. Frequencies of 2
–
4 MHz are typical at night and 4
–
8 MHz during the day.
A magnetic loop antenna radiates at all angles from horizon to zenith, making it an equally effective antenna for
both local and long-distance (DX) communication. While not specifically designed for NVIS, during field testing of
the CHA F-LOOP 2.0, both DX and NVIS contacts were made on the 30 meter ham band within minutes of each
other.
Parts of the Antenna
The CHA F-LOOP 2.0 is comprised of the following components, see plates (2) through (4):
Plate 2. CHA F-LOOP 2.0 Antenna.
a.
Tuning Unit
The Tuning Unit adjusts the resonant frequency of the CHA F-LOOP 2.0 antenna.
b.
Flexible Radiator Loop
