Dream of each of amateurs working from a hard for antenna
installation conditions to have a small invisible antenna for
all bands. I have tried to solve the dream. My all band antenna
is something middle between T2FD and loaded Loop. It is possible
to find lots about those antennas in the internet. Figure
1 shows the design of my antenna.
Antenna load is 16 two- watts resistors on 72-k connected
to bridge. The combine resistor has 32 –watts in dissipative power,
it was enough to work with my 100-watts ICOM-756 transceiver.
Transformer 1:9 was made accordingly to recommendation of G5IJ
(References 1,2). Perimeter of the loop
is 24 meters of wire in 1-mm (18-AWG). Top side of the loop was
fixed at end of a fishing rod in length 8- meters. Low side was
at 1.5-meters above the ground. The antenna has SWR low 1.2:1
and high 2.0:1 at 1.8- 50- MHz (without tuner).
The practice has confirmed the theory: that the antenna
has good amplification only if the perimeter more the used wavelength.
So, the antenna could work at 10- 50- MHz with good efficiency.
However, the antenna has amplification – 12 dBi
at 7-MHz, - 20 dBi at 3.5- MHz and – 40-dBi at 1.8-MHz. At those bands
the antenna, however, very good works for receiving. For example,
at 1.8-MHz it was noise at level 2-3 S-points with the antenna
(and two switch on preamplifiers) but with good receiving of amateurs’
The antenna could be used for receiving at 1.8- 7-MHz and for
receiving/transmitting at 10-50-MHz. Antenna with perimeter 30-40
meters could be used atall amateurs
1 Design of the Simple All-Band HF-Antenna
For the load of the antenna a usual Dummy Load on 50-Ohm
that is switched to the antenna through HF-transformer 9:1 may
be used. The load transformer may have ferrite ring in twice less
sizes compare to antenna feeding transformer.
Reference 1: http://www.qsl.net/gw6hmj/antenna.htm
Reference 2: http://www.gairney.plus.com/Radio/G5IJ_aerial.htm
More about loaded Loop Antenna:
1: Antennas for Radio Amateurs: by Igor Grigorov,