Horizontal loop for NVIS communication
The Chameleon Skyloop is a loop wire antenna, with a length tuned to the 80m band. Due to the use of a broadband transformer and with the help of a tuner this antenna can be used on higher shortwave bands as well. A horizontal loop does not require q huge height above ground to perform sufficiently well. CLose to the ground you get a strong reflection from the ground, resulting in a most skywards, steep take off angle - which is good for local traffic up to about 2000 km, depending on the time of day. DX is also possible, but the lower radiation angles are comparatively weaker than with other antenna designs.
The efficiency of such wire loop antennas is defined by the enclosed area of the loop - the larger the better. Therefore a circular loop would be ideal, because a circle has the most favorable ratio between area and circumference (length of the wire). Bot who has the space for that? The Skyloop will work nicely in near square shaped forms with excellent results. Another benefit of horizintal loops is that such antennas have a comparatively low noise level, which makes reception of weak signals much better.
Height above ground is not bvery critcal. The antenna will start top work at heights of 3 to 4 m above ground. The recommended height is about 7 to 8 m for good NVIS performance, i.e. very steep take off angles. The higher the antenna is installed the ĺower the take off angle will be - good for DX, less ideal for regional radio traffic. The Chameleon Skyloop is cut to a length for operation on the 80m band, with a tneroperations on other bands are also possible. Please note that the vertical radiation diagram has more and stronger lobes and also nulls, i.e. elevations of strongly reduced gain. So the signal strength will vary with the incidence angle. On the lower bands the antenna has no nulls and no significant lobes in the vertical pattern.
The wire of the Skyloop is approx. 76m long, which results in an area of approx. 20 x 20m when arranged in a square form. This is certainly less than ideal of the backyard of a terraced house, but maybe this antenna is an ideal experiemnt for thenext Fieldday or for a DX-pedition style vacation! The feed of the antenna is done with a 4:1 broadband transformer with PL socket, like it is used with the EMCOMM-II antenna also. The max. power load is 1000 W CW. Guy ropes are not supplied. The manufactuer recommends a minimum cable length of approx 8m, the cable should be arranged perpendicular to the antenna.