2 Element Helically Loaded Magnetic loop Antenna
Rotatable in both Azimuth and Elevation plane.
This is a duplicate design of my single element Helical Loaded loop.
2 exact duplicate elements are stacked in a figure 8 configuration and fed out of
phase. 2 elements were chosen to increase the front to side bi-directional gain
and tighten up the pattern.
The foil crosses over at the tuning point for the out of phase configuration.
The vacuum capacitor is now tuning both loops in parallel which lowered the Z.
Both loops are active and fed at one end with a gamma match. This 2 loop
design was intended to cover 20-10 meters but I missed 20 meters by 200khz
due to the error in calculating the extra foil length at the crossover point.
Due to this slight miss calculation it only tunes to 14.400 Mhz to 30 Mhz… OOPs!
Well, it tunes 17 meters thru 10 meters (4 bands) with a flat VSWR of 1.1 or less.
I can easily correct this error for the next build although I am not a 20 meter fan
plus I have 3 other antennas that cover 20 meters.
The capability of both Azimuth and Elevation rotation is a plus. Azimuth to focus
the front to side gain (Bi-directional in the plane of the loop) with the addition of
elevation angle to change polarization to anything between vertical & horizontal.
Results of 3 days of testing and comparing
I will start by claiming that my single element design has provided great results for
5 months now using an elevated fed ground plane for 17 meters for comparison.
The single loop has been very close (within 3db in most cases; both antennas are
vertical polarized. The loop of course is rotatable so exhibits more gain then the
vertical in many cases when rotated toward the station. The loop also exhibits
multi-angle radiation therefore looses some low angle compared to the ground
plane design. That being stated, the single loop has hands down better signal to
noise ratio over the ground plane for receive. This attribute is great for utilizing
the preamps in the receiver, virtually no noise to amplify thus the preamps are
extremely useful increasing the receive signal.
· So far out of approximately 100 reports in 3 days the 2 element stacked
loop utilizing A/B (fast switching multiple times) the new 2 element design has
preformed between 2 and 3 S-units better when both antennas are directed to
the station under test.
· I have also been able to get as much as 2 to 3 S-units more by rotating the
elevation angle searching for the best signal peak. This attribute has
produced results in more than ½ the tests.
· Signal reports have been far better than ever expected and the noise floor
seems to be about 3db quieter then the single loop.
Out of Phase crossover foil
Motor Drive Unit
Build in progress
Close Up view