2 Element Helically Loaded Magnetic loop Antenna

 

2 element Loop2.jpg

Rotatable in both Azimuth and Elevation plane.

Design intentions

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.

 

 

More Photos

 

Out of Phase.jpg

                                                    Out of Phase crossover foil

Motor Drive.jpg

                                       Motor Drive Unit

 

In progress.jpg

                                                 Build in progress

 

 

DSC_0414.JPG

                                                 Close Up view