Head to head tests - Less Efficient Core vs More Efficient Core - Using WSPR

The setup is as shown in the image below. The two antennas are arranged as inverted Vee in the same azimuthal orientation with the feedpoint on the south side denoted by the blue boxes. The image shows 10 foot topographic contours and also shows the global imagery to show both the presence of roads and vegetation. The two antennas are separated by about 75 feet of space. The NY4G coupler has the 2 turns primary and 14 turns secondary with the crossover and bifilar winding of the primary. The VY2AJ coupler has the 3 turns primary, 24 turns secondary with a tap instead of the bifilar winding and the turns are wound tightly together with no crossover. Both transmitters are identical 200 milliwatts WSPRlite programmed with their respective call signs. The only variables are the couplers and the relative position of the antennas with each other. They both see the same instantaneous propagation conditions. 

During the first day - NY4G was in the position of VY2AJ and vice versa.   During the second day, the positions were swapped to correspond to the image above.  The results from the first day below:

The propagation conditions varied throughout the day.   There are more watts coming from the more efficient transformer yet the less efficient transformer is keeping up with the more efficient one early in the day.  One attempt at an explanation is that there is a positional advantage from the position of NY4G on the first day - perhaps a 'yagi" effect for which the other antenna is acting like a parasitic element.  As the sun sets over Europe, with less propagation, the more efficient transformer can still hit the distant stations and the less efficient one, not as much.

During the second day, the positions were swapped to determine whether the "yagi" effect is for real.

The more efficient transformer (blue trace) hit more distant stations for most of the 6 hour period.  The advantage however is seen to be enhanced by the parasitic effect of the second antenna higher on the slope.  The only way to isolate this effect is to run identical transformers with the same setup.

With the same coupler, the lower position on the slop appears to have an 800 km advantage in reach over the one that is higher on the slope of the lot nas indicated by the DX10 Table for the entire 6 hour period.

NY4G is at this lower position. If one deducts the 800 km advantage from the previous two days results to sort of “equalize” matters from the “advantaged position” then

the average distance for Day 1 - reported by DX10 Table with adjustment
Coupler 1 VY2AJ (3 turn primary) - 5649 km Position 1
Coupler 2 NY4G (2 turn primary) -4751 km Position 2

the average distance for Day 2 - with adjustment
Coupler 1 VY2AJ (3 turn primary) - 10080 km Position 2
Coupler 2 NY4G (2 turn primary) -5509 km Position 1

the average distance for Day 3 - data reported by DXeplorer
Coupler 1 VY2AJ (3 turn primary) - 9047 km Position 1
Coupler 2 NY4G (3 turn primary) -9797 km Position 2

This suggests that the advantage of the more efficient coupler in terms of distance ratio is somewhere between 20% to 80% better reach.

Stay tuned for similar tests on the lower bands.