Questions about superposition of two antennas

[Born2bwire]

Thanks for the quick reply.

The two transmitting antennas are theoretically in phase. However, there is a very little difference in phase due to limitation of the hardware.

The receiver antenna does have 3D coils which are oriented orthogonally.

I'm talking about the phase of the field, not the antennas. Do you have a setup that can actually measure phase or are you limited to magnitude? Because if you are only measuring field magnitude and direction you can't expect to superposition to work unless you can figure out the relative phase difference between the fields at that point. But I am at a loss on how you could do that because the coupling of the antennas throws things off.

EDIT: Well I guess a first-order approximation of the phase difference would be to measure the relative path lengths of your measuring point between the two antennas. You could then calculate the relative phase shift roughly by the path difference but this neglects the secondary effects of the coupling between antennas. This requires of course identical antennas and that they be excited with signals that have the same phase.

EDIT EDIT: The above would work best if you are doing far-field measurements. For near-field measurements I do not think that it would work. Heck, I'm not quite sure if it would work well in the far-field since the calculations we do for far-field radiation still take into account the phase shift over distance between observation and source.

 

[sophiecentaur]

B2bw
I'm glad someone else has picked up on the practicalities of this experiment. It needs some serious RF knowhow to get over some of the basic problems that seem to be arising.
The frequency he's operating at and the distances he's using would make phase / distance pretty small.
Also, if he doesn't operate with the transmit antennae having patterns that are symmetrical in the plane of the paper, he's got yet another imponderable.
There is also a question of the receive probe. Is it a real 'probe' or is it yet another (possible) resonant antenna?
I can't be sure how much of this that ffj is taking on board. I think it's harder than he realizes. Possibly his supervisor hasn't seen all the factors either. It wouldn't be the first time.