Model 1, is my .625w 4 x 104" at 36' model that is not isolated (ISO)
Model 1, is a .625 wave antenna model with 4x104" radials and the antenna is not isolated at the mast/mount bracket. Notice the heavy currents (in red) noted at the top of the mast. These currents are heavy and are in-phase with the bottom of the radiator and out of phase with the working part 1/2 wave at the top of the antenna.
For me this indicates a sure sign that there will likely be Common Mode Currents (CMC) on this setup, depending somewhat on the length of the attached feed line and/or mast.
Model 2, is the same antenna with the mast ISO by 3" inches at the mount.
Notice the absence of currents on the mast. Below each image is the antenna pattern.
Also notice the difference in gain between these two. What would we figure causes the ISO model to show less gain than the model without isolation?
Admittedly I did not match the antennas, but I did notice that the match on these two shows just a few points difference. I once though the difference in gain was due to difference in the match with my models, but this project does not seem to show that. So, what could be the cause of the difference in gain, and is the difference important to performance...or does a more efficient (accurate working) model tend to show the difference as less gain?
Model 1, is a .625 wave antenna model with 4x104" radials and the antenna is not isolated at the mast/mount bracket. Notice the heavy currents (in red) noted at the top of the mast. These currents are heavy and are in-phase with the bottom of the radiator and out of phase with the working part 1/2 wave at the top of the antenna.
For me this indicates a sure sign that there will likely be Common Mode Currents (CMC) on this setup, depending somewhat on the length of the attached feed line and/or mast.
Model 2, is the same antenna with the mast ISO by 3" inches at the mount.
Notice the absence of currents on the mast. Below each image is the antenna pattern.
Also notice the difference in gain between these two. What would we figure causes the ISO model to show less gain than the model without isolation?
Admittedly I did not match the antennas, but I did notice that the match on these two shows just a few points difference. I once though the difference in gain was due to difference in the match with my models, but this project does not seem to show that. So, what could be the cause of the difference in gain, and is the difference important to performance...or does a more efficient (accurate working) model tend to show the difference as less gain?
