Yes once gamma match is set correctly I beleive it will be perfect. As it stands locally within a couple miles, station reports are 2 s-unit gain going channel 40 to channel 1 on 11 meter band. So gamma match needs to be fine tuned I would venture to say. I've already moved the top whip in so that part should be done. Just a small bit of adjustment I think is all that will be needed. Fingers crossed. And I need to write all dimensions down as well. Help others possibly. Anyway. Keep at it man. Hopefully we will talk soon on air.
It is hard to believe that you are getting that much of a change in gain in such a narrow bandwidth, especially for an antenna that is known to be very wide banded. That being said, assuming what you are saying is true, changing the gamma won't have any effect on where maximum gain is, all the gamma does is match the antenna to the feedline. If you want to move the maximum gain point of the antenna you need to physically adjust the dimensions of the antenna itself. That is the only way to change the gain characteristics of the antenna...
That being said, it is plausible with that antenna design to make adjustments that affect gain, both local and dx signal strengths. I have done it with modeling surface waves and far field gain in 4NEC2, and multiple people on this forum have done experiments with live sigma/vector style antennas (some of them homemade clones) and reported the same thing. Their process was adjusting the physical dimensions of the antenna and then tuning the gamma match to compensate for the impedance change. In those tests they changed the physical length of the antenna as well as the height of the ring. I don't recall anyone changing the diameter of the ring itself, which modeling suggests would have as much of an effect if not more than simply changing the antenna's length, and the height of the ring.
Another question, how do you know if it is your antenna or the remote antenna that is responsible for the difference in gain between the two tested frequencies reported by your s-meter? Is it possible to be caused by the remote site's system? Considering this possibility, is it possible that your antenna has a flat gain curve and the difference is the station on the far end of the connection? Have you done this same test with multiple different stations to confirm that it is your station that has this effect?
Assuming you have ruled out the far station as the cause of this change in gain over this frequency range (essentially by duplicating this same test with multiple stations), does the reported difference in s-units across the band peak inside the frequency range measured, or does it peak at a frequency that is higher than tested?
You can just throw these antennas up and simply tune impedance, or you can put in the work that others have done and tune these antennas for performance. Every report I've seen by people who have taken the time to dial these antennas in claim that as far as local distance is concerned these antennas are as good as it gets. That being said, I can count on one hand with fingers left over the number of people who have taken the time to do just that and reported on it... It is one of many experiments I still intend to do with antennas.
The DB
