Posted by Marconi
on 5/19/2007, 8:43:57
Thank you Jack for the links and the call. I always enjoy our discussions.
I sure am interested in your progress with the AstroPlane when you get to it. When we were talking about the length of the support mast you mentioned insulating it at some length, I think you said 8', extending below the bottom hoop. As I understand your comments, this is a particular good length for maximum low angle radiation in the CB band and this is also noted in the patent. You also mentioned that you wanted to be able to adjust this length shorter to see if you could effectively control the rise of this maximum low angle radiation to some higher point on the horizon in order to better accommodate the hilly terrain in your area. Could this mean then that extending this same element to longer than 8' might make the maximum radiation angle go even lower, even below the horizon and be less desirable? If this is so, then the stories about the AP working best at low heights is probably true.
Personally, I read this issue in the patent to mean that element #14 should not be made shorter than about 8' below the bottom hoop or the angle will raise up in an undesirable angle for the CB band use just like you suggest. Furthermore that physically insulating element #14 from the lower support would then not be necessary and that making #14 longer than 8' has little to no undesirable affect on the maximum low angle best result noted. How say you?
Please read lines 5 thru 14 and tell me what this really means to you regarding using a full vertical element in the top of this antenna instead of the cap loaded element. I think bandwidth is probably and efficiency issue in antennas, so doesn't this section suggest to us that a full 1/4 wave vertical up there may produce more efficiency, maybe even a effectiveness improvement, to the antenna relative to bandwidth change noted? So, wasn't Avanti's using the cap hat just a compromise to make the antenna even shorter relative to the tip and the height restrictions also noted in the patent? Or does the cap hat itself lend such significance to the top portion of the radiation pattern that it makes it vital for the best low angle performance? And if this is so, then a fully vertical element in its place would be somewhat of a negative to the antenna, right?
Does the cap hat actually help prevent high angle lobe development in the pattern for this antenna? In looking at the pattern in the patent Fig 7, there is noted a very strong null directly above the antenna. If I am correct in understanding, this pattern may also suggest that the antenna is just very close the earth. If that is so, then would raising the antenna higher likely produce an additional higher angled lobe in the pattern that could be considered a negative for CB?
I will give you my thinking as to why when I hear your response, OK?
When you get time and thanks,
Eddie
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