Homer, NB, just gave us his report on his antenna testing only one contact, and it indicated a rather large difference among the CB antennas he tested, a difference greater than 2.5 Sunits. That is a lot of difference for me, and I have never experience that much difference in signals at one time between any of the CB vertical antennas I own. Is this the kind of differences you typically might see Homer, assuming all the antenna's are working well and they're close to the same height?
I think those were large differences between the least and the greatest, too.
Nope, I have no pre-determined expectations for folks results. I haven't seen those kinds of differences here, but I haven't really focused on that as much as on whether the antennas I build work well, or better than what I had done before. Because I have more interest in DX, I look for superior performance over an extended period of time. The most consistent local radio work here is all within 15 miles, and a little occasionally further out. Folks are not doing much radio during the outdoor weather season.
I don't do a lot testing using TX signals, and maybe if I did I would see some differences that I don't see with testing RX signals only. I say this in spite of the fact most consider antennas are reciprocal in nature. In your initial remarks you suggest that capture area is what makes the difference in the results that you and NB see. I disagree that capture area is the real factor here, albeit is probably something to consider and maybe even measure under a lab control setting.
Nope, again. In fact, I think capture area is often not a factor at all. There is much more to antenna performance than that, in my opinion. For instance, a 1/4 GP actually has more physical area than a 1/2 dipole or A99, yet it is generally accepted that it has less gain.
What I failed to make clear, apparently, is that I drew the opening of this thread from another forum that was discussing the StarDuster. In that thread a member referred to the capture area in a way that clearly set it, in his opinion, as the most significant factor in antenna performance. I was simply saying I accepted completely the
general principal of capture area, yet I went on to say it had not proven up as a solid inviolable fact in my experiences with all sized antennas.
For years I have heard such claims about capture area making the difference, and just thinking and visualizing on the idea, common sense might suggest the idea has merit.
However due to my personal experience working with numerous antennas at the same location and time in most cases, I've wondered how a real test of this capture area idea would work out...were it possible.
In my opinion, if it is about capture area to such a great degree, then we might have to ignore the subject of gain as being of major significance other than how it relates to size of the antenna. We know gain does generally increase with size, but only up to a point. It is much more tied to the matter of design, which mechanical style is capable of putting the signal into a preferred direction while preventing it going in other directions. At least this is my understanding. We can see that capture area means less when we start raising a smaller antenna up higher than a larger. The reason why some whine about the unfairness of comparing antenna performances by making the tops of the antennas. Doing this begins to reduce the significance of size on the results.
I've wondered if there was some way we could take out the natural advantage that taller antennas have over the smaller designed antennas, due to increased height, because a capture area advantage, if it is an advantage, should be evident at any height.
Then I remembered an article, along time ago, discussing testing of antennas on a standardize RF test range. Much of the work was beyond my understanding, but I took away one unforgettable fact about the method and procedures of testing used by this test range. They used a rota-table platform as the test center, and they laid the antennas down flat to test. The stated purpose being...to eliminate height and it's effect on maximum gain angles as a factor in the comparisons.
If there is a way, it is likely beyond the ability of a homebrewer like me.
I'm not sure, but I think your idea here is to exclude modeling examples from this thread and go mainly by anecdotal accounts, but I don't know how we could test the affects of capture area without considering models or what modeling might show. Modeling would not produce iron clad results that fully answer the questions, but it could be informative along with the results from other's that hopefully are participating with their real world testing. iMO, most would heartily disagree with comparing antennas of different lengths with their tip heights at the same height, or their maximum current nodes at the same height, so there is a bias advantage for the longer antenna going in, if we are to consider capture area differences. So what can we do to get around this bias?
I have not meant to exclude modeling, but in fact, agree with what you just said about its relevance to this kind of discussion. I was simply making it clear that I wished for a thread that gave an equal hearing for anecdotal information as it would to modeling, or other scientific materials. In fact, I hoped that anecdote would set the tone, and that discovery by means of trying to figure out why one might have seen the results they had rather than folks just shouting
' there's no way because of so-and-so" when someone has just stated they they had.
Off topic, but as an example, I've read one several threads that it isn't possible to get extra channels from a Uniden Pro510, yet I owned one that had them a few years ago, and saw and spoke to folks on those lower channels who were also using the 510. I know this isn't either antenna thory or science, but it does serve to show that sometimes we don't know what we think we do because of a predisposition or bias.
IMO, when folks start talking about the differences, this or that makes, I'm provoked to ask the simple question, how much difference are we talking about?
So Homer, without holding you accountable for NB's numbers, are you suggesting that it is capture area that is responsible for the advantages his report shows?
Nope. I don't know why he sees what he does. What I said was that his numbers are more like what others report for their experiences than for what I, fr instance, see with my Astroplane,or you do with some of your antennas.
I think not to be including modeling in this discussion is like leaving the wheat flour out of your bread, so I'll ask this question:
If I modeled each of these antennas laid down on their sides at 36' above the Earth, could this be a fair test for comparing the capture area?
.25 wave GP,
.50 wave end feed,
.625 wave,
.64 wave,
How do you think these four will rank regarding gain and angle in this position?
Go ahead and model them and serve up the results. DO it sideways and see. Do it upright, too. And when you are done try to figure out why people see differences in their antenna experiences.
As a matter of fact, at least two or three users of the GM on some of the British forums have pt up the antenna to turn around and take it down offering it up for sale because they saw better results from other antennas at their QTH. I believe one of them I read was putting his A99 back up!!!
Are they lying? I think not when you're shelling out nearly $200 for the GM. Something
significant is afoot with the very real differences folks see, and saying
"science so it can't be so" is becoming a convenient scapegoat for those who have no imagination.
One of these days I'd like to see someone post the results of their optimum tuned V4k tested with an analyzer. What will it look like? My homebrew Sigma4 looked like a doo-doo sandwich on the analyzer. I know the Qv4k had this quirky undulating SWR curve on the SWR meter that I never could tune out, but it worked quite well.
