03-30-2010, 01:11 PM
| || |
| || |
Join Date: Oct 2005
Location: Houston & Corpus Christi
BM, I just posted some modeling work done by a local ham using Eznec demo version. Worldwide DX Amateur Radio Forums - Ham - CB - HF - VHF - UHF BTW, the models are all listed backward, start with the last-first. Keith modeled a 1/4 and 1/2 wave end fed vertical, as well as several variations of 5/8 wave verticals with different radial lengths and angles. He also modeled the 5/8 with one, two, and 4 radials to see how that affected the RF gain, angle, and patten. He use to have these models on his Website, but the Website was redone and he mostly shows his other interest now. http://home.comcast.net/~nm5k/ He notes that he used the Eznec demo version, which allows very few segments to be used in modeling the elements and therefore the results may be skewed a bit compared to using the Pro version. Some of the models with increased gains shown may be due to his increasing the number of segments he was allow to use per element. For example, notice the nice increases when he modeled the 5/8 wave with only one and two radials he was able to increase the number of segments per element and still stay within the limit---which I think is 15 segments. Without some type of real world testing, I would only take these results with a grain of salt, but Keith says these models support his real world applications and some other studies along the same lines. So, this gives me pause to think differently about using very long radials rather than shorter radials on the 5/8 wave radiator. I know that Bob85 and Multimode200 found increased signals when increasing the length of horizontal radials on the A99 and the knockoff version 200 used. I wish Keith had modeled the EFHW using radials too. I would like to see what that pattern looks like. This idea with 5/8 wave radiators may be more practical with higher frequency antennas however. I would like to try out the two radial configuration, it looks easy with what I have here. The only problem is, the current distribution view he shows may well be the model he did in free space, because he does not show the support or feed line. This could mean that the view over average ground is no where near as good as suggested. I have called him several times and left a message that I wanted to talk to him, but he has not returned my calls.