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There does seem to be a problem with EZNEC when modeling this antenna. As has been said, the program reports close to unity gain or 0dbd when the antenna is modeled with diameters other then wire size. This result is in contradiction to in field tests with the antenna compared to a dipole in field strength tests. When modeled as a wire the antenna closely matches the results in the field from Avanti's original gain claims to what I've seen also.

Until someone can figure out this discrepancy, this seems to be the only way to get the model to match real world results. I think most people will agree radiator diameter effects bandwidth, not gain. The only logical way this should effect gain in the Sigma design is if the diameter change causes a change in distance between the cone and the radiator. Even when you keep this distance the same, the model still shows a huge drop in gain that is false.

<blockquote data-quote="Shockwave" data-source="post: 212135" data-attributes="member: 10882">There does seem to be a problem with EZNEC when modeling this antenna. As has been said, the program reports close to unity gain or 0dbd when the antenna is modeled with diameters other then wire size. This result is in contradiction to in field tests with the antenna compared to a dipole in field strength tests. When modeled as a wire the antenna closely matches the results in the field from Avanti&#039;s original gain claims to what I&#039;ve seen also. Until someone can figure out this discrepancy, this seems to be the only way to get the model to match real world results. I think most people will agree radiator diameter effects bandwidth, not gain. The only logical way this should effect gain in the Sigma design is if the diameter change causes a change in distance between the cone and the radiator. Even when you keep this distance the same, the model still shows a huge drop in gain that is false.</blockquote>

[QUOTE="Shockwave, post: 212135, member: 10882"] There does seem to be a problem with EZNEC when modeling this antenna. As has been said, the program reports close to unity gain or 0dbd when the antenna is modeled with diameters other then wire size. This result is in contradiction to in field tests with the antenna compared to a dipole in field strength tests. When modeled as a wire the antenna closely matches the results in the field from Avanti's original gain claims to what I've seen also. Until someone can figure out this discrepancy, this seems to be the only way to get the model to match real world results. I think most people will agree radiator diameter effects bandwidth, not gain. The only logical way this should effect gain in the Sigma design is if the diameter change causes a change in distance between the cone and the radiator. Even when you keep this distance the same, the model still shows a huge drop in gain that is false. [/QUOTE]

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