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CDX, I think the extra set of downward radials on a Sigma makes the gain drop because the portion of mast directly under the antenna radiates some energy that is in phase. This would be based on the same reason the upward cone confines the out of phase radiation of the first 1/4 wave on the main radiator. Extra horizontal radials seemed to do nothing because they do not cancel radiation (in phase or out of phase) and the Sigma is not looking for a reflection under it. All of my tests to this point have been far field from about 40 to 50 miles.

One possible area of improvement may be to construct some type of wire mesh screen around the cone to confine a higher percentage of out of phase radiation. Just like the fourth radial added some gain on the Vector from the original Sigma, this could help further. Very old prior art work contained in the Sigma patent showed this wire mesh cone dated from 1939! Who would have guessed the basic design has been around that long?

This diagram did not show a matching network and obviously the gamma would complicate a mesh. It may have to be pulled inside the mesh cone or a void in the mesh for the gamma could be tried. It's unlikely the added gain would be worth the cost to mass produce this mesh design. However there are plenty of us that would make any reasonable attempt to add any gain to our antennas.

<blockquote data-quote="Shockwave" data-source="post: 228751" data-attributes="member: 10882">CDX, I think the extra set of downward radials on a Sigma makes the gain drop because the portion of mast directly under the antenna radiates some energy that is in phase. This would be based on the same reason the upward cone confines the out of phase radiation of the first 1/4 wave on the main radiator. Extra horizontal radials seemed to do nothing because they do not cancel radiation (in phase or out of phase) and the Sigma is not looking for a reflection under it. All of my tests to this point have been far field from about 40 to 50 miles.One possible area of improvement may be to construct some type of wire mesh screen around the cone to confine a higher percentage of out of phase radiation. Just like the fourth radial added some gain on the Vector from the original Sigma, this could help further. Very old prior art work contained in the Sigma patent showed this wire mesh cone dated from 1939! Who would have guessed the basic design has been around that long? This diagram did not show a matching network and obviously the gamma would complicate a mesh. It may have to be pulled inside the mesh cone or a void in the mesh for the gamma could be tried. It&#039;s unlikely the added gain would be worth the cost to mass produce this mesh design. However there are plenty of us that would make any reasonable attempt to add any gain to our antennas.</blockquote>

[QUOTE="Shockwave, post: 228751, member: 10882"] CDX, I think the extra set of downward radials on a Sigma makes the gain drop because the portion of mast directly under the antenna radiates some energy that is in phase. This would be based on the same reason the upward cone confines the out of phase radiation of the first 1/4 wave on the main radiator. Extra horizontal radials seemed to do nothing because they do not cancel radiation (in phase or out of phase) and the Sigma is not looking for a reflection under it. All of my tests to this point have been far field from about 40 to 50 miles. One possible area of improvement may be to construct some type of wire mesh screen around the cone to confine a higher percentage of out of phase radiation. Just like the fourth radial added some gain on the Vector from the original Sigma, this could help further. Very old prior art work contained in the Sigma patent showed this wire mesh cone dated from 1939! Who would have guessed the basic design has been around that long? This diagram did not show a matching network and obviously the gamma would complicate a mesh. It may have to be pulled inside the mesh cone or a void in the mesh for the gamma could be tried. It's unlikely the added gain would be worth the cost to mass produce this mesh design. However there are plenty of us that would make any reasonable attempt to add any gain to our antennas. [/QUOTE]

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