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How The Sigma / Vector really works!

When placing my last order for stock from Sirio I was able to correspond with one of their design engineers. The new Vector was computer modeled using CST Microwave Studio. We now have the answers behind how the Sigma / Vector radiates. Here are the facts behind how it works. It turns out Avanti did not lie about the entire antenna radiating, it just doesn't accomplish this like one might think. The lower 1/4 wave of the main radiator is indeed out of phase with the top 1/2 wave. The upward radials effectively confine the out of phase radiation within the cone. The confined out of phase radiation is replaced by in phase radiation from the radial cone.

The radiation angle is also lower on the horizon then the common 5/8 wave. They have modeled the antenna in a real environment with a mast. Many of us know that it's not unusual for a vertical end fed antenna to cause the mast to radiate. With the 5/8 wave antenna, the mast radiation is out of phase near the base of the antenna where it matters most. With the Sigma / Vector design, the mast radiation is in phase and desirable. DO NOT isolate this design from the mast, you will lose gain on the horizon. You can use a choke to stop the coax from radiating but let the mast radiate in this case.

<blockquote data-quote="Shockwave" data-source="post: 228130" data-attributes="member: 10882">How The Sigma / Vector really works!When placing my last order for stock from Sirio I was able to correspond with one of their design engineers. The new Vector was computer modeled using CST Microwave Studio. We now have the answers behind how the Sigma / Vector radiates. Here are the facts behind how it works. It turns out Avanti did not lie about the entire antenna radiating, it just doesn&#039;t accomplish this like one might think. The lower 1/4 wave of the main radiator is indeed out of phase with the top 1/2 wave. The upward radials effectively confine the out of phase radiation within the cone. The confined out of phase radiation is replaced by in phase radiation from the radial cone. The radiation angle is also lower on the horizon then the common 5/8 wave. They have modeled the antenna in a real environment with a mast. Many of us know that it&#039;s not unusual for a vertical end fed antenna to cause the mast to radiate. With the 5/8 wave antenna, the mast radiation is out of phase near the base of the antenna where it matters most. With the Sigma / Vector design, the mast radiation is in phase and desirable. DO NOT isolate this design from the mast, you will lose gain on the horizon. You can use a choke to stop the coax from radiating but let the mast radiate in this case.</blockquote>

[QUOTE="Shockwave, post: 228130, member: 10882"] [b]How The Sigma / Vector really works![/b] When placing my last order for stock from Sirio I was able to correspond with one of their design engineers. The new Vector was computer modeled using CST Microwave Studio. We now have the answers behind how the Sigma / Vector radiates. Here are the facts behind how it works. It turns out Avanti did not lie about the entire antenna radiating, it just doesn't accomplish this like one might think. The lower 1/4 wave of the main radiator is indeed out of phase with the top 1/2 wave. The upward radials effectively confine the out of phase radiation within the cone. The confined out of phase radiation is replaced by in phase radiation from the radial cone. The radiation angle is also lower on the horizon then the common 5/8 wave. They have modeled the antenna in a real environment with a mast. Many of us know that it's not unusual for a vertical end fed antenna to cause the mast to radiate. With the 5/8 wave antenna, the mast radiation is out of phase near the base of the antenna where it matters most. With the Sigma / Vector design, the mast radiation is in phase and desirable. DO NOT isolate this design from the mast, you will lose gain on the horizon. You can use a choke to stop the coax from radiating but let the mast radiate in this case. [/QUOTE]

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