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Marconi,

I do not have these models and I'll email you soon so I can see them. What you noticed with the masts falls inline with some of my earlier post regarding the phase of the currents where the mast meets the antenna being the determining factor on insulating the mast or not. The Sigma / Vector has currents that are in phase at this point. Take away it's mast and you lose some gain. You should actually see a slight improvement in gain when removing the mast from a 5/8 wave ground plane. Mast radiation on the 5/8 wave is out of phase below the ground plane elements.

The Sigma is also not a ground plane and adding the standard 90 degree or downward sloping radials is detrimental to it's gain. In field test did show some increased gain when a second set of upward flaring radials was added with a reduced angle. The gain increase was far from worth the mechanical nightmares. At HF frequencies you will want to choke off the coax on the Sigma. The longer wavelength makes a larger section of coax radiate before the currents diminish then I see on FM.

<blockquote data-quote="Shockwave" data-source="post: 243022" data-attributes="member: 10882">Marconi,I do not have these models and I&#039;ll email you soon so I can see them. What you noticed with the masts falls inline with some of my earlier post regarding the phase of the currents where the mast meets the antenna being the determining factor on insulating the mast or not. The Sigma / Vector has currents that are in phase at this point. Take away it&#039;s mast and you lose some gain. You should actually see a slight improvement in gain when removing the mast from a 5/8 wave ground plane. Mast radiation on the 5/8 wave is out of phase below the ground plane elements.The Sigma is also not a ground plane and adding the standard 90 degree or downward sloping radials is detrimental to it&#039;s gain. In field test did show some increased gain when a second set of upward flaring radials was added with a reduced angle. The gain increase was far from worth the mechanical nightmares. At HF frequencies you will want to choke off the coax on the Sigma. The longer wavelength makes a larger section of coax radiate before the currents diminish then I see on FM.</blockquote>

[QUOTE="Shockwave, post: 243022, member: 10882"] Marconi, I do not have these models and I'll email you soon so I can see them. What you noticed with the masts falls inline with some of my earlier post regarding the phase of the currents where the mast meets the antenna being the determining factor on insulating the mast or not. The Sigma / Vector has currents that are in phase at this point. Take away it's mast and you lose some gain. You should actually see a slight improvement in gain when removing the mast from a 5/8 wave ground plane. Mast radiation on the 5/8 wave is out of phase below the ground plane elements. The Sigma is also not a ground plane and adding the standard 90 degree or downward sloping radials is detrimental to it's gain. In field test did show some increased gain when a second set of upward flaring radials was added with a reduced angle. The gain increase was far from worth the mechanical nightmares. At HF frequencies you will want to choke off the coax on the Sigma. The longer wavelength makes a larger section of coax radiate before the currents diminish then I see on FM. [/QUOTE]

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