[TowerTalk] 12/17 antenna interaction

[Wayne Kline]

Last week I installed a  3 element 17 an a 4 element 12 interlaced on a 14ft boom  7 ft above my Bencher SkyHawk tri band antenna.

The feed point impedance and band width of the 12/17 antennas  were as expected.  A quick  plot of the  SkyHawk   was another issue.
14 MHZ had no change in feed point impedances and band width,  the 21 MHZ still exhibited the charteristics of the original SkyHawk.
But 28 MHZ was another story,   From it’s original flat arcing SWR curve   28.000 to 29.100  I now have a SHARP rising 2.3:1 standing wave ratio @ 28.475 that descends to 1:3 :1  at
28.655 MHZ    the band width and top end impedance cure resembles  the prier measurement B-4  the new installation.

The antenna in question has only one driven element insulated ( the director and reflector at ground potential)   and  it used cell illumination for the 12 meter segments. ( all 4 elements are  at ground potential )   on a 14 ft  boom .

Wayne W3EA

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