force12@interserv.com wrote:
>
> Hi, Scott.
>
> Have already read N3RR's reply, so will not duplicate his comments.
>
> There appears that there might be a situation in how the antennas were
> interconnected. Both antennas need to be in phase. This means that the center
> conductor of the coax must be on the same "side" of the drivers in both
> antennas. If they are not, the two antennas will be 180 degrees out of phase
> and
> the array will show reduced performance whenever it is switched in. Instead of
> enhancing either of the upper or lower, the stack will decrease the signal
> levels. With a voltage balun, this is not necessarily a simple thing to check.
> The easiest thing to do is to switch the feedpoint on one of the antennas,
> probably the lower one, if it is more accessible.
>
> You probably already have both feedlines equal lengths, so that should be all
> right.
>
> 73, Tom, N6BT
> Force 12 Antennas and Systems
>
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I have no experience with stacking tri-banders but have several monoband
stacks... Easiest way I have ever found to check to see if antennas were
in phase is check swr with both antennas pointed the exact same
direction --- rotate one of the antennas 180 degrees and check swr
again.
If in phase, antennas should have lowest swr when in same direction and
higher when in opposite. If u dont get this strongly suspect the out
of phase operation.... This didnt come from a EE book but with almost
40 years of playing with antennas.... try it before u say it wont work!
--
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