Jorge,
I took a six element 15 design I had and put three of them with 50 foot spacing
in EZNEC Pro.
In free space the SWR was as follows, driving all three:
21.000. 1.035
21.225. 1.028
21.450. 1.290
The free space gain at 21.200 was 15.65 dBi and front to back 39.02 dB.
Then I put three more down six feet from the first three and turned them 75
degrees and just drove the original stack of three.
The SWR was:
21.000 1.45
21.225. 1.49
21.450. 1.95
The free space gain at 21.200 was 14.15 dBi and the front to back with a skewed
pattern was 19.95 dB.
Different antennas may react differently - better or worse and obviously there
could be something done to improve the detrimental interaction. You will
definitely see a difference when you go from EU to USA but you will be putting
up a lot of antennas to have the overall performance degraded by enough that I
would not do it.
73...Stan, K5GO
Sent from my iPad
On Feb 24, 2014, at 5:20 PM, Stan Stockton <wa5rtg@gmail.com> wrote:
> Big problems with that, Jorge. Even if 90 degrees off and I think you won't
> be positioning them that far off (more like 70 degrees or so?) with only 6
> feet of separation (your example used two feet but even with 6 feet) your SWR
> will likely be higher than you want to see, you will lose gain and the
> patterns will be disturbed.
>
> Stan, K5GO
>
>
> On Mon, Feb 24, 2014 at 3:40 PM, Jorge Diez - CX6VM <cx6vm.jorge@gmail.com>
> wrote:
> Hello
>
>
>
> Thinking on fixed antennas to avoid rotor problems, I have a question/doubt.
>
>
>
> if I have a stack of 3 antennas (15 mts monobanders) on the same tower, how
> worst will be to add a second stack of 3 antennas on the same tower at 6 ft
> of separation each one?
>
>
>
> For example, a stack fixed to Europe at 50/100/150 ft. Then I add a stack
> fixed to USA at 48/98/148
>
>
>
> This is possible or will damage the performance?
>
>
>
> Will use any combination, each stack at a given time for quick switch
> between Europe and USA and also will want to use both stacks at the same
> time
>
>
>
> Thanks,
>
> Jorge
>
> CX6VM/CW5W
>
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