[TowerTalk] multiple antennas on same tower

[Stan Stockton]

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 at 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 at 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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