When stacks are modeled, you can see changes in element currents of the
adjacent yagis, they are not independent of one another. These changes
reduce the 3db intuitive figure to something over 2db, depending on the kind
of antenna.
If you look at the pattern of a single yagi in free space, there is a fair
amount of radiation straight up and straight down. When the antennas are
directly above one another, this vertical radiation "interferes" somewhat
with the antenna above or below, resulting in the 2.x dB figure for stacking
gain.
If the yagi used as array elements is 4.6 dB gain, then 10 dB is really very
good. Most likely 9.x, given harnesses, etc.
73, Guy
-----Original Message-----
From: Eric Gustafson <n7cl@toontown.mmsi.com>
To: towertalk@contesting.com <towertalk@contesting.com>
Cc: jlogan@bewellnet.com <jlogan@bewellnet.com>
To: <towertalk@contesting.com>
Date: Monday, October 19, 1998 11:09 AM
Subject: Re: [TowerTalk] A Question of GAIN
>
>
>Josh,
>
>I think it would go more like:
>
>4.6 (for array element) + 3 (for the next one) + 3 (for the next
> two) - (losses in harness and connectors)
>
>So I wouldn't expect more than 10 dBd net. And then only on the
>band where the spacing was optimum.
>
>73, Eric N7CL
>
>
>>From: "Josh Logan" <jlogan@bewellnet.com>
To: <towertalk@contesting.com>
>>Date: Sun, 18 Oct 1998 16:17:14 -0600
>>
>>Assume a person built a 4 stack of C3 Force 12 multi band yagis
>>
>>The C3 is given 4.6 dbd net gain for 20m
>>
>>IF stacked at say 35ft, 65 ft, 95 ft and 125 ft
>>What would be resulting GAIN?
>>
>>I would guess around 4.6 + 3.0 + 3.0 + 3.0 = 13.6 dbd net gain
>>
>>Is this reasonable?? What is a good spacing ? 30 ft ?
>>assuming 20m performance is important.
>>
>>Josh N7XM dreaming of Four Stack
>
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