[CQ-Contest] Be careful
n4zr at contesting.com
Sun Jan 2 21:07:59 EST 2005
If I recall the original analysis, the point was not how much gain could be
developed in an absolute sense, but how the gain at desirable angles of a
beach vertical compared with a portable triband yagi at the typical
DXpedition height of 30 feet or so. Both modeling and the fabulous results
obtained by Team Vertical demonstrate that there really is no comparison.
73, Pete N4ZR
At 06:12 PM 1/2/2005, Bill Tippett wrote:
> >And how much extra effort is involved in installing a "small 3-stack" vs.
>verticals? Particularly in a DX-pedition setting?
> Answer: a LOT more effort.
> >Is that worth less than an S-unit?
> Answer: more like 2 S-units (11.7 dBi).
>Gain Summary (NEC-2, HFTA, YO7, etc.):
>1. Single 4-square over salt water = 10.2 dBi
>2. Four phased 4-squares over salt water = ~16 dBi
>(I suggested this option just to show what kind of vertical
>array it would take to be more competitive with a Yagi stack).
>3. Single 6 el Yagi over average ground = 16.7 dBi
>(10.7 antenna + 6 ground reflection, TOA depends on height)
>4. Dual 6 el Yagis over average ground = ~20 dBi
>5. Triple 6 el Yagis over average ground = 21.7 dBi
>BOTTOM LINE: On 10 meters, a single 4-square over salt
>water will only beat a dual stack of Yagis only at TOA's
>below 3 degrees, which represents only about 15% of the
>W4>EU propagation statistics according to HFTA. Its
>advantage is a single broad lobe covering a wide range
>of TOA's, but it cannot compete with a switchable stack
>which can be focused on particular TOA's as conditions
>change. Someone asked about a Yagi over salt water...
>HFTA shows virtually no difference between salt water
>and very poor grounds. You should ask N6BV why that is
>but it may because the incident angles are small enough
>that ground gain is achieved independent of conductivity
> This thread began with a few blanket statements by Yuri:
> >Verticals on the beach will outdo Yagis at low angles and DX performance.
>I have played with them as N2EE on 10m from Cape Hatteras (US LP record), NC
>and can vouch for it. Now using some real arrays....
> >Just to bring to attention that verticals can be awesom, beat Yagis when
>properly used (on salty beaches).
>These statements are not necessarily true, either theoretically
>or in real world results. As K2KW and I both stated, a verticalarray's
>advantage improves as you go down in frequency, mainly
>because stacked Yagi systems are more difficult to implement there.
>There is no doubt in my mind vertical arrays are the best choice for
>portable operations on salt water, but let's not kid ourselves that
>they are ALWAYS better than Yagi stacks.
> 73, Bill W4ZV
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