[CQ-Contest] Be careful

K3BU at aol.com K3BU at aol.com
Sun Jan 2 21:07:43 EST 2005

In a message dated 1/2/05 6:47:11 PM Eastern Standard Time, 
btippett at alum.mit.edu writes:
>>         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<<

3 el. K3BU Quad Vert. pol., half wave up, over salt water  = 15.5 dBi at 0 
deg  (unachievable by any stacked Yagis)
same quad over regular ground  13.48 dBI at 6 deg
same quad horiz. pol. 13.7 at 24 deg same over any ground.
That is what EZNEC says, reality may vary.

>>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....<<

Let's get real, we should be comparing similar antennas, like 4 square, 3 - 4 
el. Yagi, 3 el. Quads. I said at "low angles and DX performance"

>Just to bring to attention that verticals can be awesome, 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.<<

They are true, for the same number of element arrays and for low angles. 
That's what we are discussing. Not 4 el. vs. 18 el. stack!!

Yuri, K3BU.us

More information about the CQ-Contest mailing list