[CQ-Contest] Be careful

Bill Tippett btippett at alum.mit.edu
Mon Jan 3 07:03:42 EST 2005

KK9A wrote:
 >Bill, your gain figures seem to favor the yagi(s), but if the gain is not at
the desired radiation angle it's useless.  For example your single 6el Yagi
(if 1W.L. high) has a radiation angle of 14 degrees.  Depending on
conditions the optimum angles for 10m can be much lower.  The verticals over
salt water have a very low radiation angle and likely beat the yagi at 5
degrees.  They also don't have the lobes that a horizontal antenna has so
there's no angles that are not covered.   I've played with a simple two
element 40m parasitic beach vertical array as ZF2JB and I was impress with
the performance.

         We are in complete agreement.  Previously I wrote:

"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

         The advantage of a Yagi stack is that you can steer
higher gain to the angles needed at any time.  Very low
angles (<3 degrees) only represent 15% of the conditions
from W4 to Europe according to HFTA/VOACAP.  Actually it's
been quite surprising to me how often high-angle radiation
is better to Europe in good conditions.  Of course the
operator must have some idea of when to select which Yagi
combinations to optimize TOA's.  It took me a few seasons
to refine my understanding of that.  The other advantage
of a stack is the ability to skew in orthogonal directions
simultaneously (e.g. EU and SA, or JA and ZL).  That is
also possible with some vertical arrays (like K1ZM's 3X2
array on 160) but not a 4-square.

         As I said above, vertical arrays are a great portable
antenna for salt water locations, but my point was that a
single 4-square over salt water is NO match for a Yagi
stack.  Here's a very recent example from 2-point land:

[3830] 2004 CQWW SSB - Non-USA Final Claimed Scores

Non-USA M/2 HP
VP2E             17097   190   807    48 43,431,314 NTCC

I'm not exactly sure what is up at VP2E now but I suspect
there are a few Yagis from Gordon's old N5AU station.  ;-)

 >BTW, I wouldn't call a 105' 6/6/6 as a small stack - especially when
comparing it to a few 8' whips in the sand.

         Maybe not but I consider my real 10m competition the top USA
M/M's.  At last count KC1XX had over 70 elements on various arrays,
and most (K3LR, W3LPL, K9NS) have at least a 3-stack of 7 elements
on 48' booms.  By those standards, mine IS small (3-stack of KLM 6's
on 27' booms).

                                         73,  Bill  W4ZV

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