donderdag 28 november 2013

3 element Steppir yagi on 10m analysis

Problem : during 22 hours of contesting in the CQ WW DX SOSB 10 HP A, I wasn't able to work zone 19 and I had problems with Japan.

The Japan issue seems a general problem, this has also been reported in other logs of the nearby countries.

But the zone 19 problem ...   I've done the analysis of my log with SH5 software.
This is the results of the percentage of QSO's versus distance.  Of course it has been easier to work 6.000 km in stead of 10.000 km but the dip between 3000 and 5500 km is remarkable.

One reason is of course the water of the Atlantic ocean, but also zone 19 is situated in this dip.


When looking at the antenne, the yagi was at 21m, i.e. around 2 wavelenghts above the ground.

The diagram of a single yagi above the ground is shown hereunder in blue :

In fact this is the diagram of a 15m 3 ele yagi about 1,5 wavelengths above ground (I couldn't find a picture of 2 lambda).   I know that my 10m yagi shows a first lobe at 7 degrees and a second one around 22 degrees.  My problem is that zone 19 is situated in the nil-zone of my yagi.  At lower heights (red line), zone 19 should have been much more workable, with a loss of workability to the real dx countries.

The only rights solution is putting two yagi's in a vertical stack (green line) and play with the possibilities of the stack.

Does this effort make sense ?  Of course it will provide a better result.

Take this one : the nice 10m array of OK7K




This installation is about 8x the size of my simple 3 el Steppir + stacking hardware + control cabling etc...

The stations claims a score that is about +20% higher as my score.
One extra zone (zone 19 ? :-) ) and 12 extra countries
About 130 more QSO and some more operating time.  This means 4-6 extra QSO/hour.





Is this worth the effort ?
Not for me (anyway, I can't place a stand-alone tower only for one band, I'm not a contest club but a "well muscled Litte Pistol" in a residential area, and 10m is not my favourite band)
.
I've not the ambition to win a big contest, nor to build a big station.  Until now, I've always followed the Pareto principle which is also here true : obtain 80% of the result with only 20% of the effort.

My score is 80% of the OK7K score.  My antenna is 20% of the OK7K array.
Pareto, you're right !

 My ultimate goal to have a DXCC on all HF bands, 5B-WAZ and 5B-WAS is possible by this way of working... until Today !
I hope that this will continue when focussing on the 80m WAS and 160m DXCC.








Geen opmerkingen:

Een reactie plaatsen