Saturday, September 30, 2017

Location, Location, Location - Quarter Wave GP vs Quarter Wave GP

VE3LDP and VA3IMI are more or less identical antennas running a 200 mw WSPR .   IMI is feed with 100 ft of LD4 and is just behind the house with a clear LOS from 170 through 350 deg and a GP that is tilted towards 260 deg. . LDP is feed with 500' of LDF4 and is at the apex of the hill and has a clear LOS 360 deg and a GP that is tilted with the exception of 350 through 10 DEG.    The hill has an average 25% grade.

Local Sunrise is 07:21 am est or 11:21 gmt.

So I am quiet surprised with the preliminary results it shows that LDP outperforms IMI during the night but during the day its the other way around.   I still need to quantify the statement and will need to collect data over a period of time. 

Below is a capture of 6 hours of simultaneous spots from 5 hours before Sunrise and an hour afterwards.   The Yellow highlighting better performance from IMI the Red highlighting deliminates Sunrise and the Green highlighting is better performance from LDP  and no highlighting is equal levels.   

So it looks like a have a " Day Antenna " and a " Night Antenna " for 40 Meters!


LDP is at the APEX of the Hill the ground plane slopes away from the antenna at about a 25 deg angle with the exception 350 to 10 Deg where the angle is about 0 deg.

Sketch of this antenna...

IMI is behind the house 75' below the APEX.  the GP tilts up about 15 deg bearing 10 deg and down 25 deg bearing 200 deg...basically its tilted towards the W SW! 

Now another very important thing to make note of is the hill that these antennas are located on is basically a big ass pile of gravel thanks to the last ice age.   Gravel is not a very good conductor so essentially its these antenna relying totally on the man made ground plane. 

Another consideration is the topography.... to the East the land rises and it slopes to the West with Lake Huron almost LOS. 

I always felt that the GP being tilted favoring the US SW and VK land was giving me  a bit of an advantage but the jury is out on that.   This morning my little 200 mw WSPR was hear in VK land with simultaneous spots.....

 So yeah one spot both IMI and LDP -25 SNR from ...go figure! 

Looked at all the spots that VK5UV reported on 40m and I was 3 of 2 200mw spots that were reported ...

In conclusion it appears that the antenna on the top of the hill has a lower angle of takeoff then the antenna on the side of the hill...I think.   I will gather more data over time but I have a pretty good idea what to expect.

Up next 14avq vs 1/4 GP....they are few feet apart both at the top of the hill. 

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