Sunday, 3 July 2016

Doublet analysis (II) - 4nec2 & Voacap

4NEC2 integrates VOACAP engine. So it is easy to simulate your antenna and run point to point predictions and coverage maps.
Below is an example of my Inv-V doublet

Inv- V Doublet - 4nec2 - 14Mhz, max gain 6.84dBi @ ~30 deg elevation

Birmingham - New York path example
I have worked plenty of contest stations over the last few months with the doublet
DX bearing from here is 286deg
Antenna max gain [beam] bearing is 330 deg N/NW - Delta = 44deg [dictated by small garden]
4NEC2 generates a type 14 model for the antenna at the specified azimuth for [1-30MHz]
This is what the elevation gain plot looks like for 14Mhz towards the DX bearing
Gain @ 10deg elevation is -2.8dBi
It is useful to run VOACAP method 13 to check that the TX antenna gain pattern is correct
For RX antenna I use a 3dBi isotrope

Inv-V doublet Gain at 14Mhz - bearing 286deg

Below is the generated SNR plots for the path, also showing the MUF & FOT for the specified reliability [70%]

VOACAP -  Bham -> NY path, SSN 43,  rel 70%, 

It is also possible to run area coverage simulations
4NEC2 generates a type 13 model of the inv V antenna for a given freq [14Mhz in example below]

VOACAP coverage - 500W - 14Mhz, 21UTC, SSN 43, TX antenna = inv V doublet
73 Angel

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