Microbit RRC-1258 MkII(s) Uživatelský manuál stáhnout pdf (Strana 12)

Computers in Amateur Radio

Click on the Trans Lines button in the Control Centre window to

open the blank Transmission Line window – Fig 4.5.

We now enter the required transmission line parameters. End 1 of

the line is in the centre of Wire 1 at 50%. End 2 would normally be

another wire defined in the Wires window. However, to make life simpler,

we use an EZNEC specific shortcut and use a ‘Virtual wire’ (v1), which

does not require a physical location to be defined.

Fig 4.6 shows the completed Transmission Line Window. Close

the window.

Note that EZNEC V5.0 has a transmission line calculating engine

built in, which will calculate the transmission losses for any given fre-

quency and subtract these when calculating the antenna model gain.

Impedance transformations down the line are also calculated.

We now move the source from the centre of the wire to the virtual

wire at the far end of the transmission line.

Open the Sources window. Change the Specified pos from wire 1

to v1 – Fig 4.7.

Note we are using a ‘Current’ type source with amplitude of 1-amp.

Click on OK to close the window.

We will now change a number of other model parameters to better

reflect real life conditions.

Click on the Ground Type button. In Real Ground Types, click on

the High Accuracy button to change from MININEC ground - Fig 4.8.

The High Accuracy gound model is more accurate than the MININEC

ground. Click OK to close the window.

The High Accuracy gound model takes into account losses

through the ground close to the

antenna, the MIMINEC ground does

not. The downside is wires can not

be directly connected to ground with

the High Accuracy ground making

accurate modelling of vertical anten-

nas more difficult.

Click on the Ground Descrip

(Ground Description) button.

Fig 4.5: Blank

Transmission

Line window.

Fig 4.6: The

Transmission

Line Window

completed for

the G5RV.

Fig 4.7: The

Sources Window

completed for

the G5RV.

Fig 4.8: The

Ground Type

Window for the

G5RV.

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