ANTENTOP- 01- 2012, # 016

EH Antenna for the 20- meter Band

Do two holes in diameter 2- mm near the lower end of the tuning inductor. Pass through the holes wires from the input inductor and ground of the RF- Socket (Figure 11). Length of the wires should be allowed to remove the cap from the tube without desoldering the wires from the tuning inductor and RF- socket. It may be needed for adjusting of the input inductor. Then fasten the cap to the tube by screw.

Figure 12 shows EH- Antenna with the cap. Wire going from the input inductor is initially soldered to the 4th- tap of the tuning inductor. Wire going from the ground of the RF- Socket is soldered to the lower end of the tuning inductor. Figure 13 shows the soldering to the tuning inductor.

Figure 12 EH- Antenna with Cap.

Figure 13 Soldering Wires to the Tuning Inductor

All set! EH- Antenna is made!

Tuning of the Antenna

At the tuning process antenna should be hanged up in the way that any subject should be placed no more the 0.5- 1.0- meter apart from the antenna.

Initially it would be good to measure a resonance frequency of the antenna. Best way is to use an RF- Spectrograph with a screen. I used to a surplus Russian X1-50 spectrograph.

Several words are here about of using of the spectrograph. Almost any spectrograph has two pairs of terminals for analysis of the "Black- Box" First terminal is "Output" from where an RF is going.

Second terminal is "Input" to where the signal that came through the Black Box is going. So we need a Black Box with Antenna inside in it. For the Black Box I used to an RF- Bridge made by schematic of RZ4HK (Reference: Radio #1, 1980, p.22). Figure 14 shows the Bridge. Turn on the bridge to the spectrograph and turn on the antenna to the bridge.

Now it is possible to find with help of the spectrograph the amplitude frequency characteristic of the EH- Antenna. Figure 15 shows RF Bridge connected to the spectrograph. Figure 16 shows screen with the amplitude frequency characteristic of the EH- Antenna. EH- Antenna should be turn on straight away to the Bridge. RF Output and Input of the spectrograph may be turn on to the bridge by the Spectrograph's cables.

If the resonance frequency of the antenna is lower the 14.15- MHz turn by turn remove turns from the upper end of the tuning inductor. Stop on the frequency near 13.5-13.8 MHz. Then the tuning antenna into resonance it is possible to do by changing gap between the turns of the tuning inductor. After that turn on the EH- Antenna through SWR meter to the transceiver. SWR meter should be connected straight away to the EH- Antenna. Input inductor at the time should be closed. Change tap on the tuning inductor by minimum SWR. Figure 17 shows SWR Vs Tap at my EH- Antenna. Open input inductor. Change quantity of the turns or geometrical sizes of the inductor by minimum SWR. Check the resonance frequency of the antenna during the tuning.

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