ANTENTOP- 01- 2018 # 022

Antenna Switching Units

To prevent connection of a receiver antenna to a transmitter output or to simultaneously switch two transmitters to one antenna, switches S2 and S4 should be independent of each other (however it need pay attention when switching).

How it works: Switch S1 selects operational transceiver. Switch S2 selects an antenna for use with this transceiver. Other auxiliary transceivers or receivers may be connected to other antennas with help of switches S3 and S4. All antennas connected to ASU are permanently grounded with help of R3, R4, R5 and R6 (100 K/2W) for electro-static bleed-off. Resistors R2 and R7 were old commercial made 75 Ohm/25W dummy load. To one of the dummy load was connected to bridge resistor 180 Ohm/5W that created new 50 Ohm dummy load. Figure 2 shows the views of the front panel (Figure 2A) and inside design (Figure 2B) of the universal ASU.

There were used usual ceramic galette rotary switches that work well for power levels up to 200W. For higher power levels it is necessary to use special powerful ceramic galette rotary switches intended for operation in high-current, high voltage circuits. Montage and component mounting should meet RF guidelines.

ASU for RF-Bridge/ATU

If in the shack there are several separately units such as an ATU, transceiver, and RF-bridge it is possible to hook up the equipment with help of special ASU. In this case it is possible tune the system ATU plus Antenna with the RF-bridge. Even though a transceiver or the ATU may have an SWR-meter built-in it, it would be useful to use an RF-bridge for antenna tuning. RF-bridge gives the real impedance of the system Antenna plus ATU. Figure 3 shows schematic for such unit.

Figure 2

Front Panel (A) and Inside Design (B) of the Universal ASU

When S1 switched to the Control position, RF power from transceiver goes to the RF-bridge and ATU with antenna as well connected to the Bridge. In tuning mode it should be used level of RF power that intended for operation of the RF- bridge. My RF-bridge required near 0.5 W of RF power. When the system is tuned, S1 should be switched to Operation position and RF power may be increased. Figure 4 shows the system Transceiver- ASU- ATU- RF-bridge.

Figure 3 ASU for RF-bridge

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