10
5.2 RF connections
RF INPUT
The RF input is an SO-239 female connector. A 50 ohm coaxial cable line of good quality terminated with a
PL-259 coaxial connector is required to connect the transceiver or exciter output to the input connector of
your DX-3 amplifier.
RF OUTPUT
The RF output is also a female SO-239 connector. The use of a high quality RG-8A/U, RG-213 or similar 50
ohm coaxial cable line terminated with a ‘VHF’ type PL-259 connector is essential. Similarly, a VSWR of
2.6: 1 or better is mandatory. Remember too, that the EMTRON DX-3 amplifier can deliver 3000 W
continuously and up to 4 kW PEP in the SSB mode. Not all antennas can handle such power.
5.3 Transceiver control
ALC
The ALC output is via a black female RCA connector.
This is an ALC system for use with transceivers or transmitters having a negative-going ALC system and
possessing an external ALC input jack. A shielded patch lead with an appropriate connector at one end and a
male RCA connector for the DX-3 at the other end is required. Check the specifications of your transceiver
for a suitable connection.
PTT
The PTT input is a female RCA connector (red). This line controls the transmit / receive switching system.
This jack must be connected to transceiver or exciter relay contacts which are open on RECEIVE and closed
on TRANSMIT. The voltage at the PTT input is typically 28V loaded (up to 35V unloaded), with an
impedance of about 240 ohm. A current of about 0.12 A has to be switched by the transceiver or exciter.
ALC CONTROL
This is a user-accessible control for setting the negative voltage at the ALC output. Further details are given
in section 10.2
6
FRONT
PANEL
The following controls and indicators are present on the front panel:
6.1
Controls
BAND SWITCH
A nine position switch selects the desired frequency range. The operating bands are indicated in metres.
PLATE TUNE
Tunes the amplifier operating frequency. A chart of approximate starting settings is given in Table-1
LOAD TUNE
Tunes the amplifier output loading. A chart of approximate starting settings is given in Table-1
ON/OFF
Switches the AC power on and off. On initial switch on, the standby mode is enabled. Note also the
appropriate switch down sequence, given in Section 11.
OPR/STBY
Enables the amplifier once it has warmed up. In STANDBY mode, the screen voltage is removed and any RF
power applied to the input, is bypassed to the output. If this switch is changed to OPERATE before the
READY light comes on, the FAULT light will turn on. This is not a fault, but it is better to leave the switch in
STBY position until the amplifier is ready to operate.
