Print Date 08/04/14 Page 7 of 34 S79005-00MA-05
If a fault should occur within the E2023, manually operated switches on the E2026 Drive Changeover
/Output Monitor Unit can be used for basic control of the Transmitter. This enables it to be kept ‘on-air’
whilst the E2023 is replaced.
1.1.4 : E2026 Drive Changeover/Output Monitor (and Splitter) Unit
This single unit interfaces between the Exciter(s) and the two E2021 Amplifier Module inputs. The
splitter section within the unit is a two way Wilkinson utilising standard coaxial cable and is thus easily
repaired if any become damaged. All outputs are brought to TNC connectors at the rear of the unit.
Phase length matched, 50
Ω
coax leads then connect these outputs to the E2021 inputs.
This unit also contains circuitry to measure the Transmitter’s final output forward and reverse powers,
via a coupler in the E2029 Combiner, and to measure the temperature of the Combiner’s dumping
load heatsink (see 1.1.5). Front panel red/green displays indicate any fault condition. Two multi-turn
preset High or Low Power potentiometers are accessible via the front panel to enable independent
setting of two Transmitter output powers. They are selected using various forms of local, external or
remote control or via a link on the rear left hand side Bus Board (see section 3.4.2). A front panel
connector is provided to give a harmonically filtered test sample of the Transmitter’s output forward
power.
As with the E2023, the rear of the E2026 has separate connectors for the two independent internal
Transmitter control buses. As previously detailed, each control bus has its own RS485 data bus, one
of which is used to carry the monitored serial information from the E2026 to the E2023 Control Unit.
For these two buses, the E2026 also provides two equal but independent power level control voltages
(derived from either the front panel High or Low Power potentiometers) to set the power level of the
E2021 Amplifier Modules and thus the final transmitter output power. One control voltage is used for
the Amplifier Module on the left hand side of the Transmitter and the other for the Amplifier Module on
the right hand side.
A front panel lockable toggle switch is provided to manually mute or start (i.e. demute) the Transmitter
or can be set to enable the E2023 Control Unit to select high/low power or to mute/demute the
Transmitter as part of an automatic control sequence. An interlock switch connector is also provided
on the rear to enable the open-circuiting of external switches placed at safety points (e.g. at Antenna
access gates) to automatically mute the Transmitter. The state of this circuit is displayed on a front
panel indicator.
The E2026 can also provide manual or automatic dual drive changeover in conjunction with the E2023
Control Unit. A second front panel lockable toggle switch is provided on the E2026 to manually select
which Exciter (i.e. ‘Drive’) is to be used, or to enable the E2023 to automatically select the second
Exciter should the first one fail. Switching is performed by two coaxial RF relays within the E2026.
These direct one of two Exciter’s outputs to the internal splitter and the other to a dumping load. This
dumping load has to be provided (externally to the E2026) whenever two Exciters are supplied and the
Exciter not in use is required to remain ‘active’ or be tested. Three TNC connectors are provided at the
rear of the unit to connect to Exciter(s) and dumping load. Front panel indicators show which Drive is
selected
1.1.5 : E2029 Two Way Combiner Unit
This single unit interfaces between the two E2021 Amplifier Module outputs and the antenna. Phase
length matched, 50
Ω
coax leads connect the E2021 outputs to the TNC connectors at the bottom rear
of this unit. The combiner section within the unit is a two way Wilkinson, utilising standard
handformable coaxial cable. The combiner section is preceded by integral low pass filters (one for
each E2021) these removing harmonics of the wanted frequency.
An output directional coupler is provided with an N Type output socket for connection to the antenna.
This coupler provides output forward and reverse power samples, via coax connections, to the E2026
Drive Changeover/Output Monitor (see 1.1.4). The combiner dumping load heatsink is fitted with a
temperature sensor, which is also connected to the E2026 to allow monitoring and over-temperature
warnings.
