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User's Manual | ACOM 2S1 | Automatic XCVR Commutator
June 2022 S e c t i o n MAINTENANCE | Page 21 of 32
4. MAINTENANCE
4.1.
Periodic Maintenance
Periodically (but at least once per year) check all connections, contact cleanliness and the tightening of all
connectors, in particular the coaxial ones.
Check the integrity of the cables, in particular when they are laid on the floor. Check also if the cables are
secured well in the area where they come out of the connector body.
4.2.
Cleaning
CAUTION
Do not use any solvents for cleaning. They may be dangerous to you and damage
commutator surfaces, paint and plastic components.
Do not open the commutator. Cleaning of the commutator outer surfaces can be done with a piece of soft
cotton cloth lightly moistened with clean water.
4.3.
Schematic Diagram
Please, see
Figure 4-1 | Schematic diagram, Part 1
and
Figure 4-2 | Schematic diagram, Part 2
.
Power supply is fed to the commutator from any transceiver via diodes D1 and D2. Both transceiver RF paths
are controlled by the contacts of relays K1 and K2 (shown in RX position). When A transmits, INA is connected
to the OUT via K2, while INB is grounded via K1. Relay's contacts are monitored through chokes RFC1...RFC4.
Respective signals GA and GB are used by the logic to disable transmission while the opposite antenna input is
not yet grounded. Two other signals PA and PB disable transmission if no RF input is connected to the output.
The transmission requests *TXA or *TXB are controlled via a trigger-logic composed by U3B, U3C, U4A, and
U4B. It judges which request is earlier and disables the other until the first one finishes transmission. The
opposite RF relay is switched over via U4 (A or B) in order to save its RX input. Simultaneously, the
transmission request is passed to the KEY OUT through U3D, U2C, and the transistor Q1. At least one of PA
or PB is wanted to be logical high by U3A, otherwise U2C would prevent KYE OUT going low.
The logical low KEY OUT signal must be returned to the KEY IN by the amplifier and/or antenna selector
when they are ready to transmit. A direct jumper must be placed between KEY OUT and KEY IN if no
external apparatus is used. After *KIN signal is tied low, a second trigger (composed by U1 and U2) is
enabled. It is intended to check GA and GB signals, i.e., whether the opposite relay has already grounded
the second transceiver's RX input. When grounded, the respective inhibit signal (INHA or INHB) is enabled
and its LED lights. This returns a low INHIBIT confirmation signal to the transceiver that requested
transmitting earlier. The other INHIBIT signal remains HIGH in order not to let simultaneous transmission.