K9JM CI-V User Manual - page 27
description leaves much to be desired. There are many good resources on the net.
http://www.qsl.net/icom/pw1/pw1pro2.html
These are the fundamentals:
There are two connections between the ICOM radio and a transceiver, the accessory cable and the
rmeote cable (which provides the CI-V bus).
First, while there are two CI-V connections on the back of the PW-1, there is only one CI-V bus.
The two connectors on the back of the PW-1 are wired together. The CI-V connection to the radio
can be made to either jack.
Second, is the accessory connector that brings 12 volts, transmit and ALC information from the
exciter to the PW-1. There is a switch on the back of the PW-1 that selects between one or two
transceivers. In the one transceiver mode, it wires the accessory connections of the two radios
together. On the PW-1 there is a front panel means of selecting which of the two transceivers is
selected. If the switch is in the two transceiver mode, the amplifier will take the accessory
information from the correct connector and will respond to the correct baud rate and radio “ID”
with the transceiver that it is synced up.
The synchronization process is one whereby the PW-1 is driven into a state where it listens to the
CI-V bus and does an auto baud rate detection and radio “ID” identification. Once the PW-1 has
learned this data, it should never have to re-learn, unless the PW-1 microprocessor is “reset” by
holding down the up and down buttons while turning on the unit.
So that the PW-1 can quickly follow band changes of the transceiver, the transceiver(s) must be run
in “transceive” mode. In this mode, whenever the radio dial is moved, or a memory is recalled, or a
band change occurs, the radio sends out a 'transceive' broadcast frequency update message.
If there is only one transceiver connected to a PW-1, there are no problems. If there are two
transceivers, this is when things get difficult.
If two radios are connected to the bus and are operating at the same baud rate, then both
transceivers are running in “transceive” mode. In this configuration, both transceivers will tune in
unison. To get around this when running with the PW-1, each radio is typically set to a different
baud rate. The PW-1, when doing it's synchronization will auto discover the baud rate of each
transceiver and when that transceiver is selected through the front panel of the PW-1, the PW-1 will
respond only to the 'transceive' broadcast frequency update message.
The CI-V router could direct only the 'transceive' broadcast frequency update messages from the
correct transceiver to the PW-1 at the correct baud rate, only if it knew the status of the input switch
selector on the PW-1. Unfortunately, CI-V router can not determine nor set the input selector in the
PW-1. Since the CI-V router doesn't know the state of input selector, it can not change the baud
rate of messages sent to the PW-1 based upon which is the active transceiver. The CI-V router can
not change baud rate on a packet by packet basis. What it can do is send broadcast messages from
both transceivers to the PW-1 and let it choose which to respond assuming the two transceivers
have different ID's. Both transceivers will need to be at the same baud rate. To keep the two
transceivers from tracking one another, 'transceive' messages can be suppressed being sent to
another radio port, but this only works when the CI-V router is in operation. When the CI-V router
is in bypass, both transceivers will track one another.
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