MICOM-3F/3T/3R HF-SSB Owner’s Guide
36
•
In a network of nine channels used by eight members, a 30-minute sounding cycle would result
in 80% occupancy; a 60-minute cycle would result in 40% occupancy; a 90-minute cycle would
result in 27% occupancy and a 120-minute cycle would result in 20% occupancy.
•
If there are only two or three channels in the network, a sounding cycle of 30 minutes allows
enough channel-free time, even for as many as ten users.
Under field conditions, occupancy will usually be less than the value obtained from the chart because
not every station receives all the soundings that are being broadcast on all channels.
To increase channel-free time for the users by reducing network occupancy, you can try one of these
four methods (in this order):
1. Increase the sounding cycle time (to 90 or 120 minutes).
2. Reduce the number of channels in the network (for example, by using different nets for
different times of day).
3. Reduce the number of stations in the network by re-arranging the hierarchical
subgrouping of stations.
4. Request all stations to set the fast scan rate option.
Manual Sounding
When it is necessary to perform a rapid sounding cycle on all channels instead of, or in addition to
the automatic sounding cycle, manual sounding can be used.
LQA Memory
The ALE builds a database of connectivity information based on calls and the ALE sounding messages
transmitted by other stations in the network. This information is stored in a special LQA memory and
is used to determine the link quality of all channels in the networks. The data in the LQA memory is
time-weighted
, that is, recent information is given more value than old, thus compensating for
changing propagation conditions.
Bidirectional Handshake
The bidirectional handshake is an operator-initiated procedure used to exchange LQA scores with
other stations without establishing a link.
Note
The MICOM-3 can also be programmed to automatically initiate the call to the
station after finishing the bidirectional handshake (using the BDLK parameter
reached under the ALE programming options).
This procedure is useful in the following cases:
•
The radio has only recently been switched on and the automatic sounding cycle has not yet been
completed.
•
The operator wishes to update the LQA scores before initiating a call to another station, for
example, for example, because of abrupt atmospheric charges, or other propagation changes.
•
A new or passive station has joined the system.
A bidirectional handshake can be carried out with a single station or with all stations in the net. It can
be carried out either on a single channel, or on all the net channels. When required, a message can
also be added to the procedure.
