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AX25_MAC.INI file

The individual commands that can appear in AX25_MAC.INI:

T TX-DELAY

This is the delay, in 10 ms units, between keying up the transmitter (PTT) and the actual transmission of data. This delay is needed because it takes some time between keying the transmitter and the actual transmission of a stable carrier. The value depends on the switching speed of the transmitter.

Example:

T 1:30 ; (10 ms) TX-Delay: PTT on -> transmission of data

P PERSIST

This is the Persistence access parameter, used to add a random time before transmissions to allow more users to use the same frequency. Before transmission a random value between 0 and 255 is generated. If the value is below or equal to the Persist value, the transmission will be started. Otherwise transmission will be postponed for one slot time (see W). Then a new random value is generated and compared again with the Persist value, until transmission can be started.

Example:

P 1:64 ; (8-255) Persistent value for transmission (=P/255)

W Slottime

With this command the time of a Slottime is defined in units of 10 ms. This is used in conjunction with the Persist value and is the wait time between comparing random numbers with the Persist values until the transmission of Packets is granted.

Example:

W 1:10 ; (10 ms) Slottime

X PTT enable

With this parameter you can enable and disable the PTT. When disabled AX25_MAC will 'transmit' data without actually keying the transmitter. Value '0' is used to disable the PTT, value '1' will enable it.

Example:

X 1:1 ; (0-1) PTT (0=off, 1=on)

@C DCD-Working

AX25_MAC has a Soft-DCD (software squelch). When using slow transceivers (slow meaning a slow squelch circuit) you can leave the squelch of the receiver fully open. AX25_MAC will determine for itself whether or not a packet signal is being received.

The Soft-DCD can be controlled by means of the '@C' command, the given parameter controls the noise-canceling level. This parameter can be a number between 0 and 63. When using '@C0' the Soft-DCD is switched off (default)- all other values activate the Soft-DCD. The lower the value the more unstable and faster the Soft-DCD becomes, the higher the value, the more stable and slower it becomes. The ideal DCD should be both stable and fast. Therefore the best setting will good compromise between the two extremes. To simplify the job of finding the right value you can use the DCD indicator (see option '-C'). When using a small value you will see the unstable DCD indication, when using a large value you will see slow and inaccurate recognition of signals. The best way to set this correctly is to slowly increase the parameter value while listening to the signals on the PR QRG, until the indication is correct. A good start value is '@C25'.

When using SCC, PAR96 or PICPAR ports an adjustment is not really needed, all values above 0 will activate the Soft-DCD and they all have the same meaning for the operational software. I was, however, annoyed by the constant flickering of the indicator, so you can still adjust the value to reduce the flicker. For the YAM96 modem the @C command will not work at all since it always uses a hardware DCD.

IMPORTANT!

The soft-DCD only recognizes PR-Signals at the same baud rate. You can _not_ use the soft-DCD on packet QRG's which carry PR signals at different baud-rates.

When using KISS or THD7, the TNC handles the DCD, and this command only defines the time (in 10ms-Units) after which the RX indication will be removed from the screen if no further data was received from the TNC.

Example:

@C 1:10 ; (0-63) DCD (0=Hard-DCD, >0 Adj speed for Soft-DCD)

@D DUPLEX

With @D full duplex can be switched on or off. When 0 is specified the port works in half duplex, when 1 then full duplex is selected. In full duplex transmission takes place regardless of the DCD state.

Example:

@D 1:0 ; (0-1) Duplex (0=off, 1=on)

@TA TXTAIL

You can specify the TXTAIL value in 10ms units (0-6000) but this value is in normal cases (for the selected baudrate and timer inaccuracy) already set to the most optimal value (@TA=4 for 300 baud, @TA=1 otherwise). When using KISS the correct value depends on the used TNC, therefore it is not set automatically in this case.

Example:

@TA 1:4 ; (10 ms) TX-Tail: end of frame -> PTT off

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