remotetrx.conf - Man Page

Configuration file for the SvxLink remote transceiver server

Description

remotetrx is the SvxLink remote transceiver server. This man-page describe the configuration file format for it.

The RemoteTrx application can handle more than one transceiver at a time. You may for example want to handle both a 2m and a 70cm receiver on a site. One sound card is sufficient for doing this since the left channel can be used for one receiver and the right channel can be used for the other receiver. The Global/TRXS configuration variable is used to tell the RemoteTrx application which transceivers to set up. Each transceiver have an uplink that is used to interface to the main SvxLink server. The most common type is the net uplink which link to the main SvxLink server over the Internet using TCP/IP. It is also possible to have an uplink via RF but the functionality is then limited.

The term "uplink" might be a bit confusing for some people. In this case it does not refer to any specific direction in which the data or audio is flowing. It's just the name for the link up to the main SvxLink server.

RemoteTrx look for configuration files in a number of places. First it tries to find a user specific configuration file. It will look for a user specific configuration file in two places: $HOME/.svxlink/remotetrx.conf. If no user specific configuration file can be found, remotetrx will look for the system wide configuration file /etc/svxlink/remotetrx.conf. The --config command line option may also be used to specify an arbitrary configuration file.

File Format

The configuration file is in the famous INI-file format. A generic example of how such a file might look like is shown below.

[SECTION1]
VALUE1=1
VALUE2="TWO "
VAULE3="Multi "
"line"

[SECTION2]
VALUE1=2

This is a simple format that contain name=value pairs that belong to a section. In written text, a specific configuration variable can be referred to as SECTION1/VALUE2 meaning "configuration variable VALUE2 in section SECTION1".

The same variable name can exist in two different sections. For example VALUE1 in section SECTION1 have the value 1 and VALUE1 in section SECTION2 have the value 2. Values containing spaces at the beginning or end of the line must be surrounded by citation characters (see SECTION1/VALUE2). Likewise with a multi line value (see SECTION1/VALUE3).

Configuration Variables

Here is the description of all configuration variables that remotetrx understands. The configuration variables are described section for section.

Global

The GLOBAL section contains application global configuration data.

TRXS

This configuration variable specify a comma separated list of transceiver configuration sections.

CFG_DIR

Specify the path to a directory that contain additional configuration files. If a relative path is specified, the path will be relative to the directory where the main configuration file is at. All files in the specified directory will be read as additional configuration. Filenames starting with a dot are ignored.

TIMESTAMP_FORMAT

This variable specifies the format of the timestamp that is written in front of each row in the log file. The format string is in the same format as specified in the strftime(3) manual page. The default is "%c" which is described as: "the preferred date and time representation for the current locale". The environment variables LC_TIME, LC_ALL and LANG will affect how this time format will look. For example, setting LC_TIME="sv_SE.UTF8" will give you swedish timestamp representation. Other examples of format specifiers are:

%d - The day of the month as a decimal number (range 01 to 31)
%b - The abbreviated month name according to the current locale
%Y - The year as a decimal number including the century
%H - The hour as a decimal number using a 24-hour clock (range 00 to 23)
%M - The minute as a decimal number (range 00 to 59)
%S - The second as a decimal number (range 00 to 61)

So, TIMESTAMP_FORMAT="%d %b %Y %H:%M:%S" would give a timestamp looking something like: "29 Nov 2005 22:31:59".

CARD_SAMPLE_RATE

This configuration variable determines the sampling rate used for audio input/output. SvxLink always work with a sampling rate of 16kHz internally but there still are som benefits from using a higher sampling rate. On some sound cards the filters look pretty bad at 16kHz and the amplitude response will not be uniform which among other things can cause problems for the software DTMF decoder.

Some sound cards also sound very bad at 16kHz due to insufficient anti-alias filtering or resampling effects. These, often cheeper, sound cards sound OK at 48kHz.

The downside of choosing a higher sampling rate is that it puts a little bit more load on the CPU so if you have a very slow machine (<300MHz), it might not have the computational power to handle it.

Supported sampling rates are: 16000 and 48000.

CARD_CHANNELS

Use this configuration variable to specify how many channels to use when opening a sound card. For normal sound cards the only practical values to use are 1 for mono and 2 for stereo. The latter is the default.

When using the sound card in stereo mode it is possible to use the left and right channels independenly to drive two transceivers. When using the sound card in mono mode, both left and right channels transmit/receive the same audio.

Network uplink transceiver section

The network uplink transceiver section is used to specify the configuration for a network link to the main SvxLink server. In the default configuration file there is a network uplink transceiver section called NetUpLinkTrx.

TYPE: Always "Net" for a network uplink transceiver configuration section.
RX: Point out the receiver configuration section to use. Set to NONE if no RX is used. A receiver is configured in the exact same way as in the SvxLink server. Have a look at svxlink.conf(5) for more information on how to configure a receiver.
TX: Point out the transmitter configuration section to use. Set to NONE if no TX is used. A transmitter is configured in the exact same way as in the SvxLink server. Have a look at svxlink.conf(5) for more information on how to configure a transmitter.
LISTEN_PORT: The TCP port to listen on. Make sure to choose a unique port for each network uplink transceiver configuration. The default is 5210.
AUTH_KEY: This is the authentication key (password) to use to athenticate incoming connections. The same key have to be specified in the client configuration. If no key is specified, all logins will be unauthenticated. A good authentication key should be 20 characters long. The key will never be transmitted over the network. A HMAC-SHA1 challenge-response procedure will be used for authentication.
MUTE_TX_ON_RX: If set to a value >= 0, will stop the transmitter from transmitting when the squelch is open. The value represents a delay, in milliseconds, after the squelch has closed, that the transmitter will be muted. For example, if set to 1000, the transmitter will be muted one second after the squelch has closed. The default is not to mute the transmitter when the squelch is open.

RF uplink transceiver section

The RF uplink transceiver configuration section is used to specify the configuration for an RF link to the main SvxLink server. In the default configuration file there is an RF uplink transceiver section called RfUpLinkTrx. The section name could be anything. It should match what is specified in the TRXS configuration variable in the Global section.

The use of Rf uplinks is very EXPERIMENTAL and still have some flaws. Among other things, detected tones (like CTCSS or 1750 tone burst) are not relayed and all relayed DTMF tones are always 100ms long no matter how long the received digit was. Signal level measurements are not relayed either.

Any way, it's used to link remote receivers coming in on the Internet to a site that do not have access to Internet.

TYPE: Always "RF" for an RF uplink transceiver configuration section.
RX: Point out the receiver configuration section to use. Set to NONE if no RX is used. A receiver is configured in the exact same way as in the SvxLink server. Have a look at svxlink.conf(5) for more information on how to configure a receiver.
TX: Point out the transmitter configuration section to use. Set to NONE if no TX is used. A transmitter is configured in the exact same way as in the SvxLink server. Have a look at svxlink.conf(5) for more information on how to configure a transmitter.
UPLINK_TX: Point out the uplink transmitter configuration section to use. The configuration for an uplink transmitter looks exactly the same as for any other transmitter. In the default configuration file there is an uplink transmitter configuration section called UplinkTx. If there is no uplink transmitter, specify NONE.
UPLINK_RX: Point out the uplink receiver configuration section to use. The configuration for an uplink receiver looks exactly the same as for any other receiver. In the default configuration file there is an uplink receiver configuration section called UplinkRx. If there is no uplink receiver, specify NONE.
MUTE_UPLINK_RX_ON_TX: Specify if the link receiver should be muted or not when the link transmitter is transmitting. Set it to 0 if a full duplex link is desired. Default is 1.
LOOP_RX_TO_TX: Set to 1 to loop incoming RX audio (not link RX) directly to the TX (not link TX). You figure out when to use it. Default is 0.
FALLBACK_REPEATER: This function is useful if running RemoteTrx as both RX and TX for a repeater. If the connection to the SvxLink base station is lost due to network errors, the RemoteTrx provides a very basic repeater function (SQLELCH controlled) until the the connection has been established again. Set to 1 to enable this function or set to 0 to disable it. Default is 0.