Remote or Hard-Wired?
There are two ways a repeater can be connected to EchoLink.
With the "hard-wired" approach, the PC on which EchoLink runs is co-located with the repeater controller, and interfaced
directly to it, with no additional RF hardware. This allows positive carrier and PTT control between the repeater controller
and EchoLink, and eliminates extra "hops" in the audio chain. It also eliminates the need to ID a link transmitter. One disadvantage
of this technique, however, is that it requires reliable Internet access at the repeater site, which may be in a remote location.
With the "remote-link" approach, an FM transceiver is connected to the EchoLink PC at a convenient location in range of
the repeater, and tuned to the frequency pair of the repeater. In this configuration, the transceiver behaves very much like
an ordinary local repeater user, transmitting on the repeater's input frequency (on behalf of EchoLink users) and receiving
on the repeater's output frequency. Although this allows the EchoLink equipment to be placed in a more convenient location,
it presents some challenges with respect to RX control.
With either approach, EchoLink should be configured with a callsign with a -R suffix, to indicate that the node is a gateway
to a repeater, rather than a simplex frequency. If a remote link is being used, the software should be configured to identify
itself on the air with the host station's callsign, which is not necessarily the same as the EchoLink callsign (or the callsign
of the repeater). Since the link itself is not a repeater, a suffix such as /R in the ID is usually not appropriate (for U.S.
One of the most important considerations for an EchoLink repeater node is the method of detecting the presence of a local
RF signal. Although the best approach is usually to wire a COS signal into the COM port of the PC, it is often necessary (or
desirable) to use VOX instead. Several techniques are described below.
COS from Repeater Receiver: If the node is hard-wired to the repeater controller,
the best source of carrier detect is the COS output from the repeater receiver itself -- or an equivalent signal from the
repeater controller. This ensures that EchoLink transmits to the Internet only when a signal is being received on the input.
Also, the audio connection to the sound card should come from the receiver's audio output, rather than the repeater transmitter's
COS from Link Transceiver: If the node is remotely located, it may be desirable
to use the COS signal from the link transceiver -- but only if the repeater's "tail" is extremely short. Otherwise, EchoLink
will keep transmitting to the Internet 5 to 10 seconds after the local user finishes a transmission, severely interrupting
the flow of a QSO. Some repeater-node operators have successfully incorporated DTMF tones in their custom Connect and Disconnect
announcements to automatically shorten the repeater's "tail" while an EchoLink station is connected, on repeaters which support
this type of remote command.
If the node is remotely located, but the repeater's "tail" cannot be shortened, VOX can be used. When properly adjusted,
EchoLink will detect voice signals coming through the repeater, but ignore other incidentals such as the "tail", the courtesy
tone, and the squelch crash at the end. This is very important when two repeaters are linked to each other, to prevent endless
ping-ponging of one repeater bringing up the other. Here are some tips for adjusting the VOX for use with a repeater:
- Set the VOX threshold carefully. (This is the horizontal slider below the
audio-level indicator.) The VOX threshold should be set just above the audio level of the repeater's dead carrier, so that
it "trips" on voices, but not on the repeater's tail. Watch the purple SIG annunciator while adjusting the VOX threshold.
- If necessary, adjust the VOX delay. The default value of 1200 ms is appropriate