TNC4 User Guide
Before First Use
The battery ill not be fully charged hen you receive the TNC. It is al ays best to plug in a USB-C
cable and charge the battery before first use. When the red LED turns off, the battery is charged. The
battery ill typically last for 48 hours of continuous use.
TNC Cable
The TNC must be connected to the radio via a cable. Mobilinkd sells cables for a ide range of hand-
held radios, as ell as data cables for mobile and base radios ith TNC ports.
The cable connects four signals:
1. Audio in (this is the speaker or data out on the radio)
2. Audio out (this is mic or data in on the radio)
3. PTT signal
4. Common (GND)
On some hand-held radios, the PTT signal is multiplexed onto the audio output. In this case, the
dedicated PTT signal is not used. The radio must have its VOX setting turned off.
The TNC is expected to operate properly ithout a ferrite bead on the cable. Ho ever, some radios
emit excessive RF through the speaker-mic port, especially hen the antenna is poorly matched or
damaged. In this case, a ferrite bead may be necessary.
Radio Settings
Each radio is different, so having a comprehensive list of optimal settings in a document like this is not
possible. Ho ever, it is important to understand hat radio settings impact the performance of the
TNC and its ability to decode packets.
The squelch should be left open on the radio hen connected to the TNC. The TNC4 ill detect the
presence of data on the audio signal (it uses DCD or Data Carrier Detection). With a closed squelch,
part of a packet preamble ill be missed before the squelch on the radio opens. This ill prevent
decoding of packets.
The “Battery Saver” option should be disabled. This should have no impact on the life of the battery
hen the radio is run ith an open squelch.
If you have an inexpensive Chinese radio (Baofeng, Wouxun, and many others) ith a “Dual Receive”
feature, this must also be disabled. This essentially operates the receiver as a scanner, s itching the
receiver bet een t o frequencies. In general, with these radios, every setting that can be turned of
should be turned off. That is especially true for any squelch tail elimination settings.
Please allo me to editorialize for a moment. The quality of the radio ill directly impact the ability of
the TNC to decode packets. Do not connect the TNC4 to a cheap radio and expect miracles. The
system is only as strong as its eakest link.
