TNC4 User Guide
Before First Use
The battery will not be fully charged when you receive the TNC. It is always 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 will 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 wide range of hand-
held radios, as well as data cables for mobile and base radios with 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 without a ferrite bead on the cable. However, some radios
emit excessive RF through the speaker-mic port, especially when 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. However, it is important to understand what radio settings impact the performance of the
TNC and its ability to decode packets.
The squelch should be left open on the radio when connected to the TNC. The TNC4 will 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 will be missed before the squelch on the radio opens. This will prevent
decoding of packets.
The “Battery Saver” option should be disabled. This should have no impact on the life of the battery
when the radio is run with an open squelch.
If you have an inexpensive Chinese radio (Baofeng, Wouxun, and many others) with a “Dual Receive”
feature, this must also be disabled. This essentially operates the receiver as a scanner, switching the
receiver between two 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 allow me to editorialize for a moment. The quality of the radio will 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 weakest link.
To Next Page