Retevis RT-95 VHF/UHF
Posted: Tue 05 Jan 05 2021 3:47 pm
This is a 25W dual-bander. The EU version of this radio fits nicely within the IMDA requirements for such radios. There are 3 output power levels:-
LO: 5W (drawing around 2.1A@13.8V)
MID: 10W (drawing around 3.5A@13.8V)
HI: 25W (drawing around 5-6A@13.8V)
The MIC port has an 8-pin interface that looks like this:- What is not apparent from this diagram is that the radio has an option to output the received audio through the port as well. This audio is amplified by an internal 1W-amplfier (LM4890) in the handheld unit. This audio is somehow multiplexed into the "UP" line - pin-5 (fourth from the top in the diagram.) When the "UP" button is pressed, there is a noticeable drop in the audio coming through the mic speakers, confirming our theory of the double use of the "UP" line.
*update: This does work and the audio is coming through with a DC blocking 0.1uF to 1.5uF capacitor.
The PTT line is pulled to ground through a 1k resistor to activate TX.
To interface to a sound-card TNC, the lines that are needed would be:-
RX audio (pin-5 UP)
TX audio (Mic pin-3, Mic-ground pin-4)
PTT (pin-2)
GND (pin-1)
That calls for a 5-pin connector. The RX audio will need to be coupled through a DC-blocking capacitor before being passed on to the sound-card input.
We will use a standard Ethernet cable for this with colour assignments as follows:-
GND - brown
PTT - white/brown
Mic - green
Mic-ground - white/green
Audio - blue
LO: 5W (drawing around 2.1A@13.8V)
MID: 10W (drawing around 3.5A@13.8V)
HI: 25W (drawing around 5-6A@13.8V)
The MIC port has an 8-pin interface that looks like this:- What is not apparent from this diagram is that the radio has an option to output the received audio through the port as well. This audio is amplified by an internal 1W-amplfier (LM4890) in the handheld unit. This audio is somehow multiplexed into the "UP" line - pin-5 (fourth from the top in the diagram.) When the "UP" button is pressed, there is a noticeable drop in the audio coming through the mic speakers, confirming our theory of the double use of the "UP" line.
*update: This does work and the audio is coming through with a DC blocking 0.1uF to 1.5uF capacitor.
The PTT line is pulled to ground through a 1k resistor to activate TX.
To interface to a sound-card TNC, the lines that are needed would be:-
RX audio (pin-5 UP)
TX audio (Mic pin-3, Mic-ground pin-4)
PTT (pin-2)
GND (pin-1)
That calls for a 5-pin connector. The RX audio will need to be coupled through a DC-blocking capacitor before being passed on to the sound-card input.
We will use a standard Ethernet cable for this with colour assignments as follows:-
GND - brown
PTT - white/brown
Mic - green
Mic-ground - white/green
Audio - blue