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Retevis RT-95 VHF/UHF

Posted: Tue 05 Jan 05 2021 3:47 pm
by Daniel Wee
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:-
RT95-port.jpg (18.88 KiB) Viewed 1342 times
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

Re: Retevis RT-95 VHF/UHF

Posted: Tue 12 Jan 12 2021 12:16 am
by Daniel Wee
Based on what we built, the RT-95 should be set to output audio on the hand mic:-

(1) FUNC -> (16) SPK -> HAND (or M&H)

VOL is 8
BND is W

On the Rock64, alsamixer has the CAPTURE level set to 76.
20210111_225836.jpg (2.76 MiB) Viewed 1307 times
20210111_222949.jpg (2.58 MiB) Viewed 1307 times
20210111_222934.jpg (2.4 MiB) Viewed 1307 times

Re: Retevis RT-95 VHF/UHF

Posted: Tue 12 Jan 12 2021 12:22 am
by Daniel Wee
USB sound card used is a Vention VAB-S13&VAB-S17 sound card, based on the HS-100B chip.
AKERS19112586tEH.jpg (10.28 KiB) Viewed 1306 times
This enumerates as plughw:0 in linux.

Re: Retevis RT-95 VHF/UHF

Posted: Tue 12 Jan 12 2021 7:27 pm
by Daniel Wee
Attempting to use USB tethering through an Android phone to the rock64 board. The connection needs to be made and then USB tethering can be enabled on the phone. Note that a reset of either the phone or the rock64 board will turn this off and requires manually re-enabling.

In order for the usb0 interface be recognized for use:-

Code: Select all

sudo ifconfig usb0 up
sudo apt install dhcpcd5
sudo dhcpcd usb0