Connections
The RS-UV3A provides multiple connection options for power, audio, control, and expansion. This page covers all physical connections on the board.
Board Layout
Section titled “Board Layout”The RS-UV3A has the following major connection points:
- VIN — DC power input jack
- USB — Micro USB for power and serial
- ANT — SMA antenna connector
- JP1 — Arduino/serial header
- ICSP — PIC programmer header
- AMP — Power amplifier header
- I/O — DE-9 external interface
- SPK/MIC — 3.5mm TRRS jack
- JP2 — FTDI cable header
- 26M — Oscillator output
- PW — Power switch header
- PA — Internal PA header
- I/O_P — I/O power jumper
DC Power (VIN)
Section titled “DC Power (VIN)”The main power input uses a 2.1mm barrel connector.
| Parameter | Value |
|---|---|
| Connector | 5.5 × 2.1 mm barrel |
| Polarity | Center positive |
| Voltage | 3.5V – 16V DC |
| Protection | Reverse polarity diode |
| Recommended Fuse | 1A |
The on-board buck-boost converter provides stable power across this wide input range. Power consumption is approximately 1.6W maximum; actual current draw varies inversely with input voltage.
Micro USB
Section titled “Micro USB”The USB connector provides both power and serial communication.
- Power: 5V from USB host
- Serial: Driverless FTDI chip (most OS)
- Baud Rate: 19200 (default), configurable via
B1command
USB and VIN power are diode-isolated—you can connect both simultaneously for backup power operation.
Antenna (ANT)
Section titled “Antenna (ANT)”The SMA female jack handles both TX and RX.
| Parameter | Specification |
|---|---|
| Connector | SMA female |
| Impedance | 50Ω |
| Max RF Input | -10 dBm |
| Max DC | 25V |
Internal filtering:
- RX: 100 MHz high-pass filter, LNA with band-equalizing filter
- TX: Individual low-pass filters for 2m, 1.25m, and 70cm bands
Arduino Header (JP1)
Section titled “Arduino Header (JP1)”Four signals for microcontroller integration:
| Pin | Signal | Direction | Description |
|---|---|---|---|
| 1 | DIN | In | Digital input (PTT, SQ open, or disabled via AI command) |
| 2 | RXD | In | Serial data to RS-UV3A (connect to MCU TXD) |
| 3 | DOUT | Out | Digital output (configurable via AO command) |
| 4 | TXD | Out | Serial data from RS-UV3A (connect to MCU RXD) |
| 5 | 3.3V | — | 3.3V output for accessories |
| 6 | GND | — | Ground |
Logic levels:
- Input: 3.3V and 5V compatible
- Output: 2V–5V, set by VIO pin voltage
DIN Pin Functions (AI command)
Section titled “DIN Pin Functions (AI command)”0— Disabled (default)1— Squelch open input2— PTT input
DOUT Pin Functions (AO command)
Section titled “DOUT Pin Functions (AO command)”0— Always low (default)1— High when squelch open2— High when DTMF detected3— High when transmitting4— High when CTCSS detected5— Always high
I/O Connector (DE-9)
Section titled “I/O Connector (DE-9)”| Pin | Signal | Description |
|---|---|---|
| 1 | TX Audio | Line-level TX input, adjustable via VR3 |
| 2 | PTT | Ground to transmit (-24V to +24V tolerant) |
| 3 | GND | Ground |
| 4 | RX Audio | Line-level RX output, adjustable via VU command |
| 5 | COR | Open-drain, low when squelch open (150mA @ 12V max) |
| 6 | PWR | 8.5V if I/O_P jumper installed, otherwise N/C |
| 7 | E_TX | External serial TXD or TX indicator (see EX command) |
| 8 | E_RX | External serial RXD or squelch indicator (see EX command) |
| 9 | GND | Ground |
E_TX/E_RX Functions (EX command)
Section titled “E_TX/E_RX Functions (EX command)”0— E_TX high during TX, E_RX low when squelch open1— TTL serial port (default)
Speaker/Mic Jack (SPK/MIC)
Section titled “Speaker/Mic Jack (SPK/MIC)”Standard 3.5mm TRRS connector for speaker-microphones:
| Contact | Signal |
|---|---|
| Tip | Speaker (+) |
| Ring 1 | Microphone |
| Ring 2 | PTT |
| Sleeve | Ground |
Internal Audio/PTT
Section titled “Internal Audio/PTT”Direct solder points for internal enclosure mounting:
| Pad | Signal | Notes |
|---|---|---|
| SPKR | Speaker out | Low-impedance (8Ω), level via VR1 |
| MIC | Microphone in | 3.3V bias for electret |
| PTT | Push-to-talk | Ground to transmit |
Adjacent pads provide ground connections.
Microphone Bias
Section titled “Microphone Bias”The MIC input includes 3.3V bias through R6 for electret microphones. To use a dynamic mic or external preamp:
- Remove R6 and install in R7 position, OR
- Add a DC blocking capacitor in series
USB Serial Header (JP2)
Section titled “USB Serial Header (JP2)”For FTDI cable connection (alternative to on-board USB):
| Pin | Signal |
|---|---|
| 1 | GND |
| 2 | CTS |
| 3 | VIO (reference voltage) |
| 4 | TXD (from RS-UV3A) |
| 5 | RXD (to RS-UV3A) |
| 6 | RTS |
Amplifier Header (AMP)
Section titled “Amplifier Header (AMP)”For connection to RS-UVPA power amplifier:
| Pin | Signal | Description |
|---|---|---|
| 1 | RC1 | Digital control 1 |
| 2 | RC2 | Digital control 2 |
| 3 | AN1 | Analog input 1 |
| 4 | AN2 | Analog input 2 |
| 5 | +8.5V | Power output |
| 6 | GND | Ground |
Power Switch Header (PW)
Section titled “Power Switch Header (PW)”Direct connection to VIN power. Ships with jumper installed.
- Remove jumper to install external power switch
- Can also be used as alternate power input or to power peripherals
PA Header and SJ1
Section titled “PA Header and SJ1”Internal connection for RS-UVPA integration:
- SJ1 (Solder Jumper): Factory-installed, routes RF to SMA jack
- PA Header: RF connection when using internal amplifier
To use RS-UVPA: Clear solder from SJ1 and connect amplifier to PA header.
I/O Power Header (I/O_P)
Section titled “I/O Power Header (I/O_P)”Install jumper to put 8.5V on DE-9 pin 6. Useful for powering:
- GPS receivers
- Bluetooth modules
- Other 5V–8.5V accessories
26 MHz Output (26M)
Section titled “26 MHz Output (26M)”Access to the 26 MHz TCXO reference oscillator. Intended for sub-receiver applications—advanced use only.
ICSP Header
Section titled “ICSP Header”Programming header for the PIC18F45K22 microcontroller. Pins are staggered to allow connection without soldering a header.