Specifications

General Specifications

Parameter	Specification
Frequency Range
2m Band	136–174 MHz
1.25m Band	200–260 MHz
70cm Band	400–520 MHz
Modulation	FM with switchable pre/de-emphasis and LP filters
Channel Spacing	12.5 kHz or 25 kHz (configurable)

Transmit Frequencies

The RS-UV3A is designed to transmit only on amateur radio frequencies. TX operation outside the amateur bands may exhibit reduced power due to output filter configuration.

Receiver Specifications

Parameter	Specification
Sensitivity	< -120 dBm for 12 dB SINAD
Input Filtering	100 MHz high-pass filter
LNA	Low-noise amplifier with band-equalizing filter
Squelch	RSSI-based, 10 levels (0–9)
Tone Squelch	CTCSS/PL, 3 sensitivity levels
Audio Output	Low impedance (8Ω speaker)
Volume Range	40 dB (0–39, 1 dB steps)

Maximum RF Input

Parameter	Limit
RF Power	-10 dBm
DC Voltage	25V

Transmitter Specifications

Parameter	Specification
Output Power (High)	> 200 mW (23 dBm)
Output Power (Low)	~10 mW (10 dBm)
Spurious Emissions	< -50 dBc (amateur band TX)
CTCSS Encoding	Selectable standard frequencies
Modulation Input	Electret microphone (3.3V bias)
Mic Gain Range	30 dB (0–15, 2 dB steps)

Output Filtering

The transmitter includes individual low-pass filters for each band:

• 2m band filter
• 1.25m band filter
• 70cm band filter

Power Specifications

Parameter	Specification
Input Voltage	3.5V – 16V DC
USB Power	5V from USB host
Power Consumption	1.6W maximum
Converter Type	Buck-boost DC-DC
Internal Rails	3.3V, 8.5V

Polarity Protection

• Input is diode protected against reverse polarity
• USB and VIN can be connected simultaneously (diode isolated)
• Recommended: 1A fuse in series with positive lead

Physical Specifications

Parameter	Specification
Board Size	120 × 75 mm (4 11/16” × 3 15/16”)
Height	16 mm (5/8”) excluding connectors
Weight	34 grams (1.2 oz)

Connectors

Connector	Type	Purpose
ANT	SMA female	RF antenna
VIN	5.5×2.1 mm barrel	DC power input
USB	Micro USB	Power + serial
SPK/MIC	3.5 mm TRRS	Speaker-microphone
I/O	DE-9 male	Audio, serial, control
JP1	0.1” header	Arduino interface
JP2	0.1” header	FTDI cable
ICSP	0.1” header	Programming
AMP	0.1” header	Power amp interface
PW	0.1” header	Power switch

Serial Interface

Parameter	Specification
Interface	FTDI FT230X USB-serial
Logic Levels	3.3V/5V TTL
Default Baud	19200
Available Bauds	1200, 4800, 9600, 19200, 38400, 57600
Serial Ports	2 (USB/JP1 and DE-9)

Not RS-232

The DE-9 connector uses TTL logic levels (3.3V/5V), NOT RS-232 voltages. Do not connect to standard RS-232 equipment.

Environmental

Parameter	Specification
Operating Temp	0°C to +50°C (typical)
Storage Temp	-20°C to +70°C
Humidity	Non-condensing

Reference Oscillator

Parameter	Specification
Type	TCXO
Frequency	26 MHz
Accuracy	< 50 Hz frequency error (factory calibrated)

Transceiver Chip

The RS-UV3A uses the RDA1846S single-chip transceiver:

• Integrated VCO, LNA, mixer, IF filter
• Programmable via SPI from PIC microcontroller
• CTCSS/DCS encode/decode
• DTMF encode/decode
• RSSI and audio S/N measurement

Microcontroller

Parameter	Specification
Chip	PIC18F45K22
Programming	ICSP header
Bootloader	mikroBootloader compatible

Block Diagram

                    ┌─────────────┐
    SMA ───────────►│   RF SWITCH │◄──────────── TX LPF
         │          └──────┬──────┘                 │
         │                 │                        │
    ┌────▼────┐      ┌─────▼─────┐           ┌─────▼─────┐
    │  HPF    │      │   LNA     │           │   PA      │
    │ 100MHz  │      │           │           │           │
    └────┬────┘      └─────┬─────┘           └─────┬─────┘
         │                 │                        │
         │           ┌─────▼─────┐           ┌─────▼─────┐
         │           │   BPF     │           │ RDA1846S  │
         │           │ Equalizer │           │    TX     │
         │           └─────┬─────┘           └───────────┘
         │                 │                        ▲
         │           ┌─────▼─────┐                  │
         │           │ RDA1846S  │                  │
         │           │    RX     ├──────────────────┘
         │           └─────┬─────┘
         │                 │
         │           ┌─────▼─────┐      ┌───────────┐
         │           │   Audio   │◄────►│  PIC MCU  │
         │           │   Codec   │      └─────┬─────┘
         │           └───────────┘            │
         │                                    │
         │                              ┌─────▼─────┐
         └──────────────────────────────│   FTDI    │
                                        │  USB-SER  │
                                        └───────────┘