UHF NBFM Vibration immune Multi Channel Receiver

The HVR2 receiver is the high vibration resistant version of the low cost RLC2 receiver. Its unique local oscillator design makes the unit almost immune to mechanical vibrations below 500Hz. This makes the HVR2 (with the matching TLC2 transmitter) to be used in mechanically troublesome areas such as crane and machine tool control, and remote operated vehicles.


  • Conforms to EN 300 220-3 and EN 301 489-3
  • High performance double superhet, PLL synthesizer with TCXO
  • DDS local oscillator
  • SAW front end filter
  • Data rates up to 5 kbps for standard module
  • Usable range over 500m
  • Fully screened. Low profile
  • Feature-rich interface (RSSI, analogue and digital baseband)
  • Re-programmable via RS232 interface
  • Low power requirements
  • Immunity to mechnical vibration up to 500Hz


  • Handheld terminals
  • Heavy vehicle/machinery (e.g. crane) controls
  • EPOS equipment, barcode scanners
  • Data loggers
  • Industrial telemetry and telecommand
  • In-building environmental monitoring and control
  • High-end security and fire alarms
  • DGPS systems
  • Vehicle data up/download

Technical Summary

  • Operating frequency: 433.875-434.650MHz
  • Any custom frequency on 433.05 - 434.775MHz
  • 32 channels
  • Supply range: 3.7-15V
  • Current consumption: 30mA
  • Data bit rate: 5kbps max.
  • Receiver sensitivity -118dBm (for 12dB SINAD)
  • Serial configuration by inverted RS232 at 3V CMOS level

Evaluation Platform: Narrow Band Evaluation Kit

Figure 2: HVR2 block diagram

Figure 3: HVR2 Footprint (Top view)

Pin Description

Pin Name Function Serial mode Modem mode
1A RF Gnd RF ground
2A RF in/out To the antenna
3A RF Gnd RF ground
1 TXD DC copled input for TTL/COMS logic NC
2 TXE Transmit enable. Low = RX. High = TX (10kΩ pulldown) NC
3 GND 0V
4 Vcc DC supply input. (3.6 - 15V)
5 P3 Parallel channel select MSB Serial read back BYSY
6 P2 Parallel channel select TBA MOD TXD
7 P1 Parallel channel select TBA MOD RXD
8 P0 Parallel channel select LSB PGM in PGM in
9 RSSI DC level between 0.5V and 2.5V. 60dB dynamic range
10 RXD Open collector output of data slicer. NC
11 AF out 500mVp-p audio. DC coupled, approx. 0.8V bias


1. Serial programming is by a 2400 baud inverted 'RS232' (3V CMOS levels) datastream applied to the P0 pin. If connection to a true RS232 port is desired, then a suitable inverting level shifter / buffer (MAX232 or NPN switch transistor) is needed.
2. Parallel channel select is by a 4 pin parallel input. 3V CMOS levels should be used.
3. As supplied the frequency table is thus:
ch 0-15       433.875 - 434.625 MHz (50KHz steps)
ch 16-31    433.9 - 434.65 MHz (50KHz steps)

Channels 00-15 cannot be accessed by the parallel port , only by a serial GOCHAN command.

This format maintains compatibility with RLC2 radios (which are supplied with their P4 jumpers unfitted, therefore accessing channels 16-31).
If no connection is made to the ports, the unit operates on channel 31 (434.65MHz).

Serial interface commands

HVR2 frequency/channel can be serially configured using HyperTerminal or any other terminal program configured with following setup:

2400 baud RS232, 8 bit data, no parity, 1 start bit, 1 or 2 stop bits. No flow control
Serial data is sent to the unit on one of the parallel channel select pins (P0). It is very important that the unit does not 'decode' switch bounce in ordinary operation as a command string, or spurious re-writing of the EEPROM will result. For this reason the user must send the 16 character string ENABLESERIALMODE to fully enable the serial command mode before sending any of the command strings listed below. Command mode is disabled on power down, or on reception of a # character.

Owing to the complex nature of the DDS programming in the HVR2, the user does not have direct access to the synthesizer registers (as is the case in the simpler RLC2). Instead, the user has a table of 32 channels (accessible by parallel port, or by the GOCHAN command). Each of these channels can be assigned to one of the HVR2's pre-set frequencies (433.05 - 434.775MHz)
(note: the parallel port accesses the higher 16 channels, from 16-31, as if a '5th parallel select bit' is always high).

GOCHAN aa Serial select of channel aa (0 to 31) (stored in non-volatile EEPROM)
HOPPER nn Temporary select of frequency number nn (0 to 69)
LOAD aa nn Set a frequency (nn) for channel aa (channels 0 to 31)
RVALUE rrrr Set value for R register
SETPAR Channel selected by 5 bit parallel inputs (4pins P0-P3 + P4 always high)
SETSER Channel selected by most recent GOCHAN operation
<cr> Process entry
/ Clear all buffers
# Disable command mode

aa = a two digit channel number from 00 to 31 (values 00-15 can only be selected by a GOCHAN command)
nn= abstract 'frequency number' relating to one of the pre-set operating frequency

Channel frequency = 433.05 + (nn x 0.025) MHz

For example:
nn = 01 relates to a channel frequency of 433.075MHz, and the commnd:
LOAD 00 01 will set channel number 0 to 433.075MHz

A pause of at least 25ms must be allowed between command strings (EEPROM programming time).
The HVR2 has no equivalent to the RLC2 'SINGLE' command. The 'HOPPER' command provides some similarity, but on power up (or SETPAR, SETSER or GOCHAN command) the radio reverts to ordinary operation.

Condensed specifications

Frequency 433.05 - 434.775MHz
Custom variants on 433-435MHz

Frequency stability

+/- 1.5kHz
Channel spacing
Number of channels

32 channels controlled via RS232 interface
or 16 channels by parallel port

Operating temperature -10 to +60 °C (Storage -30 to +70 °C)
Spurious radiations Compliant with ETSI EN 300 220-3 and EN 301 489-3
Interface                 user 5pin 0.1" pitch mole


4pin 0.1" pitch molex
RF 2pin 0.1" pitch molex
Sensitivity -118dBm for 12 dB SINAD
-112dBm for 1 part per 1000 BER
image / spurious better than -55dB
blocking better than -85dB
LO re-radiation -60dBm
adj. Channel better than -55dB (Tested per. ETSI EN 301 489-3)
Voltage 3.7V - 15V
Current 30mA
outputs RSSI, audio, digital data
Power on to valid AF <10ms
Power on to stable RXD <10ms (for 50:50 mark / space)
Intended approval ETSI EN 300 220-3 (radio) and EN 301 489-3 (EMC

1. The data slicer cannot be depended upon for data waveform frequencies below 250Hz
2. When RX is on and a transmitter keys up, again a 10ms period is required to stabilise data output mark/space. i.e. allow at        least 10ms of preamble

The high vibration resistant HVR2 receiver differ from the Low Cost RLC2 receiver in the following key features:
The high vibration resistant HVR2 receiver differ from the Low Cost RLC2 receiver in the following key features:

Frequency band 433.05 - 434.775 433 - 435 MHz
Channels 32 serial or 16parallel 32 parallel/serial
Parallel channel select 4 pins 4 pins (and 1 jumper link)
Supply 3.7-15V, 30mA 3.7-15V, 18mA
Image / spurii / adj. chan <-55dB <-60dB
Ultimate S/N 25dB (min), 30dB (typical) 35dB (min), 40dB (typical)
Start up time (preamble) <10ms 50ms
Channel to channel hop <5ms 25ms
Reprogramming (frequency) Limited Full
Vibration resistant High, up to 500Hz Limited
Local Oscillator Direct Digital Synthesiser (DDS) Voltage Controlled (VCO)

Antenna requirements

Three types of integral antenna are recommended and approved for use with the module:

A) Whip: This is a wire, rod, PCB track or combination connected directly to RF pin of the module. Optimum total length is 16cm (1/4 wave @ 433MHz). Keep the open circuit (hot) end well away from metal components to prevent serious de-tuning. Whips are ground plane sensitive and will benefit from internal 1/4 wave earthed radial(s) if the product is small and plastic cased

B) Helical: Wire coil, connected directly to RF pin, open circuit at other end. This antenna is very efficient given it's small size (20mm x 4mm dia.). The helical is a high Q antenna, trim the wire length or expand the coil for optimum results. The helical de-tunes badly with proximity to other conductive objects.

C) Loop: A loop of PCB track tuned by a fixed or variable capacitor to ground at the 'hot' end and fed from RF pin at a point 20% from the ground end. Loops have high immunity to proximity de-tuning.

Ultimate performance
Easy of design set-up
Immunity proximity effects
Range open ground to similar antenna

The antenna choice and position directly controls the system range. Keep it clear of other metal in the system, particularly the 'hot' end. The best position by far, is sticking out the top of the product. This is often not desirable for practical/ergonomic reasons thus a compromise may need to be reached. If an internal antenna must be used, try to keep it away from other metal components, particularly large ones like transformers, batteries and PCB tracks/earth plane. The space around the antenna is as important as the antenna itself.


Figure 4: Antenna types

Ordering Information

Part No. Description Frequency band (MHz)
TLC2-433-5 UHF multi channel narrow band FM transmitter 433.875 - 434.650
HVR2-433-5 UHF multi channel narrow band FM receiver 433.875 - 434.650

Limitation of liability

The information furnished by Radiometrix Ltd is believed to be accurate and reliable. Radiometrix Ltd reserves the right to make changes or improvements in the design, specification or manufacture of its subassembly products without notice. Radiometrix Ltd does not assume any liability arising from the application or use of any product or circuit described herein, nor for any infringements of patents or other rights of third parties which may result from the use of its products. This data sheet neither states nor implies warranty of any kind, including fitness for any particular application. These radio devices may be subject to radio interference and may not function as intended if interference is present. We do NOT recommend their use for life critical applications.
The Intrastat commodity code for all our modules is: 8542 6000.

R&TTE Directive

After 7 April 2001 the manufacturer can only place finished product on the market under the provisions of the R&TTE Directive. Equipment within the scope of the R&TTE Directive may demonstrate compliance to the essential requirements specified in Article 3 of the Directive, as appropriate to the particular equipment.
Further details are available on The Office of Communications (Ofcom) web site:
Licensing policy manual