Low cost VHF Narrow Band FM receiver

The NRX1 is a VHF radio data receiver and it offers a low power, reliable data link in a Radiometrix SIL standard pin out and foot print. It is an enhanced, low cost version of the Radiometrix RX1, but in a slightly larger dimension.

NRX1 is compatible with the TX1 series of transmitters, and the BiM1 transceiver.


Figure 1: NRX1-173.250-10


  • Designed to comply with harmonised radio standard EN 300 220-3 and EMC standard EN 301 489-3
  • Frequencies available as standard: 151.3000MHz, 169.4125MHz, 173.2250MHz and 173.2500MHz
  • Other custom frequencies from 120MHz to 180MHz available to order
  • Data rates up to 10 kbps with 25kHz channel spacing
  • Usable range to 10km+ with matching transmitter
  • Fully screened

NRX1 is a VHF equivalent of Radiometrix UHF NRX2 receiver and it is available for licence-exempt operation in the UK 173MHz bands and European 169MHz band. It is also available in the Australian frequency of 151.300MHz. NRX1 modules combine effective screening with internal filtering to minimise spurious radiation and susceptibility thereby ensuring EMC compliance. They are particularly suitable for one-to-one and multi-node wireless links where longer ranges are required at low to moderate data rates. Applications include building security, EPOS and inventory tracking, remote industrial process monitoring and data networks. Because of their small size and low power consumption, these modules are ideal for use in battery-powered portable applications such as handheld terminals.

Technical Summary

  • Double conversion FM superhet
  • Supply range: 2.9V - 15V @ 10mA (internal 2.8V voltage regulator)
  • Data bit rate: 10kbps max.
  • Receiver sensitivity: -120dBm (for 12dB SINAD)
  • Local Oscillator (LO) re-radiation: <-60dBm
  • Adjacent Channel: -70dBm
  • Blocking: -86dB

Evaluation Platform: Universal Evaluation kit or Narrow Band Evaluation Kit
Matching Transmitters: TX1 , TX1H , HX1, BiM1T or BiM1HT

User interface

Figure 2: NRX1 Footprint

Pin Description

1 RF in 50W RF input from the antenna
2 RF GND RF Ground is internally connected to the module screen and pin 4 (0V). These pins should be directly connected to the RF return path - e.g. coax braid, main PCB ground plane etc
3 RSSI Received Signal Strength Indicator with >60dB range. DC level between 0.5V and 2V
4 0V Ground
5 Vcc 2.9 - 15V DC power supply
6 AF 500mVpk-pk audio. DC coupled, approx 0.8V bias
7 RXD Received Data output from the internal data slicer. The data is squared version of the Audio signal on pin 6 and is true data, i.e. as fed to the transmitter. Output is "open-collector" format with internal 10kΩpull-up to Vcc (pin 5). Suitable for bi-phase codess

Note: Pinout and footprint as RX1 (but larger dimension and lacks Enable pin) and UHF NRX2.

Condensed specifications

Frequency 151.3000MHz
173.2500MHz (other VHF 120-180MHz by special order)

Frequency stability

+/- 2.5kHz
Channel spacing
Number of channels
Supply                Voltage 2.9V - 15V
Current 10mA
Operating temperature -10 to +60 °C (Storage -30 to +70 °C)
Size 47 x 17 x 8 mm
Spurious radiations Compliant with ETSI EN 300 220-3 and EN 301 489-3
Interface           user 5pin 0.1" pitch SIL


2pin 0.1" pitch SIL
Sensitivity -120dBm for 12 dB SINAD
image / spurious -60dB (or better)
blocking -86dB (or better)
adjacent Channel -70dB
LO re-radition <-65dBm
outputs Audio, Data, RSSI
Power on to valid audio 2ms
Power on to stable data out (50:50 mark / space) 10ms

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