Radiometrix Ltd, SILRX-UHF Data Sheet

page 9

AF output

This output is the FM demodulator’s output after buffering and filtering. Since it is taken before the

data slicer in the module, it may be used to drive external data slicers / demodulator’s in cases where

the internal data slicer is not suitable. This is the case where an analogue subcarrier is being employed

e.g. 2 tone AFSK or DTMF tones. In these cases the AF output is used to drive the FSK / DTMF decoder

directly.

The AF output is also a very useful test point for monitoring signals or interference. The AF output is

DC coupled to the FM demodulator thus the DC level Varies with the frequency of the incoming signal.

Supply requirements

The module requires a clean supply. Noise and ‘hash’ in the 5 to 500 kHz band and 16 MHz ±1 MHz

must be less than 2 mV, We recommend a 10 µF capacitor to ground on pin 5 (Vcc) and a 10Ω series feed

resistor in cases where the cleanness of the supply is in doubt.

.

Additional Reading

BS 0799

British standard for Wire-free intruder alarm systems

BS 4737

British standard for intruder alarm systems in buildings from British standards

institution - Tel. 44 171 629 900

MPT1340

DTI type approval specification for 418 MHz Telemetry from department of

Trade

and Industry - 44 171 211 0502/0505

ARRL Handbook

Excellent radio engineering text

ARRL Antenna Book Practical antenna design book

Warning:

Don’t be tempted to adjust the trimmer on the module, it controls the receive

frequency and can only be correctly set-up with an accurate RF signal generator!