Sub - audible tone decoder
using MX165CP from MX-com
This circuit is a perfect upgrade for old FM transceivers
, that do not offer Tone Sqelch. The IC detects 39 different tones in the
range between 67 Hz -250 Hz.
A filter is included (0-300Hz) to keep the low tones
off the speaker. To monitor stations transmitting without a tone, you should
use pin OTL ( open to listen).
DTMF Decoder
Touch tone decoder
using IC 145436
decodes 16 different pairs of tones.
Pin DV (data valid) enables a demultiplexer.
Max current on each output of 74LS154 is 20mA. Maximum AF input is
1,2Vss on C3.
DTMF Decoder
Touch tone decoder
using MT8870
Resistor R at the input is dependent on input voltage ( see table). Pin
TOE is useful to enable THREE Sate Output of MT8870.
Combine this circuit with CD 4028 decoder or 4514 demultiplexer.
Ideal for remote controll of a repeater or ATV station.
Single tone decoder
using IC NE567
R1 and C2 define the frequency range.
For good sensitivity only minimum of input AF-Voltage is recommended.
(50mV)
The circuit has a bandwith of 2-15% and is extremely useful for CW-decoders,AFSK-RTTY,
TV sync-decoder and ultra sonic applications.Do not use ceramic C but high
quality capacity.
Tone Burst 1750 Hz
for European repeater operation
very simple and stable circuit to produce 1750Hz tone from 12Volt single
supply.
Use a 4060 IC and a 455khz filter with minimum of parts.
