As used
in MMSSTV, CPIX, AGWPE, PSK31 etc
| Transformer:
The type of transformer is determined by the source of the RX
audio. If you take it from the radio's microphone or data
jack, you'll use a 600 to 600 Ohm (1:1) transformer. If
you take it from the radio's speaker jack (8 Ohm impedance),
you'll need a 1000:8
transformer. |
| R1
= |
Resistor, e.g. 1K2, to reduce voltage on the IC pin
1
|
| IC
= |
Integrated Circuit; this sketch shows an IC, such as a
4N33
or PS2603 Optocoupler, which uses a Darlington pair
transistor.
(Note: to identify pin #1, look for a small
embossed circle on
the top of the IC above pin 1; or
looking into the notch in one
side of the IC with the pins
down, pin #1 is to the right of the
notch.) |
| D1
= |
Diode, e.g. IN4001, would shunt any potential reverse
voltage
that might damage the sensitive diode/emitter in
the IC.
(Note: the band printed on the diode marks the
cathode end,
which attaches to the Serial Port/IC Pin 1
line in the sketch above.
The opposite/anode end attaches
to Ground.)
|
| The ideal components for your circuit may
vary because of your radio's requirements. For example, you
might be able to use a different type of IC, such as a 4N25 or
PS2601, but that may require a different value for
R1. |
Use the RTS ( Request to send ) pins NOT the DTR (
Data terminal ready ) pins
On a DB 9 Serial connector
use RTS pins 7 ( PTT ) & 5 ( Ground
)
On a DB 25 Serial connector
use RTS pins 4 ( PTT ) & 7 ( Ground )
