4-WAY PTT sequencer
This is simply 4-way PTT sequencer. It is designed on LM3880 IC with fixed delay time 60ms. Outputs are made by FET transistors. When active = connected to ground.
Inspiration a few years ago from Rob N4GA and his article.
Parameters:
- Sequencer delay is fixed 60 ms
- Sequencer from RX to TX PTT IN to: T0 = 0 ms, T1 = 60 ms, T2 = 120 ms, T3 = 180 ms
- Sequencer from TX to RX PTT IN to: T0 = 0 ms, T1 = 180 ms, T2 = 120 ms, T3 = 60 ms
- Optocoupler isolator protection at PTT IN port
- OUTPUTS are open while input PTT is in RX, shorted to GND while input is in TX
- When you need to switch positive voltage (LNA) you can use P-FET switch example
- Input PTT logic: active when grounded
- Input PTT logic current typ. 15mA
- Output FET switch 50V 500mA for each port
- DC power supply 9 V to 15 V typ. 30 mA DC cable connection (included for enclosure version)
Internal board
Board without connectors
Schematic:
Sequencing between outputs:
Positive voltage FET switch - LNA voltage etc:
You can buy it assembled as a board without connectors or assembled in enclosure at our e-shop
