Saturday, May 27, 2023

 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.

- 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


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

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