PC5M TX RX Sequencer

If you are running a large station with one or more pre-amplifiers and power amplifiers then controlling the switching between transmit (TX) and receive (RX) becomes important to protect the RF relays, the pre-amplifiers and the power amplifiers.

I use a modified version of the PC5M V2 sequencer in my personal 4m, 2m and 70cms station as well as in most of the stations that the BlackSheep Contest & DX Group use.

Unlike the W6PQL relay sequencer which is all analogue in its design approach the PC5M sequencer employs an 8-pin Atmel ATtiny13a microprocessor that provides several advantages:

  • accurate timing
  • individual times for switching between receive, change-over to TX
  • individual times for switching between TX, change-over to RX
  • error lock-out input from amplifiers
  • flexible operation: easily reconfigured for different systems by changing firmware
  • hardware watchdog and brown-out protection

The original code for the ATtiny13a was a bit tangled, so being an embedded systems coder in a previous life I re-wrote it to clean it up, make it more readable and more flexible.  The latest code is on Carol’s website, if if you’re stuck drop me an email.

I do NOT have PCBs available for this or offer a kit of parts but CArol can provide the Gerber files and you could probably get a small quantity make at one of the Chinese PCB houses – alternatively as there’s nothing special about the design you can make it on a bit of Veroboard…

In addition from time-to-time you will find someone selling a knock-off version of the design with all of the connections on a DB9 connector – search Ebay for “PC5M sequencer” or “TX RX sequencer”.

Mike G8TIC