A while back, I decided to make a board that combined T/R relays, a relay for a RX only antenna, and a relay for sequencing bias, etc. The board contains a 2 relay sequencer that gives me control of the antennas separate from the transmitter. It is the same sequencer circuit I used in my 813 plate modulated rig. I also included a small 24V power supply if needed for control voltages.
It is turning out to be a very handy board. I plan to use it on this project.
That's a good plan. In my station, since I am changing transmitters all the time, I ended up (about 50 years ago) building a master sequencer. There are 2 lines coming from this sequencer - the antenna/driver/receiver mute line and the transmit enable line.
To these lines connect various relays that are involved in the functional aspects of controlling the various pieces of equipment.
One thing I also suggest is somewhere in the RF driver, configure a relay that closes when the MOSFETs have drive. In my case, I use a 1N34A diode connected to one of the gate drivers, working into a 1k resistor and then a .001uF capacitor to ground. This drives the base of a 2N3904 (through a 10k resistor), which pulls in a 12VDC relay.
The contacts of the 12V relay are in series with the relay coils that enable the modulator / power supply. No drive? No key up of the modulator and power supply. This is a PREVENTATIVE circuit - in other words, the relay in the RF deck not pulled in prevents the modulator from working.
The modulator/power supply itself is keyed in the 2nd sequence, whereas the RF drive for the gates of the MOSFETs is keyed during the 1st sequence. However, once the 2nd sequence is active, the modulator/power supply won't actually start doing anything unless RF drive is detected and the associated relay is operational.
I am a fan of preventative circuitry - where some part of the system cannot operate unless all of the dependencies (RF drive, etc.) have been first satisfied.
