Hello the NET:

A sequencer is needed to properly transition the PA, IPA, transverter, transceiver, and preamplifier when going from RX to TX and TX to RX.

The objective is to add a very short time delay to avoid sending QRO RF power into the preamplifier or into an open, just closing relay contact, like "hot switching" which significantly reduces contact life.

I use my IC-706MK2 transceiver with a Lunar Link QRO amp for terrestrial modes.

These techniques are applicable to any transceiver, PA, IPA preamp configuration. Just different microphone connectors are used. I apply the same techniques to the FT-847 and the FT-1000MP (IF rig).

DEMI offers a sequencer kit at about 35$US, Advanced Receiver Research, SSB, JWM engineering, LNA technologies, W1GHZ, and others also offer non kit versions. The DEMI design uses relays with a 2 amp contact rating, others can be much less. All have their unique variations.

I grab the microphone PTT line, before it gets to the radio, route it to the sequencer input, then take the sequenced outputs: DC power to the preamp and bypass RF relays, 2 each SPDT legal limit rated RF relays PTT, ground to TX, to the QRO PA, PTT, ground to TX, to the IPA (or transverter) PTT ground to TX, to the transceiver

For RX to TX, preamp and transfer relay power is dropped, bypassing the preamplifier time delay ~ 250 milliseconds in the unmodified DEMI sequencer PA TX is enabled time delay, ~ 250 milliseconds IPA/transverter TX is enabled time delay, ~ 250 milliseconds transceiver TX is enabled for SSb , CW, FM, whatever modulation

This timing constant, in the DEMI sequencer, is a RC network and can be modified for a faster time delay.

For TX to RX, The sequence is reversed. Some sequencers simultaneously change all output states, without a sequenced delay.

Most sequencers allow enough flexibility to configure PTT ground to TX, or PTT +V to TX Mostly with "dry"relay contact closures for a real 0.00V on grounding, unlike a solid state switch.

I put the sequencer in a diecast box with a 4 pole multi position mechanical switch to route the sequencer outputs. pole #1 is for local indicator LEDS to show what band I am controlling. pole #2 for the preamp/bypass relay power pole #3 for the PA PTT control pole #4 for the IPA/transverter PTT control

The transceiver PTT is always the same, and not switched. Your configuration may vary.

Avoid any break in CW keying. always force TX mode (with a manual PTT switch), before using CW

One switch position per band.

Stan, W1LE FN41sr Cape Cod