antenna switch

photo of the rx/tx switch, a rectangular white box. on the front panel, there are three LEDs, labelled PWR, RX, and TX, and a toggle switch. none of them are functional, i never ended up bothering to hook up the front panel.

This is an antenna switch that I made for automatically switching between my receive and transmit antennas when the PTT on my IC7300 is pulled low. For the receive antenna, there is an integrated 8V bias tee. My transmit antenna is a 78' EFRW, and my receive antenna is an MLA-30 active loop, which is being powered by that bias tee. A linear regulator is used, replacing the noisy and poorly implemented switching power supply that comes with the MLA-30.

interior photo. sloppily done manhattan-style with QRPme pads.

full schematic (pdf)

In the first iteration of this build, there was an issue where the relay wouldn't stay on during transmit. I determined that power from the transmitter was causing too much ripple at the MOSFET gates, and added C4 and C5. Since then, I have had no issues.