Slight design changes to the RF Multiplexer design.
This is the third prototype for the 1:8 RF-multiplexer (https://www.ohwr.org/projects/rf-mux-8ch). The board is now simplified with only one 10-pin ribbon-cable attaching it to the Arduino MKR Zero + Ethernet shield. Traco PSU for 5V supply.
Update: Insertion-loss measurement with a spectrum analyzer:
RF-multiplexer v2 board in enclosure, controlled by Arduino Due with Ethernet Shield. SATA-cable for 4 SPI-lines (SI, SO, SCLK, CS).
When issuing commands to change state as fast as possible this combination seems to do a state-change in about 45 milliseconds - this is not verified on the RF-side (didn't measure that there is actual RF contact made/broken in those 45 ms).
Version two of the RF Multiplexer adds more relays to the 8 pcs HF3 I was using in the first attempt. The added relays keep the RF-path from the selected input to the COM-output as clean as possible with no unterminated branches or stubs. The cost is anothe 7 relays with associated darlington-drivers and control-logic.
Next test is to see if there is any measurable change to the rise-time of a fast pulse-edge, e.g. from a distribution amplifier.
And now an entry in the "Plan to throw one away" section.
RF Multiplexer, 8 inputs, 1 output, BNC-connectors, TE HF3 relays specified to 3 GHz, an ULN2803A to pull the relay-coil, and an SPI I/O expander to drive the ULN - should be easy - right?
Well no, PCB trace-geometry does strange things beyond VHF. I clearly don't grok UHF very well.
Onward towards version 2! (any thoughts and advice on simulation or trace-geometry optimizers appreciated!)