Time will tell how robust these are and if there are any failures in continuous use... Initial results from the field are good however.
We connect these in a depth-2 tree. One 1:8 mux is the top-level switch, with the remaining 5 providing 40 input-channels. This easily expands to 64 channels by adding one more 1U box. Beyond that I guess a depth-3 tree connection is required.
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.
The second multiplexer prototyped, with a slightly larger enclosure placing the Arduino Due + Ethernet Shield directly in the front panel. This requires desoldering the DC-connector on the Arduino Due.
Bandwidth, insertion loss, and pulse-shape distortion measurements should be done next.
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.