3 to 1 low level VHF RF switch

[kj7e]

Needed a 3 input 1 output low level RF switch for 100 MHz for a work project.  Not wanting to pay $500-800 for some commercially available switches, I built this one for about $50.  Used some Panasonic HD video relays, needed to be 24v and these fit the bill.  Tested, <0.1dB insertion loss, <1.15:1 VSWR, >65dB port to port isolation.  May also just be an excuse to play with the VNA upgrade on the Siglent Spectrum Analyzer.

[joeqsmith]

I have an old HP 59307A which has 2 X 4:1 relays.  BNC connectors.  It uses GPIB to control it.  These show up on eBay from time to time.  Here is one for $50 with shipping.

https://www.ebay.com/itm/235324953012

[kj7e]

Joe, those are nice, not seen those before.  For this project the switch needs to fit inside another box we build.  PLC based transmitter and audio switchers we deploy at our TX sites.  The 3 -> 1 relay I built is to switch and select which transmitter RF sample to feed a modulation monitor.

This one will be for our KRTH site on Mt Wilson (completed front panel photo attached).  Attached are some photos of a previous unit we built for KNX AM.