We used the excellent Leo Bodnar GPS for years,
USB and Windows interface allow selection of F and V, 800 hZ..800 MHz, out to 32 dbm
We set the F to 10.000 MHz and output to MAX.
We distribute the ref to all our TEK/HP/other via Mini circuits splitters, one Leo B GPS drives 5..10 50 Ohm ref inputs.
Enjoy
Jon
Froggie the Gremlin