Hi John,
For connectors, the SDS200 has a BNC Female antenna connector. The OmniX base antenna has an N Female connector. So your cable will need to be BNC Male to N Male.
I have two cable recommendations, LL240FLEX and LL400.
The LL240FLEX is a 0.240" diameter cable and has a stranded center conductor which makes it very flexible and easy to install. It will work great for 800Mhz and a 75' cable run. Here is a link to purchase:
https://www.jefatech.com/collections/jefa-tech-coax-cable-assemblies/products/ca-240f-c1-c2-l?variant=33788793928
For Connector 1, choose BNC Male
For Connector 2, choose N Male
As an alternative, you might consider LL400. LL400 is about twice the diameter at 0.400" and has a solid center conductor which makes it a bit stiff. However, you'll get about double the signal strength with LL400 compared to LL240FLEX, so that's the tradeoff if the larger size and stiffness of the cable is not an issue for you. Here is a link to the LL400:
https://www.jefatech.com/collections/jefa-tech-coax-cable-assemblies/products/ca-400-c1-c2-l?variant=33789384136
For Connector 1, choose BNC Male
For Connector 2, choose N Male
Be sure to get the COAX-SEAL tape to seal the connection where you connect the cable to the antenna.
Thank you!