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Hey folks I just received my KG 935G and discovered a menu option that isn’t shown in the included manual. Anyone know what menus option:53 SIM-RX does? 
thanx in advance. 

I'd be more concerned about having a stack of adapters as long (and as bulky) as the apparently highly rigid antenna itself presenting a risk of physical damage. Most rubber ducks at least have some give when something hits them on the side.
That stack (which appears to be SMA->TNC, TNC->SMA) looks to have left a large torque point on the radio's SMA connector; nothing braces the bottom of the stack against the body of the radio (in my experience most SMA rubber ducks make contact with the retaining ring of the SMA connector, or provide a washer/o-ring to fill any gap).
But then, I also still own HTs that use BNC connectors for the antenna... (RatShack and Midland CB; Maxon GMRS-210+3, RatShack (Maxon) HT-202, Pryme PR-52 -- the only one still on the market, to my knowledge, is the Midland)

It's not ideal, and you will likely loose some TX power due to a higher SWR than normal, but it wont cause any harm - however beware of the "experts" that will leave a 10-paragraph long response telling you that it will cause damage to the radio.  To them, I say, just watch this video about the KG-935G to see that a little high SWR wont hurt it  -> https://youtu.be/yrLB7augoQU