@cherubim.rjv 

Hello, the two external antennas are indoors 4G LTE antennas, it is not suggested putting them outside, which will cause damage. If the 4G LTE signal is not good in your house, and you want to have the antennas work in the balcony, ensure it is well protected first.

Considering that the extension cable will cause signal attenuation, the longer the extension cable, the more signal attenuation, so it is not recommended using a very long extension cable.

The interface type of the 4G LTE antennas on the MR200 is SMA male, the connector on the MR200 is SMA female, you may search the 4G LTE antenna extension cable online, ensure the connector matches. As for the cable length, I'm afraid we cannot give you a specific value, you may check how long you need to extend to the balcony, then the shorter, the better.

Hopefully, that answers your question but let us know if you need more details.

@cherubim.rjv 

No, I don't think the LMR400 type cable is suitable. You can search for the 4G LTE antenna extension cable on Amazon, you may find some, just confirm the connectors match the specifications that we previded earlier.

I searched on Amazon, and I can find this:

https://www.amazon.com/Magnetic-Mounting-Extension-Cellular-Amplifier/dp/B081S3PPSL/ref=sr_1_1?dchild=1&keywords=Archer+MR200+LTE+antenna+extension+cable&qid=1611718370&sr=8-1