Overview of LMR400
Times Microwave'sLMR-400 is designed for adaptability, low loss, RF shielding, and weatherability. The LMR-400 has the narrowest bend radius of any cable of comparable size and performance due to its cable architecture. The cable has the lowest loss of any comparable cable. This cable offers 90 dB of RF shielding and is ideal for EMI-prone environments. The LMR-400 is suitable for both indoor and outdoor use. Use Times Microwave's LMR-400 cable for any application that necessitates a low-loss, conveniently routed RF cable (e.g. WLL, GPS, LMR, WLAN, WISP, WiMax, SCADA, Mobile Antennas). The LMR-400 cable can be used in place of an RG-8 cable.

Overview of LMR300
When compared to corrugated copper cables, the Times Microwave LMR-300 5/16 in low loss coaxial cable provides similar performance but with more flexibility and a simpler connection. For a 1 in bending radius, this 50 Ohm coaxial cable has a bare copper center conductor and a stranded outside conductor. The usage of a 90 percent braided shield results in little loss. Insulation is provided by polyethylene foam.

Couclusion of LMR400 VS LMR300 Specifications
LMR400 and LMR300 have different Inner Conductors. The inner Conductor of LMR300 is Solid BC, while the inner Conductor of LMR400 is Solid BCCAI. But LMR400 and LMR300 have the same Outer Conductors. The Outer Conductor of LMR400 and LMR300 are all Aluminium Tape. LMR400 and LMR300 are similar in many aspects, such as the operating temperature, capacitance, Inductance and so on. The major differences between them are Dia Inner Conductor, Dia Outer Conductor, frequency, and attenuation. The attenuation of LMR400 is higher than LMR300 regardless of any parameters. So If you want to choose the coaxial cables between LMR400 and LMR300, please look their specifications more carefully.

If you want to learn more, try to follow the below link tosee the article about LMR400 VS LMR300.