Loss in a coaxial cable at 2.45 GHz
Here are some loss value for common coaxial cables:
RG 58 (quite common, used for Ethernet): 1 dB per meter.
RG 213 ("big black", quite common): 0.6 dB per meter.
RG 174 (thin, seems to be the one used for pigtail adapter cables): 2 dB per meter.
Aircom : 0.21 dB par meter.
Aircell : 0.38 dB per meter.
LMR-400: 0.22 dB/m per meter.
From:
Radio theory and link planning for Wireless LAN (WLAN)