Wikipedia
KCWT-CD, virtual channel 21, is a low-power CW affiliate in McAllen, Texas, owned by Entravision Communications.
Previously, KCWT was a low-powered translator of KXFX-CA and KTFV-CA.
Until 2014, KCWT broadcast on analog channel 30. KCWT launched a digital feed on RF channel 23 that March; however, through the use of Program and System Information Protocol, the station maps to virtual channel 21, as nearby Mexican station XHAB-TV in Matamoros, Tamaulipas, whose digital broadcasts use RF channel 30, also maps to virtual channel 30 rather than its analog channel 7 due to Mexico not fully following the PSIP standard. (Channel 23 is itself unavailable to KCWT as a virtual channel, as it is used in the Rio Grande Valley by KVEO-TV.) Even before then, KCWT, as had previous CW affiliate KSFE-LD (channel 67, now KFXV-LD), has long branded as "CW 21" in reflection of its channel 21 slot on area cable systems.