Another option would be a AM21 tuner and OTA antenna for your rv. The following channels should be available in South Padre Island:
KVEO-DT 23.1 NBC BROWNSVILLE, TX
KGBT-DT 4.1 CBS HARLINGEN, TX
KLUJ-DT 44.1 REL HARLINGEN, TX
KRGV-DT 5.1 ABC WESLACO, TX
XERV-DT 9.1 SPA MATAMOROS, TX...