I have a Direct TV box connected to one TV using an HDMI cable (the only hookup option). I want to connect this box to a second TV. The cable feeding the second TV is coax (can't be changed).
You can use an HDMI distribution amp to split the DTV box output and use HDMI over coax adapters like this one https/www.amazon.com/single-75ohm-Extender-Sender-Receiver/dp/B00HWIWEMU
https/www.amazon.com/dp/B00UJD072E/ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=1944687542&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B00HWIWEMU&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=81660R5S58VB28WYMTC1
You can use an HDMI distribution amp to split the DTV box output and use HDMI over coax adapters like this one https/www.amazon.com/single-75ohm-Extender-Sender-Receiver/dp/B00HWIWEMU
https/www.amazon.com/dp/B00UJD072E/ref=pd_lpo_sbs_dp_ss_1?pf_rd_p=1944687542&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B00HWIWEMU&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=81660R5S58VB28WYMTC1