I want to ask about recording in SRT 4930, When i start to record from a channel everything is fine, but when i want to record from another one in the same frequency at the same time nothing happened ! i have checked my USB External hard disk to see the record from the second channel but i found that is empty ! nothing happened when i try to record from another channel, i can record now from one channel in the same frequency. before i was recording from two or more channels in the same frequency .... so what is the problem ?