It really sounds like the local TV (TV1) is generating some sort of RF interference to the OTA module when it is on. Best to check the connector on the cable coming from the antenna to make sure it's not loose, or has a "twist on" connector...
To rephrase; sounds like there's plenty of signal getting to the OTA module until... you turn on the TV set. Some sort of "noise" is being generated by the set is stronger than the weaker signals coming from the antenna. This interference is over powering, or "drowning" the real signal. Most times this is due to a bad connector.
One more question, you drew a set top "rabbit" ears antenna. Is that what your parents are using, or is it an outside antenna? It's entirely possible that if it's a set of rabbit ears, the "noise" is going directly into the antenna & not the cable. If this is the case, I'd suggest moving the antenna from where it is to see if it still happens. For troubleshooting, a 50ft cable w/ ends from WalMart isn't too expensive. Get one of those & a barrel connector, put the antenna where TV2 is, see if you get all the channels w/ TV1 on, then turn on TV2 to see if they disappear like you have now...
Bad connector from ?
Thanks, I'll try this out. They originally were using the DB2, we now have a Radio Shack (local store here in Texas) amplified antenna but nothing has changed.
As I mentioned above, I would use my OTA module on the 722 and always get 100% signal with this same HDTV. The minute I switched tv's with them, ISSUES!