Have TV Questions? Ask a TV Technician
The wireless signals from the new modem may be causing interference, or some other wiring may have got disturbed during its installation, or it may just be coincidence and due to other external environmental factors.
A lot of other viewers have also reported loss of Channel 7 signal recently, and to improve the TV reception they have installed a signal booster on the antenna cable:
Let me know if that resolves your question.
Have a good day!
You will need to buy a signal booster and fit it to the antenna cable, then connect it to your TV to improve the signal.