I have bought this TCL 21K77 last year. But just last week, it can no longer pick-up tv signals even using indoor/outdoor antenna. But I assure that TV stations have good coverage in our area.

Is the TV set to air or cable? It has to be set to air/antenna and a channel search has to be done first before a picture will show.

Dominic, you do not state whether you want large outdoor antenna or simple indoor.
If you bought your HDTV anytime during the past 8 years or so, it should have a built-in tuner for receiving digital over-the-air broadcasts. If you have an older "HDTV-ready" TV that only receives analog signals, you'll need to connect it to a separate HDTV tuner.
link below tells how to install outdoor digital TV antenna.
press the helpful button.
How to Install Digital TV Antenna Digital TV Help

Your indoor antenna will plug into the same RF Antenna input jack as would an outdoor antenna. It will take some time but let the unit go through its entire auto tuning mode. If stations are available in your area and signals strong auto tuning will pick them up.

Signal not strong enough in your area for this indoor ant...Does it work with an outdoor ant?

You may have to find a direct replacement for the remote, no real solution.... Let me know the brand....

If you're using an indoor antenna (rabbit ears), you'll find that there's little difference between them. Yes, you'll see all the fancy knobs, but mostly all they do is delay the signal from making it to your antenna jack, hopefully enough to reduce ghosting on analog channels...or a resistor circuit that reduces the signal strength. Receiving a good signal with an indoor antenna can be difficult...there can be obstacles between your tv and the broadcasting station, you could be too far away...it's hard to tell. Before you use an outdoor antenna (consider a good RV antenna if you need to use it indoors), try an antenna amplifier. It'll have to handle both VHF (at one time channels 2-13) and UHF (channels 14-69 analog). If it's an "antenna amplifier," it will be sufficient. If it's a cable amp, it would be a hit-or miss. The amp may be able to boost your signal with the indoor antenna you have now. Alternately, you can buy an indoor antenna with the amp built in. Hope this helps.

You will need to have an outdoor aerial installed, the signal area you're now living in will not be a strong enough reception for an indoor aerial no matter how good or expensive. You could try the indoor aerial in different positions around the room especially by a window to try & pick up some other channels but the long term this will cause some of the programmes to break up or freeze. An aerial on the roof or in the attic will be your best solution to pick up all the digital channels on freeview.

the frequency catcher of the antenna may be weaker then required.to receive the digital channels u can attach a network booster which will solve the problem.

I don't know the menu system on your model, but you have to check that the tuner is in the proper mode. Also, some of the new TV set models cannot receive a standard analog TV signal from its tuner.

As for the distance from the transmitter sight, this depends mostly on the antenna quality, antenna location, the power output of the transmitter sight, compatiblity of the TV to the received signal, and also the capability of the TV's tuner.

Modern TV sets are really designed to be used with a satellite or cable TV box with their respective service.

Terrestrial TV is dying out, and in a matter of a number of years, it will be gone.

Jerry G.