I have a couple of USB units that will bring signals into the computer to record them, but neither connect direct to aerial, I did get a card once, and my laptop has one built in, except I don't have a connector, but I have found the signal strength required was more than my aerial could provide, likely too cheap.
Today we work on multiplex signals, and some times a card will be able to record all the programs on that multiplex signal if the PC is fast enough, but this is where the cards fall down, they need the PC to have the power to start with, the second problem is the EPG, it seems even with stand alone TV receivers the EPG varies a lot, and it does matter, if it works well then all you need to do is select a program you want and click record, however without that it's a lot of messing around to get the timer set up.
I use a very old Sky box, the program guide is A1, and before sky had record built in, the box could be set to auto change channel as a selected program was about to start. The sky box in turn is connected to PC with a USB converter dongle.
The main problem receiving TV direct is the software, often software is provided but quality varies, and with the dongle flameport links to it states "Software CD (Trial Version)" which means you will need to buy software as well at some point. The card or dongle only receives the signal the software allows you to click and record using the EPG so software is really important.
I use the dongle to get my camcorder pictures into PC. That is the main reason for having it, so I don't need expensive software. Just as well as after hard drive failed I lost all built in software so no longer have a copy. Today my set top box which receives both terrestrial and satellite TV will record direct onto a hard drive, so I can record HD with that, then watch on PC, also my cheap Smart TV will record terrestrial TV onto exterior hard drive, and my old TV's have hard drive built in. So as a ball park my terrestrial and satellite HD box cost about £120 from Maplin so you would not want to pay even half that for a card.
Non of the adverts I can find for TV dongles or cards tells you about the software, and it is the software which is all important.