Sorry, but for two reasons, I disagree.
First, when group at LinuxTV.org were first developing the drivers for the Hauppauge HVR1600 and Linux, they stated that w_scan would be modified to detect ATSC signals later (I don't know why, they just did).
The second reason is I can run w_scan on my own system and it errors out. I tried the switches that you recommended using and w_scan errored out for most of them, starting with -c. The following shows the switches I used and the resulting error messages. I also did a directory list that shows why it failed.
[Neal@mack ~]$ su -c 'w_scan -f t -F -t 2 -x -vvv > /home/Neal/Desktop/w_scantest2.conf'
w_scan version 20070909
Info: using DVB adapter auto detection.
Info: unable to open frontend /dev/dvb/adapter1/frontend0'
Info: unable to open frontend /dev/dvb/adapter2/frontend0'
Info: unable to open frontend /dev/dvb/adapter3/frontend0'
main:2173: FATAL: ***** NO USEABLE DVB CARD FOUND. *****
Please check wether dvb driver is loaded and
verify that no dvb application (i.e. vdr) is running.
[Neal@mack ~]$ ls -al /dev/dvb
drwxr-xr-x. 3 root root 60 Mar 25 21:19 .
drwxr-xr-x. 23 root root 3900 Mar 25 21:20 ..
drwxr-xr-x. 2 root root 120 Mar 25 21:20 adapter0
[Neal@mack ~]$ ls -al /dev/dvb/adapter0
drwxr-xr-x. 2 root root 120 Mar 25 21:20 .
drwxr-xr-x. 3 root root 60 Mar 25 21:19 ..
crw-rw----+ 1 root video 212, 0 Mar 25 21:19 demux0
crw-rw----+ 1 root video 212, 1 Mar 25 21:19 dvr0
crw-rw----+ 1 root video 212, 3 Mar 25 21:20 frontend0
crw-rw----+ 1 root video 212, 2 Mar 25 21:19 net0
As you can see, w_scan can not find the card - it's looking for adapter1/2/3 when the correct (?) adapter is 0.
Hope this explains my position on w_scan.
As for the rest, vvvmay states in his first post that he can get one TV channel with VLC. This most likely means that the card is working and sending a signal (most likely tuned to the last channel that M$ had left it at). There still may be a problem with the firmware, but I think not, Fedora does a good job of loading the firmware and will generate an error message if it can not find it.
FWIW, the drivers were referred to as cx18 series, I do not think that they changed that. In fact if you look at the LinuxTV.org site, they will tell you that the cx18 driver are used with CX23418 hardware.
I am sorry about the length, but it seems you were looking for info.
should have all the information needed, including instructions on how to install and setup a tuner card.
For what it is worth, I run Fedora 14 on an Intel Q9550 Core 2 Quad.
Later, it's past my bed time.