can't we transmit video signals using frequency modulation?

i read some where that we can't transmit videos signal by using FM.
what is the reason for it?
In TV transmission we are using FM for audio,AM for video why don,t we use other combinations like both as either FM or AM or AM for video,FM for audio.

If FM is used for video, it results in ghost images. Hence FM is not used for video signals. Compare the spectra of VSB and FM.

There are many low-cost wireless cameras which do use FM at 2.45 GHz, also many satellite TV systems use wideband FM. There is no problem with it.
I have never saw any reason why FM should generate "ghosts". This phenomenon occurs rather in AM TV due to signal reflection from terrain or buildings; the delayed signal is seen as "ghost".

The answer is, as usual, a little complicated.

Analog video signals have a very large dynamic range. Particularly the synch pulse (that keeps the image from rolling) has to have a pretty big on/off analog modulation depth. Since FM systems often use a compressed IF stage in the receiver, it can strip off that synch pulse and cause all sorts of problems in the picture quality. But it can be done. Back in the 1980's, TV news crews would arrive at the scene, crank up their mobile antenna towers, and send video over analog FM.

IF one first digitized the video signal, it would not be an issue, and could be transmitted with pretty much any modulation format

Dear Biff:
You are completely off! IF limiter in a FM receiver will NOT affect a FM-modulated signal like you wrote! Only if you send an AM signal through a FM receiver, the limiter will clip the AM modulation.

As I wrote, FM modulation in TV is common in low-cost wireless cameras as well in satellite TV. Only new satellite TV channels use QPSK.

Every analogue satellite up/down link uses FM for vision! Every microwave vision link uses FM as above and in fixed links to TV broadcast transmitters. Its not used for domestic terrestrial reception because of the increased bandwidth required (27 MHZ instead of 6MHz) for each channel.
Frank

FM for video has been used in geostationary satellite transmission for over 40 years. For space satellite transmission, power is the most precious commodity (not bandwidth). For terrestrial transmission, bandwidth is the most precious commodity (not power).

I think it's the reason.

If you can convert the video signal into digital format-so there are many video encoders in the market- in this case you can use this digital signal to transmit that video signal by using FM. the advantage of this method is to occupy less bandwidth, so compression is possible...

Ghosting does occur when FM is used. I was assuming analog, terrestrial TV transmission. Thats why FM is used only for audio signals and not video signals. It also induces phase distortion if the design is not proper. Video signals are extremely sensitive to phase distortion. Audio signals have quite a bit of resistance to phase distortion.

The French color TV system SECAM uses FM modulation to encode chrominance information on the sub carrier.
Even the system was &%@#, it has some advantages over PAL or NTSC (which use quadrature amplitude modulation for chrominance). The saturation of the colors can reach the limits without distortions.

On the other hand, radio amateurs use FM in ATV (amateur television) for more than 30 years, on different frequencies and bandwidths.

FM ATV Equipment