Updated Channel Tx plugins (markdown)

Channel-Tx-plugins.md

@@ -8,6 +8,10 @@ The plugins documented here are:
 
 This plugin is used to produce a relatively narrowband (1 to 40 kHz) AM modulated signal. The user interface is described [here](https://github.com/f4exb/sdrangel/blob/master/plugins/channeltx/modam/readme.md)
 
+## ATV modulator plugin
+
+This plugin is used to produce analog TV signals suitable for Amateur TeleVision. Some of the standards are compatible with commercial analog TV sets (PAL 625 lines and PAL 535 lines). Images are gray scale (Black and White) and there is no sound carrier. Interface is described [here](https://github.com/f4exb/sdrangel/blob/master/plugins/channeltx/modatv/readme.md)
+
 ## NFM modulator plugin
 
 This plugin is used to produce a narrow band FM signal (1 to 40 kHz) with deviation up to 25 kHz. The user interface is described [here](https://github.com/f4exb/sdrangel/blob/master/plugins/channeltx/modnfm/readme.md)