why 30 just by curiosity i know no1 atm who has one to test if mine works i got midland 77-104 and cant tell if i can send or recieve anything very rarely i get 1 red led come on but dunno if this should be lit all the time looks like http://entertainment.webshots.com/photo/2722320170104295761zWzetJ
Channel 19 is a national calling channel, historically for mobile stations whereas channel 14 was the reserved calling channel for base stations. As time went on and users dwindled most regions adopted channel 19 for all stations use and these days with the all time low of CB users the channel 19 is often a free for all chat channel. Other than channel 19 and 14 the only other reserved channel was channel 9 which was/is the emergency channel (unmonitored).
I think channel 30 was just a random picked channel adopted as the official mud club channel to use in convoy, laning and offroad. If leading a group I pick channel 10. The Salisbury Plains navigation run uses channel 22, a bunch of local farmers use 10 and 40. There are quarry lorries around Warminister using 22( I think) and there is a night time net around Westbury of old biddies trying to out do each other on their current health problems. Salisbury is down in a dip on other side of Plain from here so most activity your going to hear is from the South towards the coast and from the East. Go park up a hill and have a listen and aks for a rig check on channel 19.
With your light...drop the squelch when the light comes on to see if there is someone there in the noise, though it probably just the white noise level you are seeing, if you moved the rig near your computer it will probably light up all 4 LED's due to the interference increase. The LED readout on those radio's is not the greatest indicator, back in the day I used to turn the meters sensitivity down because the locals up to 5 miles away would light up all 4 LEDS (20dB over S9) with it turned down you would know if someone was parked up outside your house or across across town.
