I don't understand all this stuff. tp 6 means transponder 6?
correct. That only means on the AMC4 satellite, not the recievers
The satellite is split amongst 24 or 32 transponders.
Can 3ABN add additional channels to that transponder? Is AMC4 too full already and there is no room for 3ABN to add more channels?
short version-yes to 1st question, no to second. AMC4 is no where near full. IA5 (G25 at 97 West) has twice as many channels on that satellite as AMC4 does.
long answer-the transponder they use is digital. In the old days (analog) you could put one channel per transponder and that was it. Now with digital, you can put much more. 3ABN could put up to 12 channels per transponder but then you'd have major blockiness of the channel.
adding 2 or 3 channels to a transponder that has 2 video & 2 audio channels on it right now is nothing.
As an example, PAX (ION) has 12 channels in their transponder
TLN has 6 stations in their mux (mux is a techy term for a group of channels on a transponder). TLN has a cable feed, the three local stations they have, the feed for Sky Angel and a aux (backup) channel
So they could add those 2 or 3 channels with no issues and probably no loss in picture quality.
Would the expense of adding more channels be extrodinary?
nah. They already have the transponder so all they have to do is assign the new channels PIDS (that is how the receivers know what channel is what on a digital tranponders) and uplink the channel. Won't cost them much at all since the new stations will be beamed from the same uplink.