I second Saket's answer here. As you have seen, not all channels are available once the recording button is pressed.
Technically, this is how two tuner system works. One tuner is used for recording and other one for live viewing. In LNBF, depending on the channel, Vertical "V" or Horizontal "H" polarity is switched on using 13V or 18V sent by the STB. For example, if you are watching Channel A, which is on H polarity, even the loop out from tuner will provide only H polarity channels. So, channels with V polarity will not work on the other tuner or vice-versa. This is what is happening to you.
May be in case of ADTH, they have configured dual output from LNBF such that one cable is for H and other for V polarities. That is the reason, you get only partial channels with one cable.
D2h must be actually providing H&V polarities in both the cable. That way you will get all the channels even if you connect single cable. But, dual tuners are not utilized in that case as expected.
