Is it possible to connect Hughes HN7xxx modem and Seatel antenna or any another (non-Hughes) BUC.
If no, which another Hughes modem can connect to Seatel or use with "normal" BUC.

The HX150 model appears to have a normal L band frequency / 10 MHz reference interface, on transmit, so that it will work in conjunction with standard BUCs. The physical/cable transmit interface is TNC plug and 50 ohm!
See:
Hughes HX50 modem remote terminal specification (86k pdf file)
Hughes HX100 modem remote terminal specification  (93k pdf file)
Hughes HX150 modem remote terminal specification  (87k pdf file)

I suggest you talk to your Hughes hub to clarify what will or will not work for you.  Why don't you use a HN7xxx modem with rigid/flexible waveguides from the Hughes BUC to the Seatel OMT waveguide interface flange?.

Best regards, Eric.

Yes, we think about this. But weight Hughes Anubis 2W is 1,5 kg and BUC which installed in Seatel antenna Codan 6908-W/S-48/IF has 6,5 kg.

It can come to rebalansing Seatel system.

Another question sbc.cfg file has tehe following:
[LinearTransmitRadioList]
NJRC_4W_Ku=NJRC,NJT5017,4,Ku,1,0,36,56,24
NJRC_5W_C=NJRC,NJT5669,5,C,1,0,37,58,24
NJRC_8W_Ku=NJRC,NJT5018,8,Ku,1,0,39,59,49

What does it mean, posible to connect to HN7xxx these BUCs?

I repeat "I suggest you talk to your Hughes hub to clarify what will or will not work for you." They may also be able to explain the content of the sbc.cfg file. Don't assume that the content of the sbc.cfg file makes something possible. We have seen sbc.cfg file containing quite irrelevent options.  

The higher wattage BUCs need more DC power and 10 MHz reference - as well as a modem with compatible L band transmit output.

Consider the power connection problem and how this gets across the rotary joint.

Maybe talk to Seatel as well and ask if they have solved the problem already and how did they do it?.

Best regards, Eric.