“double antenna”, you mean two outputs ? Because the two ouputs can be connected to only one crosspolar antenna.
So 4 TRX into 1 ANC = 2 outputs = 1 Crosspolar antenna
Instead, you want to plug 4 TRXs in order to have only 1 output ?
You’ll have to use 1 ANy and 1 ANC
4 TRXs –> ANy –> ANC
Possible, but you will not have RX DIVERSITY (obviously)
Total loss : 7.9 dB
The other choice : just 1 ANC with 2 outputs, it gives you only 4.6dB loss.
Delta loss is 3.3dB.
The delta power between MP TRX and HP TRX is +1.3dB in GSM900 and +2.4dB in DCS1800.
Therefore, in GSM900, by using a single output configuration with HP, compared to double output configuration with MP, you loose 2dB. In rural area, this is lead to an important loss of coverage.
In urban area, the difference in coverage is hardly visible in outdoor, but can have a big impact for indoor subscribers.