
I have 2 HD51’s and a Vu+duo 2. If I connect the HD51 I never get anything more than late 70’s snr. The VU+ on the same connection gets 100 SNR. It’s never been a issue as it has never affected the quality of the channels being watched.
Most likely your Cabling, LNB etc but if its not an issue don’t worry about it.
https://forums.openpli.org/topic/52120-new-tuner-si2166d-mutnt-51hd/page-10