We build a websdr for 2m in Maasbree (NL). One band is the lower 1 MHz and the other is the upper 1 MHz. We would like to optimize the lower band to bring a good DX horizontal websdr closer. So, we are going to eliminate the QRM to the max first. For that we use a HB9CV (see other site) with a SDRPlay1a receiver with SDRUno on a laptop.Then we install a pre-amp with very low noise figure to compensate for the long coax (15-20 meters) and a bit more amplification. To eliminate as much QRM/noise on the input of the receiver, we install a band pass filter.
Here the pictures and the measurements.