The definitive answer is adjust antenna for best reception.
Here are antenna comparisons ,
http://www.antennahacks.com/AntennaComparison.htm.
The CM4228HD does have about 2 to 5 dB better gain then the DB8 at bottom end of the UHF channels 14 thru 51 , channels 14 to about 30.
The CBC is UHF channel 20.
This can help with reception and can push the signal up over the edge to get reliable reception.
However do not expect super fantastic results.
In hilly terrain , sometimes lowering the antenna height can improve signal strength.
At tvfool the antenna height can be adjusted up and down to see what happens with signal strength , from 1 foot to 500 foot antenna height , lower and raise the antenna heights , get the NM (dB) number to increase by 5 or more.
A model number of the Nfusion would help in the research.