I'm trying to replicate your results, on a laptop/RTL but cannot get any signal at all using kalibrate-rtl !
Does this help? ..
It, and a reddit thread, suggest you need to give kalibrate a rough estimate of the ppm error to start...
here's a pic, you can tell it's not rooftop ready yet. The dimensions are a little different from my 'best' viz:
vert=127mm, hori=66mm hgap=4mm stub=58mm sgap=4mm diam=1.6mm
xnec2c program tells me these dimensions should give gain=7.9db and VSWR=1.4 .
So far it performs _nearly_...
I've been experimenting with Franklin co-linear antennas made up from 14 gauge single strand
copper ( from scraps of stripped 14-2 electrical wire ). I'm getting a range of just over
100 mile radius with the antenna strapped to a broom handle about 6 feet off the ground,