[600MRG] Determining noise floor in my location

[michael polia]

I've been trying to determine the noise floor at my location for 630m. 
I am using a local AM station (WTAG) at 580 KHz as a reference. 
The contour map for this station claims a field strength of about 2.0 mV/m at my location with a published field strength of 141 mV/m at 1 Km along the contour plot azimuth between the station antenna and my QTH.
When I compare the relative received signal strength of this station against the received noise level, the difference is about 47 dB (measured using HDSDR program). 
If I am correctly calculating this, the noise floor at my QTH is 9 uV/m which seems too high for any meaningful reception of stations on 630m.
Any thoughts?
Thanks
73MikeAB1AW
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