WSPR receive antenna comparison

My normal 40m antenna here is in the back yard hanging between the house and a tree. Operating position is at the front of the house so a long run of co-ax is used. I've tried dipoles at the front of the house but they've always seemed more noisy - presumably because of the power lines in the street.

Yesterday I ran WSPR receive on both antennas and found just how amazingly more noisy the antenna at the front is than the normal one out the back.

The front antenna is reported as VK2TPM/1. As you can see, signal to noise ratio is consistently 13dB worse out the front. Now, these are different receivers but I doubt they would make that much difference. There is also a 3Hz difference in reported frequency.

Keen eyed observers might notice that I'm searching WSPRnet for "vk2tpm*", yes wildcards do work in some contexts. The app here is WSPR Watch.