Efficiency of a magnetic loop antenna

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WSPRnet opens up the possibility to measure the efficiency of my magnetic loop antenna (I3VHF, Baby, 1m diameter, direction 330 degrees), which stands on a balcony. Radiation in west direction (up to the zenith) is unobstructed in contrast to the east, south and north direction, where the antenna is near (1-2m) iron concrete walls with a hight of 10m. I compared the reception reports of my station (DL1MMK) with DG7RJ (distance 20 km), who uses a homemade Dipole 2*9m at 7.5m heights in SW/NE direction.

For the 30 m band:
Transmitting efficiency: In west direction (long path) the report by VK7ZL (23457 km) is 6,5db better for DG7RJ as compared to DL1MMK.
In west direction the report by W3HH (7930 km) is 5 db better for DG7RJ as compared to DL1MMK. Theoretical efficiency is -2,5 db.
In south east direction (4Z4TJ) DL1MMK is received with -18 db as compared to DG7RJ.
In north east east direction (RK3IK) this difference is - 15 db.
Receiving efficiency: Interestingly DL1MMK receives W3HH with the same signal to noise ratio as DG7RJ.

For the 40 m band:
Here the theoretical efficiency of the magnetic antenna is reduced -6db. Consistently K1JT receives DL1MMK (transmitting west) now 12 db worse than DL1MMK receives K1JT (see attachement).

Certainly the magnetic antenna could work much better if it would stand on the top of the roof, with unobstructed radiation in all direction. However the excellent reception of WSPR signals even under such impaired conditions opens up possibilities for SWL.

Best DX 73 DL1MMK Mike