As for the affect of trees on EM waves, below are the results of some simple
measurements I posted earlier on another board.
___________________
Recording the relative readings on the dBµ and S/N displays of a Tecsun
PL-310 tuned to a directional station about 52 miles east of me on 790 kHz,
radiating about 1 kW in my direction:
Location dBµ S/N
(dB)
(Tecsun 4-1/2 ft AGL)
Area clear for 50 ft around 32 15
Pin oak tree, 3' diameter trunk, 42 24
east side against trunk
Ditto, but west side of trunk 34 14
Gnd Wire of 50' utility pole 48 24
(Tecsun 9 ft AGL)
Gnd Wire of 50' utility pole 50 24
These locations were all within 100' of each other, in my back yard.
(later)
I just went back out to my pin oak tree, tuned in the 790 kHz station east
of me, and found that the field improvement when the rx is held against the
east side of the trunk is completely gone when the receiver is moved to the
east about 15 feet. So this is quite localized, and probably wouldn't have
much of an affect on a DA unless an MP was poorly located.
R. Fry
_______________________________________________
Stew Perry Topband Distance Challenge coming on December 29th.
|