Topband: BOG near noisy powerline on 160

[donovanf at starpower.net]

Hi Pete, 


Unfortunately you've installed your BOG so that the power line 
is in the near field of your antenna. 



Antennas fully develop their directive patterns in the far field, not 
in the near field. Large antennas develop their directivity far 
from the antenna, small antennas develop their directivity much 
closer to the antenna. 


Very large arrays such as phased 1000 foot Beverages and 350 foot 
diameter 8 circle arrays develop their directivity 1000 feet or more 
from the antenna. 


Small antennas such as "magnetic" loops, K9AY and VE3DO loops 
develop their directivity less than 100 feet from the antenna. 


In your situation the best choice is a small antenna such as a VE3DO 
loop as far from the power line as possible. A small magnetic loop 
is capable of completely nulling a single RFI source but it has much 
lower sensitivity that a VE3DO loop. Talk to PVRC member N3HEE 
about his results with a small magnetic loop in his challenging RFI 
environment on a small lot. 


73 
Frank 
W3LPL 

----- Original Message -----

From: "N4ZR" <n4zr at comcast.net> 
To: "topband reflector" <Topband at contesting.com> 
Sent: Friday, February 8, 2019 4:31:29 PM 
Subject: Topband: BOG near noisy powerline on 160 

Recently I put down a 220' BOG, using the KD9SV hardware, including the 
preamp. Because of my yard's layout, the forward end of the BOG fell 
within about 20 feet of what the power company has identified (but not 
fixed yet), a noisy line with a number of broken insulators. 

I came in to listen to the antenna, and was surprised to note that my 
noise (mostly from the powerline, by ear) is worse on the BOG than on my 
jury-rigged sloper transmit antenna. It is much (maybe 20 dB) worse in 
the direction toward the power line than in the opposite. While I take 
this as encouraging evidence that the BOG has some directivity, I don't 
think I'm even hearing any atmospheric noise that may be present, 
because of the power line. 

So now I'm wondering, is the BOG in this position worth keeping, even 
assuming that I can eventually get the power company to fix the line. Or 
should I look at another type of receiving antenna, such as a K9AY loop 
or SAL, which can be placed much farther from the power line? 

-- 

73, Pete N4ZR 
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