Topband: How Good is Good Enough?

[Pete Smith N4ZR]

I have about 350 feet of quad-shield RG-6 going out to a receiving 
antenna hub which has a 20-db ARR preamp on the end of the line, 
followed by an 8-way relay switch.  The feedline is lying on the ground, 
or more correctly on the stubble of a mowed hayfield.  At the moment, it 
has only one BOG on it, but I plan to add other BOGs and a K9AY loop for 
some comparative tests.  The feedline has a center tapped common mode 
choke about 15 feet from the hub, a la ON4UN and K9YC references - 14 
turns of RG-6 on each of 2 #31 toroids.

My question is this.  If I disconnect the one BOG, and listen to the 
feedline and preamp, how quiet should it be?  How would I go about 
testing its quietness?  If it is not quiet enough in this configuration, 
what would my next step be?  Another common mode choke at the shack 
entrance?

-- 
73, Pete N4ZR
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