Topband: Where to ground the Beverage feedline?

[ZR]

----- Original Message ----- 
From: "Tom W8JI" <w8ji at w8ji.com>
To: <topband at contesting.com>
Sent: Tuesday, November 20, 2012 9:00 AM
Subject: Re: Topband: Where to ground the Beverage feedline?


>> Um -- what did you say was the typical skin depth of soil at 2 MHz? 
>> Somehow,  I seriously doubt it was down that far. :)
>
> Common mode suppression requirements depend on things:
>
> 1.) The sensitivity of the antenna to all signals, either bad unwanted 
> signals like noise or good wanted signals. This is the good signal and bad 
> noise power output of the antenna.
>
> 2.)  The level of unwanted signals and noise fed down the feeder towards 
> the antenna.
>
> 3.) The ratio of series and shunt impedances along the system, but only 
> **if** the system has enough unwanted CM junk to overcome antenna signal 
> power.
>
> For some reason beyond my understanding, I think we are going far over the 
> top of what is reasonable....and it is getting worse.
>
> I was at a friend's house and he told me about installing very long bead 
> strings in Yagi antenna feeders. Please, let's all stop this needless bead 
> insanity and get back to some common sense.
>
> Any conductor very near earth for a long distance has considerable 
> attenuation along the conductor. If it didn't, we could bury our NVIS 
> antennas or run longwires laid right on dirt with high efficiency. It's 
> all about ratios everywhere in the system, including the CM injected and 
> signal level sensitivity of the antenna.
>
> I make enough measurements of antennas here every year, some right in my 
> driveway near noise sources, to know when something is getting overblown.
>
> 73 Tom


Its easy to see the attenuation; just compare a 160M dipole at 30-50' to one 
on the ground and also compare resonance points.
On my rock pile its significant and crud pickup goes way down. In the desert 
it may be less significant.

Carl
KM1H