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Subject:
From:
Butch Bussen <[log in to unmask]>
Reply To:
For blind ham radio operators <[log in to unmask]>
Date:
Fri, 18 Nov 2011 14:01:20 -0800
Content-Type:
TEXT/PLAIN
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TEXT/PLAIN (44 lines)
I went to the link you previously gave, and I disagree with one thing 
totally, and I've been doing this stuff for over 40 years.  A qarter 
wave length is not not a good length to use.  Think about it, a quarter 
wave at the given frequency is oposite of what it is.  In other words, a 
shorted length appears open and an open appears shorted.  If you put a 
dummy load at the end of an open quarter wave stub, it won't appear as 
50 ohms, it will appear shorted.  I'd stay away from a quarter wave 
length unless you're doing it for fazing and such as that.  The only 
systems I ever saw a quarter or 3/4 wave lengh used was on sual mirror 
mounts I use to sell to truckers.  These were actually 72 ohm cables and 
were in parallel feeds.  Ideally, the whips should be a half wave apart, 
but seldom where.  This gave a figure eight pattern front and behind the 
truck.
73
Butch
WA0VJR
Node 3148
Wallace, ks.


On Fri, 18 Nov 2011, Steve wrote:

> BlankMike,  I agree with what you said in principle.  If you have a perfect
> match, feedline length is completely irrelevant except that you want to keep
> the feedline shorter to avoid signal loss.  Of course, at 160 meters, this
> is not really much of a consideration.
>
> But, sometimes, trimming a bit from the feedline can help the tuner because
> of the VSWR measurements.  I was always taught that if you can't measure the
> SWR at the antenna feedpoint, there could be differences as you measure
> along a feedline unless you measure at true half-wave equivalents.
>
> Here is a good discussion of SWR and how it is really unimportant in antenna
> radiation, as long as it is reasonable it hardly contributes to signal loss.
> Most signal loss is due to inefficient antennas.
>
> http://www.antennex.com/preview/vswr.htm
>
>
> Steve
> Lansing, MI
>
>

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