I didn't read the website, so don't know what he said.  I think Butch and I
are agreeing more than I initially thought.  

If a load resistor has the same impedance as the transmission line (like a
50-ohm dummy load connected through 52-ohm Coax, the SWR will be 1:1
regardless of the length of coax.  If the 50-ohm resistor was connected
through a 72-ohm transmission line, however, the SWR (using a bridge
designed for the 72-ohm characteristic impedance) would be 1.4:1 for any
length, with 50 ohms at any multiple of a half-wavelength from the dummy
load, and about 100 ohms for any odd multiple of a quarter wavelength, and
mixtures of resistance and reactance for intermediate points.  The point is
that SWR remains constant along a transmission line if that line is
lossless, but the actual amount of voltage and current and their phase
relationships change along the length of the transmission line.
73,
Lloyd Rasmussen, W3IUU, Wheaton, Maryland
Home:  http://lras.home.sprynet.com
Work:  http://www.loc.gov/nls
 

> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Butch Bussen
> Sent: Friday, November 18, 2011 5:01 PM
> To: [log in to unmask]
> Subject: Re: SWR continued
> 
> 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
> >
> >