[TenTec] Re: Rudimentary SWR question...

[ac5e at comcast.net]

Well, if I may - Krauss passes over it with a casual comment to the effect that "under the best conditions half the signal is lost to the medium and half is delivere to the transmission line."  Excuse the semi-quotation, I'm a few miles from my library. But to continue....

Back in the 1930's Stephenson put it a bit more plainly. He said that if the transmission line impedance matches the antenna half the signal that impinges on the antenna will be reradiated, and the other half will be delivered to the transmission line and eventually to the reciever. If the match is less than perfect the percentage of reradiation increases while the signal delivered to the reciever decreases. Followed a series of equations showing that the signal down the transmission line decreased by half when the mismatch was 6:1, etc., etc.. In fact - the percentage of reflected power on transmit is the same as the percentage of reradiated power on recieve. 

Now - in these days when most recievers have enough excess gain to run you out of the house when you short the antenna terminals and turn the volume up that reradiation is not really all that critical. After all, what difference does it make if the signal is 100 microvolts or only fifty. Besides a mark on the S meter face. 

However, in Stephenson's time most hams were lucky to make fifty cents a day and even the $39.95 for a Halliscratcher 5-T Sky Buddy was far beyond the typical hams means. So a lot of the fraternity used whatever parts they could scrounge from the dump to build one and two tube "recievers." My first, thanks to a very patient Elmer, was a double TRF circuit driving a 36 "grid leak detector" and another 36 "amplifier," and we were lucky to hear much of anything at all on it. So recieving antenna efficency was of critical interest. 

So yes, there was a lot of interest in resonant antennas, tuned feeders, and anything else that would persuade a weak signal from the other end of the state to become a copyable signal. Without spending any money! Sweat was readily available, money might have been on the other side of the moon. 

Nowadays, that's mostly academic. Except for one thing. Computer modelling of the highly touted "all band wonderwires" on the market show feedpoint SWRs in excess of 100. I have tried several, under circumstances where I could compare them on on one with a dipole, and have not been impressed with either the transmit or recieve performance of any of them. 

73  Pete Allen  AC5E
 
> To George and All,
> 
> George - I read your first email on the conservation of energy and agree in
> part, but my experience with non-resonant antennas has proven that a
> resonant antenna will nearly always be a more efficient radiator than a
> non-resonant antenna.  Case in point.   80 meter dipole, 5 feet off the
> ground, will transmit much better than my 8 foot whip on the rear of my car
> with an tuner.  Mainly because of the loss (heat) being consumed in the
> tuner and feed line.   Take a non-resonant antenna connected to a tuner with
> 1000 watts and feel the tuner/feed line and even the antenna itself will
> become warm or even hot, due to system mismatches..   It will still work,
> but at a much lower efficiency..
> 
> Just my experience.
> 
> Thanks and 73's,
> Dudley
> WA5QPZ
> 
> 
> 
> 
> 
> ----- Original Message ----- 
> Wrom: FVWRKJVZCMHVIBGDADRZFSQHYUCDD
> To: <tentec at contesting.com>; <aa4nu at ix.netcom.com>
> Sent: Tuesday, October 21, 2003 11:08 AM
> Subject: Re: [TenTec] Re: Rudimentary SWR question...
> 
> 
> >
> > ----- Original Message ----- 
> > Wrom: JBLVLMHAALPTCXLYRWTQTIPWIGYOKST
> > To: <aa4nu at ix.netcom.com>; <tentec at contesting.com>
> > Sent: Tuesday, October 21, 2003 10:05 AM
> > Subject: Re: [TenTec] Re: Rudimentary SWR question...
> >
> >
> > > I see now that the problem is that some of you are caught in an old on
> > > going argument between non-resonant antennas and resonant antennas.
> >
> > <skip>
> >
> > > What is it about resonance, conservation of energy, equilibrium and Q
> that
> > > makes this discussion do difficult.
> >
> > Not a thing, Bill, other than the fact that some folks confuse the
> physical
> > size and length of a wire antenna with its capture area, which relates to
> > gain and not to size.. Using that erroneous concept, they cannot see how a
> > shorter antenna can perform virtually the same as a long antenna. A few
> > minutes with any good modeling program makes the point. That, plus a
> little
> > common sense in applying the Law of Conservation of Energy.
> >
> > Thanks for your note and perspective.
> >
> > 73/72, George
> > Amateur Radio W5YR -  the Yellow Rose of Texas
> > Fairview, TX 30 mi NE of Dallas in Collin county EM13QE
> > "Starting the 58th year and it just keeps getting better!"
> > w5yr at att.net
> >
> >
> >
> >
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> 
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