[TowerTalk] (no subject)

[K7GCO@aol.com]

<< In a message dated 9/11/00 5:26:32 AM Pacific Daylight Time, K7GCO writes:
 << 
   Date sent:       Sun, 10 Sep 2000 15:58:22 EDT
    Subject:            [TowerTalk] 80-75M Inverted Vee or Dipole
    To:                 towertalk@contesting.com
     > 
    > Let me drag you all kicking a screaming back to the last Century.  
    > 1.) Cut an Inverted vee or dipole (no bow tie needed) for 1/2 WL at 3.6
    > MHz.  2.) Connect 136' of open wire line (121.6' 450 ladded line).  This
    > really works great on 160M also but the feedline is twice as long.  
    
           I assume on 160 the dipole length is doubled also? 
    
    > 3.) Short out feedline and grid dip to 3.6 MHz.
    
           By trimming the feedline?
    
    > 4.) Connect one feedline wire to center of coax switch or directly to 
rig.
    > 5.) Connect other feedline wire to stator of BC 3 gang variable all tied
    >      together. 
       6.) Connect rotor frame to coax switch or rig ground. 
    
    How do you make the antenna go below 3.6 MHz (poor grammer), with only a 
    series capacitor, if the antenna and feedline is resonant on 3.6? (it's 
called 
     "RF Fudging!" and it takes practice).
    
    I understand how a series capacitor will cancel inductive reactance 
    as frequency is increased, but how does it cancel capacitive 
    reactance when you move below 3.6?   
    
    73, Tom W8JI
    w8ji@contesting.com
     >>
   Tom:  You are either kidding or are lacking in the most elementary of 
creative  
      antenna fundamentals or experience. 
   
   Yes the dipole is twice as long on 160M and perhaps I should have laid it 
out crystal clear for everyone but you are the only one that is never sure of 
what to do.  I was trying to emphasize that 272' of feedline for 160M can be 
hard to handle in a normal lot when it has to be run around the yard but I 
have done that.  I'll have 6 acres in SD and will have open wire line running 
all over the place (10' off the ground for safety purposes of course).  I use 
coax also.  Mostly 100 ohm balanced (2-50 ohm equal length coaxes series 
connected--shields only) for dipoles, horizontal quad loops, beams etc.
   
   When one shorts out a resonant 1/2 WL length feedline connected to a 
dipole, grid dips and finds the resonant frequency other than 3.6 MHz, you 
can add or subtract to either the feedline or antenna.  It's based on a Basic 
Law of Reactance and Feedline Lengths.  You either "give away or take away" 
(add or subtract) in a manner that "creates the desired results" and can be 
done without great knowledge of theory--who gives a damn.  Too much 
"personally massaged theory" is thrown around here all the time.  Everyone 
has their version.  I haven't even found a new Appliance Ham that couldn't 
get the hang of this simple resonant frequency adjustment problem with a 
little instruction.  Consult some of those books you keep referring to in 
your Posts.
   
   One of the design concepts I incorporated into this antenna concept for 
simplicity is this.  If resonant at 3.6 MHz, the bandwidth is  S O   W I D E  
that you may not even want to try and lower the SWR at 3.5 MHz with which in 
this case as I'm sure you almost suggested--an inductor, a longer feedline or 
antenna.  With 1:1 at 3.6 MHz (it was 1:1 with coax also) I saw no need to 
lengthen either when it's 1.2:1 SWR at 3.503 MHz.  (Note I'm 3 kHz inside).  
It's called "Proper Application and Placement of the SWR Curve 101" on the 
low side to get minimum SWR on the high side.   As one operates higher in 
frequency above 3.6 MHz, a low SWR can be obtained all the way to 3.997 kHz 
and higher within the range of the BC 3 gang variable Xc (capacitor) with a 
single wire dipole and no Bow Tie construction is needed.  I did use 5 wire 
cage dipoles however, before I came up with this idea 60 years ago.  These 
variables came out of AM Broadcast Radios and had 365 uufd/section and can 
still be found in flea markets real cheap.  That's particularly handy with 
the 50 ohm output rigs as you just adjust the variable Xc for max output.  
The height of a dipole or angle of an inverted vee can be adjusted to 50 
ohms.  A half wave of feedline repeats this 50 ohms to and at the end of the 
feedline ragardless of it's Zo.  The open wire feedline used had a 12:1 SWR 
but didn't really care.  Guess it's Zo.  This is the lowest loss feed system 
in Ham radio that tunes the whole 80M band.  160M also with BOTH components 
doubled.

I do this in mobile also with a BC variable in series (inside the car in a 
box) right at and in series with the feedpoint at the top of my Porsche.  I 
actually cut a hole in it.  I can get 100 kHz of SWR less than 1.5:1 at 75M 
and 160M MOBILE.  Remember: Resonate low (in the band) and operate high.  
Many have mastered it without further instructions.  One ham at a convention 
talked to me about it for 10 minutes how well it worked.  I suggested he buy 
me lunch so I could keep my attention and he did.  10 minutes is about all I 
can take without food.  I also suggested he use the Automatic Resonating (No 
Touch) system Don Johnson has.  I hope to have plenty of time when I run into 
him again near a restaurant.  I should record some of these performance 
testimonials and play it to the TT Nay Sayers.   
   
   In line with the desire to keep Post short as possible, I usually leave 
out the most elementary of concepts but unfortunately have to frequently 
explain them to you....  Don't complain if I make my Posts a bit longer from 
now on as my spare time is needed to explain new ideas to others.  Those who 
follow my instructions usually by sheer creative imagination and high 
intellect figure out the rest which is the desired goal.  It's designed to be 
a "learning experience" like many of us used to developed our tune up skills. 
 After class instruction can be arranged for "calculating antenna lengths, 
trimming feedlines or optimum application of SWR curves" if needed.  I am 
always glad to help everyone learning to use better and simpler techniques in 
the never ending technical challenge of transferring the RF from "F-F"--Final 
to Feedpoint.  I use conventional antenna tuners only when I have to.  With 
link coupling (before Art Collins) we didn't need external complex expensive 
automatic unbalanced only tuners with about the same range with balanced or 
unbalanced feedline loads of up to 1000 ohms (2-8 turn link and one variable 
Xc.)  You are being ripped off.  That looks like "RF Black Magic" today to 
some who have never used anything but coax and 50 ohm output no-dip finals.  
It's like those who grew up after TV.  They don't know what it was like 
before TV.  We actually watched the radio and created visual images from the 
great Radio Writing of the "Detective Mystery Thrillers."  When I hear them 
replayed I can usually remember what was going to happen as the images were 
so vividly created.  

We need more open minded attitudes for better ways to do things with shorter 
delays.  Just think what Ham Radio would be without Sideband.  I however will 
be on AM again with a Art Collins KW-1 and heavy audio.  I may change it to 
Link Coupling--I'm just kidding.  Mine was given to me by an appreaciative 
manufacturer for technical tips and I hear they are selling for Big Bucks.  
K7GCO


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