[TowerTalk] (no subject)

[K7GCO@aol.com]

In a message dated 25.04.00 17:01:51 Pacific Daylight Time, jreisert@jlc.net 
writes:<<    Sparks,
 
 The ORIGINAL Windom was a half wave dipole fed at 1/3 from one end with a 
 single wire dropped to the transmitter (using the return through a ground). 
 Later, the single wire feedline was replaced with, I think, a 300 Ohm piece 
 of twinlead.
 
 When I was first licensed, the Windom with twin lead and a 4:1 Balun using 
 two special bifilar wound coils made by B and W .      73, Joe, W1JR
 
 At 10:35 AM 4/25/00 -0600, sparks wrote:
 
 >I have been traveling, no antenna books. How is standard WINDOM antenna 
fed?  at 1/3 point ??-1/3 length, feedpoint, 2/3 length?Is that correct?    
Sparks
 > 
******The first article describing the 300 ohm feed for the windom was by 
WzeroWO Karl Dreher in a ''52 or 53 Radio Electronics Mag.  I was in the Army 
in Denver and met him.  I have the original article in my files which are 
packed.  What he did was this.  He graphed the current loops on log graph 
paper as I remember for 80, 40, 20 & 10M wire antennas using a length of 
about 136' plotted against R values of 72 in the center of the current loops 
and 3600 ohms for the ends of each current loop.  The current loops for all 4 
bands crossed at one point 1/3 from the end and at a R of 276 ohms which was 
close enough for 300 ohm line.  

The currents are unbalanced in the feedline, are other than 180 degrees out 
of phase and it radiates some.  It was hard to match at the end of some 
feedline lengths and making it longer would usually match the link coupling 
and series Xc of the day and sometimes Pie networks which were somewhat new 
then.  It's been 47 years since I read the article, I will try and find it 
and see how close I came to remembering the details.  If I had some log graph 
paper here I think I could duplicate his graph as I remember the concept he 
used.  I called him in about '70 on my way through Denver and he had passed 
away.  I made a practice to meet a lot of the antenna authors of the day in 
my travels, wrote them or called them on the phone.  He said "I was the only 
person to respond to his article."  I though it was a very clever way he came 
up with the common 276 ohm feedpoint for all 4 bands that occurs at the same 
point 1/3 from the antenna end, I've never seen one reference to him for his 
original article when the 300 ohm Windom was discussed.  Very sad.

One of the few I never met was the Author of the Clements Match in QST about 
35 years ago.  I have Clements article around here some place also.  Few ever 
referenced his article which is the best matching system of all for a single 
coax.  The English Publications show it.  I have used it extensively as it's 
a way to get absolutely balanced feed with coax.  He commented that when he 
installed the new match to his 10M beam, his wife's sewing machine noise went 
away.  It was that noise that inspired him to come up with a new way to feed 
a beam that didn't cause "RF Spill Over" on transmit and have "RF Spill Up" 
of mostly vertically polarized noise RF picked up by the coax feedline shield 
on receive and fed right in the coax opening at the top.  Donut toroids are 
needed at the top for RF--going both directions.  Few recognized the 
significance of this advantage.  The gamma is the worst affender of this.  

The Clements Match had another outstanding feature.  It gave more bandwidth 
than a gamma also due to the use of a shorted 1/4 wave coaxial stub connected 
to the series Xc used which was a length of coax also.  Some smart mfg. 
should add this to their beams and use the proper fine tuning procedure to 
assure a perfectly balanced feed with no balun.  Clements ranks in the "10 
K7GCO All Time Best Designers and Honor Roll."  Only 2 others in print have 
recognized the sins of the "Dreaded RF Spill Over."  Bailey in a Radio Mag 
article in the late 30's and Remington Rand in a '52 QST article on a 2M 
sleeved vertical addressed it and took steps to reduce or eliminate it.  

I had a 6M AEA Loop fed with a gamma and no series Xc.  The SWR varied all 
over the place as the loop shape was bent or the gamma wire moved slightly.  
Adding the series XC helped greatly but the coax shield and mast were still 
hot with RF Spill Over and Spill Up which deteriorated it's performance 
greatly.  I added the Clements Match and by adjusting the 2 tap points and 
the series Xc I got 1:1 SWR and absolutely no RF Spill Over or Spill Up on 
the mast or shield.  I could place my hand on the mechanical center of the 
loop and mast connection and there would be no change in SWR.  When I get 
time I'll write this up for some mag.  I use this hand affect balance test on 
all my antennas.  

One way to visualize the Clements Match is to visualize the Hair Pin Match 
pictured in WWII Radio Handbooks.  Then physically pull the ends of the 
dipole out.  The coax center lead cross over wire extends between the 2 tap 
points now that gives a gamma type 25 ohms on each side of center.  This 
longer crossover wire now has inductive reactance like a gamma and a series 
Xc is needed to cancel it and leave a resistive 50 ohms.  It's a T Match for 
unbalanced coax.  I have a variety of ways to mechanically and electrically 
create the Clements Match and the broadbanding feature that are what's called 
a Robust Design.  Clements design worked but needed refinement.

Clements a W9 as I remember like Carl Dreher WZeroWO never got the 
recognition they should have.  Perhaps someone can look up the Clements Match 
and inform TT what issue it is in so it can be reviewed.  I plan an article 
with the variations I have on it --when I get time.  Perhaps someone can look 
the 300 Ohm Windom article in Radio Electronics in about '52 or '53 and 
inform TT of it.  Some Libraries should have it.  K7GCO


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