[TowerTalk] Carolina Windom-WZeroWO 300 Ohm Windom

[K7GCO@aol.com]

 Tom: Your memory is very good about the "Original 2 Wire 300 Ohm Windom".  
It brought back many memories from over 45 years ago. The article was by 
WZeroW0 Karl Dreher of Denver, Colo.  I knew him, discussed antennas and this 
antenna with him and W Zero AJL Walt Nettles (one of my early Mentors) 
several times in the early 50's when I was in the Army there.  

The basic idea came from the single wire fed Windom of the 30's that I, AJL 
and many others used.  There were discussions of this antenna in Walts Store 
office of Radio Product Sales on the SW corner of Laramie St.  He had a 
Collins KW-1 and a tuner that he expected to use. The graph of the antenna Rr 
was done on log paper ploting Rr vs Length.  72 oms was selected as the 
center Rr on 80M and 3000 ohms on the ends.  I pointed out to Karl that the 
72 ohms actually increased on each higher band about 10% but it was close 
enough.  If the current loops of the various bands are drawn on this graph 
paper, a Rr of about 280 ohms results at the feed point on all the various 
even harmonic bands when it is fed off center at the 1/3 rd mark from the 
graph on the various bands.  It showed this antenna could be fed with 300 ohm 
line and Walt sold a lot of 300 ohm line.  I still have a copy of his article 
and an original graph I drew with colored pencils on the different bands for 
clarity in my packed files.  It had a history of being difficult to load 
depending at the length of the 300 ohm feedline.  Increasing the number of 
turns in the link helped as many only had 2 turns for 50 ohm loads. The feed 
line did radiate some due to other than 180 degree out of phase currents as a 
result of feeding off center of the current loops.  It didn't always hurt 
you.  Coax feed without a balun will radiate regardless where it is fed.  One 
hot (106 degree) and very dry day I remember static electricity coming off 
the end if the feedline. 

I used this antenna at the Rocky Mt Arsenal MARS Station in Denver I started 
and used the 160 and 80M versions.  My "Magic Length" of 1/2 wave multiples 
seemed to work well (Ft=492 X V.P./3.562 MHz).   I installed it for W Zero 
CND (Milt Schradsky) on top of an apartment but it had TVI with his Collins 
32V2 and it didn't load well into the 50 ohm pi.  A dipole fed with the 
Collins Bazooka gave greater bandwidth and no TVI but just one band.  He had 
a 2 element 40M loaded beam on the roof also.

QST had an article on a similar antenna fed with coax and a step up balun for 
matching and even Toroid donuts as I recall about 5 years ago which would 
limit any RF radiation that got by the balun.  Review that article for more 
info.  Yes indeed many fond memories.  

My favorite all band antenna is an 80M horizontal quad loop 20-60' high fed 
with 135' of open wire line.  It will have a Lo-Z at the end of the feedline 
on all bands and can be used on 160M also--over the whole band just using a 3 
gang BC variable Xc in series with one leg.  It's pattern is straight up on 
160/80/75 M and end fire progressive gain all the way around on each higher 
frequency.  No balun needed
K7GCO
  

In a message dated 10/20/00 4:11:17 AM Pacific Daylight Time, n4kg@juno.com 
writes:<< 
    I saw an article from the 1950's (Radio and TV News?) that
 demonstrated that a wire that is 1/2 WL long at the lowest
 frequency of use will exhibit a 300 Ohm feed impedance
 at that frequency and all EVEN harmonics.  This type
 of antenna has also been reported in QST and CQ. The 
 pattern of course will depend on the electrical length, i.e., 
 it will behave as a halfwave dipole on the lowest frequency,
 a 1 WL LW on the second harmonic (4 lobes), a 2 WL LW
 on the 4th harmonic (8 lobes, major lobes ~30 degrees
 from the wire), and a 4WL LW on the 8th harmonic.
 (WL=Wave Length,  LW=Long Wire).  With coax feed
 hanging straight down there is NO feedline radiation.
 
 de  Tom  N4KG
  
 On Tue, 17 Oct 2000  "WA9ALS - John" <jfleming@shelbynet.net> writes:
  > 
 > > A ham has asked me to comment on the Radio Works Carolina 
 > Windom(cw).  I have one of these, and have used it for a couple of years, 
 > interchanged with my G5RV and ladderline fed dipole.
 > >
 > I was afraid this antenna would come up in the thread on vertical
 > radiators - HI.  Considering the lengthy discussion about the G5RV, 
 > surely there will be no end to it regarding the CW!  HI  I'm not sure 
 > ANYone really knows how it works, exactly, but theories absolutely 
    abound and have been discussed in other forums.
 > *********See Above.  k7gco
 > I have the 265 ft version.  I will only comment that it works great 
 > (most huge wire antennas would do pretty good).  It's a gangbuster on 
 > 160M.  I did lose 2 of the "Dedicated Matching Units" (proprietary
    balun) ? lightning once, ?unknown the othr time, maybe too much power 
    despite the specs. Depending how it's suspended, it's not easy to use BIG 
    coax to feed it. Radio Works says that you can use RG-58 even at full 
power,
    but we know that's stretching things a bit.  On my third DMU, I've 
limited my 
 > high duty cycle power (RTTY) to 500W and haven't lost another.  (Replacing 
the 
 > DMU with a rowboat is tricky!)
 > 
 > Mine initially had a 2:1 SWR EVERYWHERE in the 10-160 ham bands.  
 > With "age", I now need a tuner on some bands.  FOr the money and space
 > considerations, it's a great antenna, especially if you don't run 
 > too much power or op heavy duty cycle.  I tune mine with the Nye-Viking.
 > 
 > IMHO, TT would not be the best forum to get into a looonnng thread 
 > about whether it radiates vertically or not...  Doubt there's much
 proof  out there!  73 

--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com