[TowerTalk] vertical antennas math & 1/2 waves

[K7GCO@aol.com]

  In a message dated 11/15/01 12:37:53 PM Pacific Standard Time, 
aa4lr@arrl.net writes:<< On 11/5/01 8:57 AM, K7GCO@aol.com at K7GCO@aol.com 
wrote:
    >Actually most all this radial math nonsense goes away with 1/2 wave 
   >verticals.  With the finances of the average DXer today, I cannot see why 
   >any DXer screws around with 1/4 waves.  A 1/2 wave is already resonant 
and 
   >doesn't need any more help in that department.
   
   Maybe it is because 1/4 waves are half as tall?
  
   Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
   Quote: "Not within a thousand years will man ever fly!"
               -- Wilbur Wright, 1901
    >>
  "Not within a thousand years will TT'ers ever try other than a 1/4 wave 
either ."  (Old K7GCO Axiom 1948) 
  
  Bill I guess I have to explain it ever further for you.  Yes a 1/4 wave 
half as tall and more convenient--everyone on TT know that.  But is has 
PERFORMANCE LIMITATIONS with many many of its own inconveniences such as the 
need for an extensive and often expensive radial system that is some 
locations MAY NOT BE POSSIBLE and at one time I had one--too much Black Top 
around me.  I could go up and not out and it turned out to be a "Blessing in 
Disguise."  I've even called 1/2 waves ''Black Top Verticals." 
  
  Then there is the need to read hundreds of Articles, Posts on TT on radials 
that would take a lifetime to do.  Then there's all that complicated math and 
cost that has dominated TT for some time arguing over total nonsense of a 
difference between .025 vs .026 WL spacing at the open end---on and on and 
on.  With a 1/4 wave the high current section is next to the ground and is 
interfered with by surrounding objects far more than a 1/2 wave is with it's 
high current section 1/4 WL higher and it gives a slight gain increase and a 
useable lower angle of radiation.  A 5/8's wave has a slightly better pattern 
but is dependent on a radial system again with the disadvantage of Lo-Z 
feedpoints although slightly higher.   
  
  If everyone feels your "it's half as tall advantage," then they have a 
certain performance level they and you have to live with.  If anyone is of 
the competitive nature and has a few buck to spare, I suggest they install a 
1/2 wave and enjoy the advantages of a feedpoint Rr of around 3500 ohms 
instead of 35 ohms typical of a 1/4 wave--that is 100 TIMES LESS Rr.  Do you 
understand the full significance of that?  The current flow difference in the 
feedpoint for 1.5 KW is .7A instead of 6.6A--9.3 times LESS current in the 
ground connection and area!  I think even you can understand this advantage.  
A review of ohms law should show you why that will result in a substantial 
reduction in that vicious disease that plagues the Antenna World called 
"Ground Losses."  I call a 1/2 wave a "Vaccine" for 1/4 wave vertical 
deficiencies and it's various sicknesses.  It's as bad as that White Stuff.   
It's so deadly we need a "Ground Loss Insurance Policy" for it.    
  
  In fact since the 1/2 wave is ALREADY RESONANT the only need for a ground 
at the base is to cool the coax shield connection to the L network.  A screen 
or short radials underneath in the local area underneath is desirable to 
reduce E field losses--even WWVH does that.  NOTE! The base doesn't have to 
be right on the ground--the higher the better.  40-10m 1/2 waves fed with 1/4 
wave of open wire line used extensively by EL4A can easily be mounted high in 
a tree etc where in this case the ground losses below it are not relevant.  
I've fed even 80M 1/2 waves with a 1/4 wave of open wire line of such 
adjusted Zo that it inverted the antenna Hi-Z to 50 ohms for coax--no ground 
needed for at least a match--period.  That's not the full criteria of 
performance but there are times when you can give up some of this local 
ground loss (however exaggerated by those who never ran a test) for other 
advantages of a 1/2 wave with the high current area 1/4 WL or more off the 
ground.  I will be running 2 1/2 wave side by side reasonably separated, one 
with a radial system and one without just to see what the actual difference 
is.  Few ever do things like that.  All I knew was I was very competitive 
with no ground radials and feeding it with a 1/4 wave of open wire or the L 
network with a ground ROD only.  
 
 The installation area dictated a different antenna design than the normal 
brainwashing so many are subjected to and it worked JUST GREAT or no antenna 
at all.  Wouldn't even you try something different if it solved a problem?  
Something effective VS nothing is an easy choice.
 
 Why do those who try different things that even work better have to 
CONTINUOUSLY JUSTIFY to those who never try anything new?  I JUST CHECKED AND 
IT'S ACTUALLY LEGAL TO TRY NEW THINGS--SO FAR!!     
 
 If what I do continues to upset your antenna philosophies I really can't do 
anything about it expect try and bring you up to speed.  Get out of your 
"this is what everyone else does rut."  You might even try what I suggest as 
have many others.   
  
  Now if the "Completive DX" wants an edge over the others that follow the 
conventional thinking and has few more bucks to spare--go for it.  A 1/2 wave 
is really only is a problem on 160M and horizontals actually work quite well 
above 100'.  If I could find a used BC vertical I'd be tempted to buy it.  
(Keep this quiet but I used to work at the College Radio Station KUSD--late 
at night--you know, amplifier problems) 

 I have never set limits on improvements--many have.  There is little on 1/2 
waves printed other than some of the articles I've had over the years 
including a 75m top loaded 1/2 wave (poor mans 1/2 wave) 55' high modified Hy 
Tower I described in CQ some 35 years ago.  It was fed with a L network and 
right over a limited ground system and all those "Evil E Field Losses" I 
didn't even know of at the time--it worked just great.  The DX called me at 
times and I was 10-15 dB stronger on the East coast.  If as a DXer they can't 
afford a 1/2 wave on 80M they have "Limited Horizons" and I'd suggest they 
take up a new hobby (Hey that's a full 1/4 on 160M also--go for it).  It's 
far cheaper than a 100'+ tower with stacked 20m beams on it.   
  
  One of my plans for 160m is to have a 135' vertical with a 135' wire 
extension held by a "Sky Hook" called a Dirigible that bucks the wind with a 
rope on it so I can pull it down when the contest is over or big winds are 
coming.  I already have interesting data on this.  An 80m version with a 67' 
fixed vertical is also possible.  I would suspect that you still use a 33' 
vertical on 40m-- even an 8.5' vertical on 10m .  You need to read some new 
books and listen to other advisors.  There are various multiband 1/2 wave 
vertical now also.  The GAP does "unusally well" on 20-10m
  
There are creative ways to reduce the inconvenience, cost problems and the 
major job and cost of laying 120 long radials or even not doing it al all in 
Black Top Areas.  Just pretend you have one. 
  
  I'm thinking of getting an ATV for use in SD as I can mount a snow plow on 
it, a ground plow, rototiller for a garden, pull a grass mover for my very 
big lawn and use it for hunting.  Now with the rototiller just using one 
curved blade, I can dig trenches for radials "real fast."  Unfortunately I 
will have to lay ground system for all the comparisons I want to run.
  
Eventually I'll have an Antenna Web Site using my old call W0LMB assigned to 
the SD Antenna Club.  I'll have all these new "old" antennas described and 
comparative data along with several other antennas and embarrassing 
measurement data that just don't work for some.  Perhaps I can drag you from 
the Stone Age of the last Century being locked in on 1/4 waves and their many 
many limitations with all kinds of "Band Aid" solutions that dominate all the 
literature and TT today.  Yes Bill there is that Term "Band Aids" again I've 
used many times you had to ask about also a few months ago what that meant?  
Just stick with me--I won't lead you astray.  I have no profit motive on 
TT--just a usable information motive for you and others that does cost me a 
lot of time and money.  You might actually consider trying what I have 
suggested on other areas also and I'd forget the use of rivets in antennas.  
Bill the 1/4 wave is just a passing fad--it will go away.  No more rehash 
after rehash in the mags and TT.  Would you believe all these articles are 
written by those with Stock in Anaconda Copper?                      
 
 I might suggest you buy the Dec issue of 73 mag for current updates on NEW 
concepts in yagis.  Put your "New Idea" hat on when you read it.  K7GCO
  

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