[TowerTalk] Coils vs Linear loading on 80M yagi

[i4jmy@iol.it]

Any upgrade is good when the original design, either electrical and/or 
mechanical, is wrong and the after sales support unexisting.
Generally speaking, it's also true that a number of people is unable to 
give valuable informations to technical support so making the less 
critical and simple antennas the most succesful ones.
True also that larger the antenna, less easy and acceptable is to deal 
to fix some problem.
Anyway, there are a number of well designed low band yagis with linear 
loaded elements where replacing with coils would be a "crime" against 
bandwith and gain.
  
73,
Mauri I4JMY


> ---------- Initial message -----------
> 
> From    : owner-towertalk@contesting.com
> To      : <towertalk@contesting.com>
> Cc      : 
> Date    : Wed, 19 Jul 2000 11:11:30 -0000
> Subject : [TowerTalk] Coils vs Linear loading on 80M yagi
> 
> 
> Folks,
> 
> There has been a long thread about coils Vs linear loading on lower
> frequency yagis.  I think it is too bad that the impracticalities of 
having
> an A/B switch for the larger yagis makes actual testing a bit of a 
pain and
> rules out all but the most exotic stations from even thinking about 
this.
> However there are several good hints that one has when a yagi works or
> doesn't work and so I would like to relate an anecdotal story here 
because I
> believe it has some merit.
> 
> I ordered a 80M yagi.  It came with linear loading wires.  The 
instructions
> indicated I should set the director to resonate at such and such a 
frequency
> and the reflector at such and such and tune the driver and fire 
away.  This
> approach left a lot to be desired because I really didn't know where 
the
> heck the parameters of this beam set the pattern or the max front to 
back.
> It was just impossible to tune properly.  I really didn't get much 
help from
> the factory on this either so it turned out to be a case of what you 
see is
> what you get and enjoy.
> 
> However there was a larger problem lurking in the woods. 
loading wires whipped around so in the wind that the yagi was 
essentially
> unusable in even a small breeze.  The elements swaying in the breeze 
caused
> the loading to vary.  It also caused the pattern to change.  It also 
caused
> some other things like fatigue of the elements causing one section to
> slightly rotate back and forth wearing the individual fasteners 
between
> element tubes so that eventually a black dust appeared at each element
> joint.
> 
> The linear loading wires were anchored at the boom approximately two 
feet
> above the boom meaning they went from way out on my 88 foot elements 
to a
> point two feet above the boom.  This introduced a vertical component 
into
> each element making the yagi extremely noisy.
> 
> To summarize, it had little front to back and little gain in actual 
use.  In
> a wind, I had to QSY to another band.  This happened not only on my 
80M yagi
> but also on a 30M yagi using the same linear loading scheme and 
happened on
> my two neighbors 40M yagis which were designed the same.
> 
> I pointed this out to the factory but received little help in a 
solution
> other than promises to check into it.  After a rather prolonged wait 
for a
> factory input I started to look elsewhere.  Rumors had abounded about 
a new
> approach to 80M yagis and armed with this information I contacted 
W6ANR.
> Dave was quite optimistic he could fix my yagi but it would involve 
somewhat
> of an extended schedule because between Dave and Rich, K7ZV who made 
the
> coils, there were several conversions ahead of me.  Having nothing to 
lose I
> waited and one day, a box of coils showed up on my doorstep.
> 
> I immediately started to work by totally rebuilding my yagi.  I added 
8 feet
> to either end of the boom bringing it to 62 feet.  A second overhead 
truss
> assured me of adequate guying.  I added the coils into each element 
and
> eliminated those fussy linear loading wires, instead replacing them 
with
> Phyllistran overhead guys.
uld actual
> feather the pattern to the area it was desired.  Dave, W6ANR, would 
feed me
> dimensional changes based on my measurements with a yagi on another 
tower
> but much higher than my 80.  Now, thanks to Dave and Rich, K7ZV, I 
have a
> yagi that really plays.  And another nice part about this project was 
when I
> needed help, I got it NOW!
> 
> If you doubt the efficiency of this design listen some time in an 80M
> pileup.  The guys who really rule the roost use those W6ANR converted 
beams.
> They are all over the west coast, some in the interior of the States 
and
> some in Europe.  The design is practical, tuning is a snap and 
results are,
> well fantastic!
> 
> I don't own any interest in Dave's or Rich's venture. I am just a 
satisfied
> user.  This conversion was written up in detail in K0CS's Low Band 
Monitor
> in which I do not have an interest either.  If you want to see that 
article,
> contact lance@diac.com for a back issue.  I do have a few photos I 
can send
> digitally to anyone who requests them direct.
> 
> My yagi is on top of a hill with lots of falloff in all directions.  
It is
> on a 89 foot motorized crankup which allows me to bring the antenna 
to me
> instead of me going to it.
> 
> 73,
> 
> Charlie, W0YG..>>
> 
> 
> 




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