[TowerTalk] Misc. Ramblings(long)

[wa4dou@juno.com]

Hi Gang,
  I've subscribed to several "lists" over the past couple of years. The
only one that remains 
is TT. This one has just enough serious/valuable info to retain my
interest. 

  Theres been lots of controversy about the "triband trapped" yagi.
Whether built by Cushcraft, 
Hy-Gain, Mosley, or whoever, the performance of them, while not up to the
standards of some
of the "eliteists" contesters, has proven quite adaquate and acceptable
for decades, to a large
segment of the amateur community. These tribanders provide/provided
multiband performance
with some gain, some front to side and front to back ratio, generally
acceptable swr curves, 
relatively low weight and the demands that imposed on the rotator/support
structure, and a cost 
that wasn't absolutely prohibitive to many. In view of what we know now
about trapped tribanders,
and consistent with the availability of better antennas(Force 12  C3SS is
probably an excellent 
example), the day of the trapped tribander, may well have come and gone,
at least as regards
new sales. As inexpensive used antennas, there will probably remain a
place for these, for some 
years to come (and as new antennas for the $250-$350 price range) . 

  In late 1967, living just 100 yards from the Atlantic Ocean, at
Jacksonville Beach, Florida, i built
a 2 element 10 meter yagi and installed it 30 ft. high, on a tv type
telescoping mast and Alliance
U-100 Tennarotor. It was a split driven element(coax fed), without balun,
and the parasitic element
was a reflector, spaced 1/4 wavelength behind the DE. I have no doubt
that i got the full 5-6 db of
ground reflection gain out of that antenna, to Europe and Africa and
parts of South America, because
i got generally outstanding signal reports from those areas. My rig was a
National NC-200 xcvr.,
running no more than 75-90 watts output(on 10m.). The antenna had
excellent f/s and f/b ratio, i 
clearly remember 6 s units typical(S-9 to S-3). Yet when it came to
Pacific/Asian dx, i typically had
reports of S-3, S-4, S-5. I remember one day, that a local ham cleaned my
clock, when an Asian gave
me an S-5 report and gave him an S-7 or S-9 report. At that time, i
attributed the difference to his TA-33
Sr. and his 55 ft. of antenna height. Today, i realize that it was
probably just the antenna height and
the resultng lower angle of radiation. 

  A rotatable dipole has a gain of  about 2.1 dbi(over isotropic). In the
real world, the signal resulting
from the use of that dipole, is 4-6 db stronger than in free space, by
virtue of ground reflection gain.
Now ,we're up to using an antenna, albeit, a "dipole", having a gain of
6-8 dbi. If the comparisons
that i've read about are true, and IF "trapped tri-banders" can really
exibit gain figures as low as 1-2.5
dbd of gain, from 20-10 meters, then using one of them, puts us up in the
range of  7-10.5 dbi, or
5-8.5 dbd, using a "freespace" dipole reference. Its important to know
where that reference is, real 
world or "freespace." Go back and check out some of those manufacturers
gain claims, and you can
just about tell what reference they were using, even if they didn't
clairfy that point. The antenna mfgs.
weren't stupid, they knew exactly what they were doing. And you can't say
they were taking advantage
of our ignorance, as the last word on the subject. We were ignorant, in a
relative sense, and in our
ignorance, we invited them to take advantage of us. They found all kinds
of ways to appeal to us to
promote their products, and , to whatever extent we could afford them, we
bought them. So what! It
took "trapped tribanders" to bring us to where we are now. We are no
longer dependent on "traps."
Trapped tribanders weren't low gain antennas just because of the traps.
The driven elements typically 
were split and directly coax fed. You couldn't just move one or two
parasitic elements up in close
proximity to a driven element and not lower the feedpoint impedance of
the driven element. Thats why
i chose 1/4 wave spacing for my 10 meter yagi. It allowed the feedpoint Z
to remain close to 50 ohms
but provided most of the possible gain. Since the reflector and director
had to be fixed at one spacing,
relative to the driven element, and that spacing had to be a compromise
for all three bands, not too close,
nor too far away on any band. Even then, had the trapped tribander been
optimally designed as a 
compromise over the three bands, the SWR would have probably been
acceptable on only one band,
maybe 2. That could have been acceptable if we had used very low loss
coax and antenna matchers.
But, in order to give us low SWR on three bands, the element-trap
combinations had to be detuned. 
Actually the tribanders were compromises on top of compromises. And,
really, if you think about it, they
were/are marvelous pieces of engineering. 
  The quad had/has its following. And the "multiband" crowd, that feed
their quads on 3 or more bands
typically complain of poor f/b ratio. etc. on at least one band. Quads
are/or can be cumbersome structures
and are thought to be more visually obnoxious to non hams, as well as
requiring more maintenance.
"Trapped tribanders" generally had/have a reputation for being very
reliable, over many years. Like the 
Ford/Chevy arguement, the quad/yagi arguement has been around forever, it
seems. There is no clear
winner, because there is no clear and overwhelming difference. It used to
be thought that the quad, 
element for element ,had a 2 db advantage over a yagi. Now that advantage
is thought to be no more
than about 1 db(some say .85 db). I've only had quads on 10 and 6 meters,
but my experience is that
the 2 element yagi and  2 element quad are closely matched with the quad
being just discernably better.
The same quad was "bested" by my 3 element yagi, not day and night
difference, but just discernably. 
When i lived in Key West in the mid 60's, Jules Wenglare (then W4VOF,
later W6YO) put up a 2 element
quad on 20 meters. I had a National NC-300 receiver at the time, and
Jules quad had a front to back that
was quite remarkable, the difference between S-9 and S-0 on my NC-300. It
was a very narrow notch,
possibly as low as 30 db or as high as 60 db., who can say because thats
the limitation on very amateurish
measurements. Still it was quite good, by any measure.( Jules had a Swan
20 meter monobander(SW-120, 
i think., ssb, about 100 or so watts) and he "kicked butt" on 20. I had
25 or 30 watts cw/am, and a "windom" 
at 25 ft.,
and although i worked plenty of dx, i envied Jules. He was a "big league"
operator, to me).
  We now know that 2 element  monoband yagis exibit gain of 4-5 db,
typically, and 3 element monobanders
5-6 db, 4 elements about 7 db, 5 elements about 8. This assumes that they
are optimally designed and built.
These fit into the 10-16 dbi range, depending on absolute gain and worst
case to best case,  ground reflection
gain. Keeping in mind, that real world dipoles, at the same height can
have 6-8 dbi of gain, you're talking no
more than 4-8 db of difference. Theres major league differences in cost
to buy those 4- 8 db, not to mention
the support system cost differences, and thats just for one band. And if
you decide on a larger "multiband"
yagi(or quad) and/or stacked systems, or multiple support system
structures, the cost just skyrocket, pro-
portionally. Considering these things, for casual operation, perhaps the
"trapped tribander" at  7-10.5 dbi, really
wasn't such a bad antenna. And it had some f/s and f/b ratio to boot.
After all, the difference here is only 5.5-9
db. The qrp'ers typically run 5 watts and under, 13-20 db down from the
output of the average 100 watt xcvr., 
and they go on making dx contacts, sometimes with very simple and
frequently handicapped antenna systems
at low and modest heights, sometimes even indoors or in attics. If you
had to operate with some of those
antenna systems, you'd come to appreciate a "trapped tribander" at
30-40-50 or more feet high. Wheres your
reference point? The reference point puts it all in perspective. 
  I'm a qrp'er. I've done the KW thing. QRP makes the old game new again.
With 4 watts on 30 meters, a few
years ago, i worked over 100 countries, with wire antennas in trees. With
1 watt, same band, i've worked over 50. 
Now i have a tower in the back yard, 52 ft. high. In the spring, i'll put
an antenna on top. Life is good. 
  Today, we have many choices. And being far more affluent than our
ancestors, we have far more money. Hams
typically want more than they are entitled to for their money. They
overload their towers, complain when things
fail, expect things to last forever, and don't want to do their homework.

  Ham radio isn't about communicating. Its a technical endeavor, its
about the mechanics of the undertaking. The
communicating is merely one of the methods we use, to measure the
results. 
  The diversity of opinion here on TT is just one more example of "lifes
rich pagentry."
 
  73 to all  Roy Lincoln WA4DOU Elm City, N.C.
  
  
  p.s. Rotatable dipoles for 20-10 meters and even including 30 or 40
meters, are available from Mosley and 
Cushcraft. These have good f/s ratio and cost about $200-$300. Mini-beams
have started to appear and they
may actually have some f/b ratio too. Take the gain claims with a grain
of salt. They probably have gain about
in league with the dipole, give or take a little. But consider the cost.
At $220-$340, are they really outrageous,
 in an era when a vertical can cost $200-$400 ? Clearly, dipoles and
smaller trapped tribanders had and have
a lot of bang for the buck. You decide!
  p.p.s Get in touch with a db. Build or borrow a step type attenuator
and put it in series with your antenna and
receiver. Check out what 1,2,3,4,5,6,7,8,9 and 10 db really means, in a
variety of circumstances. You may find
that the db or a few db don't mean as much to you as you thought, when
they were just vague abstract concepts.
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