In a message dated 5/25/01 9:21:42 PM Pacific Daylight Time,
w8ji@contesting.com writes:<<
> I rarely see transmission line transformer baluns, a la W2FMI,
> mentioned on this reflector. Is there a reason for this other than
> their relative construction complexity?
Transmission line baluns are poor baluns for most applications.
They are much more impedance and load critical than choke
baluns, more lossy, and don't do as good a job. They are more
difficult to make work over wide impedance ranges.
There are some specific applications where they are useful, but
those are mostly circuit applications like driving push-pull
transistors or tubes where you want balanced voltages and not
balanced currents.
73, Tom W8JI
W8JI@contesting.com
>>
There is a "Transmission Line 1:1 Balun" called the "Collins Bazooka" that is
the best balun of all. It has no power limitations other than the coax
capacity. There is nothing to saturate or heat up like the toroid donuts,
THERE IS NO RF SPILL OVER, it's easy to make, it doubles the bandwidth of a
dipole as the shorted 1/4 wave created in the Bazooka has the opposite
reactance that the antenna does which is equivalent of an open 1/4 wave. It
also works on odd harmonics. It shorts out even harmonics for a bit of TVI
reduction. There is a way to make it "1:.5, 2:1 or 3:1".
Years ago when Collins was marketing the 32V1,2&3 series, they included this
Bazooka in their Instruction Manuals. Collins actually added balun info to
improve dipole performance--so their rigs would work better and they did.
I've even used it on beams. The old Workshop Beam of the late 40's on a .27
WL boom had a director 12% shorter and a reflector 8% longer as I remember
for purposes of creating 50 ohms for direct feed with coax. It had a special
plastic head that held the DE to the boom and to protect the direct feed coax
(very dumb) from water entry. Even Byron Goodman W1DX (ex of QST) remembered
it 5 years ago. I found that the coax shield was hot with RF Spill Over.
I'd get "RF Bites" off the mike on 10M etc. The SWR changed when I rotated
the beam without surrounding objects. It had 5.5 dB gain and 18 DB F/B.
Then they pulled another blunder. The direct fed 3 element 10M beam did work
well compared to what was available then. So they tried to recreate it on
20M. The used the same electrical spacing and twice the physical length but
didn't scale the tubing. It was smaller in scale diameter.and it was
resonant at 14.8 MHz. The 20M feedpoint Z was 63 ohms + some -J value I
forgot. However the bandwidth was so good on 20M they advertised "feed it
with 50 or 75 ohm coax" and it did a fair job. I had a BC-459 I converted to
a 3 band rig and I found the feedpoint resistive at 14.8 MHz using a home
made "Twin Bulb SWR Indicator" inserted under the shield of the coax. It was
not scaled diameter wise to 14.2 MHz. I grid dipped the 10M elements
independently and scaled that frequency to 20M. I lengthened the 20M
elements proportionally and that beam really took off as it did for W0AJL.
It covered all of 20M to 14.4 MHz of the day with hardly any change of SWR
using the Bazooka suspended on top of the boom. I called Workshop about
these improvements but they had closed down. Bad design has a way of doing
that. Another victim of the "Dreaded RF Spill Over Disease". There were no
antibiotics or "TT Band Aids" for RF Spill Over then. 3 element 50 ohm
yagi's with 5.5 dB (or 7.6 dBi) gain have wide vertical patterns and when
mounted 1/2 wave above ground do a great job as they fill the 30 degree
Reflection Factor with a lot of RF. I found a 2 element quad on 1/2 or less
the boom length and 2 elements has about the same gain and vertical pattern.
Slightly rectangular loops as Handlesman has found increases the gain as does
the 2 wire concept Cebik has found. More on that later.
I said "enough of this RF Spill Over in the Shack Nonsense" and made the
Collins Bazooka before Collins showed it. Using the "K7GCO Bazooka" at the
time, it totally cooled the coax shield, the SWR didn't change as the beam
was rotated, doubled what was already great bandwidth from the "50 Ohm
Detuning". It covered 10M like no other beam ever has with "No System
Losses".. It's a great design for 6M to cover the whole band. As I remember
from over 50 years ago the F/B improved also. Vertically polarized RF Spill
Over radiation radiates 360 degrees from the feedline and tower and tends to
fill in the nulls. On receive the shield picks up vertically polarized noise
and feeds it to the feedpoint. RF used to get into the AC-DC AM radios real
easy and the neighbors let me know about it. I was a 1/2 block from the
local movie theater and one night I got into the movie audio also--without
the Bazooka. It picked up far less car ignition noise on 10M which was a
very big problem in those days with no resistance ignition wire. I was on
main street and 100' from the main highway going through town so anything
that cut the ignition noise down was indeed a blessing. The gamma match
creates DE unbalance and high ignition noisy in them days. There is a way to
balance it.
The other feed system that I used then that works absolutely great on beams
tuned for "gain" is a FD of unequal diameter tubing such that it steps up a
DE Z of say 10-20 ohms to 100 ohms for 100 ohm balanced coax. Antenna
Manuals of the day had graphs of this FD design. I used 2 RG-8's "series
connected" (just tie the shields together-91' 2") and fed it into--you
guessed it the best balanced tuner of all--The Johnson Match Box. The FD DE
helped to increase bandwidth which was fairly narrow with the gain tuning I
used. The huge advantage of the Match Box was that a 1:1 SWR could be
obtained on the coax to Pi Net Rigs--anywhere in the band and I often
operated 28-29.7 MHz. The tuner reduced TVI I had also as we were 40 miles
from the TV transmitter in Sioux Falls, SD--and no cable.
100 ohm balanced coax worked great into the link coupled tank circuits of the
day regardless of the SWR. A series Xc tuned out the reactance in the link
and it presented a resistive load to the tank coil anywhere in the band. You
could swing the link in an out to adjust the loading level and not have to
redip the final. Harmonics typical with Class C finals went right out the
link. The Faraday Shields prevented this and cured a lot of TVI. The low
pass filters also helped and I used one in each leg. Receivers had balanced
inputs (I added 2 SO-239's) and this physically and electrically balanced
system had a great S/N ratio and low ignition noise pick up. Designs have
been going backwards since Art Collins introduced the 32V1 and KW-1 which I
still have.and the Pi network ever since except for the convenience of band
switching. (I have a 32V3 Instruction Manual in good shape for $50--the
Bazooka design is in there also)
Now the concept of a transmitter Mfg adding antenna info to the Instruction
Manual is very good marketing in my opinion. The way the Mfgs work now is to
sell you the rig and "you are on your own from there on." The Mfg is now
also "at the total mercy of the customers technical ignorance and Antenna
Budget insofar as proper selection of antennas is concerned". I've seen new
hams put up poor antennas, the rig didn't get out, the rig collected dust,
sold it for little money and he took up other interests like chasing women.
Those who put up good antennas got results that intensified interest and they
bought more rigs. This is a great marketing concept. Help the new ham put
up good antennas.
Mike Ercolino of Telrex told me the story of a HS kid calling CQ after CQ
after CQ near him with little results. He called him on the air and said
"kid come over here I have something for you." He gave him one of his 3
element 10M beams. His hamming "really took off." A year later his dad came
over and thanked Mike for what he did for his son. He took a real interest
in radio, his grades went way up and assorted other good things. Note! He
also had the "Same Rig." Good antennas can be "real powerful" in many ways.
I suggested he give me some antennas but he had heard me on the air. I had
also chewed him out for claiming a patent number on a 80&40M inverted vee he
was selling in the mags as a result of my article on the Inverted Vee in 8/60
QST. It turns out that he had a patent on what was equivalent to Rabbit Ears
(pointing up) fed 90 degrees out to give a cardiod pattern for DFing assigned
to the Coast Guard in WWII. I thought he "stretched it a bit".
He gave great talks at clubs. Mike practiced on a recorder he told me and
could "intermingle Fiction with Fact with such a degree of smoothness, you
couldn't tell one from the other even if you knew one from the other."
For the last 50 years I have "begged and pleaded" with every Mfg to put out
an Antenna Manual of proven antennas and tuners so that each rig they sold
saw the proper feed line and great antennas. Each rig could "dominate the
band." It's a great "Sales Concept." But it required someone on the staff
that had enough knowledge to prepare this Antenna Manual of suggested
antennas. No Mfg to this day has ever seen the light of my suggestion and/or
had such a person on the staff. Once they sold you the rig that was the end
of their interest in you.
You are sold one of the most complex products there is that often takes 20-30
years to understand and use properly. That's when "high customer interest"
should have started so as to create another sales concept few know of called
"Repeat Sales." My idea is to "educate John Q Ham how to make Maximum Use of
his new Hi-Tech Toy--in the shortest period of time". The usual learning
period is too damn long as it is now. Few can succeed without a lot of
repeat sales.
Another practice is ''if they market a lemon" you "will indeed eat it." They
don't want to see that rig ever again and they don't care if they lose you as
customer. Sales sending it back to the factory for a redesign could result
in looking for other employment.
For example I suggested to the ex-sales mgr of Ten Tec this idea (and many
many others) who was Sales Mgr of Hy Gain in the 60's I knew really well and
worked with. It was--publish and supply to all Ten Tec customers (and other
spies) the "Tec Tec Top Secret and Restricted Antenna Manual Only for Ten Tec
Rigs". This would be sought after like rare paintings. 100W from any rig is
100W. But 100W into great antennas results in many hours of use and
domination of the band. "I'm using a Ten Tec rig here" constantly being
repeated results in "the Customer doing a lot of advertisement free of charge
for the Mfg." Now you would think that some smart Mfg would pick up on that
huge concept and run with it? Not so you could really notice it. If they
didn't have anyone on the staff they could hire someone to write it--I even
made suggestions of someone that could do just that. Ahem! Alas I have to
admit this in the only sales idea I had that never caught on. Perhaps there
is a smart Mfg out there who will someday see the merit of this idea and
"steal it from me"--part way. They certainly have stolen a lot of my other
ideas.
Tom Peters the business efficiency expert once said "having satisfied
customers is no longer sufficient, you must have absolutely delighted
customers to survive the next decade." I'd like to reword that like this
---"to survive the next low sun spot cycle." Many Mfgs failed and stores
closed about 3 years ago including here in Seattle. I had my "I told you
so's." Unfortunately they realized it--after they failed. One of my
personal goals is still to get some rig Mfg to publish some kind of a "Top
Secret Antenna and Tuner Manual" (for their rigs only) they give to their
customers--and potential new customer Spies.
The concept of a Mfgs actually "doing something for their customers" is so
foreign to many, it would blow the customers mind and create a lot of "Life
Time Customers". I know what a lot of Mfgs did for me and other customers
starting back in the late 30's and what it did for and to my continued ham
interest, my budget and others "sales elegance "--during low sun spot cycles
also. During good times mfgs tend to rip off their customers. However,
customers have long memories.
Another area I've seen this comparable to the low sun spot cycle is in the
car business during a recession. Porsche I felt had severely elevated
prices, did lousy work on your car and during a past recession, customers
even with a lot of money had "long memories"--they stayed away. The Porsche
Car Club Members seldom use the dealers for repair. They go to "Private
Mechanics" that were in some cases fired by Porsche for "doing too much for
the customers." I know a lot of stories along that line. When we have a car
problem we don't call Porsche, we call the experts in the Porsche Car Club
and Private Porsche Mechanics. One is still a close friend--Ralph Meaney.
My contacts in Yaesu for example have been very helpful so I buy Yeasu. I
just got the FT-100D mobile rig. Yaesu should sell good antennas to insure
good performance of their rigs.
I still have my old Pr-813's rig from the 40's with KW coils and link
coupling and can't wait to get it on the air again. With the right number of
turns in the link, I can match any balanced or unbalanced load from 30-1000
ohms--without a tuner. I'm going to add 2 more 813's. I like them big
carbon plates--when they get red. It's beautiful.
Long Live the Bazooka! I've used them all the way to 440 MHZ. Some Mfgs
sell 144/440 MHz quads with coax direct feed to a balanced feed point. That
has to be in the "Top 5 All Time Dumities of Antenna Design". It deserves
the "Darwin Award." The Bazooka is made to order for this application. The
"patterns drastically improve."
I wonder now how this post will be convoluted? K7GCO
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