The May 2005 issue of QST had an interesting antenna article on page
33... basically discussing broadband dipoles. I am particularly interested
in the biconical (fan) dipole discussed. It is basically two dipoles
common at the feed point, with a slight divergence out to the ends. I
believe they discussed a spread of 6 feet at the ends for an 80 meter
version.

This antenna may be just what I was looking for to put up on 75M.
Do you antenna experts here on this list have any opionions on this? I
prefer "resonant" antennas fed with coax as opposed to open wire feedline
with tuners, but I would like to be able to operate over the entire 75M
band with my IC746Pro.. Comments?


Ed

Aside from a few errors in the article, (ie: 4*2.8 does not equal 10.2) If
your going to use open wire feed, make the antenna 135 feet. See Cecils
site, Cover all bands and save a bunch of wire.

I have used a number of methods over the years to cover 75/80 with a single
antenna. A 12" diameter cage works well at low heights. I used sections of
12 " sewer pipe cut 3/8" thick and 6 wires coming to a cone at the end.

Reg has a program that shows bandwidth vs. Cage diameter. My practical
results achieved greater band width than predicted by the program. Then
again It was at 30 feet.

Some things that do not work, "the bazooka", dual wires spread less than 15
feet, and any of the antennas that are terminated folded dipoles.

"Ed" wrote in message
. 93.175...


The May 2005 issue of QST had an interesting antenna article on page
33... basically discussing broadband dipoles. I am particularly
interested
in the biconical (fan) dipole discussed. It is basically two dipoles
common at the feed point, with a slight divergence out to the ends. I
believe they discussed a spread of 6 feet at the ends for an 80 meter
version.

This antenna may be just what I was looking for to put up on 75M.
Do you antenna experts here on this list have any opionions on this? I
prefer "resonant" antennas fed with coax as opposed to open wire feedline
with tuners, but I would like to be able to operate over the entire 75M
band with my IC746Pro.. Comments?


Ed

Some things that do not work, "the bazooka", dual wires spread less
than 15 feet, and any of the antennas that are terminated folded
dipoles.


Fred, I appreciate your comments on my questions. Could you elaborate on
your statement (above) that "dual wires spread less than 15 feet" do not
work? The QST article, Table 1, seems to indicate they do work, with a
spread of only 6 feet, or even 3 feet, for 75M dipoles.


Ed K7AAT

Ed, this comes from years of practical experience in trying to achieve a
broad antenna.

With all due respect to the various "NEC" programs as well as Reg's program,
they are great for comparing antennas. In the real world environment of most
hams, results do not agree with the predicted on 75.

Why?, because few of us can get a 75 meter antenna any where near a half
wave length high and in the clear. While one may be able to model the real
antenna environment, I am not smart enough. I would suggest that you model
your particular 75 meter antenna, and then measure actual results as a fun
exercise.

Now to the original question, in spite of the data in QST, I have found
spreads of less than 15 feet in a practical environment will not achieve
your goal. YMMV.

We have got to the point in ham radio, we are measuring with a micrometer,
marking with a crayola, and cutting with an axe. I doubt that anyone in the
history of the world has calculated a 75 meter dipole, put it up, and made
no adjustments unless they mis-measured.


Heck for years we have used 468/F to cut our antennas and that is incorrect
as well! Don't rob yourself of the fun of trying something based on a
program. Last night, for example, I had an enjoyable ragchew with a fellow
in England, running my barefoot Icom 706 MKIIG on 75. My antenna is 40 feet
up at it's highest point. Anecdotal evidence for sure, but the QSO was fun
anyway!

Sorry to get so long winded... Good luck on your broad antenna experiments,
the journey is the fun part.

73 Fred W4JLE




"Ed" wrote in message
. 93.175...


Some things that do not work, "the bazooka", dual wires spread less
than 15 feet, and any of the antennas that are terminated folded
dipoles.


Fred, I appreciate your comments on my questions. Could you elaborate
on
your statement (above) that "dual wires spread less than 15 feet" do not
work? The QST article, Table 1, seems to indicate they do work, with a
spread of only 6 feet, or even 3 feet, for 75M dipoles.


Ed K7AAT

Fred W4JLE wrote:
I doubt that anyone in the
history of the world has calculated a 75 meter dipole, put it up, and made
no adjustments unless they mis-measured.

I'm one of the hams who calculated a 75 meter dipole, fed it
with ladder-line, and had to make no adjustments. :-)
--
73, Cecil http://www.qsl.net/w5dxp


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Nah! Cecil you mis-measured, you can't even get the impedance right. Next
you will be telling me that you change the length of your feed line and
don't need a tuner. :)

"Cecil Moore" wrote in message
...
Fred W4JLE wrote:
I doubt that anyone in the
history of the world has calculated a 75 meter dipole, put it up, and
made
no adjustments unless they mis-measured.

I'm one of the hams who calculated a 75 meter dipole, fed it
with ladder-line, and had to make no adjustments. :-)
--
73, Cecil http://www.qsl.net/w5dxp


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Now to the original question, in spite of the data in QST, I have
found spreads of less than 15 feet in a practical environment will
not achieve your goal. YMMV.


Again, thanks for the comments. For clarification, though, could you
describe what you mean by the 15 feet spread for a 75M antenna? The QST
author is describing a biconical antenna with two dipoles tied common at
the feedpoint, but spreading out a couple degrees to the ends.... his
figures indicating 6 feet at the ends working, but 15 feet the spread if
using the recommended 2.8 degree angle from the apex.

Is this what you mean, or are you describing two dipoles separated their
full length by 15 feet?


Ed

Ed, spread 15 feet at the ends.Nothing critical once your beyond the 15
feet.

I have varied the lengths of the legs, where one is longer than the other.
For example think of two dipoles one cut for 3.6 and the other cut for 3.8.
I have also played with 4 wires spread 2 vertical and 2 horizontal.

The biconal has been around for ever and was widely used in the old TV
antennas to broadband the response.

If there is any interest, I could dig out my old notebooks and post the SWR
tables of a bunch of designs.


"Ed" wrote in message
. 92.175...


Now to the original question, in spite of the data in QST, I have
found spreads of less than 15 feet in a practical environment will
not achieve your goal. YMMV.


Again, thanks for the comments. For clarification, though, could you
describe what you mean by the 15 feet spread for a 75M antenna? The QST
author is describing a biconical antenna with two dipoles tied common at
the feedpoint, but spreading out a couple degrees to the ends.... his
figures indicating 6 feet at the ends working, but 15 feet the spread if
using the recommended 2.8 degree angle from the apex.

Is this what you mean, or are you describing two dipoles separated their
full length by 15 feet?


Ed

Ed, this comes from years of practical experience in trying to achieve a
broad antenna.

With all due respect to the various "NEC" programs as well as Reg's program,
they are great for comparing antennas. In the real world environment of most
hams, results do not agree with the predicted on 75.

Why?, because few of us can get a 75 meter antenna any where near a half
wave length high and in the clear. While one may be able to model the real
antenna environment, I am not smart enough. I would suggest that you model
your particular 75 meter antenna, and then measure actual results as a fun
exercise.

Now to the original question, in spite of the data in QST, I have found
spreads of less than 15 feet in a practical environment will not achieve
your goal. YMMV.

We have got to the point in ham radio, we are measuring with a micrometer,
marking with a crayola, and cutting with an axe. I doubt that anyone in the
history of the world has calculated a 75 meter dipole, put it up, and made
no adjustments unless they mis-measured.


Heck for years we have used 468/F to cut our antennas and that is incorrect
as well! Don't rob yourself of the fun of trying something based on a
program. Last night, for example, I had an enjoyable ragchew with a fellow
in England, running my barefoot Icom 706 MKIIG on 75. My antenna is 40 feet
up at it's highest point. Anecdotal evidence for sure, but the QSO was fun
anyway!

Sorry to get so long winded... Good luck on your broad antenna experiments,
the journey is the fun part.

73 Fred W4JLE



"Ed" wrote in message
. 93.175...


Some things that do not work, "the bazooka", dual wires spread less
than 15 feet, and any of the antennas that are terminated folded
dipoles.


Fred, I appreciate your comments on my questions. Could you elaborate
on
your statement (above) that "dual wires spread less than 15 feet" do not
work? The QST article, Table 1, seems to indicate they do work, with a
spread of only 6 feet, or even 3 feet, for 75M dipoles.


Ed K7AAT

Reg has a program that shows bandwidth vs. Cage diameter. My
practical
results achieved greater band width than predicted by the program.
Then
again It was at 30 feet.

=================================

My program, DIPCAGE2, is concerned with the bandwidth of a cage dipole
in isolation.

But the type and length, in wavelengths, of the feedline has a
considerable effect on the bandwidth of the radiating SYSTEM as a
whole. And a tuner, if used, also plays a part.

It is not surprising that practical measurements made from the shack
randomly indicate somewhat different bandwidths. But neverthless the
bandwidth of the antenna itself, as predicted by the program, plays
the principal part.

In general, the bandwidth of an antenna does not increase in
proportion to its efective diameter so much as is often fondly
expected. But it is not a critical performance characteristic.
----
Reg, G4FGQ