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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Fred W4JLE wrote:
Nah! Cecil you mis-measured, you can't even get the impedance right.

With a ~50 ohm antenna and ~450 ohm ladder-line,
a match is impossible so why fret about it? :-)
Patient: Doc, it hurts when I do this.
Doc: Then don't do that.
--
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, 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.



Fred, again, thanks for these comments. A 75M broadband biconical
antenna is apparently just what fits my needs and "tree configuration".

Question for you: The QST article does not address whether or not the
two dipoles are cut to different frequencies, as you suggested for your
personal situation you had. Do you think two exact length dipole lengths
are what the QST article author was talking about, or are two different
lengths necessary?

All I am trying to accomplish is put a a full size 75M dipole between
two tall trees (will be about 50' or 60' high dipole) and to have an SWR
across the band that does not exceed about 3:1 .


Ed K7AAT

A biconal has all the legs the same length. I varied the lengths to see if I
could get by with less than 15 feet. It was not successful. A biconal cage
however gets really wide. Less than 2:1 from 3.5 to 4.

As an aside, anecdotally the cage and biconal are both quieter than a
dipole.

"Ed" wrote in message
. 93.175...


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.



Fred, again, thanks for these comments. A 75M broadband biconical
antenna is apparently just what fits my needs and "tree configuration".

Question for you: The QST article does not address whether or not the
two dipoles are cut to different frequencies, as you suggested for your
personal situation you had. Do you think two exact length dipole lengths
are what the QST article author was talking about, or are two different
lengths necessary?

All I am trying to accomplish is put a a full size 75M dipole between
two tall trees (will be about 50' or 60' high dipole) and to have an SWR
across the band that does not exceed about 3:1 .


Ed K7AAT

:

A biconal has all the legs the same length. I varied the lengths to
see if I could get by with less than 15 feet. It was not successful. A
biconal cage however gets really wide. Less than 2:1 from 3.5 to 4.


Given the wind potential here, along with loading on my antenna support
lines, I probably should go with the biconical dipole over a cage. I do
have plenty of room to do a 15' end spacing, though.

As an aside, anecdotally the cage and biconal are both quieter than a
dipole.


I hadn't seen any reference to noise benefits from a biconical, so
that's nice to hear! Thanks for the info.


Ed K7AAT