Ed wrote:
"This antenna may be just what I was looking for to put up on 75M."

ON4UN says on page 10-13 of "Low-Band DXing" that:
"By using one of the above mentioned loading methods and a switching
arrangement, a loop can be made that covers the entire 80-m band with an
SWR below 2:1."

Best regards, Richard Harrison, KB5WZI

the search for the broad band antenna continues.
It appears putting more wire in the air is the preferred solution,
but more wire means more weight
more weight make the antenna droop - and can break a tree limb.
a dipole fed with ladder line is lightweight.
it doesn't droop
it doesn't break limbs
it works
I like Cecil's antenna at his web site. A few 4pdt ice-cube relays @ 7.50
each and the sockets @ 2.50 each can switch different lengths of ladder line
in and out. Put the line and relays in the attic.
I think you could also make use of an old TV tuner switch (The old clunker
channel changers)
I considered using a PLC to switch the relays.

"Fred W4JLE" wrote in message
...
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

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

Hal Rosser wrote:
I like Cecil's antenna at his web site. A few 4pdt ice-cube relays @ 7.50
each and the sockets @ 2.50 each can switch different lengths of ladder line
in and out.

I got my relays for $2.50 at surplus stores in Silicon Valley.
I finally settled on knife switches mounted on Plexiglas in my
hamshack window.
--
73, Cecil http://www.qsl.net/w5dxp


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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

I got a bit slicker with mine, I have an updown binary counter with an
updown switch. It feeds the relay driver circuit and a 2 digit decimal
display . One of these days I plan to have the box driven automatically from
the rig.

"Cecil Moore" wrote in message
...
Hal Rosser wrote:
I like Cecil's antenna at his web site. A few 4pdt ice-cube relays @
7.50
each and the sockets @ 2.50 each can switch different lengths of ladder
line
in and out.

I got my relays for $2.50 at surplus stores in Silicon Valley.
I finally settled on knife switches mounted on Plexiglas in my
hamshack window.
--
73, Cecil http://www.qsl.net/w5dxp


----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet
News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 100,000
Newsgroups
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Ed wrote:
"I prefer "resonant" antennas fed with coax as opposed to open wire
feedline with tuners,---"

Bamdwidth of a resonant antenna depends on its antenna Q. A high-Q
antenna can cover a wide band by retuning for the frequency to be used.

Biconical antennas are used for their feedpoint impedance of about 72
ohms and for their low-Q (wide bandwidth).

A high-Q loop antenna can be efficient and smaqll but must be tuned for
the frequency of use. An interesting example appears in the July 1968
QST. It`s the cover story.

The loop is a rectangle 8 feet long and 4 feet wide made of
copper-plated aluminum rain downspout. It is tuned and loaded with
dual-section 500-pf variable capacitors such as pmight be used in a TRF
set. With additional switched-in fixed capacitors, it matches 50 ohms
from 2.8 MHz to 7.3 MHz, and from 14 to 22 MHz. It also works to 30MHz
with an SWR under 3:1.

This mobile antenna was mounted on a car roof. Some YL`s may not
appreciate its beauty.

Best regards, Richard Harrison, KB5WZI

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