King Zulu wrote:
The impedance will still be 50-to-70 ohms if you add the extra
half-wavelength to just one end of the antenna.

Actually, it may be closer to 100 ohms. It's an OCF somewhat like
a "Windom" fed with two-conductor transmission line. The "Windom"
is supposed to have a feedpoint around 300 ohms.

i.e. The wire on one side of the antenna feed point (coax connection) is
still 32.5 feet, and the wire on the other side would be 65' + 32.5' plus
another 3.3', since there is no end-effect on the extra half-wavelength of
wire you are adding.

It's an interesting OCF antenna but probably subject to common
mode currents unless an excellent choke is used at the feedpoint.

You should get almost 2 db of gain in four directions (a
"cloverleaf") by doing that.

Since it's a one-wavelength antenna, it won't quite achieve a
cloverleaf pattern. It's about the same gain as a 1/2WL dipole
(6 dBi) but with a much wider horizontal beamwidth. For a 130
ft. long antenna, the cloverleaf pattern develops around 10 MHz.
--
73, Cecil, W5DXP



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"Cecil Moore" wrote in message
...
King Zulu wrote:
The impedance will still be 50-to-70 ohms if you add the extra
half-wavelength to just one end of the antenna.

Actually, it may be closer to 100 ohms. It's an OCF somewhat like
a "Windom" fed with two-conductor transmission line. The "Windom"
is supposed to have a feedpoint around 300 ohms.

The FW dipole I used for years had a 1.2:1 SWR, fed with RG59 and no balun.


i.e. The wire on one side of the antenna feed point (coax connection)
is
still 32.5 feet, and the wire on the other side would be 65' + 32.5'
plus
another 3.3', since there is no end-effect on the extra half-wavelength
of
wire you are adding.

It's an interesting OCF antenna but probably subject to common
mode currents unless an excellent choke is used at the feedpoint.

Never saw an indication that the feed line was radiating. On my many dipole
versions, I have tried them with and without baluns. If the resonance of the
antenna didn't change with the balun in, I figured the balun wasn't needed.
On one, where the coax could not come off perpendicular to the dipole, the
balun did raise the resonance frequency - suggesting the feedline was
radiating without the balun in. That same W2AU balun caused havoc with TVs
in my neighborhood when I used it for ten meter operation. I assumed the
core was saturating and causing the harmonics. For that reason, I don't use
baluns just for good measure; only when I need the matching (4:1 baluns) or
when there is some indication that the feedline is radiating. Plus, baluns
add weight to the antenna, loss to the power, and are susceptible to weather
problems.

You should get almost 2 db of gain in four directions (a
"cloverleaf") by doing that.

Since it's a one-wavelength antenna, it won't quite achieve a
cloverleaf pattern. It's about the same gain as a 1/2WL dipole
(6 dBi) but with a much wider horizontal beamwidth. For a 130
ft. long antenna, the cloverleaf pattern develops around 10 MHz.
--
73, Cecil, W5DXP

The 2db gain was what the ARRL Antenna Book (1964 vintage, p. 142) was
calling out for a FW collinear array gain. Actually, the FW dipole fed at
the current node would be like a 1-wavelength long longwire (a short
longwire?), and the Antenna Book shows a negligible 1/2 db gain (p. 170 on
"Long-Wire Antennas") over the dipole gain. The cloverleaf assertion was
based the Antenna Book radiation patterns shown on p. 39 (Fig 2-16) and the
discussion of "How Patterns are Formed", as well as p. 59 (Fig 2-74b)
showing the FW pattern distortion caused by end feeding.

K4YKZ

King Zulu wrote:
The FW dipole I used for years had a 1.2:1 SWR, fed with RG59 and no balun.

It still may have had a feedpoint impedance of ~100 ohms. RG59's
Z0 is 75 ohms, close to what you would need to transform 100 ohms
to 50 ohms. An odd number of 1/4WLs of RG59 will transform 100 ohms
to 57 ohms, neglecting losses.

Never saw an indication that the feed line was radiating.

We can mount a logical argument that since the feedpoint
impedance looking in each direction is different, the
currents have to be unbalanced resulting in feedline
radiation.

The 2db gain was what the ARRL Antenna Book (1964 vintage, p. 142) was
calling out for a FW collinear array gain. Actually, the FW dipole fed at
the current node would be like a 1-wavelength long longwire (a short
longwire?), and the Antenna Book shows a negligible 1/2 db gain (p. 170 on
"Long-Wire Antennas") over the dipole gain. The cloverleaf assertion was
based the Antenna Book radiation patterns shown on p. 39 (Fig 2-16) and the
discussion of "How Patterns are Formed", as well as p. 59 (Fig 2-74b)
showing the FW pattern distortion caused by end feeding.

EZNEC says that it is somewhat of a square pattern where the "corners"
of the square are just barely starting to form a cloverleaf. The "nulls"
off the ends are only 3 dB down. I suspect there was a lot of guessing
about radiation patterns in 1964. Some say there still is a lot of
guessing. :-)
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
...
King Zulu wrote:
The FW dipole I used for years had a 1.2:1 SWR, fed with RG59 and no
balun.

It still may have had a feedpoint impedance of ~100 ohms. RG59's
Z0 is 75 ohms, close to what you would need to transform 100 ohms
to 50 ohms. An odd number of 1/4WLs of RG59 will transform 100 ohms
to 57 ohms, neglecting losses.

Never saw an indication that the feed line was radiating.

We can mount a logical argument that since the feedpoint
impedance looking in each direction is different, the
currents have to be unbalanced resulting in feedline
radiation.

The 2db gain was what the ARRL Antenna Book (1964 vintage, p. 142) was
calling out for a FW collinear array gain. Actually, the FW dipole fed
at
the current node would be like a 1-wavelength long longwire (a short
longwire?), and the Antenna Book shows a negligible 1/2 db gain (p. 170
on
"Long-Wire Antennas") over the dipole gain. The cloverleaf assertion was
based the Antenna Book radiation patterns shown on p. 39 (Fig 2-16) and
the
discussion of "How Patterns are Formed", as well as p. 59 (Fig 2-74b)
showing the FW pattern distortion caused by end feeding.

EZNEC says that it is somewhat of a square pattern where the "corners"
of the square are just barely starting to form a cloverleaf. The "nulls"
off the ends are only 3 dB down. I suspect there was a lot of guessing
about radiation patterns in 1964. Some say there still is a lot of
guessing. :-)

Well, the FW dipole may not have had all the advantages I thought it did -
but it worked well enough that I stopped bothering with the 2-element wire
beam on 40m for the contests. It's a bit like fishing - if you believe in
your equipment you will usually do better than if you don't. HI

K4YKZ

King Zulu wrote:
Well, the FW dipole may not have had all the advantages I thought it did -
but it worked well enough that I stopped bothering with the 2-element wire
beam on 40m for the contests. It's a bit like fishing - if you believe in
your equipment you will usually do better than if you don't. HI

It's not a bad antenna and I didn't mean to knock it. I like
that 40m pattern where it has 280 degrees of beamwidth. It's
actually better than a cloverleaf beamwidth pattern.
--
73, Cecil http://www.qsl.net/w5dxp