Multi-wire broadband dipole ?
- Thread starter merlin
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I think you are looking for the name “fan dipole”.
A fan dipole consists of different length dipoles, cut for different frequencies fed at a common point.
An antenna with multiple conductors of the same length fed like that is known as a T antenna. They are often used for VLF and MF frequencies. This is actually a vertical antenna with a great big capacity hat. T-antenna - Wikipedia Republished // WIKI 2
An antenna with multiple conductors of the same length fed like that is known as a T antenna. They are often used for VLF and MF frequencies. This is actually a vertical antenna with a great big capacity hat. T-antenna - Wikipedia Republished // WIKI 2
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For what you are interested, you should also googlethe similar "cage dipole". It may be what you actually want for your purpose.
brainfreeze17
Member
That appears to be a T3FD (terminted folded dipole)
majoco
Stirrer
jwt873 has got it right - that's a typical "T" antenna with a capacity hat for LF antennas - except that the vertical radiator usually dropped straight down to a matching unit fed from the remote transmitter via coax cable. Works best with a wet marshy ground plane.
A "fan dipole" has a coax fed centre feed point with an Unun and a choke at the top with quarter wave dipole elements for each of the required bands. Two methods I have seen - one has spreaders from the longest element to the end of the progressively shorter elements which hang underneath - the other supports the shortest element on a long piece of rope and the longer elements are tied to the rope with insulators and allowed to dangle below the one above.
I'm not convinced that it's 'broadband' - more 'multi-band'.
A "fan dipole" has a coax fed centre feed point with an Unun and a choke at the top with quarter wave dipole elements for each of the required bands. Two methods I have seen - one has spreaders from the longest element to the end of the progressively shorter elements which hang underneath - the other supports the shortest element on a long piece of rope and the longer elements are tied to the rope with insulators and allowed to dangle below the one above.
I'm not convinced that it's 'broadband' - more 'multi-band'.
prcguy
Member
I agree, its a T3FD using usually a 9 or 12:1 balun and a 600 to 800 ohm terminating resistor. It is truly a broad band antenna that should not need a tuner on any HF frequency. I have several similar T2FDs here.
If you look at the closeup of the antenna you can see the balun at the feed and one of the insulators bridged with a resistor.
Update: I believe the one pictured in post #1 is made by Bushcomm. http://www.bushcomm.com.au/manuals/Bushcomm Product Catalogue.pdf
If you look at the closeup of the antenna you can see the balun at the feed and one of the insulators bridged with a resistor.
Update: I believe the one pictured in post #1 is made by Bushcomm. http://www.bushcomm.com.au/manuals/Bushcomm Product Catalogue.pdf
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That's one interesting link. I spent a while going over it. Would be nice to see such a company in North America..
prcguy
Member
You can make most of the antennas on that site with just some wire and various baluns. Except for the Outbacker mobile antenna.
Fan dipole isn't what I was looking for. The antenna 'IS' the T3FD and hams in the past had an unofficial pet name for it. Even an article in QST, 'how to make a ????? antenna". Just can't recall.
Yea, back in the 70s, I made and used one in inverted V fashion. The short version copy of a friends.
Have to call them BROADBAND down to 1.7 Mhz. 50Mhz, lots of lobes, 146, lobes everywhere.
The long version good down to 250 Khz.
A variant 2 wire around the edge of a roof makes it hidden, sort of strange rhombic but gain toward the terminator.
Yea, back in the 70s, I made and used one in inverted V fashion. The short version copy of a friends.
Have to call them BROADBAND down to 1.7 Mhz. 50Mhz, lots of lobes, 146, lobes everywhere.
The long version good down to 250 Khz.
A variant 2 wire around the edge of a roof makes it hidden, sort of strange rhombic but gain toward the terminator.
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I was considering Barret's HF broadband vertical mobile, and recall the T3FD used a 16:1 balun and 1000 ohm terminator, the rest is wire and insulators.
ka3jjz
Wiki Admin Emeritus
I think that T3FD is also known as a broadband butterfly HF dipole- at least the description you gave is quite similar...
Mike
Mike
prcguy
Member
That's a different antenna, more like a terminated loop. A T2FD and T3FD are "traveling wave" antennas and a loop is a loop but the one shown above and a terminating resistor to help absorb reflections and improve VSWR over a large frequency range. The B&W ACS broad band end fed V, which is basically the same as the BBTD above but in a triangle shape instead of a square. Barker & Williamson - ACS broadband end fed vee HF antenna page
I have a new in box A&W ACS that I plan on testing on my next desert camp out.
I have a new in box A&W ACS that I plan on testing on my next desert camp out.
The BBTD "HOA friendly" antenna looks a lot like a Rhombic in a smaller version than normal size Rhombic.
prcguy
Member
A Rhombic would be many wavelengths long and a diamond shape with the angles chosen to place the main lobes in phase for more gain. The BBTD is just a random size terminated loop.
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