[TowerTalk] Linear loaded KE4UYP vertical
RadioIR at charter.net
Thu Jul 24 23:26:19 EDT 2008
Don't believe everything you read in print. I just modeled an 80 meter
version of that antenna, using the recommended dimensions, top wire at
31 ft and 65 ft long, with 82 ft of wire in the vertical portion with
the bottom wire 5 ft above ground.
It resonated at 3.69 MHz with an impedance of 26 ohms. He claims the
longer wire on the vertical side off-center feeds the antenna and raises
the impedance to 50 ohms. Didn't work for me. If you matched the
antenna to 25 ohms the 2 to 1 SWR bandwidth would be about 70 KHz. (He
claims 300 KHz). The gain is 2.9 dBi straight up. (He claims 1 dBi.)
2.9 dBi is about the same as an 80 meter dipole at 18.5 feet. He claims
it is 80 to 85% efficient. EZNEC calculates 4.13 dB loss. That's
equivalent to 38.6% efficiency. He claims it is totally
omni-directional. At 30 degrees elevation it has a F/B of 3.6 dB.
I didn't include the feedline or any metal support poles in the model.
I didn't do the 160 meter version, but I would expect much poorer numbers.
Marinus Loewensteijn wrote:
>Long time lurker here but I have a question that I do not seem to be able to answer satisfactory.
>At the moment I have 44 foot doublet up for 80 and 40 and am wanting to move away from a balanced feeder to coax. I am thinking of putting a scaled version of the above antenna up for 40 first before 80m.
>If it is totally a disaster then I may put up a rotatable dipole lke the Cushcraft D40 or Hy-gain Discoverer 7-1.
>Due to size restrictions and to the location of TV satelite dishes of both myself and close neighbours I cannot put up anything larger than this.
>I wonder if any of the TowerTalkatonians has opinions or experience with this antenna. ( members.tripod.com/~KE4UYP/80m_160m_Antenna.html)
>Many thanks in advance, 73 Marinus ZL2ML ..
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