Re: The Broadband Butterfly ... an HOA-friendly all-HF antenna for your attic
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Good suggestions Jim. I’ve used the Gap Titan for years back at the old QTH up north. Loved its special “loaded half-wave vertical dipole” design, which allows it to operate without ground radials. (As everyone knows, ground radials are absolutely essential for most other types of verticals.) Currently here in the new QTH, I have just installed a 6-band, 30-ft Hustler vertical in the backyard, with 32 ground radials out along the grass. The tilt-over mounting of the antenna allows me to keep it lowered to the ground to avoid neighbor view and concerns. (I normally operate only when dark, and will soon be painting it brown for when it’s raised during the daytime.)
The original purpose of posting this Butterfly Terminated Dipole was to encourage guys here to try an easier and completely stealthy antenna mounting in the attic. Which is not to say that one couldn’t put an OCF dipole in the attic, even drooping the legs down somewhat at the ends. And such an OCF in the attic would undoubtedly have better performance than the Terminate Folder Dipole. But an OCF would likely be unable to reach the lower bands due to the inherently longer length.
Hence … antenna experimentation!
PS: We’ll soon talk about just having a “longwire” out the window or to (and into) the trees. There is some small gauge wire that strong and nearly invisible. And a simple toroid and capacitor will match it to our transmitters.
PPS: Really love your solution for “omni coverage” with the Buckmaster OCF antenna …and envious of the space you obviously have to do that!
From: TLARC@groups.io <TLARC@groups.io> On Behalf Of Jim Jenkins
Sent: Friday, February 1, 2019 7:04 AM
Subject: Re: [TLARC] The Broadband Butterfly ... an HOA-friendly all-HF antenna for your attic
The 2 antennas I recommend you look at are the 235ft long Buckmaster 8 band which covers 8 hf bands with a 1.5 vswr including 160M or the 135 ft long 7band version which covers all but 160m. The 3kw versions work better than the 300 watt versions. An antenna that takes less space and works all the hf bands except 160m is the Titan GAP antenna which is a vertical that doesn’t require any radials. The Titan GAP has an omni directional pattern so there are no holes in its coverage. The Buckmaster’s have good coverage for OCF antennas but still have holes off the ends. I’ve put up both an 8band and a 7 band version lined up at 180 degrees crossing near the feed points in the past so the holes of each was filled by the other on all bands except 160m.
That was my first thought too. As they say, even a dummy load will radiate and have flat SWR across such a wide frequency range.
In a more conventional terminated folded dipole, the terminating resistor will lower the overall gain of the antenna at the expense of getting a better SWR across the bands, with much of the power being dissipated as heat in the resistor. As you said, the efficiency stinks but you get broadband coverage.
FYI, there’s a good article on the Terminated Folded Dipole in QST for Sept 2010.
Anyway, Juan suggested it might be worthy of doing some experimentation ... It’s usually fun trying new approaches to antennas, modeling and measuring them, etc. Learn something every time.
Personally, I’m going the diametrically opposite direction with my experimentation: I’m constructing a 160m “Small” Transmitting Loop using two turns of 7/8” Heliax with 10’ diameter. With a vacuum variable capacitor, the loop (inductor) will resonate with SWR of 1.2:1 ... with a 6 KHz bandwidth!
Fun stuff, antenna experimentation!
73, George N2APB