HFU HF Underground
Technical Topics => Equipment => Topic started by: ChrisSmolinski on May 21, 2017, 2005 UTC
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A post about my active antenna made with two hula hoops:
http://www.radiohobbyist.org/blog/?p=2130
(http://i.imgur.com/GLUhAMm.jpg)
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Wayne Green would be proud of you, Chris. He loved those things.
BTW, the first time I saw an article on the horizontal loop you swear by was in "73 Magazine" entitled "What's The Scoop On The 'Lazy Loop'?" Wayne was decades ahead of his time in showing people how to piss off their neighbors with weird antennas.
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Liking the multi-way switchable amp design. :)
One possible tweak for later experimentation. Consider replacing the hulas with copper tubing, or maybe even just copper wiring. I suspect given the potential for increased resistive losses in an aluminum foil loop, a solid copper wire of a decently sized gauge placed inside each hula could work about as well (or better?), plus it also could allow for an improved electrical connection (and possibly less loss) between the antennas and amp versus the current mechanical feedpoint connections to foil.
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Liking the multi-way switchable amp design. :)
One possible tweak for later experimentation. Consider replacing the hulas with copper tubing, or maybe even just copper wiring. I suspect given the potential for increased resistive losses in an aluminum foil loop, a solid copper wire of a decently sized gauge placed inside each hula could work about as well (or better?), plus it also could allow for an improved electrical connection (and possibly less loss) between the antennas and amp versus the current mechanical feedpoint connections to foil.
Interesting idea. I went with the foil over the hula hoop to minimize inductance, I'd have to look up the resistance of aluminum vs copper to see how much of a difference there is. Another possibility would be to use copper foil. Best of both worlds?
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Wayne Green would be proud of you, Chris. He loved those things.
BTW, the first time I saw an article on the horizontal loop you swear by was in "73 Magazine" entitled "What's The Scoop On The 'Lazy Loop'?" Wayne was decades ahead of his time in showing people how to piss off their neighbors with weird antennas.
The Sky Loop truly is King. It's the best overall performing antenna I have ever built. It plus the netSDR are a formidable pair of DXing tools. If I ever clear the brush in the back acre of the lot, I could probably double the area of the loop. I've only been meaning to do that for 20 years ;D
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Exposed aluminum outside in the elements will develop aluminum oxide, an insulator, which may with time affect shielding and electrical performance.
+-RH
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Exposed aluminum outside in the elements will develop aluminum oxide, an insulator, which may with time affect shielding and electrical performance.
+-RH
Thanks for the tip, I was actually thinking about that possible problem. I wonder if covering the foil with tape might help reduce that? OTOH, I've had aluminum antennas before (such as a VHF/UHF scanner antenna) that had aluminum elements, and was OK. The elements developed an aluminum oxide coating, but as long as the electrical connections were protected, it was fine. I do have tape over the wire to aluminum connections now.
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if you use aluminum tubing that will work fine. The problem with foil is you have a number of loose layers to retain water and promote oxidation.
+-RH
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I'm considering some copper pipe, flatten it, cut it with snips into two flat strips, then make me some superconducting smolinskiloops.
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Chris,
when I build my active loop I pulled some heat shrink tubing over the copper pipe.
So far it works great for me.
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Oliver, what amp are you employing with the loop if you don't mind saying. Been looking for simple yet high dynamic range amp designs for such loops.
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Hello Josh,
I use a HDLA 3. The electronic was purchased from Henry W. Mohr here in Germany. ( www.hwmohr.de ,
info@hwmohr.de )
As far as I know from Henry he is currently out of stock on these fine electronics. But he mentioned that he is planning to build some more in fall of this year.
There are four versions of the electronic.
The HDLA 3,6,9 &12, the numbers indicate the loop diameter in meters. All electronics come with a power inserter box and are housed in a IP65 housing.
Price tag is a round €160 without S&H.
If you are interested send him a email and ask him for the current stock / building status.
Some comparison of the HDLA with other antennas electronics was done by Fenu. ( http://www.fenu-radio.ch/index1.htm#Fenu-Loop-HDLA2-3 )
I hope I could answer your question.
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Indeed and thanks Oliver.
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A short update, since I have been using this antenna for a few months now.
It's connected to my NRD 545. It actually works pretty well as a wideband antenna, from MW through most of HF. Not bad on LW either.
I've used it in the evenings when the beverage and AFE822 were already recording DGPS, and it did a respectable job picking up SWBC stations, including US and Euro pirates. Not as good as the beverage or sky loop, but still not bad.
I just strolled through the expanded part of the MW band, and it picked up everything the sky loop could, with generally only slightly to moderately weaker signals. There is certainly some directionality, certain stations are significantly stronger (or only present) on one of the loops vs the other. I notice this throughout the MW band. In same cases both loops work equally as well, this is likely a case where they are both at a 45 degree angle with respect to the azimuth of that station. Unfortunately both loop signals are not sent back to the shack, otherwise that might allow for phasing.
So while I would not consider it a "DX Magnet", it is an excellent performer for the size. Certainly something I would recommend to someone without the space for a full sized antenna. It's possible that it could be further improved with a better planned pair of loops, vs the hula hoops and aluminum foil I used. ;D