HFU HF Underground
General Category => General Radio Discussion => Topic started by: ChrisSmolinski on February 12, 2012, 1849 UTC
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I wrote up an article on my primary antenna, the 635 ft sky loop: http://www.hfunderpants.com/?p=564 (http://www.hfunderpants.com/?p=564)
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Neat Chris! Nice information to contemplate.
I have used loops for years and often times, depending on the actual location,
they often tend to be much quieter than the typical wire outside the shack.
Currently mine is "resonant" on approximately 6900Khz, one side at 35 feet and
the other three at 25, 30 and 18 feet. This current loop actually resides on
another owners property. Its fed with about 160 feet of ladder line. Using this
as a "long random wire" really works well with a simple toroid transformer to
either my TS870 or Excalibur receiver. It does very well for the NDB band which
I continue to troll once in awhile tuning it to resonance with a ham brew matching
network built on an old fax machine cardboard paper tube with taps.
In my opinion the work in putting your loop a little higher on some legs will not
buy you anything for the most part. It can't hurt of course but well....
As usual your write up is nicely done and reflects a another nice project for the
winter season.
Cheers!
weaksigs
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Thanks for the article. This looks like a fun project. Now if my antenna supports would start growing faster...
BTW, some people don't use baluns with this antenna:
http://www.qsl.net/kd4sai/loopant.html
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Very cool. I'm thinking about putting up an 80-meter full wave loop for 80m-10m use, with an L-network tuner and balanced line.
Wish I could find a beefy tuna for a good deal though, we get maybe 2 good hamfests a year :(
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I'm actually in the prep stages now for putting up a full wave delta loop for 43 meters. I moved the high end of the T2FD to another support, freeing up a rope that is 50 ft up in a tree. That will be the top support for the delta. The bottom will be about 18 ft above the ground, and the length of the bottom element is 622 ft.
I've run NEC simulations on various angles, and as of now it looks like I'll be going with a delta that has two 45 degree angles and a 90 degree angle at the top. The input impedance (if NEC can be believed) will be about 60 ohms at 6.925 kHz. The low angle radiation pattern looks to be excellent, peaking at about 18 degrees. The pattern is not symmetrical around the compass, there is about a 4 dB difference. I'm not sure that's enough to get all worked up about, so I'll orient the antenna in a direction that is easiest to install, vs trying to aim it a particular direction. That might end up being somewhat to the NE anyway, which might give me a little advantage for Europirates.
I'm still waiting on coax, and I need to measure, cut and lay out the antenna wire and insulator supports. Unlike say the sky loop, this antenna will require a little more precise dimensioning.
I'll try to do a write-up once I get the antenna up.