HF / Attic antenna questions

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batdude

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That is not a cut to fit antenna, it must be 1/2 wave resonant on 40m, which will then work on the other advertised bands. If you cut that antenna down in size it becomes a random but large coat hanger. In its original size its a good performer.
don't read too much into my cut to fit statement. what i mean is that the ~40feet on one leg and ~20 on the other leg is perfect for the dimensions of my attic and where my feedline comes in.

doug
 

prcguy

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Then you should get good use out of that antenna. If you had not purchased one yet I would have recommended the MyAntennas version. Its the same overall length but they found the best tap point and their balun design is the very best for that kind of antenna. I use an 80-10m version here and its the best all band wire antenna I've used after going through countless types.

don't read too much into my cut to fit statement. what i mean is that the ~40feet on one leg and ~20 on the other leg is perfect for the dimensions of my attic and where my feedline comes in.

doug
 

wa8pyr

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with the recommendation of a knowledgeable ham - i purchased this antenna today

offset 40m dipole

the offset feed is really "cut to fit" for the space I have available!

will keep the thread updated!
Should do well for you; I had a home-made version strung through the backyard of my old place and had good performance until a tree limb ended it's life and I went to the 40m "droopy loop" (form the QST article where I got the idea) on the roof.

Tom WA8PYR
 

ka3jjz

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I read on that site that it works for 4 bands. It's interesting - they didn't consider 30 meters, where CW and digital are used? I wonder how it would work there? And what about 18 Mhz? They didn't really spell out which 4 bands on which this is supposed to work... Mike
 

prcguy

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The offset center fed is a bit like the EFHW, its resonant on its fundamental design frequency (40m in this case) and it also operates on most harmonics. A 40m version only gives you 40, 20, 15 and 10m and the WARC bands have a pretty bad match. An OFCD is also inherently unbalanced and wants to light up the coax with RF. Mfrs like MyAntennnas use a really good design 4:1 current balun which does a great job of snuffing out much of the common mode currents on the coax, but if you operate outside the resonant areas the feedline will become a radiating part of the antenna. Not good.

The 80m OCFD depending on mfr can cover some or all of the WARC bands because the better brands have done their homework and found the best tap point in the wire to place the balun to optomize the match and get the most bands. Here we go again with my recommendation for MyAntennas and my main HF antenna at home is now a MyAntennas 133ft OCFD. Its the best performing wire antenna I have ever used period. I don't need a tuner for any of the phone portions of any band 80 through 10m including all WARC bands and I just connect my feedline right to my amplifier with no tuner and it just works. My particular 80m OCFD was modified with a capacitor in the middle to raise the 80m resonant point to 75m around 3.9MHz and they now make a version with the same mod for the phone only people like me.


I read on that site that it works for 4 bands. It's interesting - they didn't consider 30 meters, where CW and digital are used? I wonder how it would work there? And what about 18 Mhz? They didn't really spell out which 4 bands on which this is supposed to work... Mike
 
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W5lz

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A balun. Why would you use a balun, the antenna isn't balanced to start with. An 'unun' maybe, but really, why use either?
 
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