Re: Kchibo antenna experiments installment 2


Tony Germanotta
 

That's strange. Many ferrite loops have MW and LW coils on the same form and they work well. They do usually mount them at opposite ends of the ferrite rather than tap the same coil. But I have a spiral loop that I tap to receive both long and medium wave. It's not as good as my dedicated LW crate loop, has a lot fewer turns and they get pretty short as the spiral approaches the center. Still, it doesn't prevent the MW section from tuning well. But the turns are spaced about a half inch apart to minimize winding capacitance. Maybe your turns are just too closely wound. 

Then again that's what I love about antenna experimenting. We know what should work but it's all theory and, ultimately, magic. One time a group of us were on a dxpedition on the outer banks. Most of us had hundreds of feet of longwire stretched along sand dunes and scrub. But one guy got there too late to put up a proper antenna. So he dropped a tangled pile of wire on the porch under all our antenna feeds and his pile heard every little Indonesian and Papua New Guinea local station that we did. He never did stretch out his antenna. Was it inductively coupling ours? It sure wasn't a close couple. Was our location just that perfectly quiet that any signal above the radio's noise floor would work? He had a great radio, a top of the line JRC if I recall correctly. Who knows. It was great fun to try to find something he couldn't hear. And we never did. 

Reminds me of the music theory class I took in college a million years ago. The professor took a Beethoven symphony and came up with all these theories about why each chord sounded right. Of course Ludwig had none of that theory to work with. Wonder how he was able to compose. The FSL antennas are apparently a wonderful solution looking for an explanation. Perhaps it really does have to do with polarized waveforms dancing around each rod, resonating together to increase efficiency and signal to noise ratio. Sort of a sum of each individual ferrite feeding one loop antenna. Or maybe it's just the magic of a lot of ferrite combining with the wide aperture to give the best of air and ferrite loops. Don't know. I missed the Ukrainian window of opportunity and can't justify the cash to try it out now. I guess you'd have to bake up a huge hollow ferrite rod the same diameter as an FSL to see if there is any polarization going on. 

Back to your antenna. Have you tried to inductively couple it with a portable? A sony 2010 is great because when you peak a signal those red LEDs all light up. Sometimes a loop can have such a tight peak it's hard to hear. The inductive coupling will also eliminate any loading effect all that unused coil might have on a pickup loop in case that is what's happening. 

Otherwise I defer to those with more knowledge and experience. You might have to cut away loops after all and stick to MW. Or just whip up another 4 foot box with 7 or 8 turns spaced a half inch apart and have two loops. 



On Mar 18, 2015, at 5:29 PM, "farmerik@... [ultralightdx]" <ultralightdx@...> wrote:

 

Not sure what's going on. I can't get the cap to resonate 7 turns between taps  on the 4 foot box loop. So I tried the cap on a much smaller Diamond or Rook loop [I don't know which this one of several  I had made for me is] and it clearly resonates on an AM frequency so I think the cap and where I connected to it are good. The 4 footer does boost signals all over the AM band, but does not peak anywhere, and if I momentarily disconnect one side of the cap from the coil I do hear a click in the radio. . One guess is the unused turns are still adding capacitance putting the total beyond the range of AM tuning? As you can tell, I am not knoledgable about Radio theory. - FARMERIK

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