Любопытная дискуссия в РСГБ, решил оставить у нас.
Напомнил им там про эксперименты Маркуса, кажется в передающей ферритовой антенной.
http://136.su/index.php/topic,119.msg21759.html#msg21759The smallest 137Khz antenna in the world?I needed a small 137Khz antenna to be able to do some test transmissions from a WSPR generator at the other end of my block. Here is the result.
20 turns on a 100mm former with 20nF of resonating caps. A 4:1 transformer feeds the coax to the Tx. Sweeping with a VNA shows 1:1 VSWR at resonance. I am feeding it with 30mW and I am am amazed how well it works, in fact, I have to use an attenuator as the signal at the Rx antenna is too strong.
It also works quite well as a Rx antenna for local signals. I am going to build a slightly larger version and see how well it performs in suburbia at a friends place.
Cheers,
Peter - VK2AN
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Hi Peter,
Well, in my old BC receiver I have a ferrite rod antenna that works well for reception down to 137 kHz with an additional cap. It could be used for TX at milliwatt range, hi!
73, Reino OH3mA
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Hello Peter,
nice antenna.
It might even work a bit better if you place the toroid outside the loop.
And as Reino said, a ferrite rod antenna might be a good alternative at mW level. Roger, G3XBM, has some information on his website (
https://sites.google.com/site/g3xbmqrp3/antennas/ferrite_tx). And also
http://www.antentop.org/017/files/ua6ca_017.pdf.
73, Rik ON7YD - OR7T
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Hi Rik, Reino,
Yes I did try moving the toroid in and out of the loop. It does make a slight shift in the resonant frequency when it is perpendicular (as in the photo) However if you turn the toroid in the same plane as the loop, it makes almost no difference. I suppose this shows that a toroid had a "closed" magnetic field.
I have a very large rectangular piece of ferrite, it weighs more than a kilo! I may try to use that for an antenna as you suggest, and see if it is better or worse.
Cheers,
Peter
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Да, у меня что-то аттач, что прислал Рейно - не виден в почте. У кого виден - занесите, плс.
