HELICAL UPDATE

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scudGB

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Aug 11, 2019
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HI ALL
way back in aug 2019 i posted my dissapointment with my 1st helical ,,well i finaly got my nanovna 2 in 4 1/2 days from china ! ,,found that my heli was resonant at 1679 MHZ a bit high for my interest zone so i managed to find a helical calculator that allowed different coil spacings resulting in a coil plan better suited to my tube and as the new plan was for a greater coil spacing i just detatched coil from tube cleaned everything up and had a second attempt ,it seems to work as i have been testing it the last two days and bearing in mind that is mounted in my loft with a huge tree full of leaves (summer here uk) i am seing a 4 to 5 db increase in old ant from last winter
STRANGE THING though marine and aero signals all seem to drop as we go into evening cloud seems same for both days as in very light only things i can think of is
is alphasat drifting around or do trees suck up ground water as temprature drops and leaves gett fatter ??? any ideas anybody pic of nano below scudrewire.jpg
 

RFI-EMI-GUY

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Dec 22, 2013
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4,316
I have no idea what you are trying to recieve or what receiver you have. However, Helical antennas, while truly magical and great performers, have resonances on different modes and frequencies. Usually you can go by the cookbook formula and they will work off the bat.

The problem is that these off mode resonances mean that it is a good long wire or normal mode helix for cellphone transmissions, broadcast and other bands. If your receiver has no preselection for the frequency of interest, it will become overloaded. If you are doing SDR, and have no preselector, this can happen. Software cannot fix laws of physics.
 
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