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8419RE: [loopantennas] Re: What type of capacitor is used for loop antenna?

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  • Ray Phillips
    Apr 1, 2011
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      Is it possible that you are confusing MHZ (millions of cycles per second) with KHz (thousands of cycles per second)? If you are trying to build a loop to receive MHz transmissions but plugging KHz figures into formulas, then your calculations will be wildly inaccurate.

      As frequencies fall below 500KHz (0.5MHz) the amount of man-made signals reduce. At 1KHz I would expect all signals to be either natural or man-made noise rather than coherent signals. At 1KHz I, personally, would be using audio techniques not radio techniques. At 1MHz, however, I would definitely use radio techniques such as a loop and capacitor.

      Don't give up. Let the forum know what signals you are looking for and I am sure you will get help aplenty. If you are definitely looking for VLF signals then there are websites devoted to that pursuit. Take a look at http://www.vlf.it/harald/strangerec.htm or http://abelian.org/vlfrx/ for starters.

      Ray, vk5ugs




      To: loopantennas@yahoogroups.com
      From: mowypt@...
      Date: Fri, 1 Apr 2011 13:25:46 +0000
      Subject: [loopantennas] Re: What type of capacitor is used for loop antenna?




























      Thanks for your reply. Yes, I figured that I need more coil. I don't know, I read somewhere "just add more capacitance" but obviously that only works to a point.



      --- In loopantennas@yahoogroups.com, "longjohn119" <some_oil_with_your_teaparty@...> wrote:

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      > --- In loopantennas@yahoogroups.com, "mowypt" <mowypt@> wrote:

      > >

      > > With the loop I have, 6uf is what I need for below 1KHz and I don't know enough about capacitors. The one I have I guess it's called a "run" capacitor. It says 6uf 450 volts AC. I assume I need a different type of capacitor. Well thanks for your replies.

      > >

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      > You need a loop with more windings/inductance not a big cap. Having a way to measure the actual inductance is very helpful also ....

      >

      > Those run caps do make excellent bipolar caps in speaker crossovers (The + and - marks are for phasing not DC polarity), especially for high power sound reinforcement speakers .... Otherwise not much use for them other than AC motors, if it's got a plastic case it's a start cap limited duty cycle, if it's got a metal case it's a run cap 100% duty cycle. Only the run caps make good crossover (Or AC coupling) caps although their size limits their applications mainly to speakers although I do have a circuit similar to this one by Dallas Lankford only using coil values (Crossover coils oversized that I took windings off of until I reach the desired inductance) tweaked to work with available start cap values. Mine will work on any amp up to 50 watts, you just plug it into a Speaker Out and then plug an external speaker into the filter.

      >

      > Elliptic Low Pass Audio Filters (Used to counter fading distortion on AM)

      > http://www.kongsfjord.no/dl/Audio/ELPAFs.pdf

      >

      > JR

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