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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
      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.

      > >

      >

      > 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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