Time Radio Signal Antenna Design 40kHz JJY, 60kHz WWVB, 75.5kHz DCF77...

Discussion in 'Wireless & RF Design' started by markmain, Sep 17, 2014.

  1. markmain

    Thread Starter Member

    Dec 28, 2008
    13
    0
    I would like some helpful advice to make my own 60kHz antenna for the WWVB atomic clock signal here in the US; however it would be nice if discussion was inclusive for other frequencies used in other world clocks. I've done a fair bit of research and the problem quickly becomes information overload because you can't tell what is good advice.

    Ferrite Rod Antennas. What are good design rules to follow when making a ferrite rod antenna? Please correct me if I'm wrong, after looking over the Fair-Rite specs, for the low frequencies 200kHz and below, it seems that material type 98 is the very best choice if kept at room temperatures (not subjected above 50C) and assuming you can find some of it (I can't find a distributor who sells it), and material 78 is another great choice and perhaps more readily found. Material type 77 has a maximum useful range up to 100kHz and just a bit more loss than material 78. These seem like the best choices other than perhaps material 95 and 97 where I can't find a distribution source for either of them as well.

    Is a bigger diameter better? Always? Is there a diminishing return as the diameter gets larger (e.g. resistance increases rapidly)? I read the antenna only works well if the rod length is 5 to 30 times the diameter size, and that the best results are found between 10 and 25--i would like to confirm this and understand what is optimal. Is optimal 17.5x? close to 20x? I learned from this link here that you can glue small lengths of ferrite rods together end-to-end and get nearly the same performance as a single piece with the same length.

    Litz wire seems to be best, but what are the trade-offs with various gauge sizes? What formulas do we use to optimize the winding design? Also, bank winding seems to be highly praised but I did not understand what design parameters are used to optimize the design; e.g. can we bank 5 or 6 layers high? 10? when is there diminishing return?

    Square Loop Antennas. They seem to be powerful if designed correctly, size is one of downfalls, but what are good design rules for them? Can I make a rectangle loop?... a circle, triangle or other shapes? What shapes would not work (e.g. I suppose a figure 8 would be bad).Are there any shapes that make an antenna more directional to maximize pointing them correctly toward the source? This link is a software tool to help with the windings and this link talks about building a square loop antenna.

    Balanced Design. Section 1.2 on the C-Max site shows how to balance the antenna (see 1.2c). I've read this site, but for someone learning this does not speak to the beginner enough to help out.

    Other Links. This is a schematic to make a sensitive receiver.
    Some good information here about building a WWVB receiver.

    Help. I have read a lot, but would appreciate some coaching on what the best design practices are to build a strong antenna. I live in Fort Lauderdale, FL and so receiving the signal from Denver is more of a challenge here. Thanks you in advance for your help.

    Mark
     
    Last edited: Sep 17, 2014
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    the loop antennas are used to null out interference, power line noise and such. a square, triangular or circular are normally used, a figure 8 never. google "elf antenna" for designs. also, there are a few ideas for this on this page.
    http://www.techlib.com/
     
    Last edited: Sep 19, 2014
  3. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
    2,040
    287
    You'll definitely want to use a ferrite core antenna for this....air frame loops would require too much wire!
    For receiving, you just want as much permeability as you can get, so get the material with the highest value. Diameter is not too much of an issue, except you can get more wire in a smaller length coil. You'll definitely need to tap the coil for the different bands, as this antenna will be NARROW! But always go for the largest L/C ratio for best performance.

    ERic
     
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