[time-nuts] Re: WWVB Loopstick Antenna Project

[paul swed]

The header seems to say the application. A wwvb antenna.
If you look in any of the simple cheap atomic clocks you will find a rod
about 2-3" long.
Typically a resonating cap right on the antenna for 60 KHz. These work well
enough to receive wwvb at night when the signals much stronger than during
the day.
As insight near Boston 60 uv day and last night 1500 uv on a 5' loop tuned
for 100 KHz not wwvb. The 10' square loop is something like 200/10,000 uv.
Honest. Not every night but many of them. I have used bundled rods for a
number of years but the square loops are better. More importantly no
ferrite was ever harmed in building them.... So that must mean the square
loops are more green. Right?
OK sorry went of topic.
all things are a tradeoff. Large loops are hard to install and then manage
over time. Especially when a large branch crashes through the loop after 5
years. Thats why at 100 KHz I went to a 5' loop. Less of a target.
Whats nice about the rods are they really are pretty small.
Regards
Paul
WB8TSL

On Sun, Sep 11, 2022 at 12:08 AM glen english LIST via time-nuts <
time-nuts at lists.febo.com> wrote:

> The referred article by Richard Q. Marris is a good one but liekly mass
> overkill for this application.
>
> Seek a rod that is good at the 125kHz RFID frequency. Type material 78
> comes to mind,  but almost any Manganese Zinc Ferrite is going to work.
>
> Although they'll probably be fairly small . All the higher frequency
> rods will be fine on losses but have low perm and need lots of turns.
> Something with an initial permeability of at least 2000 will be suitable.
>
> greater Length/Diameter will increase mu-rod. 6" x 3/8" sounds good.
>
> You might not need that much rod, I dont know what the field strengths
> are (does anyone know) but something like this might be suitable  :
>
> https://www.fair-rite.com/product/antennarfid-rods-3078990901/
>
> a ferrite rod is not necessary if you have space... if this is a fixed
> application,  many turns around a foot square will be just as
> effective.  No need for a ferrite rod.
>
> Suggest electrostatic shield and balanced  feed for the wire , coreless
> loop.
>
> For a small ferrite  rod, put the rod length wise in a deep aluminium
> channel section.
>
> It's certainly easier to build a ES shielded small rod than a loop.
>
> -glen
>
>
>
> On 11/09/2022 12:38 pm, Lux, Jim via time-nuts wrote:
> > On 9/10/22 7:59 AM, D. Resor via time-nuts wrote:
> >> I exploring the parts needed to construct this particular VLF Loop Stick
> >> Antenna by Richard Q. Marris G2BZQ.
> >>
> >> I have uploaded the article to my DropBox Account here:
> >>
> >>
> https://www.dropbox.com/s/niv64xqmghu76z3/1_1201157_4_Ultima_loopstick_VLF_a
> >>
> >> ntenna.pdf?dl=0
> >>
> >> The project explains you should use 9.5mm (3/8") Diameter X 15cm (6")
> >> Length
> >> Ferrite rods.
> >>
> >> The closest I have been able to find are 10mm (0.393") Diameter X 160mm
> >> (6.299) Length.
> >>
> >> Will it make much of a difference?
> >>
> >> Thank You
> >>
> >> Don Resor
> >
> >
> > Not much difference.. the diameter 0.375 vs 0.393 isn't much. Length
> > doesn't much matter, as long as the windings fit.
> >
> > A bigger issue might be the permeability of the rod.
> >
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>
> --
> Glen English
> RF Communications and Electronics Engineer
>
> CORTEX RF
>
> Pacific Media Technologies Pty Ltd trading as Cortex RF
>
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>
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