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Old 07-13-2016, 01:12 AM
Jeff Pearson Jeff Pearson is offline
Senior Member
Join Date: Jan 2012
Location: Taos NM
Posts: 186
CRI coil for 1340Khz Kvot

Corrected 1/4 wavelength= 142.25 ft.
using .7752 correction factor. 102% velocity factor X 76% burden factor.
I avoided all rounding till the end
Length per turn= 85.35 inches
At this point I figured for an octagon instead of a circle since my coil form is an octagon and I'm trying to be as accurate as possible so I calculated 10.67 inches per facet of octagon
Diameter of circle would be 27.18 inches
Height= 5.44 inches

The tuning seems to be right on. With topload and ground connected I can hear the radio station clearly through a regular crystal detector consisting of a germanium diode, demodulation capacitor, load resistor and crystal earpiece. It makes noise but unintelligable with no ground or top load.
At the moment the detector is connected across the secondary. I put together a simple amplifier using a LM386 IC driving a piezo element.
With the amplifier 1340Khz comes in clear with the secondary connected to nothing. When I add the top load the signal gets a little bit stronger and when I connect the ground the signal gets a lot stronger. I have tuned it up to 1510Khz by tapping the top load at the 16th or 17th turn. And I have accidentally tuned it down to 950Khz by adding a long ground wire one day when I didn't want to carry it out to the ground rod.
That's what I have done for testing so far. Oh and I did put a temporary primary on it with variable capacitor. There is a sweet spot where it raises the power of the secondary. Getting ready to rewind the whole thing. I am happy with the frame. More appropriate wire for the secondary and some 4 inch wide copper flashing for the primary coming soon.

Great Looking coil Leebob.
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