66 lines
2.3 KiB
Markdown
66 lines
2.3 KiB
Markdown
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# vim: ft=markdown
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title = 'I built some ferrite chokes'
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summary = '''I built two ferrite chokes and measured them already,
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but I never presented the results to the internet audience :winking_face:'''
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date = '2023-09-23T21:22:14+0200'
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#lastmod = ''
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categories = [ 'amateur-radio' ]
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tags = [ 'diy', 'portable' ]
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Before we start: there is a short wikipedia article about [Ferrite beads][1]
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that I wanted to share with you. Just in case you are new to the hobby and want
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a quick read about this topic.
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[1]: https://en.wikipedia.org/wiki/Ferrite_bead
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## Calibrate the nanoVNA(-F)
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Going through the calibration process with the full lenght of the used
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adapters. All measurements happen on port S11 except <kbd>ISOLIN</kbd>, where
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we connect both ports together.
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1. <kbd>OPEN</kbd>
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Leave the cables as they are (open).
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2. <kbd>SHORT</kbd>
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Connect the red and black croco clips (shorten the circuit).
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3. <kbd>LOAD</kbd>
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Clip a 50Ω load to the croco clips (red one to the core, black one to the shielding).
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4. <kbd>ISOLIN</kbd>
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Leave the load connected. (Maybe add another one to the second cable on the port S21).
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5. <kbd>THRU</kbd>
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Shorten both cables (S11 & S21; red to red, black to black).
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## PL259 socket
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This is my selfmade choke for the good old PL259 sockets.
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There are **9 turns of RG174** on a **FT-140-43** ferrite core.
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Connecting the red croco clip from port S11 to the shield of one PL259 socket
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and the red croco clip from port S21 to the shield of the other PL259 socket.
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Also connect both black croco clips together.
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I got -30dB at 14.340 MHz and -25dB at 3.610 MHz.
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## BNC socket
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I made a smaller version with BNC sockets for portable operations as I switched
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my gear to a more lighter setup (which made me use QRP transceivers basically).
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We measure the choke like the first one: connect the core (red croco clips) with
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the choke's shield and shorten the shield of the nanoVNAs ports (black croco clips).
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