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content/posts/2023-09-23-i-built-some-ferrite-chokes/index.md

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+# vim: ft=markdown
+title = 'I built some ferrite chokes'
+summary = '''I built two ferrite chokes and measured them already,
+but I never presented the results to the internet audience :winking_face:'''
+date = '2023-09-23T21:00:11+0200'
+#lastmod = ''
+categories = [ 'amateur-radio' ]
+tags = [ 'diy', 'portable' ]
+
+draft = true
+
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+
+Before we start: there is a short wikipedia article about [Ferrite beads][1]
+that I wanted to share with you. Just in case you are new to the hobby and want
+a quick read about this topic.
+
+[1]: https://en.wikipedia.org/wiki/Ferrite_bead
+
+## Calibrate the nanoVNA(-F)
+
+Going through the calibration process with the full lenght of the used
+adapters. All measurements happen on port S11 except <kbd>ISOLIN</kbd>, where
+we connect both ports together.
+
+1. <kbd>OPEN</kbd>  
+    Leave the cables as they are (open).
+2. <kbd>SHORT</kbd>  
+    Connect the red and black croco clips (shorten the circuit).
+3. <kbd>LOAD</kbd>  
+    Clip a 50&ohm; load to the croco clips (red one to the core, black one to the shielding).
+4. <kbd>ISOLIN</kbd>  
+    Leave the load connected. (Maybe add another one to the second cable on the port S21).
+5. <kbd>THRU</kbd>  
+    Shorten both cables (S11 & S21; red to red, black to black).
+
+
+
+## PL259 socket
+
+This is my selfmade choke for the good old PL259 sockets.
+
+![alt_text](pl259_choke.jpg)
+
+There are **9 turns of RG174** on a **FT-140-43** ferrite core.
+
+Connecting the red croco clip from port S11 to the shield of one PL259 socket
+and the red croco clip from port S21 to the shield of the other PL259 socket.
+Also connect both black croco clips together.
+
+![alt](pl259_measurement.jpg)
+
+I got -30dB at 14.340 MHz and -25dB at 3.610 MHz.
+
+## BNC socket
+
+I made a smaller version with BNC sockets for portable operations as I switched
+my gear to a more lighter setup (which made me use QRP transceivers basically).
+
+![alt](bnc_choke.jpg "The BNC version is basically the same as the PL259 version mentioned above.")
+
+We measure the choke like the first one: connect the core (red croco clips) with
+the choke's shield and shorten the shield of the nanoVNAs ports (black croco clips).
+
+![al](bnc_measurement.jpg)
+
+![al](bnc_nanoVNA.jpg "The first chokes graph looks like the same. My nanoVNA does not
+support saving screenshots, so I use these crappy screen shot :smirking_face:")
+