oe7drt-website/content/posts/2023/53-i-built-some-ferrite-chokes/index.md

+++
title = 'I built some ferrite chokes'
aliases = '/posts/2023-09-23-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 = '2023-09-23T21:22:14+0200'
#lastmod = ''
categories = [ 'amateur-radio' ]
tags = [ 'diy', 'portable' ]

+++

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:")