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High Frequency Choke for Bitx40

 

Hello

I'm planning to do the filtering mods for the Bitx40 described here.



The only question I have is what sort of toroid I should get.? The notes mention a High Frequency Choke, but I don't really know what that is.? Various websites mention chokes using different mixes for optimal operation at different frequencies.? Which one should I go for?? What frequency range do I need for this?

Craig (VE6TBW)
 

I think you are looking for something like this.

For fun use the calculator on that page, enter?160 or higher bands in MHz ?along with the 12 turns of wire you link shows. Compare results with the other ferites (ones beginning with "F") to the other toroids beginning with "T".
Also, you may find something suitable in an old computer power supply if you have a bad one laying around.
Tom KF5NWC
 

Here's the simple calculator I've been using.??
 

Thank you for the links to the calculators.? The part I don't understand is what frequency range I'm trying to filter.? The choke that Akira JJ1EPE calls for goes in the power supply line for the Raduino.? What frequencies or type of interference is it meant to block???
 

Just a hobbyist here so keep that in mind. The link I sent previously is to what could be similar to the toroid in question, no guarentees. The link has the application notes for that toroid which lists:
RFI Suppression 5 - 500 MHz
That should be its application as a choke. If you look at the other items on that page you will see different applications noted for each with its performance characteristics in that role.
Tom
KF5NWC
 

Here's my obligatory "I'm no expert, but.." statement.? ?I'm no expert but I bet what's being done here is an "LC" filter or "Inductance / Capacitance" filter.? Or perhaps an enhancement of the existing one.? This circuit is commonly used to smooth out ripples and other such nasties in A/C or varying D/C current.? The choke filters out higher frequencies above some certain value, and the capacitor allows lower frequencies that you want thru and smooths them out.

Here's a pretty well written overview.

http://www.learnabout-electronics.org/PSU/psu12.php
 

Wow...I just read my description above and it's pretty bad!? ?But the link is really good :)
 

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The learning module referenced is an excellent source for ALL electronics theory. ?Add it to your home page. ?This winter when it is too nasty to go outside and you are tired of making contacts you can sit by the fire and update your electronics knowledge.?


Thanks to DaveT.

Dave K8WPE

On Oct 13, 2018, at 7:11 PM, davedt1e@... wrote:

Here's my obligatory "I'm no expert, but.." statement.? ?I'm no expert but I bet what's being done here is an "LC" filter or "Inductance / Capacitance" filter.? Or perhaps an enhancement of the existing one.? This circuit is commonly used to smooth out ripples and other such nasties in A/C or varying D/C current.? The choke filters out higher frequencies above some certain value, and the capacitor allows lower frequencies that you want thru and smooths them out.

Here's a pretty well written overview.

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