Powdered Iron core selection criteria for Low Pass Filter (LPF) - Page 1
Forum section: electronics / rf-microwave

author: VK4KYT
author_rank: Newbie
timestamp: October 09, 2024, 07:31:37 am
content: Hi all,I'm planning on building a 600w HF linear amplifier. As part of that process I will need a low pass filter setup for each band.In terms of the filters themselves, most bands will have a 7th order Chebyshev filter utilising 3 series inductors and 4 shunt capacitors.I've got the values of the components identified, however I am learning that the process of selecting appropriate core sizes and materials is an art all on its own.Apart from the maths side of things (flux density etc) has anyone got any additional criteria that they use to determine core size and material types?

author: radiolistener
author_rank: Super Contributor
timestamp: October 09, 2024, 07:41:45 am
content: Amidon provided an application note for calculating the required core volume based on the current through the winding. The amplitude can be estimated in a simulator by applying the appropriate power to the filter's input, with its output loaded by a resistor.Without complex calculations, you can simply evaluate the core by checking its heating in your circuit.

author: Andy Chee
author_rank: Super Contributor
timestamp: October 09, 2024, 11:52:37 am
content: Tube final or MOSFET?

author: VK4KYT
author_rank: Newbie
timestamp: October 13, 2024, 09:52:29 am
content: Quote from: Andy Chee on October 09, 2024, 11:52:37 amIt will be a MOSFET amplifier ... MRF300s in a push pull configuration.

author: VK4KYT
author_rank: Newbie
timestamp: October 13, 2024, 10:00:32 am
content: Quote from: radiolistener on October 09, 2024, 07:41:45 amok, I have already calculated the current for each configuration of core size and material type ... but having also already calculated the flux density for each scenario; wouldn't it follow that heat generated would be proportional to the fulux density ... therefore the smaller that number, the cooler the operation?That being the case, the secondary considerations are core size, and along with that, the practicality of the number of windings required to achieve the inductance. (a small core would not be able to easily cater for a huge number of turns)I think I have all bases covered ... what do you think?

author: radiolistener
author_rank: Super Contributor
timestamp: October 13, 2024, 01:25:29 pm
content: here is some article about it:https://www.bytemark.com/products/powercon.htmhttps://www.bytemark.com/products/ipmatsat.htmhttps://www.bytemark.com/products/iplschr.htmhttps://www.bytemark.com/products/acvolt.htmhttps://www.bytemark.com/products/accurr.htmhttps://www.bytemark.com/products/powdiss.htmhttps://www.bytemark.com/products/propcht.htmhttps://www.bytemark.com/products/ipmaterl.htmhttps://www.bytemark.com/products/qcurv01.htm

author: iMo
author_rank: Super Contributor
timestamp: October 13, 2024, 02:29:50 pm
content: T94 or T106 powdered iron cores (with up to 2uH and 4Amp_rms) might be ok, imho..

author: VK4KYT
author_rank: Newbie
timestamp: October 14, 2024, 07:30:26 am
content: Quote from: iMo on October 13, 2024, 02:29:50 pmThe selection will depend on frequency, subject to saturation,flux density, and core material selected.Are you talking about type 2, 6, 7, 10 materials, and at what frequency? There is a significant number of variables to consider and an opinion based on size along falls short ... sorry to be blunt.But thank you for your interest and input.

author: VK4KYT
author_rank: Newbie
timestamp: October 14, 2024, 07:32:38 am
content: Quote from: radiolistener on October 13, 2024, 01:25:29 pmThank you ... a brief look, and these seem quite informative.Cheers

author: Andy Chee
author_rank: Super Contributor
timestamp: October 14, 2024, 07:48:18 am
content: Micrometals is another goto site for powdered iron design tools and application info.https://micrometals.com/

author: VK4KYT
author_rank: Newbie
timestamp: October 14, 2024, 10:03:28 am
content: Quote from: radiolistener on October 13, 2024, 01:25:29 pm

author: iMo
author_rank: Super Contributor
timestamp: October 14, 2024, 12:40:02 pm
content: Quote from: VK4KYT on October 14, 2024, 07:30:26 amTell me what frequency and what inductance and I will tell you which material and size..73