Filters

Filter Types



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QRP Labs' Band Pass Filter kits

QRP Labs' Band Pass Filter kits
QRP Labs' Band Pass Filter kits  https://www.qrp-labs.com/bpfkit.html - HF Filters

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Filters Designed for the Rpi

Simple and Effective Lowpass Filters and Amplifier for Raspberry Pi 2 and 3:
https://www.dk0tu.de/blog/2016/05/28_Raspberry_Pi_Lowpass_Filters

A short guide to harmonic filter for QRP transmitter output [PDF]:
http://www.gqrp.com/harmonic_filters.pdf

RockingD Labs - RF Filter for a Raspberry Pi Transmitter:
http://rockingdlabs.dunmire.org/exercises-experiments/bpf-analysis [Top][Home]

This kit is a daughter board, designed by Jan G0BBL and Tony KB9YIG, that provides four electronically switched band-pass filters for the Softrock Lite + Xtall V9.0 RX, replacing the single-band daughter board in the original design.
HF BPF Project:
https://wb5rvz.com/sdr/hf_bpf/index.htm

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Coils

How to construct a loading coil for 80m
http://blog.templaro.com/a-loading-coil-for-80m/

Coil-Shortened Vertical Antenna Calculator
Coil-Shortened Vertical Antenna Calculator

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Telewave Cavity Filters

A Brief Guide to Telewave’s Cavity Filters:
https://www.telewave.com/2017/07/31/brief-guide-telewaves-cavity-filters/
https://d1jiktx90t87hr.cloudfront.net/185/wp-content/uploads/2016/06/Telewave-Cavity-Tuning-July_2017.pdf

https://pronto-core-cdn.prontomarketing.com/185/wp-content/uploads/2016/06/Telewave-Cavity-Tuning-July_2017.pdf

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Air Cored Coils

This is a theory based introduction to the air cored coil.

http://info.ee.surrey.ac.uk/Workshop/advice/coils/air_coils.html#bsl

Image
Source: http://www.k0bg.com/images/choke/chokechart.jpg

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Cavity Filters

Cavity Filters

What is a Cavity Filter?
Resonant cavity filters are used as building blocks in duplexers, pre and post selector filters, and in receiver and transmitter multicoupling configurations. Individual cavities may also be used for a variety of interference management applications.

Amateur Radio Wiki - Explanation of a cavity filter?:
https://www.amateur-radio-wiki.net/index.php?title=What_is_a_cavity_filter%3F

RFI Technology Cavity Filters:
https://www.rfiwireless.com.au/multicoupling-monitoring/cavity-filters.html

http://www.repeater-builder.com/antenna/pdf/w6nbc-duplexer-book.pdf

Video - Fun with Cavity Filters:
https://www.youtube.com/watch?v=HyCtuviE1bE&fbclid=IwAR2CG6mJ_lT3CgUn1eXXCUYZChfgNvDvyXSycr1cmN6ffVjAzTyOsH-c6dA

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Measuring Cavity Filters with a VNA

https://www.nonstopsystems.com/radio/frank_radio_coax-sw.htm

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Series Combiners

Series Combiner

What is a Series Combiner?
Band Pass and Series Combiner responses are similar; however the Series Combiner is used specifically to provide two distinct and isolated signal paths. One path from a primary input/output to a common feeder line port, which exhibits a the band pass characteristic centred at the resonant frequency of the cavity and the second path from a secondary input / output port to the common feeder line port behaving as a low loss transmission line at frequencies other than the resonant frequency of the cavity.

RFI Technology Combiners:
https://www.rfiwireless.com.au/multicoupling-monitoring/cavity-filters/series-combiner.html

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References

http://www.repeater-builder.com/antenna/ant-sys-index.html

https://www.redclifferadioclub.org.au/images/RDRC%20Cavity%20Filters%20130617.pdf

http://www.hb9amo.net/procom.php

An experimental Coaxial Tank V.H.F. (Bandpass) Filter Designer (Cavity) https://www.changpuak.ch/electronics/Coaxial_Tank_VHF_Filter_Designer.php

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Glenn Lyons VK4PK
glenn@LyonsComputer.com.au
Ver:gnl18042019 - pre published v0.9