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cavity filter - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.

Post subject: cavity filter
Unread postPosted: Wed Feb 11, 2004 1:40 am

I am a RF engineer and I'd like to implement narrow cavity filters for catv.
bandpass examples are 62.25MHz, 399.25MHz and 793.25MHz which must reject 25dB 7MHz apart of these pilot carriers.
notch examples are same frequencies but also 7MHz wide to suppress a TV channel.
I am using Eagleware softwares.
I don't understand the mechanical part of implementing a cavity filter (dimensions, how to hold the vertical coils, how to fix the tuning screws,...)
I have found the Zverev old book but it is no as clear for a beginner in this field.

Can somebody help me ?



Post subject: cavity filter
Unread postPosted: Fri Feb 13, 2004 2:47 pm

Welcome to Forum!

RF Cavity filters like any other filters (passive or active) require experience, but you are moving in the right direction here. There are some many technical issues to discuss in order to accomplish this design. Before, I help you design (if you want me to help) these cavities, you must provide some critical information such as: Max RF output power, Max Insertion Loss (desirable), Is there Max Time Delay and Phase Linear requirement (remember you are dealing with video and audio)? ...These are high Q coaxial cavities. Size, loop setting, critical coaxial cable length...etc are very critical to know in order to design these cavities. For 62.25MHz, it is not going to be that small and customized rack mounting panel will be required! As for 399.25MHz and 793.25MHz, you will be able to fit them into standard 19” rack mounting panel. Again, you will have to decide on rack mounting panel. For your information, if you choose round or square cavity, it will not make any difference as far the performance goes! In order to give you an exact answer on electrical & mechanical specs, I suggest you contact me via email at or and I will be keen to help you.

John Pereira


Post subject: cavity filter
Unread postPosted: Fri Feb 13, 2004 8:37 pm

Hi Marc,

I understand you want to design these cavity filters. As an alternative and in case you would like to buy them there are many CATV (cable tv) filters manufacturing around the world. Following are some companies:

John Pereira

Posted  11/12/2012

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