Electronics World articles Popular Electronics articles QST articles Radio & TV News articles Radio-Craft articles Radio-Electronics articles Short Wave Craft articles Wireless World articles Google Search of RF Cafe website Sitemap Electronics Equations Mathematics Equations Equations physics Manufacturers & distributors Engineer Jobs LinkedIn Crosswords Engineering Humor Kirt's Cogitations RF Engineering Quizzes Notable Quotes Calculators Education Engineering Magazine Articles Engineering software RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Forums Magazine Sponsor RF Cafe RF Electronics Symbols for Visio RF Electronics Symbols for Office Word RF Electronics Stencils for Visio Sponsor Links Saturday Evening Post NEETS EW Radar Handbook Microwave Museum About RF Cafe Aegis Power Systems Anritsu Alliance Test Equipment Amplifier Solutions Anatech Electronics Axiom Test Equipment Berkeley Nucleonics Bittele Centric RF Conduct RF Copper Mountain Technologies Empower RF everything RF Exodus Advanced Communications Innovative Power Products ISOTEC KR Filters Lotus Systems PCB Directory Rigol RF Superstore San Francisco Circuits Reactel RFCT TotalTemp Technologies Triad RF Systems Windfreak Technologies Withwave LadyBug Technologies Wireless Telecom Group Sponsorship Rates RF Cafe Software Resources Vintage Magazines Thank you for visiting RF Cafe!
Copper Mountain Technologies (VNA) - RF Cafe

Non-Reflective, High Power HF harmonic filter wanted - RF Cafe Forums

RF Cafe Forums closed its virtual doors in 2010 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts.

NOTICE: The original RF Cafe Forum is available again for reading, and the new RF Cafe Blog is an active board.

-- Amateur Radio

-- Anecdotes, Gripes, & Humor

-- Antennas

-- CAE, CAD, & Software

-- Circuits & Components

-- Employment & Interviews

-- Miscellany

-- Swap Shop

-- Systems

-- Test & Measurement

-- Webmaster


Post subject: Non-Reflective, High Power HF harmonic filter wanted

Unread postPosted: Sun Feb 13, 2005 10:34 pm

Using MRF154 x2 in a 3-50Mhz, 1KW HF amp. Currently using 7 pole Butterworth LC filters. The reflections, harmonics, from this type of filter slowly smokes the highpower FETs (MRF154). Any ideas on a filter that would block these reflected harmonics from the FETs?

Thanks for any ideas!



Post subject: Filter

Unread postPosted: Wed Feb 16, 2005 8:46 pm

If I understand you correctly, what you need is what's variously called a "branching" filter, a "complementary" filter, or a "dissipative filter". The power that doesn't go out the output port has to go somewhere. Right now, it's reflected back and absorbed by your output stage transistors. The only other place it could go is into a resistive load.

There's a discussion of this kind of filter in the book by Anatol Zverev, "Handbook of Filter Synthesis". It's kind of pricy, but a nearby university library may have it. What you need is only a few pages.

Good Luck!



Post subject: mrf154 filters

Unread postPosted: Wed Mar 16, 2005 9:01 pm

Hi--I am using 7 section, eliptical filters with my mrf154's with no problems. The steeper roll off of the eliptical allows you to move the corner frequency further from the operating frequency and thereby allows you to look into a better impedance at the operating frequency. My 2nd harmonic was down about 55 db and the 3rd was down 15 db with a matched pair of mrf154's without the filters. This allows you to move the corner out even further.

I hope this helps

Posted  11/12/2012

Boonton RF Power Measurement
Lotus Communication Systems Modular RF Component Building Blocks - RF Cafe
Innovative Power Products Passive RF Products - RF Cafe
Innovative Power Products Passive RF Products - RF Cafe
Windfreak Technologies Frequency Synthesizers - RF Cafe

Please Support RF Cafe by purchasing my  ridiculously low−priced products, all of which I created.

These Are Available for Free


About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website: