Anatech Electronics (RF Filters) - RF Cafe
Exodus Advanced Communications Best in Class RF Amplifier SSPAs

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:

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 App Notes Calculators Education Engineering magazine articles Engineering software Engineering smorgasbord RF Cafe Archives RF Cascade Workbook 2018 RF Symbols for Visio - Word Advertising RF Cafe Homepage Thank you for visiting RF Cafe!
Anatech Electronics

Impedance matching attenuator - RF Cafe Forums

RF Cafe Forums closed its virtual doors in 2012 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. If the folks at phpBB would release a version with integrated sign-in from the major social media platforms, I would resurrect the RF Cafe Forums, but until then it is probably not worth the effort. 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.

-- Amateur Radio
-- Anecdotes, Gripes & Humor
-- Antennas
-- CAE, CAD, & Software
-- Circuits & Components
-- Employment & Interviews
-- Miscellany
-- Swap Shop
-- Systems
-- Test & Measurement
-- Webmaster

Post subject: Impedance matching attenuator Posted: Mon Aug 15, 2005 12:02 pm
Hi all,
I'm trying to impedance match a non-50Ohm DUT to a 50Ohm VNA. I've seen an explanation of how to do this using minimum loss pads (see "Spectrum and Network Measurements" by Robert A. Witte), but any commercial attenuators I see are simply rated in dB attenuation. Do I need a special 'impedance match' attenuator, or can I use any which attenuate more than the theoretical minimum loss? Thanks for your help.



Post subject: Posted: Mon Aug 15, 2005 1:03 pm

Site Admin

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hello Brian,

Any resisive element has an attenuation. Therefore, an attenuator that is based on resistors will have an attenuation. This kind of attenuator will decrease (improve) the return loss by 2dB for each dB of attenuation.

The only type of matching networks without loss (theoretical) are reactive matching networks i.e networka that are based on capacitors and inductors. However, practically, these network are lossy due to the Q of its components -especially the inductors.

Hope this helps.

Best regards,

- IR


Post subject: Min loss PadsPosted: Mon Aug 15, 2005 2:58 pm
Yes, you do need special matching attenuators for this task. Most standard attenuators are 50 ohm in and out.

If you are looking to match from 50 to 75 ohms there are some sources out there. I have used a relatively inexpensive source in the past. The insertion loss is 5.7dB. ... ngpads.htm

You can also make your own for any impedance combination using 1 series and 1 shunt resistor.

Min Loss Pad:




K=SQRT(Z1/Z2) + SQRT(Z1/Z2 - 1)



Post subject: Posted: Tue Aug 16, 2005 7:16 am
IR / Joe,
Thanks for the replies.


Posted  11/12/2012
RF Superstore (RF Components) - RF Cafe
Werbel Microwave - RF Cafe
Axiom Test Equipment - RF Cafe

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

These Are Available for Free