Formulas & Data:
- Electronics
- Mathematics
- Physics
- RF & Microwaves

Parts Vendors:
- all hand-selected

- Amateur Radio
- Vintage Articles:
- Electronics World
- Popular Electronics
- Radio & TV News
- Radio Craft
- Short Wave Craft
- Wireless World

- Events Calendar
RF Cafe Homepage
Copyright 1999-2015   •−•  ••−•    −•−•  •−  ••−•  •   "RF Cafe" in Morse Code  >> Listen to It <<
- EW & Radar Handbook
- Quizzes       - Software
- App Notes
- Calculators
- Advertise on RF Cafe
- About RF Cafe™
- RF Cafe Shirts & Mugs
- RF Cafe Archives
RF Cafe Book Contest
- RF Cafe on Visit RF Cafe on Facebook Visit RF Cafe on Twitter Visit RF Cafe on LinkedIn
- Tech Humor
- Forums Archive
- Job Board
- Donate to RF Cafe
- Kirt's Cogitations
Custom Search
More than 10,000 searchable pages indexed.
Greetings: There is so much good stuff on RF Cafe that there is no way to list or link to all of it here. Please use the Search box or the Site Map to find what you want - there is a good chance I have it here. Thanks!

Fast Frequency Measurement - 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: Fast Frequency Measurement Posted: Sat May 20, 2006 12:47 am


Joined: Sat May 20, 2006 12:29 am
Posts: 1
I need to track resonant frequency changes in a resonator. The resonant frequency is about 230 kHz. I would like to measure resonant frequency changes with noise level on the order of 1-5 mHz with a large dynamic range, and I would like to sample this frequency at about 100 Hz or better.

I was wondering if a PLL could help me. Essentially, I would like to take my signal (230kHz), convert it to a voltage proportional to the resonant frequency, so that I can measure this output voltage with a DAQ card. I'm not very competent when it comes to electronics, so it would be great if someone could suggest circuits and components.
Thanks in advance!


Post subject: Posted: Sat Jun 10, 2006 6:07 am


Joined: Fri May 19, 2006 5:01 am
Posts: 25
Location: Netherlands
Hi Tura,

Just a thought, might be silly.. you could heterodyne the drifting 230KHz signal with a PLL'ed 230KHz (the calibration frequency so to speak). If the frequencies differ, their difference frequencies will be produced. This frequency should be so low that it's easily measurable.

Kind regards,


Post subject: Posted: Mon Jun 12, 2006 8:43 am

Site Admin

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

What I woud suggest is simply to use an FM detector. The detector provides a voltage relative to the frequency offset from the carrier (The center frequency of 230kHz in your case). You can adjust the center frequency by means of an inductor and capacitor (Variable). I worked with such an IC 8 years ago in an FM receiver circuit. I am sure that since then there are many new IC's availabel. Simply run a search in Google I am sure you will get up on something.

Good luck!

Best regards,

- IR

Posted  11/12/2012

Your RF Cafe
Progenitor & Webmaster

Click here to read about RF CafeKirt Blattenberger… single-handedly redefining what an engineering website should be.

View the YouTube RF Cafe Intro Video Carpe Diem!
(Seize the Day!)

5th MOB: My USAF radar shop

Airplanes and Rockets: My personal hobby website

Equine Kingdom: My daughter Sally's horse riding website