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!

Debugging a bug - crystal controlled - have you met one? - 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: Debugging a bug - crystal controlled - have you met one? Posted: Mon Feb 05, 2007 6:45 pm


Joined: Sun Apr 30, 2006 2:22 am

Posts: 1

I have several UHF "bugs" and I wish to understand several things:

All the bugs I have work on the 433MHz band. SMD components.

Several use a simple metallic case crystal, U49, and several use SMD, and I suppose they work on the third overtone and then doubled, meaning I think the crystals are around 87MHz. The SMD ones have 4 "legs" - no idea which kind of crystal is this one, or it may be even an oscillator. I cannot debug it to know which kind of device is it. I need your help, maybe someone may know this device: 4 legs - one from each side, black, about 6mmx4mm. All I could do is to measure the frequency with a counter - at 3 legs it shows me 433.9MHz - but I'm not 100% sure it's not inductance from the PCB. I'll be very thankful for any help - maybe a link to similar device.

It confuses me very much, as it is written 480 - no doubt, but it works on 433.9MHz - so it has no sense. As it uses only 3 transistors and 1 diode - which I guess it's a varicap (maibe a PIN diode), it's a "miracle"... 2 AF transistors and one (the one which you can see at the end of the PCB - and it's "deleted" or in any way I cannot read what is written on it) - I suppose it's an RF amp....

It doesn't make me any sense...





Post subject: Posted: Thu Feb 08, 2007 10:50 am


Circuits & Components Forum 13

Joined: Tue Dec 26, 2006 5:39 pm

Posts: 10

That circuit is quite simple. If you would provide us with a schematic, I am sure that some reader could tell you everything you need to know.

Are finding these transmitters in actual service? I mean have you found them in someone's office or laboratory ? If so, I would be investigating the laws concerning industrial espionage in your locale.

Does this unit operate FM or AM ?



Post subject: BugPosted: Thu Feb 08, 2007 1:24 pm


Joined: Wed Feb 22, 2006 3:51 pm

Posts: 104


I'd bet that the 4-terminal block is a SAW-stabilized oscillator. That might give you something to Google on.

Good luck!


Posted  11/12/2012

RF Cascade Workbook 2018 - RF Cafe
Amplifier Solutions Corporation (ASC) - RF Cafe
Windfreak Technologies Frequency Synthesizers - RF Cafe
Innovative Power Products Passive RF Products - RF Cafe
RF Cascade Workbook 2018 by 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: