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Amplifier Circuits: 
RF (Radio Frequency)

RF Amplifiers:  #'s - C      D - K        L - R       S - Z

Amplifier -- Main Page
 

Last Updated: November 30, 2017 10:27 AM

Circuits Designed by Dave Johnson, P.E. :
Display RF Signal Strength   -  Many cordless telephones, computer networks and cell phones use a RF transmitter left on the 2.45GHz band.  Using a microwave diode detector and 100uA meter, this passive circuit will display the strength this signal.  The drawing shows how a bent piece of wire can be used as the antenna.   . . . Hobby Circuit designed by David Johnson P.E.-July 09, 2006

DIY Cell Phone Charger   -  it seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme . . . Hobby Circuit designed by David Johnson P.E.-June 04, 2000

Do It Yourself Portable Cell Phone Charger   -  It seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme . . . Circuit by Dave Johnson P.E.-June 04, 2000
Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

DC40-40M Direct Conversion receiver -  Last year my cousin had to submit a class project towards her engineering degree and I suggested that a direct conversion receiver might be a good idea.  This receiver is the result of that project.   Usual construction write-ups only deal with a finished design that is logically explained and the performance is discussed clinically.  Such texts overlook the unpredictable path that an experimenter takes during a project.  The final form is often a result of initial specifications, personal choices, accidents and availability of time and material.   Hence, this article: a journal that follows a receiver's birth.  This receiver was made over several evenings, spending less than an hour each day.   For those real hams who never read the entire articles, I follow my convention of key caveats and some tips. __ Designed by Ashhar Farhan VU2ESE

DDS Controlled ultra high resolution PLL synthesizer / VTXO  -  This DDS driven PLL synthesizer was designed to allow any input reference to be locked to a 20 MHz master crystal oscillator.  This design substitutes two DDS synthesizers for the N and R counters of a standard PLL circuit giving nearly infinite resolution.  Spurious performance is the main concern here as the master reference oscillator cannot have any 'extra' spurs on it after locking to the external source.  Phase noise __ Designed by Steve Hageman

Design an Ultra-Low-Noise S-Band Amplifier -  06/04/12  EDN-Design Ideas Use capacitive reactance to save energy while holding a solenoid in the energized position.   Solenoid loads generally exhibit large hysteresis.  Application of the rated voltage actuates these loads.  Once they are in position, however, you can use a significantly lower voltage to thereafter reliably hold them on.  A lower sustaining voltage results in less heat production and higher efficiency. __ Circuit Design by Jessica MacNeil

Designing RF Probe -  make your self simple and heighly useful RF probe.  An essential tool for every home brewer.  

Digital display & VFO stabiliser -  Digital display & VFO stabiliser using a PIC microcontroller & LCD __ Designed by EI9GQ homebrew radio

Digital wireless for the bench top ATtiny12 -  This section describes an experimental low power, low bandwidth data signaling system that was initially made to operate at 55 MHz (television channel 2 in the U.  S.).  Before operating a radio transmitter, find out what kind of transmitter operation, if any, is permitted in your locality.  Radio transmitter operation is a serious legal matter.  This design __ Designed by Dick Cappels

Direct conversion 7MHz receiver using NE602 -  Schematic only, no circuit description

Direct Conversion Receiver for Radio Amateurs-Part 1 -  It covers from 7-7.3MHz, can tune both morse and SSB signals and reads out the tuned frequency in morse code!__ SiliconChip

Direct Conversion Receiver for Radio Amateurs-Part 2 -  This article has the full construction and alignment details.  We also include tips on using it.__ SiliconChip

Direct Crystal radio receiver examples -  Ham RadioV-U)HF AMPLIFIERSchematic __ Designed by Guy Roels ON6MU

Display RF Signal Strength -  Many cordless telephones, computer networks and cell phones use a RF transmitter lefted on the 2.45GHz band.  Using a microwave diode detector and 100uA meter, this passive circuit will display the strength this signal.  The drawing shows how a bent piece of wire can be used as the antenna. . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

DIY Cell Phone Charger -  It seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme . . . Hobby Circuit designed by David Johnson P.E.-August, 2009

Do It Yourself Portable Cell Phone Charger -  It seems that as cell phones become more sophisticated, their operating times become shorter and shorter.  If you are on the go all the time and have difficulty finding AC or DC outlets to charge your phone, you might consider this simple scheme. . . Circuit by Dave Johnson P.E.-August, 2009

Doodle Labs DL435-30 420-450 MHz OFDM Transceiver Experiments -  Experimenting with high-speed data in the 440 MHz ham band. __ Amateur Radio circuits from Green Bay Professional Packet Radio

Dopler RDF (radio direction finder) -  36 LEDs display; center LED when green = good signal, when red = no signal ,  the direction is frozen to the last good signal.   -   Uses 3 PICs; a PIC16F628A for the display, a PIC18F4520 as the main processor and a PIC12F675 as a frequency divider.   -   Filters; a Max 267, the best bandpass filter that I have ever seen, followed by the Roanoke switch cap filter for very narrow band width (+/- 0.5Hz).   -   My DopplerII integrating and phase detection software in the main PIC.   -   LM386 for monitoring the audio independently from the doppler. __ Designed by Jacques VE2EMM  &  Claude VA2HDD

DSP-RDF Doppler Radio Direction Finder-complete kit available -  This kit is based upon the N0GSG DSP Doppler featured in the November 2002 QST Magazine.  Doppler RDF units determine the bearing to a signal's source by electronically rotating four antennas, arranged in a circular pattern, at a high rate of speed.  The signals received at each antenna are combined and passed on to your FM receiver which is tuned to the frequency of interest.  The FM receiver detects the incoming signal and produces an audio tone which is then passed back to the Doppler unit. __ Designed by W6DFW

Dual 6 to 1, 30 GHz RF switch matrix (Solid State)  -  This dual 6:1 RF switch matrix was built for a RF test system (Test and measurement application).  The four layer PCB was designed with Coplanar waveguide over groundplane and Stripline techniques for very low sensitivity to manufacturing tolerances and very low assembly costs.  One of the key tasks of the design was to carefully characterize the temperature performance of the matrix loss versus temperature so a loss correction versus temperature algorithm could be developed. __ Designed by Steve Hageman

Duplexer coupling loops & how they affect performance -  An analysis of factory-built vs home-built loops, __ Designed by Kevin Custer  W3KKC

Electronic Eavesdropping Devices Detector -  Copyright of this circuit belongs to smart kit electronics.  In this page we will use this circuit to discuss for improvements and we will introduce some changes based on original schematic. __ Contact: IQ Technologies

Electronics enclosure heater -  This is one of the more "Unique" designs that I have had the pleasure of doing.  The client needed to keep an outdoor electronics enclosure from freezing during those long, cold winter nights in Fargo, ND.  Originally silicone based heaters were to be used but the unregulated input power supply of 18-56 VDC would have meant that the heating rate would change by 100:1 from low line to high line input __ Designed by Steve Hageman

Enhance Week QRP CW with Stereo Processing -  One of the biggest problems encountered when engaged in QSO with QRP stations is the weak signal strengths encountered.  QRM and adjacent "QRO" stations can completely obliterate the weaker stations making them impossible to copy.  But there is another "trick" we can use to "fish" the weaker stations out of the noise.  Use our own sense of STEREO hearing. __ Designed by Harry Lythall-SM0VPO

Exciter for SSB Tranceiver -  Now that people are getting married, and having babies on the internet, isn't it about time someone designed and built an SSB rig on the net?.  The rig will be built up from various modules, starting with the SSB exciter board.  The first prototype board has been built and tested on the bench but not on air.  The resulting SSB signal looks good on the scope, and sounds ok on a monitor receiver. __ Designed by EI9GQ homebrew radio

Experimental DSB/CW QRP rig for 20 & 40 meter bands -  The building of an HF phone rig today isn't shurely a simple job, however I'd like to propose an easytomake project, suited for portable or emergency use.  As usual, some compromise must be accepted.  Let's briefly consider good and bad points. __ Designed by Francesco Morgantini IK3OIL

Experiments with Detector Diodes -  When building crystal radios or other simple receivers, the experimenter often wonders about the relative performance of the different diodes in the junk box.  Here are the results of several experiments using the typical. __ Contact: Charles Wenzel of Wenzel Associates, Inc.

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RF (Radio Frequency) Amplifiers:  #'s - C      D - K        L - R       S - Z


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