75 Meter SSB Transceiver
 
75 Meter SSB Transceiver


 

75 Meter SSB Transceiver

 


Here's 75 Meter QRP SSB Transceiver. In general, the transceiver switches the 4-element 1500 ohm xtal BPF ends between the inputs and outputs of the two SA602s to reverse the signal flow for R/T operation. Since no IF amplifier is used in the design, 20 dB of additional receiver gain is produced by the 2N2222 receiver RF amplifier, while automatic gain control (AGC) is produced by the peak DC swing of the LM386 output passed through a rectifier and filtered by a capacitor and fed to the gate of a BS170 enhancement mode FET acting as a variable resistor across the input of the LM386. Both receive and transmit band pass filtering are done by the same half-pi BPF. The diode pair in the mic circuit reduce the "chirp" that occurs during the R/T transition. Additional BS170s could easily be used to mute both the mic and audio instead of the R/T switch directly. These BS170s would be controlled by the +R and +T voltages on their gates while their drains would be tied to 1) the mic circuit between the two coupling capacitors and 2) pin number 1 (audio in) of the LM386 (BS170 sources to ground). Additional power output (perhaps 60 mW) could also be attained by connecting the RF output transistor's collector choke (10 uH) to a 9 V supply instead of the 5 V. Additional biasing current might also be required for this change.


75 Meter SSB Transceiver

The R/T switches are from Radio Shack and are of the slider-type with silver plated brass connectors. I removed the detent springs from two of them and weakened the third. I then drilled holes through the switches' handles to connect them with a piece of tempered copper-plated steel wire. The switches are marked on their sides with the word "ALPHA." Low current-drain type DPDT relays (10 to 12 mA @ 12 V) could also be used in place of the switches. I used switches to reduce transmit current, and they work very smoothly.

The intent of this design was to minimize the parts count (about 85) and size, reduce power consumption (17 mA receive and 40 mA transmit), run on a 9 V battery, be self contained (except for antenna), have good rejection of unwanted signals, have good sensitivity and selectivity, and have automatic gain control (AGC)--with enough parts left over to build another rig. Finally, the variable tuning capacitor of the local oscillator (LO) could be replaced with a varactor diode circuit.

The home brewer should be able to build this transceiver in a "week of evenings," if all of the parts are available. Should a commercial circuit board version be developed, the circuit could easily be completed in one evening! Good luck with your project.

Receiver:
50 ohm antenna feeds half-pi band pass filter (BPF, element Q=5) which feeds receive-transmit (R/T) switch which feeds 2N2222 receive RF amplifier which feeds 1st SA602 which feeds R/T switch which feeds 4-element 1500 ohm xtal BPF which feeds R/T switch which feeds 2nd SA602 which feeds LM386 which feeds 1) diode which feeds capacitor which feeds gate of BS170 which produces audio automatic gain control (AGC) and 2) speaker attenuator which feeds speaker.

Transmitter:
Mic feeds 2nd SA602 which feeds R/T switch which feeds 4-element 1500 ohm xtal BPF which feeds R/T switch which feeds 1st SA602 which feeds LC BPF (Q=15) which feeds emitter follower (2N2222) which feeds final (2N2222) which feeds half-pi BPF (element Q=5) which feeds 50 ohm antenna.

Below. 2 views of the transceiver prior to final wiring. The layout is impeccable.

QRP SWR Meter With LED Indicator

Above, a schematic diagram for a broadband QRP SWR metering circuit for use in a QRP antenna tuner. One could simply hold a momentary DPDT switch down and watch the LED while tuning the capacitors of the antenna tuner for minimum or zero light.

QRP Filter Design Software

These are the two synthesis programs that were written to design the xtal and band pass filters for the QRP transceiver. These might be useful for anyone who wants to build the transceiver for different IF and output frequencies. The seperate files can be downloaded as individual exe files or combined in one zip file. These programs are DOS applications and are 36-42 KB file size.

Crystal Ladder Sweep Analysis Application

Band pass Filter Sweep Analysis Application

Both Applications In A Compressed Zip File
Phasing Exciter for 75 Meter SSB

Above and below; the schematic and the outcome project in a complete transceiver.

Three Frequency Crystal Marker

EMF Field Intensity Meter


75 Meter SSB Transceiver


75 Meter SSB Transceiver


75 Meter SSB Transceiver

75 Meter SSB Transceiver

75 Meter SSB Transceiver

75 Meter SSB Transceiver

75 Meter SSB Transceiver

75 Meter SSB Transceiver

75 Meter SSB Transceiver




Accurate LC Meter Capacitance Inductance Meter with 16F628 and LCD
Volt Ampere Meter with 16F876 Microcontroller and LCD display
 
Accurate LC Meter

Build your own Accurate LC Meter (Capacitance Inductance Meter) and start making your own coils and inductors. This LC Meter allows to measure incredibly small inductances making it perfect tool for making all types of RF coils and inductors. LC Meter can measure inductances starting from 10nH - 1000nH, 1uH - 1000uH, 1mH - 100mH and capacitances from 0.1pF up to 900nF. The circuit includes an auto ranging as well as reset switch and produces very accurate and stable readings.
PIC Volt Ampere Meter

Volt Ampere Meter measures voltage of 0-70V or 0-500V with 100mV resolution and current consumption 0-10A or more with 10mA resolution. The meter is a perfect addition to any power supply, battery chargers and other electronic projects where voltage and current must be monitored. The meter uses PIC16F876A microcontroller with 16x2 backlighted LCD.

50MHz 60MHz Frequency Meter / Counter with 16F628 & LCD
1Hz - 2MHz XR2206 Function Generator
60MHz Frequency Meter / Counter

Frequency Meter / Counter measures frequency from 10Hz to 60MHz with 10Hz resolution. It is a very useful bench test equipment for testing and finding out the frequency of various devices with unknown frequency such as oscillators, radio receivers, transmitters, function generators, crystals, etc.
1Hz - 2MHz XR2206 Function Generator

1Hz - 2MHz XR2206 Function Generator produces high quality sine, square and triangle waveforms of high-stability and accuracy. The output waveforms can be both amplitude and frequency modulated. Output of 1Hz - 2MHz XR2206 Function Generator can be connected directly to 60MHz Counter for setting precise frequency output.

BA1404 HI-FI Stereo FM Transmitter
USB IO Board PIC18F2455 / PIC18F2550
BA1404 HI-FI Stereo FM Transmitter

Be "On Air" with your own radio station! BA1404 HI-FI Stereo FM Transmitter broadcasts high quality stereo signal in 88MHz - 108MHz FM band. It can be connected to any type of stereo audio source such as iPod, Computer, Laptop, CD Player, Walkman, Television, Satellite Receiver, Tape Deck or other stereo system to transmit stereo sound with excellent clarity throughout your home, office, yard or camp ground.
USB IO Board

USB IO Board is a tiny spectacular little development board / parallel port replacement featuring PIC18F2455/PIC18F2550 microcontroller. USB IO Board is compatible with Windows / Mac OSX / Linux computers. When attached to Windows IO board will show up as RS232 COM port. You can control 16 individual microcontroller I/O pins by sending simple serial commands. USB IO Board is self-powered by USB port and can provide up to 500mA for electronic projects. USB IO Board is breadboard compatible.

RF Remote Control 433MHz Four Channel
100m 4-Channel 433MHz Wireless RF Remote Control
 
200m 4-Channel 433MHz Wireless RF Remote Control

Having the ability to control various appliances inside or outside of your house wirelessly is a huge convenience, and can make your life much easier and fun. RF remote control provides long range of up to 200m / 650ft and can find many uses for controlling different devices, and it works even through the walls. You can control lights, fans, AC system, computer, printer, amplifier, robots, garage door, security systems, motor-driven curtains, motorized window blinds, door locks, sprinklers, motorized projection screens and anything else you can think of.
100m 4-Channel 433MHz Wireless RF Remote Control

Four button RF remote is used to turn ON / OFF four different devices independently. Any of the four outputs can be configured to work independently in either toggle or momentary mode. Outputs are buffered by BC549 NPN transistors and can drive low voltage devices directly or be connected to either 5V or 12V relays (or motors) to control appliances that use 110V / 220V mains voltage or any voltage of your choice. Multiple remote systems can be used independently to control more than four appliances in the same location by changing the address code on 433MHz receiver and remote. It is also possible to use several remotes to control the same appliance such as garage door.
 

Electronics-DIY.com © 2002-2014. All Rights Reserved.