30 Meter QRP Transmitter for Morse Code - This transmitters' intended purpose is for morse-code only in30 meter
band (Tony van Roon's 10Mhz). It is a low-power QRP type and needs to be connected to your existing tranceiver.
harmonic rejections onprototype were measured at 40dB on 20Mhz and 50dB on 30Mhz. . . [Tony van Roon's circuit]
300 MHz Prescaler - A preamp that drives the CMOS counter input and a divide by 10 prescaler
to extend the range of A Little More Serious Frequency Meter. The MCT10280 prescaler can be set to divide by 80,
40, 20, or 10, as a function of which pins are tied to the power supply. I set this one to divide by 10 since it
is adequate for my needs, and the mental calculation of multiplying the meter reading by 10 is not taxing. One
problem with the MCT10280 is that if it doesn't have an adequate input, the output is very noisy, which shows up
as counts in the couple MHz range on the frequency meter. This noise shows up if the signal amplitude the signal
frequency is too low. For this reason, I only intend to use the prescaler with inputs between 10 MHz and 300 MHz.
. . [Designer's name not included]
TRANSMITTER with 32kHz Crystal - We
have covered 27MHz (and 49MHz) links on P1 and P2 of this article and shown how to produce a simple circuit (or
buy a toy for less than $10. 00) and get 4 or 5 channels.
We also showed how to produce on/off from a single channel and how to detect 27MHz with a Field Strength Meter. .
. [Collin Mitchell's web site]
30W VHF FM Amplifier for
88-108 MHz with BLF245 MOSFET - The
achievement of this 30-watt amplifier has been designed to take place on a heatsink microprocessor PC equipped
with its fans, the advantage of this method of cooling has been selected for the fact that (French . . .
350W QRO with GK71 for 160-15m - Schematic only, no circuit description. . . [© 2001 - YO5OFH, Csaba
3Khz Filter +
Audio Amplifier - This circuit is
the audio amp section for a complete optical transmitter. The circuit amplifies and filters the voice audio
signals from an electret microphone. The circuit is described in more detail in . . . [Hobby Circuit designed by
David A. Johnson P.E., 06/04/00]
3m 100 MHz small bug - . . .
3V FM Transmitter for 88MHz to
108MHz - The important part of the
circuit is formed of the Colpitts type oscillator. C3, C4, C5, C6, CD1-CD2 and L1 determines the frequency. BF982
and dual gate MOSFET are active parts in oscillator. When the input impedance of the MOSFET gate inputs are high,
LC tank is not affected. However transistors force the LC tank and cause phase shift. Two driver stages are added
to isolate the antenna from oscillator. First stage (BF199) amplifies the low signal of the oscillator and works
as a constant load. The second stage (BFR90) amplifies the signal going through the antenna some more. . . .
3W FM Transmitter - This is the schematic for an FM transmitter with 3 to 3.5 W output power
that can be used between 90 and 110 MHz. Although the stability isn't so bad, a PLL can be used on this circuit.
This is a circuit that I've build a few years ago for a friend, who used it in combination with the BLY88
amplifier to obtain 20 W output power. From the notes that I made at the original schematic, it worked fine with
a SWR of 1 : 1. 05 (quite normal at my place with my antenna). . . . [Circuit designed by Aaron Cake]
4 channel 433MHz remote control transmitter /
receiver based on SM5162 and SM5172 chips - The radio control uses pre-calibrated 433 MHz transmitter and receiver
modules. The SM 5162 presents a code to the transmitter module depending on the status of the input switches. The
555 is configured to provide a regular pulse to the 'transmit enable' (pin 15) of the SM 5162 - this pulse runs
at a frequency of about 7 Hz (the LED will flash with each transmission). This means that the transmitter will
update the code transmitted 7 times a second. . . . [CdS Electronic's website]
4 Transistor Transmitter - This circuit provides an FM modulated signal with an output power of
around 500mW. The input Mic preamp is built around a couple of 2N3904 transistors, audio gain limited by the 5k
preset. The oscillator is a colpitts stage, frequency of oscillation governed by the tank circuit made from two
5pF capacitors and the inductor. . . [Design by Paul K Sher[by]
40 Meter, 5 Watt QRP Transmitter - As ham operators, we like to broaden our horizons by trying something
new. There is nothing more satisfying about this hobby than building your own transmitter. The circuit in figure
1 is a crystal controlled CW transmitter with at least 5 watts of power. (The prototype generated 7 ˝ watts) This
circuit was built on a Radio Shack universal board (276-168B) and worked extremely well the first time. . .
[Radio Amateur Society of Norwich]
40 Watt Amplifier for FM Broadcast - This amplifier was built based on Marconi's website, A Design for a 40W
broadband VHF RF Power Amplifier for FM broadcast. A few minor tweaks were made to the schematic and a few parts
were changed to what I had available (mostly surface mount components). The heatsink is from an old Motorola
Mostar 800 MHz radio, and has the perfect heatsink island to match the MRF171A. . . [designer's name not found
on the website]
400mW VCO FM transmitter - With good antenna (dipole placed outdoor and high) the transmitter has
very good coverage range about 500 meters, the maximal coverage range is up to 4 km. . . .
40W broadband VHF RF Power Amplifier for
FM broadcast - To boost the output
power of low power FM broadcast band exciters, a number of these are available commercially, both as kits and
ready made. . . .
Digital-to-Process Current Transmitter
- AN-21 Analog Devices App Note - Describes a 3 I. C. Digital to 4-20 mA Current Output Circuit (DAC08, REF01
and OP221) . . .
432 MHz kilowatt Amplifier - Schematic only, no circuit description. . . [by W1QWS]
434MHz short-range communications - article from Elektor 1998/5. . . . [Peter Jakab, Electrical Engineer,
Engineer of Informatics]
434MHz transmitter using SAW resonator - Scroll to find this circuit. . . [Peter Jakab, Electrical Engineer,
Engineer of Informatics]
4-Transistor Transmitter - This circuit provides an FM modulated signal with an output power of
around 500mW. The input microphone pre-amp is built around a couple of 2N3904 transistors (Q1/Q2) , and audio
gain is limited by the 5k preset trim potentiometer. The oscillator is a Colpitts stage, frequency of oscillation
governed by the tank circuit made from two 5pF ceramic capacitors and the L2 inductor. . . [Paul C. Sherby's
4W FM Transmitter - As it has already been mentioned the transmitted signal is Frequency
Modulated (FM) which means that the carrier’s amplitude stays constant and its frequency varies according to the
amplitude variations of the audio signal. When the input signal’s amplitude increases (i. e. during the positive
half cycles) the frequency of the carrier increases too. . . [Designer's name not included]
4W FM Transmitter - This is a small but quite powerful FM transmitter having three RF stages
incorporating an audio preamplifier for better modulation. t has an output power of 4 Watts and works off 12-18
VDC which makes it easily portable. It is the ideal project for the beginner. . . [by IQ Technologies Industry,
unless otherwise noted online]
4-way remote control uses series transmission - 01/18/01 EDN Design Idea A simultaneous four way remote-control system
adheres to size, cost, and reduced-complexity constraints and uses a series transmission to drive parallel loads
(Figure 1). You can use. PDF has several circuits, scroll down. . . [by JM Terrade, Clermont-Ferrand, France]