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Minimum Mass Wireless Data Coupler - Bidirectional RF
communications works like very short range (10 to 15 cm) radio but is
as easy as IR….(electronic design added 6/07)
MK-484 Receiver Chip Evaluation Board for AM & Lowfer bands. -
The basic MK484 (Replacement for the ZN414) connected in its minimum
configuration as a radio receiver for the A.M. Broadcast band and the
upper half of the United States' FCC Part 15 Lowfer (1600-1750 meter)
band....(schematic / circuit added 6/07)
Morse Code Beacon Keyer - This circuit stores a single morse
code message as bits in an EPROM chip, the message is sent to a relay
which can key a CW transmitter. The keyer can output either a one-shot
message such as "CQ DX DE CALLSIGN", or a continuous message. The
continuous mode is useful for making beacons for low power (QRP) and
slow (QRSS) transmissions.... [Designed by G. Forrest Cook]
One-Transistor Amplifier/Detector - An amplifier may be added to boost the audio
level as shown below. The current consumption of this amplifier is quite low and a power
switch is not included. Disconnect the battery when the receiver is stored for long
periods….(added 04/05/06)
Opamp Basics - The op-amp is basically a differential amplifier having a large
voltage gain, very high input impedance and low output impedance. The op-amp has a
"inverting" or (-) input and "noninverting" or (+) input and a single output. The op-amp
is usually powered by a dual polarity power supply in the range of +/- 5 volts to +/- 15
volts. A simple dual polarity power.... (circuit added 7/02)
Precision Portable Voltage Reference - It has been said that a man with one
watch knows what time it is, but a man with two watches is never sure. The same can
be said for a person who has more than one voltmeter. In my situation, I have
several voltmeters in each of two different locations a third of the way around the world
apart. The best solution ....(schematic / circuit added 6/07)
Push-Pull 300-watt Amplifier for 81.36 MHz - This article describes a 300 watt
amplifier for 81.36 MHz using a push-pull pair of plastic packaged devices. The design
techniques and construction practices are described in enough detail to permit duplication
of the amplifier. Application Note Microsemi-formerly Advanced Power Technology APT9801
(App Note added 4/08)
QRP Antenna Tuner - This circuit is for a QRP (low power) antenna tuner, a.k.a.
a transmatch, for use in the short wave amateur radio bands from 3-30 Mhz. It allows a
wide variety of antennas to be connected to a low power transmitter. When the circuit is
properly tuned, the maximum transmitter power will be delivered to the antenna. It is used
in conjunction with a standing wave ratio (SWR) meter. This is a fairly generic
antenna tuner circuit. [design by G. Forrest Cook]
RS-232 to Wireless Instrument Data Channel - This is an adapter that allows a
terminal to communicate via a 100 MHz data channel with peripherals on the same desk top.
Keystrokes from the terminal are are received through the RS-232 connection and sent
through the 100 MHz RF data channel. (ATtiny2313, AT90S2313)....(added 6/07)
