Amateur radio and communication related projects
and articles
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This article explains my setup to receive NOAA weather
satellite images using homemade turnstile antenna, RTL SDR,
and PC. Using this setup, I got weather satellite images
from all the active NOAA satellites on 137 MHz. The
antenna which I use for this project is base on the
design done by Ivo Brugnera I6IBE.
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USB Morse Keyer is PIC16F886 based automatic Morse code keyer
with USB and Morse key interfaces. Using this automatic keyer
Amateur radio operator can send Morse code messages either using
PC or conventional Morse key. This unit is designed to work
with the majority of transmitting devices, and also it includes
options to extend its feature with minimum modifications.
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This page contains details of Eddystone EC10
communication receiver repairing process and suitable AC power supply
unit.
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This article contains logs related to Trio TX-310
and JR-310 HF transmitter and receiver restorations. Both TX-310 and
JR-310 are vacuum tube and transistor base units and manufactured
around 1960’s by Trio Corporation - Japan (now Kenwood).
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This is 5 element Yagi-Uda antenna for 144MHz
amateur radio transmissions and receiving. This antenna is design using
commonly available TV antenna parts. The CAD drawing of this antenna is
available to download in above
link and all the measurements in that diagram are in mm
(millimeters). The total boom length of this antenna is around 1500mm
and maximum span is 1016.10mm.
After the construction I test this antenna on 145.625MHz and got SWR of
1:1.3 with quiet lengthy 50Ω RG-58 cable. With high quality shorter
cable I achieve SWR of 1:1.1 - 1:1.2.
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This is quick post about 100W RF dummy load which
we build to use with HF and VHF transmitters and transceivers. This
dummy load uses two non-inductive 100Ω 50W thick film power resisters
manufactured by Vishay Sfernice and both these
resisters are connected in parallel to achieve 50Ω impedance.
Outer-casing (which also act as heatsink) of dummy
load is constructed using four bonded fin 50mm × 115mm × 20mm heatsinks.
During our testing we got flat 1:1.2 SWR with this
dummy load.
Above mentioned 100Ω 50W power resisters are
obtained through Farnell element14.
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This post is about beat frequency oscillator (BFO)
module which is used to receive SSB and CW signals from ordinary
shortwave radio receiver. This module mainly consists with two general
purpose NPN transistors and commonly available 455 kHz ceramic
resonator.
In our testing we got quiet good results with this
BFO on National Panasonic RX-5090T and some of the
recorded samples are available at this soundcloud profile. Our
modified schematic and PCB design is available to download at google
drive.
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In this project we redesign original HD-1410
electronic keyer with today's commonly available components. In this
new design the key components which we replace are transistors, diodes
and power supply section of original HD-1410 circuit. Most of the NPN
transistors in original design are replaced with KSP42 and KSP10
transistors, and all the PNP transistors are replaced with KSP92
transistors. To keep everything simple we also use same TTL chip-set
with this new design. Schematic, PCB and wiring diagram of this
modified HD-1410 keyer are available to download at my
blog.
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This page contains article about ICOM IC-R71A HF
multi-mode receiver restoration project. I got this ICOM IC-R71A receiver
from one of my friend and when it comes to my workshop it's completely
dead. After recapping and fixing some dry-joints this receiver starts
to work again.
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13.8V power supplies are commonly used in amateur radio experiments.
Most of the portable amateur radio transceivers are designed to work with a
13.8V power source. I mainly build this power supply unit to power some of my
amateur radio circuits and modules. This power supply unit is based on LM338
5A voltage regulator and MC3423 crowbar sensing circuit.
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Other radios, transmitters and related projects
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This section contains some
radio, transmitter and RF based projects which are not
directly related with amateur radio. More details of these
projects are available in my blog.
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