2D Plotter using Arduino

    This is a simple mini 2D plotter which can plot an image at a maximum dimension of 40mm x 40mm. It uses a drive stepper mechanism for X and Y axis plotting and a Servo motor as you all can see for Z axis plotting.

Raspberry Pi 4B Composite Video Output

    Raspberry Pi is a single board computing product which was developed with a focus to improving computing skills among school children's in developing countries. Its a really good platform to learn hardware, coding, Linux and much more.

    Raspberry pi board supports HDMI and VGA ports to connect to display units. In older models there is a separate RCA socket to pull composite Video output . While on Raspberry Pi4 B and later versions the RCA socket was dropped and composite video is forwarded along with audio socket on the 4 pole TRRS socket. But in Pi Zero there is an unpopulated header labelled "TV" which outputs composite video.

QRP VHF/UHF SWR meter -Reflectometer

    A SWR meter is a very basic measuring instrument which is used to measure the voltage standing wave ratio (VSWR) in a transmission media. If you are working with radio waves and antenna experiments, this is a must instrument you should have. Its not that complicated to build one and our intention here is to just get the indication of level of VSWR in a particular transmission path.

ISS SSTV- "Amateur radio on Shuttle, Mir and ISS" SSTV event - June 21-26 ,2021

    Talking about history … The Shuttle–Mir program was a mission space program between Russia and the United States that involved American low earth orbiting Space Shuttles  visiting the Russian space station Mir where Russian cosmonauts flying on the American Shuttle, and an American astronaut flying aboard a Soyuz spacecraft to engage in long-duration expeditions aboard Mir.

   SSTV event was continuous from June 21 until June 26. The images transmitted were related to some of the amateur radio activities that have occurred on the Space Shuttle, Mir space station and the International Space Station.

    Used this event to test multiple antennas. Experimented with two different antennas this time, One was QFH tuned to 136 MHz obviously for WX satellite reception and one was Slim Jim antenna tuned to 145 MHz. And another setup was with VFH-UHF Yagi antenna tuned to 145 MHz frequency in VHF range. 

    The result was as expected the tuned antenna closed to downlink frequency of ISS VHF Transponder i.e. 145.800 MHz gave better results. Managed to receive few good images using my Yagi on last days of event.

ISS SSTV - ARISS 20 years of operations on ISS December 24-31, 2020

    After a long gap of Ham activity due to busy life, Finally the world wide lockdown brought a short throwback to my hobby activities. That was the time when is saw a tweet about a special SSTV event which was being celebrated  on the occasion of 20^th anniversary of ARISS operations on the ISS. The event was scheduled from December 24 through December 31. 

There we go...!!!

    Assembled a QFH antenna on my roof and connected it to my UV5R Radio. Those who are interested can find the detailed procedure to decode SSTV signals from here. And here is the details for building interface for UV5R to connect with PC Audio input. After monitoring multiple passes got some good SSTV images. Interesting thing was the there were multiple Ham communities around globe which were issuing Diploma certificates while submitting set of quality images.

    Managed to receive some quality images from ISS with my QFH Antenna, which I built to receive WX satellite (NOAA)  images. Will post about my QFH same shortly.      

PTT MIC from Junk

    Recycling junk materials to useful things can also be done by giving new meaning to them. Here presenting my PTT MIC for my home brew HF Transceiver. This is not a universal compatible but i can assure its compatible to all equipment interfaces in my shack. Its harvested it mostly from junk materials and i doubt about the reproducibility of this specimen. 

PTT MIC

HF Transceiver in my shack ..!!!

       Hombrewing a transceiver without kit is a real adventure. Learned lot of things by brewing this transceiver and tuning it without a receiver was challenging. Its BITX design i followed and VFO is DDS based. Got few contacts by first power up. Output power is not measured accurately and i believe its not more that 8 Watts. By the way i like to operate on QRP mode to save some power as well as to learn capability of qrp mode.

HF Transceiver

1:1 Ruthroff Voltage Balun

    This balun transformer can be used for impedance matching with tuned dipole. Also it gives a balance in voltage levels in the arms of dipole. Ofcource it is a voltage balun and uses Ferrite rod from old MW radio's. The Copper wire used is 18 SWG wound trifilar on ferrite rod.

19th All Kerala VHF Fox Hunter..

      On behalf of 19th All Kerala VHF Fox hunt.. along with VU3VIO Om Vishnu we managed to hunt down fox in least time expense.. Grabbed this years rolling shield.. Geographical region chosen was Alappuzha town a city well known for backwater tourism..

Prizes for Participants

My old television with vertical circuit blown

      Started my investigation from initial symptoms of my old CRT TV... Found that vertical circuit is blown. Sharing pic before and after fault rectification.

SG-230 Smartuner on my bench for fault rectification

      A smart build simple construction with a central microprocession is the overall structure of SG 230 tuner. just sharing pictures i took before and after fault rectification.

Tuner SG 230 overall

International Space Station SSTV Transmission

      It was amusing moment for the Ham radio operators to acquire Slow Scan Television Signal (SSTV) transmission experiment from International Space Station -ISS by active Russian Crew on behalf of 80th anniversary of the first cosmonaut Yuri Gagarin on December 20th, 2014 as well as January 31’st and February 1st  ,2015.

Fig:1 ISS SSTV Signal Transmitted under Call Sign RS0ISS on DECEMBER 20th, 2014

Rig- PC Interface for Digital Modes

      Hi, Described here is a circuit setup for interfacing PC soundcard with radio equipment for transferring digital as well as analog base band signal in audio frequency range. Requires modem software for modulation and demodulation of baseband signal.

Figure 1 Schematic Diagram

Slim-Jim Antenna

      Just completed my slim-jim antenna last week. The materials used are 14 SWG copper wire from old electrical cable and some old PVC's and PVC Connectors. I used a 1.9 Meter 1/2" PVC to assemble element and 1'' PVC for covering the element with an PVC end cap on top and an so239 connector at the bottom end to connect the feeder.

      I used a RG 58 feeder cable and a small balun at the antenna feeder end. And here it is at my roof top. The calculation for element length can be found in google. Do consider a parasitic effect due to PVC and build the antenna with a tuning frequency slightly greater than the required tuning frequency.

Balun for 145.000 MHz.

Cheers !!! ...

Baofeng UV-5R External Mic and PTT

     Here is the simplest circuit or just a setup to interface external condenser mic and a PTT switch to a UV-5R VHF transceiver. This setup can be used by those who wish to make a base station with fixed external antenna using UV-5R. Gain of the mic can be adjuster varying the bias resistance R1. I chose a 5KOhm which works good for me.

      The Speaker and Transceiver can be kept in a single unit like a shielded or unshielded box. An extension cable (2+1 audio grade Shield Cable) with 3.5mm plug on both ends can connect these two circuits. No external power supply is required for this circuit and can be build from scratch.

      Here is my setup using some old PVC's and the PVC connectors as these materiel are easy to source. Just build it so simple from junk... :)

Cheers!...

MINIMA TRANSCEIVER

      QRP transceiver from VU2ESE. Its a semi software defined radio for general coverage HF which uses Si570 XO from silicon labs as local oscillator controlled by Arduino controller ATMEGA328P. For more details regarding construction, features and circuit designs feel free to click this resourceful link.

      This project is in R&D stage and still you can find a crowd of audience discussing its performance which clearly states its the best of its kind. Fore those serious critical examiners there is a forum for discussion about ongoing updates and modifications regarding core issues Freelists.

MINIMA Schematic Diagram

Zeta SDR

Zeta SDR is a simplest SDR using analog mux/demux used as mixer to generate I and Q signals by mixing with oscillator signal of 45 degree phase shift, the IF signal is then passed through low pass filter. The circuit is from the web page http://www.qrz.lt/ly1gp/SDR/.

The basic block diagram is shown below.

RTL SDR Upconverter for T820 Series

Realtek RTL2832U DVB-T dongles can be used as a cheap SDR. As a DAB/DAB+/FM demodulator it’s possible to fetch 8-bit I/Q-samples from RTL. Moderate low loss sampling rate of 2.56 MS/s is suggested even the device can support upto 3.2 MS/s. For more information check official page of rtl-sdr.

85-950MHz Analog AM /WFM /NFM Receiver (DE_JUNK_BEE)

MY FIRST VHF RECEIVER ...!!!

      This is a receiver build using the Analog TV tuner used in old television sets. Its capability and real application limits it to receive analog signals only. I have done some modification to the circuit to make it more selective and flexible. The inspiration that I got to build this circuit comes from the "link" .

FLC METER USING 16F877A (DE_METAL_AMIGO)

 

Inductors and capacitors are general purpose components in AC circuits. The estimation of exact or approximate values of inductance can be found in much theoretical way with the relation that they make with their physical dimensions. But who knows what exactly the show in practice. Even the slight change in the pitch of turns in case of inductance can change the resultant value. That was the intention that leads me to the build one.

The Rotating LED Clock

Time is an illusion...!!!!  

Mechanically scanning LED displays have a great place in the future. They may eventually replace the matrix of light bulbs found on standard displays. Spinning displays require much less power to drive the lights, as there is a fraction of the number of lights required in the matrix design. Our group hopes to take advantage of this and create an aesthetically pleasing clock. This clock also should keep the time accurately, slowly rotate the time so it is visible from all sides, is inexpensive to construct and maintain, and look more appealing than the average clock. The basic principle of working is the persistence of vision POV.

LUNAR LASER COMMUNICATION

INTRODUCTION

The present trends of communication are through transmission lines, optical fiber and microwave wireless communications. Fiber-optic communication is a method of transmitting information from one place to another by sending pulses of light through an optical fiber. Microwave transmission refers to the technology of transmitting information or power by the use of radio waves whose frequencies are  spectrum ranges across of roughly 1.0 (GHz) to 30 GHz referred as microwaves. These all type of communication technologies has their own disadvantages. In optical fiber communication losses like attenuation, absorption, scattering and radiative are occurred. Losses can occur in transmission lines if it shouldn’t perfectly terminated at its characteristic impedance. Microwave devices such as MASER can cause ozone depletion due to its high area of radiation.

Inflammable gas leakage detector

Arrest Fire...!!!!!

DANGERS OF INFLAMMABLE GASES LEAKING

Some of the inflammable Gases are not toxic. But they are extremely flammable and will cause an explosion; it will also kill you by asphyxiation if it leaks into an enclosed space and deprives you of oxygen. In case of methane it only becomes poisonous when it forms part of another gas and is subject to certain circumstances. The bad news is that this happens quite often.

Don’t worry…. Here is a solution for detecting the inflammable gas leakage. The circuit uses a gas sensor which can detect the presence of LPG, Propane, Methane and Hydrogen also other combustible streams. 

Follower the Command Line :)

INTRODUCTION

What is a line follower?

            Line follower is a machine that can follow a path. The path can be visible like a black line on a white surface (or vice-verse) or it can be invisible like a magnetic field.

Why build a line follower?

Sensing a line and maneuvering the robot to stay on course, while constantly correcting the wrong moves using feedback mechanism forms a simple yet effective closed loop system. As a programmer you get an opportunity to ‘teach’ the robot how to follow the line thus giving it a human-like property of responding to stimuli.

PCB from scrach

INTRODUCTION

A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board (PWB) or etched wiring board. A PCB populated with electronic components is a printed circuit assembly (PCA), also known as a printed circuit board assembly or PCB Assembly (PCBA). Printed circuit boards are used in virtually all but the simplest commercially produced electronic devices. The credit goes to Arthur Berry in 1913 patented a print-and-etch method in Britain.