A Simple Crystal Radio

         A crystal radio is a simple radio receiver that was popular in the early 20th century. It requires no external power source and is able to pick up radio signals using only the energy present in the radio waves themselves.

        The basic components of a crystal radio include a tuned circuit made up of a coil of wire and a capacitor, a diode (typically a germanium diode), and a set of headphones. The coil and capacitor are used to tune the circuit to a particular frequency, while the diode acts as a detector, allowing the radio waves to be converted into an audio signal that can be heard through the headphones.

LoRa 433MHz TinyGS Satellite Ground Station

     TinyGS is an open network of Ground Stations distributed around the world to receive and operate LoRa satellites, weather probes and other flying objects, using cheap and versatile modules. Here we will be discussion about tracking and receiving data packets from LoRa supported satellites.

    This project is based on ESP32 boards and currently it is compatible with sx126x and sx127x LoRa modules but we plan to support more radio modules in the future.

Baofeng UV9R (Waterproof) Programming with Arduino

    This is simple method to program UV9R Plus or similar waterproof radio's belonging to Baofeng family of radio's. Here we will be utilizing the USB to Serial interface of Arduino Uno to perform the required programming. Also we will be describing method to prepare radio interface adapter using easy to procure items like Common PCB , berg pins and jumper cables.

    UV9R Plus is IP57 dust and water proof resistant radio which requires special water proof interface cables to program the channels and update radio related settings. Today we will go through the programming part of this radio. The inspiration to use Arduino to program the radio comes from here. We will be focusing more on building an interface adapter to avoid direct soldering in radio interface contact points.

 

Baofeng UV5R Programming with Arduino

     This is simple method to program UV5R or similar radio's belonging to Baofeng family of radio's. Here we will be utilizing the USB to Serial interface of Arduino Uno to perform the required programming. Also we will be describing method to prepare radio interface cable using simple audio jack and few wire.

HF VHF RF Power/SWR meter with Oled Display

    Presenting here is a simple Arduino based homebrewed HF/VHF RF power & SWR meter. This compact and light weight equipment which is powered by recycled Nokia BL-5C batteries and entire unit is mounted inside a PVC junction box. A DC power socket is provided to recharge the battery using external power supply as we as an option to power the device using external power supply.

QRP EFHW SOTA TUNER

             This is a mini QRP tuner for EFHW antenna tuner. End Fed Half Wave is a type of dipole antenna of which the feeder point is at one end instead of the traditional dipoles where feeder line is connected to the middle point where the impedance is very low. 

ARISS end of year ISS SSTV 2021--Expedition 66 - ARISS Series 19 Lunar Exploration

     Thanks to ARISS team to encouraging SSTV operations from the ISS during the period of Dec 26-31. Used this opportunity to collect fabulous images related to lunar exploration. The transmissions were available worldwide on 145.800 MHz with PD 120 mode.

    Due to limited access to apartment roof have no other option left over than to use 1/4 lambda antenna replacing rubber duck antenna of my classic UV5R handy.

My Setup 😎

    Managed to receive following images of specific passes from North to East and vice versa due to limited open space from apartment balcony.

Moscow Aviation Institute (MAI) SSTV experiment -"Inter-MAI-75" Dec 1 ,2021

     Managed to receive SSTV image from ISS on Dec 1 "Inter-MAI-75 event. SSTV images were transmitted at 145.800 MHz from ISS in PD-120 SSTV format .

    Scheduled on December 01, 2021 (Wednesday) - from ~ 12:25 UTC - ~ 18:45 UTC.

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.