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" .