Automatic Battery Charger

Here is a simple battery charger circuit intended for 12 Volt gell-type battery. Current is limited by the 7805 regulator IC and the limiting resistor (62 ohms) to approximately 250 milliamperes, anyway most small sized gell-type battery capacities ranges from 2.5AH to 7.5AH so charging time should take several hours. When the battery is full, the regulator adjust its voltage output from 15 volts down to 5 volts automatically terminate the charging process.  ---73 de hevir

OPC-478 Cloning Cable

Another evening project is this OPC-478 cloning cable for my Icom IC-2200H. Credit is given to Icom which the original circuit was taken and also to the cloning software (CS-2200H) used on this project. The prototype board supply was taken from the RS232 port of the computer while if this does not work, the 5 volts can be supplied externally. A quick check on the COM port setting of your PC before running the cloning program will prevent any conflict. If your PC does not have RS232, you can have an RS232-to-USB converter available in computer shops. ---73 de hevir

Solid State Relay (SSR) using MOC3020

The circuit  uses the MOC3020 optocoupler that drives the triac to switch 220V of AC volt to a load. We have this project after one of our incubator heater failed due to a faulty mechanical relay. The triac on this circuit can be directly mounted on a suitable heatsink without a need for an insulator. The original circuit was taken from the MOC3020 Motorola datasheet.    ---73 de hevir

Transmit Beacon for Hand-held Radio

The circuit is run by 555 timer IC for its PTT sequence that is 4 seconds "on" and 4 seconds "off". Transmission is about 50% duty cycle that minimize the transmitter heat. Tone IC is any thing that generates sound, I got mine from a magnetic door open sensor which I bought from Japanese Store in Festival Mall. The prototype when connected to a portable transceiver is ready to go on air.  ---73 de hevir

Server Interface Set-up

Here is a sample interface unit configured as a server. At the left of the interface is an IC-T2H portable transceiver where the interface is connected.  During installation, there are some points to consider. Avoid putting rubber ducky antenna on the radio since rf radiation can interfere the interface function, also never put too much strains on the shielded wires since these can be easily damaged. Adjust the unit for proper sensitivity for a continuous transmission when the audio is present at the input. After tune-up had been completed, the server is good to go on-air. If you wish to include a station identifier on the server, you can download Say The Time at www.4shared.com , and if you want a simplex repeater just download the program with this link http://www.4shared.com/file/251787798/7e70eb78/simplex.html . There are lot of things you can do with the interface, its for you to discover.  ---73 de hevir

The Result of the Regular Examination Held at NTC Batangas

The exam was held last October 3, 2009 at NTC Batangas. I took the exam for my upgrade (Class B license). Thanks to 4F1DY(Jyrus) of DX1CW who shared me the reviewer that made possible for me to pass the exam. ---73 de hevir

Microphone Preamplifier

Another weekend project is this microphone preamplifier which came from my new book Hints and Kinks for the Amateur Radio. The amplifier is a single transistor powered by the 8 volts from the radio transceiver. I can't find any vintage desk microphone casing so I ended up with this pink jewelry box which I obtained from a novelty store, anyway the output audio was very nice and a little treblish. All the needed parts are available at my favorite electronic store at very minimal cost. ---73 de hevir