Posted on Monday, April 15, 2019 • Category: Headphone Amplifiers
This little tube amplifier is easy to build and will fit into a small metal Altoids box and can be carried around. It can be build with few common parts, that should be readily available. Amplifier works with many tubes like 6DJ8, ECC88, 6922, 12AT7, 12AX7, DAF96, 1T4, etc. It is powered by 12V supply and power consumption may be optimized to allow for small rechargeable battery packs.
Posted on Monday, February 25, 2019 • Category: Power Supplies
Presented here is a Laboratory Power Supply with 0-30V voltage and 0-3A current regulation. The schematic is pretty straightforward, it uses standard dual opamps such as TL082, TL062, TL072, NE5532, RC4558 and MC34072. The trimmer P3 adjusts the minimum current limit. P4 adjusts the maximum output voltage. After the final adjustment you may replace the trimmers with standard resistors. Power transistor dissipates quite a bit of heat and thus require a heatsink with optional fan. We may use two or tree transistors in parallel with emitter resistors to achieve more power. The transformer must be 100-120W with 27-30VAC output voltage.
Posted on Friday, February 1, 2019 • Category: FM Transmitters
This RF Amplifier designed for FM broadcast using a single 2SC1946 VHF Power Transistor. This 10-30W RF amplifier circuit provides an appropriate power boost with an input of 1-3 watt. Tower are 30 meters high will send signal surrounding air should be around 15 km.
Posted on Tuesday, January 22, 2019 • Category: FM Transmitters
That small circuit transmitter it is ideal for ready espionage for strip from radio Fm or receiver of VHF. Of course the recreational purpose also exists and the children will adore to have a transmitter that allows to speak for a radio FM placed at distant place and like this pretend the secret agent.
Posted on Wednesday, November 14, 2018 • Category: FM Transmitters
Powerful microtransmitter that can cover 3km range. To amplify the signal, a 2N3866A transistor is used that can provide up to 1W with gain > 10dB (24Volt). In our case the output power is about 100mW depending on the input power of 10mW and 9V battery power supply. The transistor Q1 must be mounted with a heatsink, the heatsink must have small dimensions (cylindrical) in order not to increase the parasitic capacitance. The trimmer R2 serves to adjust the bias of the transistor, start with the trimmer fully open and close by measuring the current absorbed by the 9V, in my case you get 100mW at the output with a current of 50mA not increase this value as you only increase the absorption by heating the transistor without increasing output power, because the input power is too low. Clearly the 9V battery will be able to provide 50mA only for a few hours, if necessary have greater autonomy should be used a larger battery, but it is no longer a bug but simply an FM transmitter.
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