60W Linear amplifier

The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these transistors are used in inverters and smps they are easily available for around Rs: 20/-.

The IRF linear amplifier can be connected to the out put of popular VWN-QRP to get an output of 60 Watts. The circuit draws 700 ma at 60 Volt Vcc. Good heat sink is a must for the power transistor.

Alignment of the circuit is very easy. Connect a dummy load to the out put of the circuit. You can use some small bulb like 24V 6Watts as the dummy load. I have even used 230V 60Watts bulb as dummy load with my IRF840 power amplifier working at 120Volts. Adjust the 10K preset to get around 100 ma Drain current. I used gate voltage of 0.8V with my linear amplifier. A heigh gate voltage can make the power transistor get distroyed by self oscillation. So gate voltage must be below 2V and fixing at 1V will be safe.

Bifalar transformaer T1 is wound with 8 turns 26SWG on 1.4 x 1 balun core.

The coil on the drain of IRF is 3 turns 20 SWG wound on 4 number of T13.9 torroids (two torroids are stacked to form a balun core). The RFC at the Vcc line is 20 Turns 20 SWG wound on T20 torroid.

Audio Video RF Modulator With LM2889

The LM2889 is designed to interface audio video RF modulator signals to the antenna terminals of a TV receiver. It consists of a sound sub carrier oscillator and FM modulator, video clamp, and RF oscillators and modulators for two low-VHF channels.

Audio Video RF Modulator with LM2889 allows video information from VTRs, video disk systems, games, test equipment, or similar sources to be displayed on black and white or color TV receivers.

Features :

• Pin for pin compatible with LM1889 RF section
• Low distortion FM sound modulator (less than 1% THD)
• Video clamp for AC-coupled video
• Low sound oscillator harmonic levels
• 10V to 16V supply operation
• DC channel switching
• Excellent oscillator stability
• Low inter modulation products

For the detail about this audio video RF modulator, please follow this link for datasheet.
http://www.ziddu.com/download.php?uid=bKufnJynZa+emZqnsayZlJyiY62WlZur3
Application Note
http://www.ziddu.com/download.php?uid=a6yflJimZqqcluKnZKqhkZSoYaugnZqu4

TV RF Amplifier 5W With BLW98

This application circuit is a TV RF amplifier for driving small UHF TV transmitters, with gain is 7dB and can amplify a signal between 470-860 MHz. Drive input the circuit with 1 to 1,5 Watts signal. Better use double layer PCB with the second layer connected to earth.

Use a stabilized power supply 24 volts and at least 5 Amps. The transistor case is the SOT-122A and be careful because the transistor is very toxic for your health. Tuning of this tv rf amplifier can be achieved turning the two variable capacitors. Do not forget to use heat sink for both transistors, specially for the BLW98 and it would be better if you place a small fan as well.

For more details for constructing this tv rf amplifier, please download datasheet

( http://www.ziddu.com/download.php?uid=ZbCcnJamZq6ampenr6yZlJyiYa2Wl5Wn1 )

20 dB VHF RF Amplifier

This RF amplifier is to strengthen a small signal in the region of VHF or FM, or it is we lead a body, or a receptor. The preamplifier that to you we propose offers 20dB in all the region of VHF and it still can reach also their 500MHZ.

The amplifier is a circuit of high frequency RF with distinguishable materials. The amplifier as circuit strengthens the tendency of signal with concrete aid, depending on the frequency of signal. If the frequency of signal is included in the limits of spectrum of frequencies of amplifier, then it is strengthened, otherwise it is downgraded. Each amplifier of this category, accordingly with his designing, strengthens a concrete region of frequencies and obeys in same characteristics. The one that to you we present today concerns the regions of VHF where they exist and the corresponding television stations for channels 5 until 12. His circuit he is enough simple, so that it is made easily with materials that exist in the trade. It is based on transistors with aid until the 500MHZ. The type of transistor can be BF197 or some other.

It appears the theoretical circuit of amplifier. As we see it is constituted from two similar circuits (rungs). In this circuits are not included in joint action circuits. With that way is covered a wide spectrum of frequencies, without is differentiated abruptly the aid as for the frequency. With this provision we have smaller gain but big breadth of frequencies. The two rungs are same, with the same prices of materials and each rung offer aid roughly 10dB. The transistors and the remainder materials, because the industrial manufacture, have almost the same characteristics. Associates the particular characteristics of demagogues are altered mainly the aid of rung. Each rung uses a transistor of type npn in provision of common emitter that functions in order A. his rungs works in provision of common emitter with null resistance in emitter. In each rung a network of resistances between the collectors and the bases polarize the transistors and ensures the operation of circuit. The junction between the rungs becomes via ceramic capacitors of small capacity from 0,1nF until 0,22nF (at preference ceramic). In the place of two rungs we can try various transistors of independent company or even different between them. The circuit of course cannot work with all of them. The tendency of catering should emanate from stabilised power supply with tendency 12V. Depending on the tendency of catering and the type of transistor, in each rung of amplifier it needs enter also different resistances. Force of expense, under conditions of high excitation it can exceed the 1 mW.