Published:2012/12/12 21:09:00 Author:muriel | Keyword: Common Gate Amplifier
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Published:2012/12/12 21:08:00 Author:muriel | Keyword: Tuned Whip
Previous experimentation confirmed that it is easy to tune a short whip antenna by connecting it to the hot end of an L C (inductor and capacitor) tank circuit. The high impedance whip antenna was matched to a JFET RF amplifier by placing a high value (1 megohm or greater) on the JFET gate to ground. Although this method is practical, I desired a network to transform the output impedance of the tuned whip tank tank circuit to a known impedance. I do not possess the knowledge or mathematical skill to design such a network and asked Wes Hayward if he might consider doing this for me. My desired parameters for the network were 10.0 MHz, a 50 ohm output impedance and a 4 foot (122 cm) whip. Please refer to Wes' calculations and schematic in Figure 2 below. This math is difficult, however, a practical design for experimentation is provided. (View)
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Published:2012/12/12 21:07:00 Author:muriel | Keyword: experimental , broadband , cascode, JFET VPA
Many builders emailed me requesting a simple, broadband VPA (voltage probe antenna) design with more power gain than the common gate versions I have presented elsewhere on this web site. Connecting a whip antenna to a cascode JFET stage described by W7ZOI in Experimental Methods in RF Design is 1 method I considered.
I built the version shown in Figure 1 almost 2 years ago. This VPA. although more powerful, overloaded the front end of my test receiver with multiple RF signals. Clearly some tuning on the input was needed.
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Published:2012/12/12 21:05:00 Author:muriel | Keyword: Cascode 7, Experimental Receiver
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Published:2012/12/12 21:04:00 Author:muriel | Keyword: Cascode 7, Experimental Receiver
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Published:2012/12/12 21:03:00 Author:muriel | Keyword: Cascode 7, Experimental Receiver
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Published:2012/12/12 21:03:00 Author:muriel | Keyword: Cascode 7, Experimental Receiver
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Published:2012/12/12 21:02:00 Author:muriel | Keyword: Cascode 7, Experimental Receiver
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Published:2012/12/12 20:59:00 Author:muriel | Keyword: Telephone Recorder
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Published:2012/12/12 20:59:00 Author:muriel | Keyword: Telephone Hold Button
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Published:2012/12/12 20:58:00 Author:muriel | Keyword: Simple Phone Tap
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Published:2012/12/12 20:57:00 Author:muriel | Keyword: Ringing Phone , Light Flasher
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Published:2012/12/12 20:56:00 Author:muriel | Keyword: Remote Telephone Ringer
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Published:2012/12/12 20:55:00 Author:muriel | Keyword: Phone Busy Indicator
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Published:2012/12/12 20:55:00 Author:muriel | Keyword: FM Telephone Bug
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Published:2012/12/12 3:27:00 Author:Ecco | Keyword: connection , external circuit
Current signal is sampling by an external shunt, RCS is generally connected with return branch in series, and it is sent to current amplifier by pin 2 and pin 3, the output voltage of the power module input uses by 11 feet and 4 feet differential signal, and it is superimposed with circulation.
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Published:2012/12/12 2:58:00 Author:Ecco | Keyword: functional block
Figure 1 shows a functional block diagram between CAN controller and interface circuit 82C250 of physical bus. 82C250 is able to provide differential receive and transmit functions for bus to achieve electrical isolation between each node on the bus, and the maximum transmission rate is up to 1 Mb / s.
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Published:2012/12/12 2:52:00 Author:Ecco | Keyword: Timer alarm
Timer alarm circuit using NE555 is shown as the figure.
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Published:2012/12/12 2:51:00 Author:Ecco | Keyword: PWM inverter , over-current protection
It can prevent IGBT or MOSFET output stage from being damaged by large current flowing. The maximum current is 23A when the motor is overcurrent, and the overcurrent needs 3μs flowing to protection circuit.
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Published:2012/12/12 2:32:00 Author:Ecco | Keyword: dual JFET , input op amp, main characteristics
Input offset voltage is 10mV ; temperature drift is 75μV / ℃; bias current is 2pA ; Gain Bandwidth Product GB = 1MHz; conversion rate is 6V/μs ; Current consumption is 4.5mA ; power supply is ± 18V; differential input voltage is ± 30V ; common-mode input voltage is ± 15V; power consumption is 500mW.
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